International Journal of Biological Macromolecules (01418130)289
Microbial production of xanthan gum from forage sorghum straw (FSS) was investigated. The important aspect investigated was the synthesis of xanthan gum using hemicellulose as a substrate (hemicellulose-derived xanthan), a process that has been relatively underexplored in the existing literature. Xanthomonas campestris ATCC 33913 and an isolated strain from orange peel, identified as X. axonopodis, were utilized for xanthan production. The FSS hydrolysate obtained by treatment under 120 °C for 30 min and overliming, yielded xanthan gum concentration of 7.1 g/L for X. campestris and 6.9 g/L for X. axonopodis. The lower molecular weights of xanthan gum produced from FSS (590 kDa for X. campestris and 550 kDa for the isolated X. axonopodis), compared to those from glucose suggest distinct advantages for specialized applications. Xanthan gum from FSS also possessed a higher ratio of acetate to pyruvate, ranging from 1.5:1 to 1.91:1 for X. axonopodis and from 1.33:1 to 1.75:1 for X. campestris. This characteristic renders it an attractive choice for certain applications in the food industry. By utilizing this strain, 11.71 g of hemicellulose-derived xanthan gum and 13.8 g of cellulose-derived xanthan gum per 100 g of FSS were obtained, indicating a conversion rate of 25.51 %. © 2024 Elsevier B.V.
Gao, Y.,
Zhang, W.,
Asadollahi, M.A.,
Liu, C.,
Yu, G.,
Li, H.,
Li, B. Biomass and Bioenergy (09619534)193
Clean and efficient pretreatment is a critical process for producing cellulosic sugar platform for the production of advanced biofuels and chemicals. Combining a chemical treatment with ball milling is a relatively simple and environmentally friendly procedure, which may reduce the pretreatment time and energy consumption. Hence, in this study, the mineral salts (e.g. ZnCl2, ZnBr2, LiCl, and LiBr) were used to enhance the ball milling. Firstly, microcrystalline cellulose (MCC) as a model compound of pure cellulose was pretreated by mineral salt-assisted ball milling to investigate the effect of mineral salt and ball milling for promoting cellulose saccharification. LiBr showed the best effect to improve the effectiveness of ball milling pretreatment, and the glucose yield of saccharification reached up to 93.8 % under the optimal conditions. Then, corncob residue (CCR) as a distinctive starting material was pretreated by LiBr-assisted ball milling, and the corresponding glucose yield of saccharification (48 h) with enzyme dosage of 5 FPU/g-CCR was as high as 97.4 %. Characterization verified that, the effect of LiBr and ball milling could more effectively break hydrogen bonds and crystalline structure of cellulose, thus highly promoting the followed enzymatic saccharification without lignin removal and washing after LiBr-assisted ball milling pretreatment. This work can help to understand the effect of combining mineral salt with ball milling, which is beneficial to the development of clean and effective pretreatment approach for lignocellulose biorefinery. © 2024 Elsevier Ltd
Dong, L.,
Gao, Y.,
Liu, C.,
Yu, G.,
Asadollahi, M.A.,
Wang, H.,
Li, B. International Journal of Biological Macromolecules (01418130)276
Xylose plants (produce xylose from corncob through dilute acid treatment) generate a large amount of corncob residue (CCR), most of which are burned and lacked of valorization. Herein, to address this issue, CCR was directly used as starting material for high-solid loading enzymatic hydrolysis via a simple strategy by combining PFI homogenization (for sufficient mixing) with batch-feeding. A maximum glucose concentration of 187.1 g/L was achieved after the saccharification with a solid loading of 25 wt% and enzyme dosage of 10 FPU/g-CCR. Furthermore, the residue of enzymatic hydrolysis (REH) was directly used as a bio-adhesive for plywood production with both high dry (1.7 MPa) and wet (1.1 MPa) surface bonding strength (higher than the standard (0.7 MPa)), and the excellent adhesion was due to the interfacial crosslinking between the REH adhesive (containing lignin, free glucose, and nanosized fibers) and cell wall of woods. Compared with traditional reported adhesives, the REH bio-adhesive has advantages of formaldehyde-free, good moisture resistance, green process, relatively low cost and easy realization. This study presents a simple and effective strategy for better utilization of CCR, which also provides beneficial reference for the valorization of other kinds of lignocellulosic biomass. © 2024 Elsevier B.V.
Microbial Biotechnology (17517915)17(3)
Pseudomonas putida is a soil bacterium with multiple uses in fermentation and biotransformation processes. P. putida ATCC 12633 can biotransform benzaldehyde and other aldehydes into valuable α-hydroxyketones, such as (S)-2-hydroxypropiophenone. However, poor tolerance of this strain toward chaotropic aldehydes hampers efficient biotransformation processes. To circumvent this problem, we expressed the gene encoding the global regulator PprI from Deinococcus radiodurans, an inducer of pleiotropic proteins promoting DNA repair, in P. putida. Fine-tuned gene expression was achieved using an expression plasmid under the control of the LacIQ/Ptrc system, and the cross-protective role of PprI was assessed against multiple stress treatments. Moreover, the stress-tolerant P. putida strain was tested for 2-hydroxypropiophenone production using whole resting cells in the presence of relevant aldehyde substrates. P. putida cells harbouring the global transcriptional regulator exhibited high tolerance toward benzaldehyde, acetaldehyde, ethanol, butanol, NaCl, H2O2 and thermal stress, thereby reflecting the multistress protection profile conferred by PprI. Additionally, the engineered cells converted aldehydes to 2-hydroxypropiophenone more efficiently than the parental P. putida strain. 2-Hydroxypropiophenone concentration reached 1.6 g L−1 upon a 3-h incubation under optimized conditions, at a cell concentration of 0.033 g wet cell weight mL−1 in the presence of 20 mM benzaldehyde and 600 mM acetaldehyde. Product yield and productivity were 0.74 g 2-HPP g−1 benzaldehyde and 0.089 g 2-HPP g cell dry weight−1 h−1, respectively, 35% higher than the control experiments. Taken together, these results demonstrate that introducing PprI from D. radiodurans enhances chaotrope tolerance and 2-HPP production in P. putida ATCC 12633. © 2024 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd.
Golnari, M.,
Bahrami, N.,
Milanian, Z.,
Rabbani khorasgani, M.,
Asadollahi, M.A.,
Shafiei, R.,
Fatemi, S.S. Scientific Reports (20452322)14(1)
Despite the current use of some Bacillus spp. as probiotics, looking for and introducing new efficient and safe potential probiotic strains is one of the most important topics in both microbiology and food industry. This study aimed to isolate, identify, and evaluate the probiotic characteristics and safety of some Bacillus spp. from natural sources. Thirty-six spore-forming, Gram-positive, and catalase-positive Bacillus isolates were identified in 54 samples of soil, feces and dairy products. Bacterial identification was performed using 16S rDNA sequencing. To evaluate the probiotic potential of isolates, the resistance of bacterial cells to simulated gastrointestinal tract (GIT) conditions, the presence of enterotoxin genes, their susceptibility to antibiotics, antimicrobial and hemolytic activities and biochemical profiles were investigated. The results revealed that eight sporulating Bacillus spp. isolates fulfilled all tested probiotic criteria. They showed a high growth rate, non-hemolytic and lecithinase activity, and resistance to simulated GIT conditions. These strains exhibited broad-spectrum antibacterial activity against pathogenic bacteria. In addition, they did not exhibit antibacterial resistance to the 12 tested antibiotics. The results of this study suggest that these isolates can be considered as candidates for functional foods and as safe additives to improve diet quality. © 2024, The Author(s).
Ullah, H.,
Madadi, M.,
Asadollahi, M.A.,
Hu, Y.,
Dou, S.,
Yan, J.,
Huan, H.,
Sun, F. Journal of Chemical Technology and Biotechnology (02682575)99(3)pp. 567-579
The yeast expression system, Pichia pastoris, is one of the most robust and versatile expression systems in biotechnology and molecular biology, generally considered as a safe host for heterologous protein expression, especially for producing cellulases and xylanases at the industrial level. Despite the high recombinant protein expression rate, the potential of the P. pastoris expression system has still not been fully explored. Cultivation of P. pastoris under optimized conditions greatly relies on the strain and is associated with certain problems such as promoter strength, sensitivity to methanol, and oxygen demand. To address these issues, different genetic engineering strategies have been employed. Advancements in promoter engineering, optimization of gene dosage and codon usage, recombinant plasmid engineering using CRISPR/Cas9 system, and directed evolution strategies have proven beneficial to the yield of cellulase expression levels. This study will systemically review recent progress in various genetic engineering strategies to enhance cellulase and xylanase expression in the P. pastoris expression system. The utilization of alcohol oxidase 1 promoter (pAOX1), methanol-free system, and recombinant plasmid engineering for improved production of these enzymes are highlighted. Additionally, we discuss the recent advancements in the P. pastoris expression system toolbox for improved cellulase and xylanase production, thus providing a deep insight into how P. pastoris is becoming the indispensable platform for heterologous protein production. © 2023 Society of Chemical Industry (SCI). © 2023 Society of Chemical Industry (SCI).
