Bioreduction and bioremoval of hexavalent chromium by genetically engineered strains (Escherichia coli MT2A and Escherichia coli MT3)

Abstract

Studies on the removal of toxic metals from water by genetic engineering applications are becoming more and more diverse. Especially by the expression of cysteine and thiol rich proteins such as metallothioneins in bacterial cells, a high rate of removal of metal ions from the environment is ensured. In this study, we evaluated the removal and reduction of hexavalent chromium Cr(VI)from aqueous solutions with the recombinant strains obtained by cloning the human metallothioneinsMT2A and MT3 into Escherichia coli Jm109.E. coli MT2A was the most effective strain in both Cr(VI) removal (89%in 25 mg/L Cr(VI) application) and Cr(VI) reduction (76%in 25 mg/L Cr(VI) application).Cr(VI) adsorbed per dry cell (at 25 mg/L) were 17 mg/g, 22 mg/g and 19 mg/g for Jm109, MT2A and MT3, respectively. Scanning electron microscope (SEM) images showed that the morphological structures of Cr(VI)treated cells were signi cantly damaged compared to control cells. Scanning transmission electron microscope (STEM) images showed black spots in the cytoplasm of cells treated with Cr(VI).From the shifts in the Fourier transform infrared spectroscopy analysis (FTIR) spectra of the cells treated with Cr(VI) compared to the control cells, it was determined that the groups interacting with Cr were amino, hydroxyl, methyl and sulfhydryl. When all these experimental data were evaluated together, it was concluded that all three species were effective in removing Cr(VI) from aqueous solutions and MT2A strain could be used as the most effective biotechnological tool.

Equilibrium, kinetic, and thermodynamic studies on the biosorption of lead by human metallothionein gene‐cloned bacteria as a novel biosorbent

“…In our previous study, we observed that Cupriavidus necator H16 cells that we treated with cadmium (Cd) exhibited higher deformation in SEM images than cells that were not treated with Cd (Akkurt et al, 2023). In addition, changes in the structure and elemental composition of recombinant MT2A and MT3 cells after biosorption of chromium (Cr) and Cd in previously published studies confirm the findings obtained in this study (Akkurt et al, 2022; Uçkun et al, 2021). EDX results (weight percentage [%]) were shown in pie chart format in (Figure 4d,e,f).…”

“…Gene transfer experiments were carried out as described previously (Akkurt et al, 2022). MT2A and MT3 DNA fragments and the PET21 expression vector were cut with restriction endonuclease enzymes (EcoRI and NotI).…”

“…There are limited studies in the literature (Akkurt et al, 2022; Deng et al, 2007; Kim et al, 2005; Ma et al, 2019; Uçkun et al, 2021) on the use of genetically modified bacteria with MT genes in metal (cadmium, chromium, zinc, copper, nickel) biosorption, and there are no studies on Pb removal. Traditional methods used in biosorption are already weak, so more studies are needed to find the most effective biosorbent.…”

Biotransformation of protein-rich waste by Yarrowia lipolytica IPS21 to high-value products—amino acid supernatants

“…This group of alkaline protease-producing bacteria and fungi is important in the degradation of chrome tannery wastes ( 11 ): Bacillus subtilis ( 12 ), B. subtilis P13 ( 13 ), Bacillus amyloliquefaciens TCCC 11319, Penicillium spp. ( 10 ), Alcaligenes faecalis ( 14 ), Escherichia coli ( 15 ), or extracellular gelatinases and keratinases of Bacillus spp. ( 16 ).…”