Articles
Chemosphere (00456535)387
Arsenic is a highly toxic metalloid that poses significant environmental and health risks due to its widespread presence in soil, water, and industrial processes. Its accumulation in living organisms can lead to severe health issues, underscoring the need for effective bioremediation strategies. In this study, the gene encoding ArsR from Corynebacterium glutamicum (CgArsR1) was cloned into the plasmid pSEVA234 and transformed into Pseudomonas putida KT2440. Following induction with isopropyl β-D-1-thiogalactopyranoside (IPTG), the CgArsR1 protein was detected in the soluble fraction of the recombinant strain (P-CgArsR). This strain demonstrated enhanced tolerance to both arsenite (As3+) and arsenate (As5+) at higher concentrations compared to the control strain with the empty vector. The resting cells of P-CgArsR accumulated 250 μg g−1 dry cell weight (DCW) of As3+ and 150 μg g−1 DCW of As5+, while the control cells accumulated only 100 μg g−1 of either form. Optimal arsenic accumulation occurred at pH 7, reaching a maximum of 200 μg g−1 DCW, while NaCl negatively affected accumulation, reducing it to 100 μg g−1 DCW at 120 mM NaCl. These results indicate that engineered strains could effectively remediate arsenic in wastewater with NaCl concentrations between 0 and 40 mM, highlighting their potential in bioremediation efforts. © 2025 Elsevier Ltd
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.