Arabian Journal Of Chemistry (18785352)17(1)
Bioactive glass is one interesting type of material for bone repair. In this work, a new powder (MBG2) was synthesized by a sol–gel method, in which 5 mol.% Mg and 5 mol.% Zr were incorporated into the structure, to investigate the combined effects of the simultaneous addition of these ions on the biological properties of 45S5 mesoporous bioactive glass. Then, the outcomes of various characterization techniques and in vitro biological analyses performed on this powder were compared with those of pure powder (MBG1). For instance, the XRF investigation proved that Zr and Mg ions were present in powder MBG2′s composition. Additionally, XRD, SEM, and BET tests of the powders MBG1 and MBG2 indicated their amorphous structure and spherical morphology with specific surface areas of 620 and 710 m2/g and average particle sizes of about 30 and 20 nm, respectively. The development of an apatite layer on the surfaces of disc-shaped samples produced from both powders were immersed in phosphate-buffered saline (PBS) and simulated body fluids (SBF), and the behavior of the samples' degradation were observed for 28 days. Furthermore, it was assessed how the Zr and Mg ions in the composition affected the MG-63 cells' survival, growth, and adhesion through in vitro biocompatibility testing. From the obtained results, it can be concluded that 45S5 mesoporous bioactive glass powder with minimal cytotoxicity was entitled to be a safe biomaterial due to the coexistence of 5 mol.% Mg and 5 mol.% Zr in the composition, which successfully enhanced bioactivity, cell proliferation, and biocompatibility. © 2023 The Author(s)
Biofuels, Bioproducts and Biorefining (1932104X)18(5)pp. 1554-1564
The production of value-added products from sewage sludge is considered to be one of the solutions for the sustainable management of sludge in wastewater treatment plants (WWTPs). The presence of carbon, nitrogen, and phosphorus sources has made the sewage sludge of WWTPs a valuable and low-cost substrate for the production of fermentative products. In the current study, a process was developed for microbial lipid production from two types of sewage sludge from a WWTP in northern Isfahan: anaerobic digester inlet sludge (DIS) and anaerobic digester outlet sludge (DOS). This process was based on the release of volatile fatty acids (VFAs) from the sludge by combinations of γ-ray irradiation, anaerobic digestion, and acidogenic fermentation followed by utilization of VFAs in a microbial process by the oleaginous yeast Cryptococcus aureus UIMC65. After γ-ray irradiation, the acidogenic fermentation of the treated sludge released 72% of the organic matter content of the sludge with acidification efficiency of 12% leading to 0.516 g L−1 VFAs. The oleaginous fermentation of the released VFAs for 7 days was accompanied by production of 1.58 g L−1 dry cell biomass with 40% lipid content. The results of this study indicate that the sewage sludge from urban WWTP has the potential to be used for the production of microbial lipids. © 2024 Society of Industrial Chemistry and John Wiley & Sons Ltd.
Asadollahi, M.A.,
Alizadeh, R.,
Mahmudi, R.,
Labbaf, S.,
Sadrnezhaad, S.K.,
Atari, M. Metals and Materials International (15989623)30(6)pp. 1538-1555
This study investigated the effects of solution heat treatment and multi-directional forging (MDF) on the microstructure, mechanical, and corrosion properties of an Mg–2Zn–0.2Ag alloy. Microstructural characterization by field emission scanning electron microscopy indicated that the as-cast material consists of some MgZn2 and Ag-rich MgZn precipitates. These silver-rich MgZn precipitates were entirely and partially dissolved after the solution treatment and MDF, respectively. In addition, the grain size of the as-cast alloy increased by 86% and decreased by 43% after solution heat treatment and MDF, respectively. The ultimate shear strength of the as-cast material increased by 25% and reached 149.5 MPa after MDF processing, while it did not change significantly after solution treatment. The obtained results indicated that the corrosion layer formed on the samples consists of an inner layer (magnesium hydroxide) and an outer layer (phosphate compounds). Based on the corrosion tests, it was found that solution heat treatment and MDF could significantly improve the corrosion resistance of the as-cast Mg–2Zn–0.2Ag. The corrosion resistance (Rp) obtained from the electrochemical impedance spectroscopy (EIS) test exhibited enhancements of 119% and 152% after heat treatment and MDF processes, respectively. This improvement in corrosion resistance was attributed to the higher stability of the outer layer in both solution-treated and MDF-processed samples, compared to the as-cast material. The results of cell studies also indicated a significant improvement in the cell viability of the solution-treated Mg–2Zn–0.2Ag alloy sample compared with pure Mg. Graphical Abstract: (Figure presented.) © The Author(s) under exclusive licence to The Korean Institute of Metals and Materials 2024.
Zarei, M.,
Shabani dargah, M.,
Hasanzadeh azar, M.,
Alizadeh, R.,
Mahdavi, F.S.,
Sayedain, S.S.,
Kaviani, A.,
Asadollahi, M.A.,
Azami, M.,
Beheshtizadeh, N. Scientific Reports (20452322)13(1)
The mechanical and biological properties of polylactic acid (PLA) need to be further improved in order to be used for bone tissue engineering (BTE). Utilizing a material extrusion technique, three-dimensional (3D) PLA-Ti6Al4V (Ti64) scaffolds with open pores and interconnected channels were successfully fabricated. In spite of the fact that the glass transition temperature of PLA increased with the addition of Ti64, the melting and crystallization temperatures as well as the thermal stability of filaments decreased slightly. However, the addition of 3–6 wt% Ti64 enhanced the mechanical properties of PLA, increasing the ultimate compressive strength and compressive modulus of PLA-3Ti64 to 49.9 MPa and 1.9 GPa, respectively. Additionally, the flowability evaluations revealed that all composite filaments met the print requirements. During the plasma treatment of scaffolds, not only was the root-mean-square (Rq) of PLA (1.8 nm) increased to 60 nm, but also its contact angle (90.4°) significantly decreased to (46.9°). FTIR analysis confirmed the higher hydrophilicity as oxygen-containing groups became more intense. By virtue of the outstanding role of plasma treatment as well as Ti64 addition, a marked improvement was observed in Wharton's jelly mesenchymal stem cell attachment, proliferation (4′,6-diamidino-2-phenylindole staining), and differentiation (Alkaline phosphatase and Alizarin Red S staining). Based on these results, it appears that the fabricated scaffolds have potential applications in BTE. © 2023, The Author(s).
In the quest for identifying novel renewable energy sources, higher alcohols from fermentative processes have received enormous interest in the last decades. Commercial microbial butanol production through the traditional acetone-butanol-ethanol process was common in the first half of the 20th century, and many attempts are underway to revive this process for butanol production. In addition to butanol, other linear and branched higher alcohols hold great promise as alternative energy sources. Although Clostridium species can naturally produce butanol, most of the other higher alcohols are synthesized in nonnative hosts. This requires the construction of novel pathways, the introduction of heterologous genes, and extensive genetic manipulation of host strains. Therefore, this chapter aims to demonstrate metabolic pathways for the synthesis of various higher alcohols. Moreover, in this chapter, metabolic engineering studies for the production of higher alcohols are reviewed. Recent advances and challenges associated with the microbial synthesis of higher alcohols are discussed. © 2024 Elsevier Inc. All rights reserved.
Bioelectrochemistry (15675394)149
Costly cofactors such as nicotinamide adenine dinucleotide hydrogen (NADH) are essential to have high activity in many redox enzymatic processes. Cofactor regeneration methods have been suggested to improve the economic aspects of the system. Here, we introduce a microbial electrosynthesis process to regenerate NADH in a two-chamber set-up with Enterobacter aerogenes biofilm as the bio-cathode. The effects of several important factors on the regeneration efficiency were studied and the highest NADH regeneration yield was achieved equal to 65 % at the potential of −1.5 V and the initial NAD+ concentration of 1 mM after 8 h of operation. The regenerated cofactor was highly enzymatically active (93 ± 4 %) which was a great merit of the process. Studying the kinetics of regeneration revealed that the electron transfer rate to the biofilm was the limiting factor. We tried to remove the limitation through co-culturing Pseudomonas aeruginosa and producing more electrochemical active compounds in the biofilm. Although, this modification was not effective for the regeneration yield, it showed that the external potential implicitly influenced the regeneration process by changing the internal microbial cell metabolic fluxes. Finally, it can be concluded that the microbial electrosynthesis is a promising green process for NADH regeneration. © 2022 Elsevier B.V.
