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Karimi-avargani m., M.,
Biria, D.,
Dehghanifar, S.,
Bazooyar f., F.,
Skrifvars m., M. International Journal of Environmental Science and Technology (17351472)22(4)pp. 2601-2612
The complexity of the vulcanized rubber makes it difficult to be degraded by microorganisms. It is believed that a microbial consortium can improve the efficiency of the biodegradation process. Fertile soil houses a plethora of microorganisms with innate ability to adapt to various chemical substances come into contact with its texture. Consequently, a soil sample which was in direct contact with tire wastes for more than 13 years was employed in this work to enhance the biodegradation of natural rubber (NR) gloves. The active soil microorganisms associated with the NR latex degradation were isolated and identified using 16S rRNA gene sequencing method. The biodegradation of NR gloves in the soil sample containing these bacteria was investigated and the results represented 87% and 79% weight loss in the examination and surgical gloves after 12 months of treatment, respectively. The total biodegradation was achieved after 13 and 15 months which was nearly half of the reported time in the landfill processes. Thermal gravimetric analysis (TGA) showed 15% incremental weight decrease for the treated samples after three months in comparison with the blanks and the FT-IR spectra approved the breaking of the cross-link sulfur bonds as well as the formation of carbonyl groups which indicated oxidative cleavage of double bonds of the polymer chain. A chemical mechanism for the biodegradation was suggested based on the obtained results to explain the higher efficiency of biodegradation in this work. © The Author(s) under exclusive licence to Iranian Society of Environmentalists (IRSEN) and Science and Research Branch, Islamic Azad University 2024.
RSC Advances (20462069)15(30)pp. 24624-24638
The regulation and improvement of mass transfer through the living cell's membrane is of great importance in various industrial, environmental and medical applications. Designing membrane channels based on carbon nanotubes (CNTs) has been considered as a promising approach to this end because of the geometry of CNTs, their physical properties, high chemical stability, and excellent transport features. Despite their advantages, CNTs have a few problems such as their toxicity to living cells, low bioavailability in an aqueous medium and difficulties with managing their orientation within the cell membrane which should be addressed in the first place. Here, we tried to review recent studies on overcoming these challenges and critically evaluate their advances and suggestions for future research. Functionalization of CNTs with biocompatible materials has been recommended as the main solution which decreases the inherent cytotoxicity of the pristine CNTs, enhances their solubility and dispersibility in aqueous solution, and affects their orientation in the cell membrane. Molecular dynamics simulation results for the interactions of the functionalized CNTs and the cell membrane have been reviewed as well to demonstrate the effectiveness of functionalizing CNTs for membrane channel applications. Finally, we highlighted that modified CNTs with appropriate functional groups and favorable physical and geometrical conditions can be considered as an effective tool to make artificial channels in the cell membrane. © 2025 The Royal Society of Chemistry.
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.
Journal of Environmental Management (03014797)325
The adverse effects of high strength wastewaters on the microbial activities have created a challenge to biological treatments. Microbial fuel cell has been considered as a promising process because the electrical potential generation can stimulate microorganisms and overcome the inhibitory effect. However, several issues (e.g., scalability, high costs and maintenance) have prevented the process from the industrial applications. Elimination of the proton exchange membrane has been suggested as a remedy to the mentioned problems. In this work, a membrane-less microbial fuel cell was modified by putting the cathode within a thin sand layer (instead of the proton exchange membrane) to treat a high strength wastewater sample. The influences of the feed organic load and time of treatment in the modified system were studied in batch and continuous operations. It was revealed that the batch operation efficiency was higher for the lower feed loadings as a 5-day batch treatment removed 66 ± 4% of the 15,000 ± 500 mg/L initial chemical oxygen demand while the continuous process efficiency with 9-day hydraulic residence time was slightly more than 50%. However, the efficiency of the continuous operation for treatment of higher initial loading values was better than the batch mode with the removal efficiency of 41 ± 2% versus 12 ± 2% for a more concentrated leachate feed (45,000 ± 1000 mg/L). Finally, it was disclosed that the modified membrane-less MFC employed in this work can be effective in treatment of high strength wastewaters in larger scales with lower costs. © 2022 Elsevier Ltd
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).