Microbial Cell Factories (14752859)22(1)
Background: Aromatic α-hydroxy ketones, such as S-2-hydroxypropiophenone (2-HPP), are highly valuable chiral building blocks useful for the synthesis of various pharmaceuticals and natural products. In the present study, enantioselective synthesis of 2-HPP was investigated by free and immobilized whole cells of Pseudomonas putida ATCC 12633 starting from readily-available aldehyde substrates. Whole resting cells of P. putida, previously grown in a culture medium containing ammonium mandelate, are a source of native benzoylformate decarboxylase (BFD) activity. BFD produced by induced P. putida resting cells is a highly active biocatalyst without any further treatment in comparison with partially purified enzyme preparations. These cells can convert benzaldehyde and acetaldehyde into the acyloin compound 2-HPP by BFD-catalyzed enantioselective cross-coupling reaction. Results: The reaction was carried out in the presence of exogenous benzaldehyde (20 mM) and acetaldehyde (600 mM) as substrates in 6 mL of 200 mM phosphate buffer (pH 7) for 3 h. The optimal biomass concentration was assessed to be 0.006 g dry cell weight (DCW) mL− 1. 2-HPP titer, yield and productivity using the free cells were 1.2 g L− 1, 0.56 g 2-HPP/g benzaldehyde (0.4 mol 2-HPP/mol benzaldehyde), 0.067 g 2-HPP g− 1 DCW h− 1, respectively, under optimized biotransformation conditions (30 °C, 200 rpm). Calcium alginate (CA)–polyvinyl alcohol (PVA)-boric acid (BA)-beads were used for cell entrapment. Encapsulated whole-cells were successfully employed in four consecutive cycles for 2-HPP production under aerobic conditions without any noticeable beads degradation. Moreover, there was no production of benzyl alcohol as an unwanted by-product. Conclusions: Bioconversion by whole P. putida resting cells is an efficient strategy for the production of 2-HPP and other α-hydroxyketones. Graphical abstract: [Figure not available: see fulltext.]. © 2023, The Author(s).
Journal of Materials Research and Technology (22387854)26pp. 1553-1571
In this study, the effects of adding silver (0.2 and 0.6 wt%) and copper (0.1 wt%) antibacterial elements, on the microstructure, mechanical properties, and degradation behavior of the as-cast Mg–2Zn alloy were investigated. The obtained results indicate that both Ag and Cu showed significant grain refinement effects in the as-cast condition. The MgZn precipitates were formed in the as-cast Mg–2Zn–0.2Ag alloy, which contained a small amount of Ag. Increasing the Ag content to 0.6 wt% resulted in formation of the Mg54Ag17 phase. Simultaneous addition of 0.2 wt% Ag and 0.1 wt% Cu to the Mg–2Zn alloy caused the ternary Mg(Zn,Cu) precipitates to form. Solution-treated Mg–2Zn and Mg–2Zn–0.6Ag alloys had a single-phase microstructure, while some Mg(Zn,Cu) precipitates remained in the Mg–2Zn–0.2Ag–0.1Cu alloy after solution treatment. Shear punch test showed 15, 12, and 23% increases in ultimate shear strength values of the as-cast Mg–2Zn–0.2Ag, Mg–2Zn–0.6Ag, and Mg–2Zn–0.2Ag–0.1Cu alloys compared to the Mg–2Zn alloy, respectively. The hydrogen evolution rate of the as-cast Mg–2Zn–0.2Ag, Mg–2Zn–0.6Ag, and Mg–2Zn–0.2Ag–0.1Cu alloys were found to be 38, 90 and 70% higher than the as-cast Mg–2Zn alloy, respectively. However, the solution treatment reduced the degradation rate significantly. Hence, it was found in this investigation that adding Ag and Cu elements would be so effective for improving different properties of the Mg–Zn alloys by using appropriate solution heat treatment. © 2023 The Author(s)
Madadi, M.,
Bakr, M.M.,
Abdulkhani, A.,
Zahoor, ,
Asadollahi, M.A.,
Sun, C.,
Sun, F.,
Abomohra, A.E. Energy Conversion and Management (01968904)251
Pretreatment is the key factor for producing fermentable sugars and biofuels from lignocellulosic biomass. However, during pretreatment lignin repolymerization occurs which reduces the efficiency of carbohydrates hydrolysis. In the present study, three additives (2-naphthol-7-sulfonate, 2-naphthol, and mannitol) were evaluated for boosting the effectiveness of combined pretreatment (liquid hot water + green liquor) of pine-wood biomass. The results revealed that supplied additives into combined pretreatment changed the physicochemical structure of lignin, therefore, alleviating the inhibitory effect of lignin repolymerization and notably raised sugars yield (glucose, xylose) ranging from 85% to 93%. XPS and FTIR analyses confirmed that −OH groups of additives led to lower formation of phenolic hydroxyl (PhOH) and higher hydrophilic groups of lignin, accounting for reduced non-specific binding of lignin into cellulase enzymes. Furthermore, additives increased surface lignin coverage, biomass porosity, and fiber swelling by 1.96–2.59, 1.66–1.86, and 1.13–1.29 folds respectively, comparing to corresponding sample without additives caused more liquified and extractable lignin, which notably reduced the surface lignin barrier. Hence, both factors including non-specific binding effect and surface lignin barrier, contributed to reducing lignin repolymerization, thereby increased cellulose accessibility for high production of fermentable sugars and bioethanol in softwood biomass. © 2021 Elsevier Ltd
Hu, Y.,
Bai, R.,
Dou, S.,
Wu, Z.,
Abdulkhani, A.,
Asadollahi, M.A.,
Abomohra, A.E.,
Sun, F. Systems Microbiology and Biomanufacturing (26627663)2(3)pp. 498-506
To address the deficient activity of TrCel5A in naturally secreted cellulase preparation, this study used the GAP promoter to induce constitutive expression of Trichoderma reesei TrCel5A in Pichia pastoris. A recombinant TrCel5A was screened out after gene optimization, synthesis, and expression. The biochemical and enzymatic properties of the new recombinant were characterized. As a result, optimization of shake-flask fermentation of the recombinant was obtained at 28 °C, 2% inoculum volume, an initial pH of 6.0, as well as glycerol and Tween-80 additions of 30 g/L and 6 g/L, respectively. Under the above-optimized conditions, the recombinant produced 14.8 U/mL of the enzyme activity at 96 h of fermentation. To further enhance enzyme production, pilot-scale cultivation was evaluated using 5-L bioreactors. Using high-cell-density fermentation, the recombinant strain increased enzyme activity to 130.4 U/ml and protein content to 2.49 g/L. In addition, the kinetic factors, including Km and Vmax values for TrCel5A, were detected to be 5.1 mg/mL and 265.9 μmol/(min.mg), respectively. Thus, TrCel5A was effectively expressed in P.pastoris under the GAP promoter, and it demonstrated its potential in commercially relevant enzyme hydrolysis of lignocellulosic biomass. © 2021, Jiangnan University.
Journal of Materials Research and Technology (22387854)21pp. 4473-4489
The effects of zinc content (2 and 4 wt%), heat treatment (solution-Treated and T6), as well as hot deformation (extrusion and multi-directional forging (MDF)) on the microstructure, mechanical and degradation behavior of Mg-Zn alloys were studied. As the result of microstructure refinement, solid solution and precipitate strengthening (formation of MgZn second phases), the strength of pure Mg was increased after Zn addition. Solution treatment of the Mg-4Zn alloy resulted in 16% softening due to the dissolution of the MgZn second phases and also grain growth, while aging treatment increased the strength value by 8% in comparison to the as-cast material because of the formation of the fine MgZn2 precipitates. Corrosion tests showed an improvement in the corrosion resistance of Mg due to the Zn addition, which was mainly attributed to the finer microstructure and more stable corrosion film in Mg-Zn alloys. Indeed, the polarization resistance of the as-cast Mg-4Zn specimen in the EIS test increased by about 60% in comparison to pure Mg. Solution-Treatment on Mg-4Zn alloy could effectively reduce the degradation rate due to the obtained more uniform microstructure. Hydrogen evolution rate of the extruded and MDF processed Mg-4Zn alloy decreased by 73% and 62%, respectively, in comparison to the as-cast condition. Finer grain size and less volume fraction of precipitates in these two specimens, compared to the as-cast Mg-4Zn specimen, was the main reason of the observed improved behavior. © 2022 The Author(s).
Mohammadi zerankeshi, M.,
Alizadeh, R.,
Gerashi, E.,
Asadollahi, M.A.,
Langdon, T.G. Journal of Magnesium and Alloys (22139567)10(7)pp. 1737-1785
Biodegradable magnesium (Mg) alloys exhibit great potential for use as temporary structures in tissue engineering applications. Such degradable implants require no secondary surgery for their removal. In addition, their comparable mechanical properties with the human bone, together with excellent biocompatibility, make them a suitable candidate for fracture treatments. Nevertheless, some challenges remain. Fast degradation of the Mg-based alloys in physiological environments leads to a loss of the mechanical support that is needed for complete tissue healing and also to the accumulation of hydrogen gas bubbles at the interface of the implant and tissue. Among different methods used to improve the performance of the biodegradable Mg alloys to address these challenges, it appears that heat treatment is the most effective way to modify the microstructure and thus the corrosion behavior and mechanical properties without changing the composition or shape of the alloys. A desirable combination of corrosion and mechanical properties can be obtained through a precise control of the heat treatment parameters. In this report, the effects of different heat treatments (T4 and T6) on the microstructure, corrosion behavior, and mechanical properties of some of the most important heat-treatable biodegradable Mg alloys (Mg-Zn, Mg-Gd, Mg-Y, Mg-Nd, Mg-Al and Mg-Ag) are examined as well as new perspectives to enhance their clinical implementation. © 2022
Materials Science and Engineering: A (09215093)843
The effects of Sr additions (0.3, 0.6 and 0.9 wt%) on the microstructural evolution, thermal stability, and mechanical properties of a cast Mg–4Zn alloy were investigated. The extent of grain growth and stability of the intermetallic compounds were studied by optical and scanning electron microscopy (SEM), respectively. Mechanical properties of the studied alloys were evaluated by shear punch testing (SPT) method and also the hardness test. Hardness and shear strength of the base alloy were increased by Sr additions in the as-cast condition, due to the grain refinement effect of Sr and also presence of the Sr-containing Mg17Sr2 and Mg70Zn25Sr5 precipitates. However, the optimum amount of Sr was determined to be 0.3 wt%, above which no further improvement in the shear strength of the as-cast alloys was observed, due to the coarsening of the precipitates. The obtained microstructural results indicated that while both of the base and Sr-containing alloys have appropriate thermal stability at 330 °C, the grain size of the base alloy increased significantly and also the Mg4Zn7 particles were dissolved in the matrix after annealing treatment at 400 °C for 96 h, resulting in considerable decrease in the shear strength. However, grain growth was trivial in the Sr-containing alloys, due to the presence of thermally stable Mg17Sr2 particles. Accordingly, the Sr addition was found to be beneficial to improve the stability of the microstructure and mechanical properties of the Mg–4Zn alloy. © 2022
Asadollahi, M.A.,
Gerashi, E.,
Zohrevand, M.,
Zarei, M.,
Sayedain, S.S.,
Alizadeh, R.,
Labbaf, S.,
Atari, M. Bioprinting (24058866)27
Polylactic acid (PLA) scaffolds produced by the fused deposition modeling (FDM) method have biocompatibility, close Young's modulus to that of bone, and the ability to make complex shapes. However, PLA has some drawbacks like brittleness, inappropriate mechanical strength and hydrophobicity, and a low degradation rate. In this study, polyethylene glycol (PEG) (5 and 10 wt%) by solving method and titanium (Ti) particles (5 wt%) by two different methods were mixed with PLA to address the mentioned problems. Extruded filaments were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and fourier transform infrared (FTIR). Surface morphology of the produced filaments was also examined by scanning electron microscopy (SEM). Furthermore, mechanical properties of the 3D-printed samples were evaluated by tensile and compressive tests. To investigate the hydrophilicity of the samples, contact angle test was employed. Also, some scaffolds were printed from each sample to evaluate printability and print accuracy. In addition, the cell adhesion and cell viability of pure PLA and Ti/PEG-containing scaffolds were investigated. According to the obtained results, when PEG (by solving method) and Ti (by using DCM method) are simultaneously added to PLA, ductility of the sample is enhanced significantly without any loss of strength. Also, the contact angle was reduced by 25°, which was due to the simultaneous effect of hydrophilicity of PEG and the produced roughness by Ti particles. The mentioned enhancements were achieved without significantly reducing the printing quality. Also, the surface roughness of the scaffold increased to an optimum level. In addition, a significant improvement in cell adhesion and cytotoxicity was obtained in the Ti/PEG-containing scaffold compared to pure PLA. In this study, a novel method was introduced for mixing metallic particles such as Ti with PLA, which enhanced the particle distribution in the PLA matrix and avoided any agglomeration. © 2022 Elsevier B.V.
Sadeghan, A.A.,
Soltaninejad, H.,
Dadmehr, M.,
Hamidieh, A.A.,
Asadollahi, M.A.,
Hosseini, M.,
Ganjali, M.R.,
Hosseinkhani, S. Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy (13861425)247
Methylation of DNA at carbon 5 of cytosines is the most common epigenetic modification of human genome. Due to its critical role in many normal cell processes such as growth and development, any aberrant methylation pattern in a particular locus may lead to abnormal functions and diseases such as cancer. Development of methods to detect methylation state of DNA which may eliminate labor-intensive chemical or enzymatic treatments has received considerable attention in recent years. Herein, we report a DNA methylation detection procedure based on fluorescence turn-on strategy. Target sequence was selected from Sept9 promoter region that has been reported as one of the most frequently methylated sites in colorectal cancer. Probe DNA was designed to be complementary to this sequence with an additional six cytosines in the middle to form an internal loop to host silver nanoclusters. The fluorescence intensity of the synthesized silver nanoclusters with the duplexes of probe-non-methylated target was significantly different from that of probe-methylated target. The fluorescence enhanced with increasing the methylated DNA concentration with a linear relation in the range of 1.0 × 10−8 M to 5.0 × 10−7 M with the detection limit of 8.2 × 10−9 M, and quenched with non-methylated ones. The method was very specific in the presence of non-complementary sequences with maximum similarity of 40%. Circular dichroism spectra indicated that silver ions significantly affected the structure of methylated and non-methylated DNA into different extents which could further influence the nanocluster fluorescence. Finally, a method was introduced to meet the concerns in the applicability of the proposed method in real situation. © 2020 Elsevier B.V.
Ajeje, S.B.,
Hu, Y.,
Song, G.,
Peter, S.B.,
Afful, R.G.,
Sun, F.,
Asadollahi, M.A.,
Amiri, H.,
Abdulkhani, A.,
Sun, H. Frontiers in Bioengineering and Biotechnology (22964185)9
The bioconversion of lignocellulose into monosaccharides is critical for ensuring the continual manufacturing of biofuels and value-added bioproducts. Enzymatic degradation, which has a high yield, low energy consumption, and enhanced selectivity, could be the most efficient and environmentally friendly technique for converting complex lignocellulose polymers to fermentable monosaccharides, and it is expected to make cellulases and xylanases the most demanded industrial enzymes. The widespread nature of thermophilic microorganisms allows them to proliferate on a variety of substrates and release substantial quantities of cellulases and xylanases, which makes them a great source of thermostable enzymes. The most significant breakthrough of lignocellulolytic enzymes lies in lignocellulose-deconstruction by enzymatic depolymerization of holocellulose into simple monosaccharides. However, commercially valuable thermostable cellulases and xylanases are challenging to produce in high enough quantities. Thus, the present review aims at giving an overview of the most recent thermostable cellulases and xylanases isolated from thermophilic and hyperthermophilic microbes. The emphasis is on recent advancements in manufacturing these enzymes in other mesophilic host and enhancement of catalytic activity as well as thermostability of thermophilic cellulases and xylanases, using genetic engineering as a promising and efficient technology for its economic production. Additionally, the biotechnological applications of thermostable cellulases and xylanases of thermophiles were also discussed. Copyright © 2021 Ajeje, Hu, Song, Peter, Afful, Sun, Asadollahi, Amiri, Abdulkhani and Sun.
Biotechnology Letters (15736776)42(4)pp. 597-603
Objectives: The yeast cells were coated with Fe3O4 magnetic nanoparticles and employed as biocatalyst for the microbial biotransformation of benzaldehyde into l-phenylacetylcarbinol (l-PAC). Results: Saccharomyces cerevisiae CEN.PK113-7D yeast cells were coated with magnetic nanoparticles to facilitate the cells separation process. Transmission electron microscopy, powder XRD diffraction, and vibrating sample magnetometer were used to characterize magnetic nanoparticles and magnetic nanoparticle-coated yeast cells. Then the reusability of magnetically recoverable cells in production of l-PAC was investigated. Results show that coating yeast cells with magnetic nanoparticles does not affect their size and structure. Coated cells were also used in seven consecutive batch cycles and no significant reduction for l-PAC titer was observed in any of the cycles. Conclusion: Coating yeast cells with magnetic nanoparticles enabled rapid separation and reuse of cells in several successive batch cycle without affecting their ability to produce l-PAC. © 2020, Springer Nature B.V.
Industrial Crops and Products (09266690)151
Hemicellulose is a cheap and abundant substrate for biofuel production. However, industrial scale production of biofuels from hemicellulose is relatively inefficient because of expensive pretreatment processes and poor pentoses utilization by most microorganisms. In this study, a cost-effective autohydrolysis process using water as the only reagent to hydrolyze lignocellulose was exploited. Sweet sorghum stalk was also utilized as an economic source of hemicellulose. The autohydrolyzed lignocellulosic compounds from sweet sorghum were used as substrate in acetone-butanol-ethanol (ABE) fermentation by Clostridium acetobutylicum which is able to ferment pentoses and hexoses into ABE. Separation of 79 % of hemicellulose and roughly 20 % of cellulose from sweet sorghum stalk was detected as a desirable result for autohydrolysis at 210 °C; however, over-production of inhibitors made it an inappropriate pretreatment for ABE fermentation. No butanol production was detected in autohydrolysates of 210 °C, even after using detoxification methods for inhibitory compounds removal. On the other hand, only 20 % of sweet sorghum's bagasse hemicellulose was separated at 150 °C; yet, it was detected as the most desirable hydrolysate for ABE fermentation. Nevertheless, inherent inefficiency of C. acetobutylicum to ferment xylo-oligomers (as the sole carbon source) led to less than 1 g/L of ABE production in autohydrolysates at 150 °C. Co-fermentation of these hydrolysates with sorghum grain starch was investigated as a solution and it significantly increased the ABE production up to 8.3 g/L. Furthermore, the synergistic effect of co-fermentation was investigated where 35 % improvement in ABE production was detected. Accordingly, xylose utilization increased from 45 % to 80 %. © 2020 Elsevier B.V.