Medical Hypotheses (03069877)167
Finding effective drugs to treat SARS-CoV-2 infection as a complementary step to the extensive vaccination is of the great importance to overcome the current pandemic situation. It has been shown that some bio-active unsaturated fatty acids such as Arachidonic Acid (AA) can reduce the infection severity and even destroy the virus by disintegration of the virus lipid envelope. On the other hand, it has been reported that several designed peptides with an activity similar to the angiotensin converting enzyme 2 (ACE-2), which has a high affinity towards the novel corona virus spike protein, can inhibit the viral infection through concealing the spike proteins from the cell surfaces ACE-2. Binding the mentioned peptides to the bio-active lipids like AA will result in a lipopeptide surfactant molecule with the synergistic effect of both the active moieties in its structure to treat the novel corona infection. In addition, the peptide segment increases the aqueous solubility of the lipid segment and enables the targeted delivery of the surfactant molecule to the virus. The resultant lipopeptide would be a potentially effective drug for SARS-CoV-2 infection treatment with the minimum side effects. © 2022 Elsevier Ltd
Karimi-avargani m., M.,
Bazooyar f., F.,
Biria, D.,
Zamani, A.,
Skrifvars m., M. Chemosphere (00456535)278
It has been suggested that cellulolytic enzymes can be effective on the degradation of PLA samples. The idea was investigated by examining the impact of cellulase on degradation of PLA and PLA-jute (64/36) composite in an aqueous medium. The obtained results demonstrated 55% and 61% thickness reduction in PLA and PLA-jute specimens after four months of treatment, respectively. Gel permeation chromatography (GPC) showed significant decline in the number average molecular weight (Mn) approximately equal to 85% and 80% for PLA and PLA-jute in comparison with their control. The poly dispersity index (PDI) of PLA and PLA-jute declined 41% and 49% that disclosed more homogenous distribution in molecular weight of the polymer after treatment with cellulase. The cellulase promiscuity effect on PLA degradation was further revealed by Fourier-transform infrared spectroscopy (FT-IR) analysis where substantial decrease in the peak intensities of the polymer related functional groups were observed. In addition, PLA biodegradation was studied in more detail by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of control and cellulase treated specimens. The obtained results confirmed the promiscuous function of cellulase in the presence or the absence of jute as the specific substrate of cellulase. This can be considered as a major breakthrough to develop effective biodegradation processes for PLA products at the end of their life cycle. © 2021 Elsevier Ltd
Colloids and Surfaces A: Physicochemical and Engineering Aspects (09277757)603
The presence of indigenous microorganisms in the petroleum reservoirs with the capability of biosurfactants production implies the existence of significant amounts of biosurfactants dissolved in the reservoir crude oil. The extraction of these biosurfactants to the aqueous phase can be considered as a promising microbial enhanced oil recovery process in a lower cost without the common limitations and risks related to the microbial systems. Ethylenediamine (EDA) was used to extract the crude oil dissolved biosurfactants (as anionic surfactants) of a crude oil sample to the aqueous phase and form a cat-ionic surfactant complex. The biosurfactant was isolated from the crude oil and preliminarily characterized which was capable of reducing the surface tension to 48 mN/m. Various concentrations of EDA were utilized to extract the crude oil biosurfactants and their effectiveness on the oil recovery was studied in a glass micro-model. Results indicated that an incremental 22 % oil production was obtained by flooding the 10 mM EDA solution. The incremental oil production was related to the formation of the cat-ionic complex surfactant which believed to cause a significant IFT reduction and simultaneously, have a higher efficiency in the wettability alteration than the anionic biosurfactants. It can be concluded that the extraction of the indigenous biosurfactant content of the crude oil and their interaction by EDA can be considered as a low-cost low-risk potential to the enhanced oil recovery processes. © 2020 Elsevier B.V.