Biotechnology and Bioengineering (00063592)117(2)pp. 392-405
Clostridium acetobutylicum is widely used for the microbial production of butanol in a process known as acetone–butanol–ethanol (ABE) fermentation. However, this process suffers from several disadvantages including high oxygen sensitivity of the bacterium which makes the process complicated and necessitate oxygen elimination in the culture medium. Nesterenkonia sp. strain F has attracted interests as the only known non-Clostridia microorganism with inherent capability of butanol production even in the presence of oxygen. This bacterium is not delimited by oxygen sensitivity, a challenge in butanol biosynthesis, but the butanol titer was far below Clostridia. In this study, Nesterenkonia sp. strain F was cocultivated with C. acetobutylicum to form a powerful “coculture” for butanol production thereby eliminating the need for oxygen removal before fermentation. The response surface method was used for obtaining optimal inoculation amount/time and media formulation. The highest yield, 0.31 g/g ABE (13.6 g/L butanol), was obtained by a coculture initiated with 1.5 mg/L Nesterenkonia sp. strain F and inoculated with 15 mg/L C. acetobutylicum after 1.5 hr in a medium containing 67 g/L glucose, 2.2 g/L yeast extract, 4 g/L peptone, and 1.4% (vol/vol) P2 solution. After butanol toxicity assessment, where Nesterenkonia sp. strain F showed no butanol toxicity, the coculture was implemented in a 2 L fermenter with continual aeration leading to 20 g/L ABE. © 2019 Wiley Periodicals, Inc.
Biochemical Engineering Journal (1873295X)164
The microbial pathway of butanol biosynthesis is a unique route for the production of a biomass-derived advanced biofuel with high potential to be utilized in place of the fossil fuels. In the present study, Nesterenkonia sp. strain F was applied as a beneficial partner for Clostridium acetobutylicum in “starch-to-butanol process”. The capability of Nesterenkonia sp. strain F in secreting organic solvent-tolerant amylase was utilized for upgrading the yield of solvent, i.e., acetone, butanol, and ethanol (ABE), production under aerobic conditions. Monitoring the amylolytic activity and glucose concentration throughout the micro-aerobic co-culture revealed higher amylase activity and glucose concentration in comparison with the monoculture. The co-culture led to 63% higher amylase activity through the microaerobic cultivation on starch. After optimizing the conditions with response surface methodology (RSM), 10.6 g/L butanol was produced from untreated potato starch (UPS) with a high yield of 0.23 g ABE/g starch, leading to 30% improvement in ABE production. To assess its performance at larger scale, the fermentation was conducted in a 5 L fermenter continually aerated with a rate of 0.05 vvm and 150 rpm. This led to production of 9.7 g/L butanol, 5.0 g/L acetone, and 0.3 g/L ethanol with a yield and productivity of 0.20 g/g and 0.21 g/L.h, respectively. Furthermore, ABE production from tannin-containing sorghum grain was improved by about 3-fold. © 2020 Elsevier B.V.
Gounani, Z.,
Pourianejad, S.,
Asadollahi, M.A.,
Meyer, R.L.,
Rosenholm, J.M.,
Arpanaei, A. Journal of Materials Science (15734803)55(36)pp. 17134-17150
Abstract: In this study, we used electrospun polycaprolactone (PCL) or a mixture of PCL and gelatin (Gel) in a mixed acidic solvent to develop antimicrobial electrospun nanofibers. Carboxyl-modified mesoporous silica nanoparticles (CMSNs) or CMSNs loaded with antibiotic drugs polymyxin B and vancomycin (CMSNs/ABs) were mixed with the electrospinning solution in concentrations of 1%, 2.5% and 5%. The nanofibers diameter measured between 122 and138 nm. Higher concentrations of gelatin or CMSNs increased hydrophilicity and degradability of the nanofibers. CMSNs enhanced nanofibers mechanical strength. PCL/Gel nanofibers incorporated with CMSNs/ABs (2.5% and 5%) showed high antibacterial efficiency against Pseudomonas aeruginosa and Staphylococcus aureus. Also bacterial cell adhesion decreased when 2.5% and 5% of CMSNs/ABs were incorporated in PCL/Gel mats. MTT and hemolysis assays indicated excellent biocompatibility of all types of electrospun nanofibers. This study confirms that a proper mixture of PCL, gelatin and CMSNs loaded with two antibiotics could offer antimicrobial activities with high biocompatibility and biodegradability properties. Graphic abstract: [Figure not available: see fulltext.]. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
Soltaninejad, H.,
Sadeghan, A.A.,
Hosseinkhani, S.,
Asadollahi, M.A.,
Hosseini, M.,
Ganjali, M.R. Methods and Applications in Fluorescence (20506120)7(3)
The extent of DNA structural perturbation by silver ions is different in methylated and non-methylated DNA. Here, we explored the interaction of eight convenient DNA interacting molecules with methylated and non-methylated short GC rich oligonucleotides in the presence and absence of silver ions. Acridine orange, DAPI, Doxorubicin, Ethidium bromide, Hoechst 33342, Methylene blue, PicoGreen, and Propidium iodide are tested for their ability to distinguish methylated and non-methylated DNA. Among them, Ethidium bromide, Methylene blue, and PicoGreen were able to discriminate between methylated and non-methylated DNA, while DAPI and Hoechst 33342 were only able to discriminate with the aid of silver ions. A detection method is proposed using Ethidium bromide in which the silver-treated sample of DNA exposed different fluorescence intensity from the untreated one on the base of its methylation state. This phenomenon was sequence-dependent and could provide a sensing platform with a detection limit of about 4fi0 nM. © 2019 IOP Publishing Ltd.
Gounani, Z.,
Asadollahi, M.A.,
Pedersen, J.N.,
Lyngsø, J.,
Skov pedersen, J.,
Arpanaei, A.,
Meyer, R.L. Colloids and Surfaces B: Biointerfaces (09277765)175pp. 498-508
Treatment of polymicrobial infections requires combination therapy with drugs that have different antimicrobial spectra and possibly work in synergy. However, the different pharmacokinetics and adverse side effects challenge the simultaneous delivery of multiple drugs at the appropriate concentrations to the site of infection. Formulation of multiple drugs in nano-carrier systems may improve therapeutic efficacy by increasing the local concentration and lowering the systemic concentration, leading to fewer side effects. In this study, we loaded polymyxin B and vancomycin on bare and carboxyl-modified mesoporous silica nanoparticles (B-MSNs and C-MSNs, respectively) to achieve simulataneous local delivery of antibiotics against Gram-positive and –negative bacteria. Polymyxin B adsorbed preferentially to nanoparticles compared to vancomycin. The total antibiotic loading was 563 μg and 453 μg per mg B-MSNs or C-MSNs, respectively. Both B-MSNs and C-MSNs loaded with antibiotics were effective against Gram-negative and Gram-positive bacteria. The antibiotics had synergistic interactions against Gram-negative bacteria, and the antimicrobial efficacy was higher for antibiotic-loaded C-MSNs compared to free antibiotics at the same concentration even though the cytotoxicity was lower. Our study shows that formulations of existing antibiotics in nanocarrier systems can improve their therapeutic efficiency, indicating that combination therapy with drug-loaded silica nanoparticles may provide a better treatment outcome for infections that require high concentrations of multiple drugs. © 2018 Elsevier B.V.
Soltaninejad, H.,
Asadollahi, M.A.,
Hosseinkhani, S.,
Hosseini, M.,
Ganjali, M.R. Methods and Applications in Fluorescence (20506120)6(4)
Among epigenetic modifications of DNA, methylation of cytosine at its carbon 5 is the most common mark that is usually associated with gene silencing in human. Determining whether a particular DNA molecule is methylated or not, is an indispensable task in many epigenetic investigations. Presenting detection methods with less labor-intensive and time-consuming procedures has substantial value. Here a facile method based on gold nanocluster (AuNCs) fluorescence enhancement is presented. Target sequences were selected from Sept9 promoter region as its hypermethylation is demonstrated as a reliable biomarker of colorectal cancer. DNA probe was complementary to a 25 nucleotide of the target region and possessed 9 additional cytosines in the middle to allow the formation of AuNCs. Probe-AuNCs strands were first hybridized with methylated and non-methylated targets separately, and then their fluorescence intensities were recorded. Fluorescence intensity was higher with methylated targets than non-methylated one. Applying silver ions reversed the situation and fluorescence intensities of non-methylated DNA got higher than methylated one. © 2018 IOP Publishing Ltd.
Sadeghan, A.A.,
Soltaninejad, H.,
Hosseinkhani, S.,
Hosseini, M.,
Ganjali, M.R.,
Asadollahi, M.A. Analytica Chimica Acta (00032670)1038pp. 157-165
Determining methylation state of a particular DNA sequence is an essential task in many epigenetic investigations. Here a facile method based on silver nanocluster (AgNCs) fluorescence enhancement is presented. Target sequences were selected from Sept9 promoter region that its hypermethylation is demonstrated as a reliable biomarker of colorectal cancer. Probe DNA was complementary to a 25 nucleotide of the target region and possessed twelve additional cytosines in the middle to grant the formation of AgNCs. After probe strands were hybridized with methylated and non-methylated targets separately, AgNCs were synthesized, and their fluorescence intensities were recorded. Fluorescence intensity enhanced when the target strands were methylated and quenched when they were non-methylated. The Linear range of fluorescence enhancement was from 1.0 × 10-7 M to 5.0 × 10-7 M with the detection limit of 7.6 × 10-8 M. Sensor specificity was checked with non-complementary strands with the maximum similarity of 40%. Further experiments explored various characteristics of methylated and non-methylated DNAs carrying AgNC and indicated that structure of methylated and non-methylated DNAs was affected differently by silver ions that could then influence AgNC fluorescence. This effect was strongly sequence-dependent, and either fluorescence enhancement or quenching was observed with two different sequences. © 2018 Elsevier B.V.
International Journal of Pharmaceutics (18733476)537(1-2)pp. 148-161
Polymyxin B is a polycationic antibiotic used as the last line treatment against antibiotic-resistant Gram negative bacteria. However, application of polymyxin B is limited because of its toxicity effects. Herein, we used bare and surface modified mesoporous silica nanoparticles (MSNs) with an average diameter of 72.29 ± 8.17 nm as adsorbent for polymyxin B to improve its therapeutic properties. The polymyxin B adsorption onto MSN surfaces was explained as a function of pH, type of buffer and surface charge of nanoparticles, according to the ζ-potential of silica nanoparticles and adsorption kinetics results. The highest value of the adsorption capacity (about 401 ± 15.38 mg polymyxin B/ g silica nanoparticles) was obtained for the bare nanoparticles in Tris buffer, pH 9. Release profiles of polymyxin B showed a sustained release pattern, fitting Power law and Hill models. The antibiotic molecules-loaded nanoparticles showed enhanced antibacterial activity compared to free antibiotic against different Gram negative bacteria. Biocompatibility evaluation results revealed that loading of polymyxin B onto MSNs can decrease the cytotoxicity effects of the drug by reducing ROS generation. Our results suggest that formulation of drugs by adsorption onto MSNs may offer a way forward to overcome the adverse effects of some antibiotics such as polymyxin B without compromising their antimicrobial properties. © 2017
Industrial Crops and Products (09266690)125pp. 473-481
Sweet sorghum plant, a widely grown energy crop, was utilized through a biorefinery process, by which its grains were hydrolyzed by the crude amylases produced from its bagasse. The hemicellulosic part of the bagasse was hydrolyzed with 0.5–1.0% sulfuric acid at 140–180 °C for 30–60 min and applied for amylase production using halotolerant bacterium Nesterenkonia sp. strain F. In the hydrolysate obtained at 140 °C for 60 min using 1% acid, Nesterenkonia showed 73.3 U/mL amylase activity by the consumption of 16.2 g/L xylose and 8.3 g/L other sugars. Supplementation of the hydrolysates with sorghum grain resulted in 38–67% higher amylase production. Furthermore, addition of biocompatible surfactants of Tween 20 and Tween 80 (0.1 g/L) increased the activity to 93 and 97 U/mL, respectively. The resulting crude enzyme was used in the process of ethanol production from both tannin-containing and tannin-free sorghum grains (6%), leading to 17.7 and 17.0 g/L bioethanol production, respectively. Through the cultivation of Nesterenkonia on the hemicellulosic hydrolysates, 5–10 g/L volatile fatty acids (VFA), 0.36–0.69 g/L acetone-butanol-ethanol (ABE), and 468–721 mg/L single cell protein (SCP) were also produced. The obtained SCP contained most of the essential amino acids and relatively high amounts of phenylalanine (8%), threonine (7%), methionine (6%), and lysine (6%). © 2018 Elsevier B.V.
Industrial Crops and Products (09266690)108pp. 225-231
Industrial scale production of biobutanol has been hampered by substrate cost and availability. Sweet sorghum grain is an inexpensive substrate for acetone-butanol-ethanol (ABE) production by Clostridium acetobutylicum. Amylolytic activity of C. acetobutylicum eliminates the need for the hydrolysis of starchy grain prior to fermentation. However, untreated grain contains phenolic compounds, i.e. tannins, which exhibit inhibitory effects against amylolytic activity and ABE fermentation. Less than 3 g/L ABE was obtained from untreated sweet sorghum grain at different substrate concentrations. Concentration of 0.2 mM gallic acid equivalent (GAE) of sorghum tannins was detected as the critical concentration which inhibits severely ABE fermentation. Applying a multi-stage hot water treatment resulted in tannins removal and significant enhancement in total ABE production up to 18 g/L. For efficient butanol production from 40, 60, and 80 g/L sorghum grain, hot water treatment with two, five, and six stages were found to be essential for efficient butanol production, respectively. Moreover, the amylolytic activity of C. acetobutylicum was inhibited by sorghum grain tannins, more than twice as high as the effects on the ABE fermentation pathway. Furthermore, unlike most substrates, sweet sorghum grain could provide all nutrients required for ABE fermentation, eliminating the need for supplementing expensive additional nutrients. © 2017 Elsevier B.V.
International Journal of Environmental Science and Technology (17351472)13(3)pp. 763-772
Effluent sludge from an anaerobic digester was used as a source of nitrogen, phosphate, sulfur, and other nutrients in the culture medium of ethanol production by the yeast Saccharomyces cerevisiae. Several pretreatments (mechanical, chemical, thermal, and thermo-chemical) were performed on the anaerobic digested sludge (ADS) to make the nutrients accessible to the yeast cells. Preliminary experiments revealed that S. cerevisiae is not able to assimilate the carbon content of the ADS. However, when glucose was added to the medium, ethanol production was observed. The yield of ethanol using untreated ADS was only 10 % of the theoretical yield, but alkaline pretreatment improved it up to 43 %. By separating the hydrolysate of alkaline-treated ADS from the suspended solids, the ethanol yield from the supernatant was further improved up to 65 % of theoretical yield. Alkaline-treated ADS exhibited competitive performance with the mixture of yeast extract and mineral salts in ethanol fermentation. © 2015, Islamic Azad University (IAU).
Heidari, F.,
Asadollahi, M.A.,
Jeihanipour, A.,
Kheyrandish, M.,
Rismani-yazdi, H.,
Karimi, K. RSC Advances (20462069)6(11)pp. 9254-9260
Substrate cost and availability are the major bottlenecks that limit the commercialization of next generation biofuels. The possibility of using waste acorn as an abundant and inexpensive feedstock in Iran for acetone-butanol-ethanol (ABE) production with Clostridium acetobutylicum was investigated. No solvent was produced using untreated acorn due to its high contents of growth-inhibitory tannic acid. To circumvent this problem, a simple extraction in close-to-boiling water was employed to remove tannic acid prior to using acorn powder in fermentation. This pretreatment significantly improved the fermentability of acorn powder by C. acetobutylicum. The maximum yields of solvents (g ABE per g substrate) achieved in serum-bottle experiments were 0.43 ± 0.02, 0.40 ± 0.02, and 0.34 ± 0.02 for glucose, pure starch, and treated acorn starch, respectively. Volumetric ABE productivity with tannin-free acorn powder was 0.21 ± 0.01 g L-1 h-1, slightly higher than that achieved with pure starch (0.18 ± 0.05 g L-1 h-1). When scaled up in 5 L fermentors, ABE production using pretreated acorn powder and pure starch resulted in solvent profiles and yields similar to those observed in the serum bottle experiments. This study demonstrates that acorn powder can be a viable feedstock for biobutanol production in Iran. Future work warrants optimization of a two-step process including extraction of tannic acid as a valuable by-product followed by fermentation of tannin-free acorn powder to improve the economic feasibility of acorn to biobutanol conversion process. © The Royal Society of Chemistry 2016.
Mehrasa, M.,
Asadollahi, M.A.,
Nasri-nasrabadi, B.,
Ghaedi, K.,
Salehi, H.,
Dolatshahi-pirouz, A.,
Arpanaei, A. Materials Science and Engineering C (09284931)66pp. 25-32
Poly(lactic-co-glycolic acid) (PLGA) and PLGA/gelatin random nanofibrous scaffolds embedded with different amounts of mesoporous silica nanoparticles (MSNPs) were fabricated using electrospinning method. To evaluate the effects of nanoparticles on the scaffolds, physical, chemical, and mechanical properties as well as in vitro degradation behavior of scaffolds were investigated. The mean diameters of nanofibers were 974 ± 68 nm for the pure PLGA scaffolds vs 832 ± 70, 764 ± 80, and 486 ± 64 for the PLGA/gelatin, PLGA/10 wt% MSNPs, and the PLGA/gelatin/10 wt% MSNPs scaffolds, respectively. The results suggested that the incorporation of gelatin and MSNPs into PLGA-based scaffolds enhances the hydrophilicity of scaffolds due to an increase of hydrophilic functional groups on the surface of nanofibers. With porosity examination, it was concluded that the incorporation of MSNPs and gelatin decrease the porosity of scaffolds. Nanoparticles also improved the tensile mechanical properties of scaffolds. Using in vitro degradation analysis, it was shown that the addition of nanoparticles to the nanofibers matrix increases the weight loss percentage of PLGA-based samples, whereas it decreases the weight loss percentage in the PLGA/gelatin composites. Cultivation of rat pheochromocytoma cell line (PC12), as precursor cells of dopaminergic neural cells, on the scaffolds demonstrated that the introduction of MSNPs into PLGA and PLGA/gelatin matrix leads to improved cell attachment and proliferation and enhances cellular processes. © 2015 Elsevier B.V. All rights reserved.
Biotechnology Letters (15736776)38(3)pp. 503-508
Objectives: To engineer the yeast Saccharomyces cerevisiae for the heterologous production of linalool. Results: Expression of linalool synthase gene from Lavandula angustifolia enabled heterologous production of linalool in S. cerevisiae. Downregulation of ERG9 gene, that encodes squalene synthase, by replacing its native promoter with the repressible MET3 promoter in the presence of methionine resulted in accumulation of 78 µg linalool l−1 in the culture medium. This was more than twice that produced by the control strain. The highest linalool titer was obtained by combined repression of ERG9 and overexpression of tHMG1. The yeast strain harboring both modifications produced 95 μg linalool l−1. Conclusions: Although overexpression of tHMG1 and downregulation of ERG9 enhanced linalool titers threefold in the engineered yeast strain, alleviating linalool toxicity is necessary for further improvement of linalool biosynthesis in yeast. © 2015, Springer Science+Business Media Dordrecht.
Minerva Biotecnologica (11204826)27(1)pp. 43-49
Aim. The main goal of the present study was to study biotransformation of benzaldehyde to L-phenylacetyl carbinol (L-PAC) by free and immobilized cells of Saccharomyces cerevisiae. Yeast cells were immobilized both in calcium alginate and calcium alginate-PVAboric acid beads. Methods. Yeast cells were immobilized with calcium alginate and calcium alginate-PVA-boric acid beads. Free or immobilized cells were added to biotransformation medium containing benzaldehyde and acetaldehyde and incubated at 30 °C and 200 rpm in anaerobic conditions. Samples were taken every two hours. Concentrations of benzaldehyde, L-PAC, and benzyl alcohol were determined by gas chromatography. Effect of benzaldehyde concentration on L-PAC formation was investigated. Fed batch fermentation was performed using immobilized yeast cells in a 3 L bioreactor. Results. The optimum biotransformation of benzaldehyde to L-PAC was obtained at 2 g/L of benzaldehyde. Cells immobilized in calcium alginate-PVA beads produced approximately 2 g/L of L-PAC using 2 g/L of benzaldehyde in the second and third cycles. In fed batch fermentation, a concentration of nearly 3 g/L L-PAC was achieved. The highest obtained yields of L-PAC for free cells, immobilized cells in calcium alginate, immobilized cells in calcium alginate-PVA-boric acid, and fed batch fermentation were 0.55, 0.55, 1, and 0.64 g L-PAC per each gram of consumed benzaldehyde, respectively. Conclusion. This study showed that higher L-PAC titers can be obtained using immobilized yeast cells. Besides improved mechanical properties, cells immobilized in calcium alginate-PVA-boric acid beads exhibited higher production of L-PAC and lower amount of benzyl alcohol as compared to the cells immobilized in calcium alginate beads. © Copyright 2016 Edizioni Minerva Medica.
Kheyrandish, M.,
Asadollahi, M.A.,
Jeihanipour, A.,
Doostmohammadi, M.,
Rismani-yazdi, H.,
Karimi, K. Fuel (00162361)142pp. 129-133
Production of acetone-butanol-ethanol (ABE) from potato waste starch using free and immobilized cells of Clostridium acetobutylicum was investigated. The starch was directly fermented to ABE by C. acetobutylicum without hydrolysis, and the results were compared with those obtained from glucose as a reference. Maximum butanol yields from waste starch and glucose were 0.21 and 0.26 g/g of initial carbon source (20 g/L), respectively. Batch fermentation of 60 g/L of waste starch in a 5 L bioreactor with free cells resulted in production of 9.9 g/L butanol. In a repeated batch fermentation, using immobilized cells of the bacterium in calcium alginate-polyvinyl alcohol (PVA)-boric acid beads and 60 g/L of the waste starch, a final butanol concentration of 15.3 g/L was achieved. © 2014 Elsevier Ltd. All rights reserved.
International Journal of Biological Macromolecules (01418130)79pp. 687-695
Aligned poly lactic-co-glycolic acid (PLGA) and PLGA/gelatin nanofibrous scaffolds embedded with mesoporous silica nanoparticles (MSNPs) were fabricated using electrospinning method. The mean diameters of nanofibers were 641 ± 24. nm for the pure PLGA scaffolds vs 418 ± 85. nm and 267 ± 58. nm for the PLGA/10. wt% MSNPs and the PLGA/gelatin/10. wt% MSNPs scaffolds, respectively. The contact angle measurement results (102° ± 6.7 for the pure PLGA scaffold vs 81° ± 6.8 and 18° ± 8.7 for the PLGA/10. wt% MSNPs and the PLGA/gelatin/10. wt% MSNPs scaffolds, respectively) revealed enhanced hydrophilicity of scaffolds upon incorporation of gelatin and MSNPs. Besides, embedding the scaffolds with MSNPs resulted in improved tensile mechanical properties. Cultivation of PC12 cells on the scaffolds demonstrated that introduction of MSNPs into PLGA and PLGA/gelatin matrices leads to the improved cell attachment and proliferation as well as long cellular processes. DAPI staining results indicated that cell proliferations on the PLGA/10. wt% MSNPs and the PLGA/gelatin/10. wt% MSNPs scaffolds were strikingly (nearly 2.5 and 3 folds, respectively) higher than that on the aligned pure PLGA scaffolds. These results suggest superior properties of silica nanoparticles-incorporated PLGA/gelatin eletrospun nanofibrous scaffolds for the stem cell culture and tissue engineering applications. © 2015 Elsevier B.V.
International Journal of Biological Macromolecules (01418130)73(1)pp. 154-159
Metallothioneins (MTs) are low-molecular weight proteins with high Cys content and a high affinity for metals. Plant MTs are classified into four types based on the arrangement of Cys in their amino acid sequences. In the present study, the gene encoding OsMTI-3a, a type 3 MT found in rice, was cloned into pET41a vector. The resulting construct was transformed into the Escherichia coli strain Rosetta (DE3). Following the induction with isopropyl β-d-1-thiogalactopyranoside, the OsMTI-3a was expressed as glutathione-S-transferase (GST)-tagged fusion protein. In comparison to control strain, the cells expressing GST-OsMTI-3a accumulated more Cd2+, Ni2+ and Zn2+ when they were grown in the medium containing CdCl2, NiCl2 or ZnSO4. The recombinant GST-OsMTI-3a was purified using affinity chromatography. The UV absorption spectra recorded after the reconstitution of the apo-protein with different metals confirmed that GST-OsMTI-3a was able to form complexes with Cd2+, Ni2+, and Zn2+. The reaction of the protein-metal complexes with 5-5-dithiobis (2-nitrobenzoic) revealed that the order of affinity of GST-OsMTI-3a toward different metals was Ni2+≥Cd2+>Zn2+>Cu2+. © 2014 Elsevier B.V..
Biocatalysis and Agricultural Biotechnology (18788181)2(1)pp. 64-68
γ-Decalactone is an industrially important flavor compound with a peachy aroma which has been approved by FDA as a food additive. The aim of this study was to compare batch and fed-batch cultivation for production of γ-decalactone using Yarrowia lipolytica and castor oil as substrate. Microbial production of γ-decalactone from castor oil using the obligate aerobic yeast Y. lipolytica was investigated in a 3. l bioreactor. Batch and fed-batch fermentations were compared for the production of γ-decalactone. Also the effect of enhancing oxygen transfer rate by using higher agitation rates or pure oxygen for aeration was investigated. The highest γ-decalactone concentration (220. mg/l) was obtained in the fed-batch fermentation using pure oxygen which was 3-fold more compared to the batch cultivation. Using pure oxygen instead of atmospheric air in the fed-batch fermentation also resulted in 60% increase in γ-decalactone production. © 2012 Elsevier Ltd.
Isoprenoids represent a wide group of chemically active compounds that can find a wide range of applications as flavors, perfumes, vitamins, nutraceuticals, and pharmaceuticals. Many isoprenoids are naturally produced in very low quantities by plants, which make their use in broader perspectives difficult. Microbial production of plant-originating isoprenoids quickly appeared as an alternative of choice. Metabolic engineering methods were applied and proved successful to improve the supply of precursors to derive toward isoprenoid compounds of interest. Combinations between metabolic engineering and the flourishing field of synthetic biology have also been observed with researchers attempting to reconstruct and optimize complex biosynthetic pathways in well-characterized and tractable microbial hosts. In this chapter, we review recent metabolic engineering studies for isoprenoid production in yeast and try to show, through key examples, that the fields of synthetic biology and metabolic engineering can go hand in hand to establish microbial cell factories for isoprenoid production. © Springer Science+Business Media New York 2013.
Iranian Journal Of Chemistry And Chemical Engineering (10219986)31(4)pp. 21-28
A method for the controllable synthesis of silver nanoparticles based on a complexing agent method was developed. Citric acid was used as a complexing agent. The effect of pH (1.6 to 5.17) on the size and net height (as obtained from XRD analyses) of silver nanoparticles was investigated. The nanoparticles (10 to 40 nm) were characterized using XRD, TEM, SEM, EDX, UV-Vis spectroscopy and TG/DTG instrument. It was found that pH has a significant influence on both size and crystallinity of the nanoparticles. This is due to the effect of pH on the distribution of citrate ion species which in turn affects the size and crystallinity of the nanoparticles. Increasing the pH value enhances the percentage of [citrate3-] ion species which allows lower size and higher crystallinity of the nanoparticles. Thus, we were able to develop a method for the controllable synthesis of nanoparticles based on the pH.
Biotechnology and Bioengineering (00063592)106(1)pp. 86-96
The mevalonate pathway in the yeast Saccharomyces cerevisiae was deregulated in order to enhance the intracellular pool of farnesyl diphosphate (FPP), the direct precursor for the biosynthesis of sesquiterpenes. Overexpression of the catalytic domain of HMG1, both from the genome and plasmid, resulted in higher production of cubebol, a plant originating sesquiterpene, and increased squalene accumulation. Down-regulation of ERG9 by replacing its native promoter with the regulatable MET3 promoter, enhanced cubebol titers but simultaneous over-expression of tHMG1 and repression of ERG9 did not further improve cubebol production. Furtheremore, the concentrations of squalene and ergosterol were measured in the engineered strains. Unexpectedly, significant accumulation of squalene and restoring the ergosterol biosynthesis were observed in the ERG9 repressed strains transformed with the plasmids harboring cubebol synthase gene. This could be explained by a toxicity effect of cubebol, possibly resulting in higher transcription levels for the genes under control of MET3 promoter, which could lead to accumulation of squalene and ergosterol. © 2010 Wiley Periodicals, Inc.
Otero, J.M.,
Vongsangnak, W.,
Asadollahi, M.A.,
Olivares-hernandes, R.,
Maury, J.,
Farinelli, L.,
Barlocher, L.,
Østerås, M.,
Schalk, M.,
Clark, A. Bmc Genomics (14712164)11(1)
Background: The need for rapid and efficient microbial cell factory design and construction are possible through the enabling technology, metabolic engineering, which is now being facilitated by systems biology approaches. Metabolic engineering is often complimented by directed evolution, where selective pressure is applied to a partially genetically engineered strain to confer a desirable phenotype. The exact genetic modification or resulting genotype that leads to the improved phenotype is often not identified or understood to enable further metabolic engineering.Results: In this work we performed whole genome high-throughput sequencing and annotation can be used to identify single nucleotide polymorphisms (SNPs) between Saccharomyces cerevisiae strains S288c and CEN.PK113-7D. The yeast strain S288c was the first eukaryote sequenced, serving as the reference genome for the Saccharomyces Genome Database, while CEN.PK113-7D is a preferred laboratory strain for industrial biotechnology research. A total of 13,787 high-quality SNPs were detected between both strains (reference strain: S288c). Considering only metabolic genes (782 of 5,596 annotated genes), a total of 219 metabolism specific SNPs are distributed across 158 metabolic genes, with 85 of the SNPs being nonsynonymous (e.g., encoding amino acid modifications). Amongst metabolic SNPs detected, there was pathway enrichment in the galactose uptake pathway (GAL1, GAL10) and ergosterol biosynthetic pathway (ERG8, ERG9). Physiological characterization confirmed a strong deficiency in galactose uptake and metabolism in S288c compared to CEN.PK113-7D, and similarly, ergosterol content in CEN.PK113-7D was significantly higher in both glucose and galactose supplemented cultivations compared to S288c. Furthermore, DNA microarray profiling of S288c and CEN.PK113-7D in both glucose and galactose batch cultures did not provide a clear hypothesis for major phenotypes observed, suggesting that genotype to phenotype correlations are manifested post-transcriptionally or post-translationally either through protein concentration and/or function.Conclusions: With an intensifying need for microbial cell factories that produce a wide array of target compounds, whole genome high-throughput sequencing and annotation for SNP detection can aid in better reducing and defining the metabolic landscape. This work demonstrates direct correlations between genotype and phenotype that provides clear and high-probability of success metabolic engineering targets. The genome sequence, annotation, and a SNP viewer of CEN.PK113-7D are deposited at http://www.sysbio.se/cenpk. © 2010 Otero et al; licensee BioMed Central Ltd.
Asadollahi, M.A.,
Maury, J.,
Patil, K.R.,
Schalk, M.,
Clark, A.,
Nielsen, J. Metabolic Engineering (10967176)11(6)pp. 328-334
A genome-scale metabolic model was used to identify new target genes for enhanced biosynthesis of sesquiterpenes in the yeast Saccharomyces cerevisiae. The effect of gene deletions on the flux distributions in the metabolic model of S. cerevisiae was assessed using OptGene as the modeling framework and minimization of metabolic adjustments (MOMA) as objective function. Deletion of NADPH-dependent glutamate dehydrogenase encoded by GDH1 was identified as the best target gene for the improvement of sesquiterpene biosynthesis in yeast. Deletion of this gene enhances the available NADPH in the cytosol for other NADPH requiring enzymes, including HMG-CoA reductase. However, since disruption of GDH1 impairs the ammonia utilization, simultaneous over-expression of the NADH-dependent glutamate dehydrogenase encoded by GDH2 was also considered in this study. Deletion of GDH1 led to an approximately 85% increase in the final cubebol titer. However, deletion of this gene also caused a significant decrease in the maximum specific growth rate. Over-expression of GDH2 did not show a further effect on the final cubebol titer but this alteration significantly improved the growth rate compared to the GDH1 deleted strain. © 2009 Elsevier Inc. All rights reserved.
Asadollahi, M.A.,
Maury, J.,
Møller, K.,
Nielsen, K.F.,
Schalk, M.,
Clark, A.,
Nielsen, J. Biotechnology and Bioengineering (00063592)99(3)pp. 666-677
The yeast Saccharomyces cerevisiae was chosen as a microbial host for heterologous biosynthesis of three different plant sesquiterpenes, namely valencene, cubebol, and patchoulol. The volatility and low solubility of the sesquiterpenes were major practical problems for quantification of the excreted sesquiterpenes. In situ separation of sesquiterpenes in a two-phase fermentation using dodecane as the secondary phase was therefore performed in order to enable quantitative evaluation of different strains. In order to enhance the availability of the precursor for synthesis of sesquiterpenes, farnesyl diphosphate (FPP), the ERG9 gene which is responsible for conversion of FPP to squalene was downregulated by replacing the native ERG9 promoter with the regulatable MET3 promoter combined with addition of 2 mM methionine to the medium. This strategy led to a reduced ergosterol content of the cells and accumulation of FPP derived compounds like target sesquiterpenes and farnesol. Adjustment of the methionine level during fermentations prevented relieving MET3 promoter repression and resulted in further improved sesquiterpene production. Thus, the final titer of patchoulol and farnesol in the ERG9 downregulated strain reached 16.9 and 20.2 mg/L, respectively. The results obtained in this study revealed the great potential of yeast as a cell factory for production of sesquiterpenes. © 2007 Wiley Periodicals, Inc.
Maury, J.,
Asadollahi, M.A.,
Møller, K.,
Schalk, M.,
Clark, A.,
Formenti, L.R.,
Nielsen, J. FEBS Letters (00145793)582(29)pp. 4032-4038
A eukaryotic mevalonate pathway transferred and expressed in Escherichia coli, and a mammalian hydrocortisone biosynthetic pathway rebuilt in Saccharomyces cerevisiae are examples showing that transferring metabolic pathways from one organism to another can have a powerful impact on cell properties. In this study, we reconstructed the E. coli isoprenoid biosynthetic pathway in S. cerevisiae. Genes encoding the seven enzymatic steps of the pathway were cloned and expressed in S. cerevisiae. mRNA from the seven genes was detected, and the pathway was shown able to sustain growth of yeast in conditions of inhibition of its constitutive isoprenoid biosynthetic pathway. © 2008 Federation of European Biochemical Societies.
Advances in Biochemical Engineering/Biotechnology (07246145)100pp. 19-51
Saving energy, cost efficiency, producing less waste, improving the biodegradability of products, potential for producing novel and complex molecules with improved properties, and reducing the dependency on fossil fuels as raw materials are the main advantages of using biotechnological processes to produce chemicals. Such processes are often referred to as green chemistry or white biotechnology. Metabolic engineering, which permits the rational design of cell factories using directed genetic modifications, is an indispensable strategy for expanding green chemistry. In this chapter, the benefits of using metabolic engineering approaches for the development of green chemistry are illustrated by the recent advances in microbial production of isoprenoids, a diverse and important group of natural compounds with numerous existing and potential commercial applications. Accumulated knowledge on the metabolic pathways leading to the synthesis of the principal precursors of isoprenoids is reviewed, and recent investigations into isoprenoid production using engineered cell factories are described. © Springer-Verlag 2005.
