Removal of Chromium (VI) by Escherichia coli Cells Expressing Cytoplasmic or Surface-Displayed ChrB: a Comparative Study

Abstract

Various genetically engineered microorganisms have been developed for the removal of heavy metal contaminants. Metal biosorption by whole-cell biosorbents can be enhanced by overproduction of metal-binding proteins/peptides in the cytoplasm or on the cell surface. However, few studies have compared the biosorption capacity of whole cells expressing intracellular or surface-displayed metal-adsorbing proteins. In this study, several constructs were prepared for expressing intracellular and surface-displayed Ochrobactrum tritici 5bvl1 ChrB in Escherichia coli BL21(DE3) cells. E. coli cells expressing surface-displayed ChrB removed more Cr(VI) from aqueous solutions than cells with cytoplasmic ChrB under the same conditions. However, intracellular ChrB was less susceptible to variation in extracellular conditions (pH and ionic strength), and more effectively removed Cr(VI) from industrial wastewater than the surface-displayed ChrB at low pH (<3). An adsorptiondesorption experiment demonstrated that compared with intracellular accumulation, cell-surface adsorption is reversible, which allows easy desorption of the adsorbed metal ions and regeneration of the bioadsorbent. In addition, an intrinsic ChrB protein fluorescence assay suggested that pH and salinity may influence the Cr(VI) adsorption capacity of ChrB-expressing E. coli cells by modulating the ChrB protein conformation. Although the characteristics of ChrB may not be universal for all metal-binding proteins, our study provides new insights into different engineering strategies for whole-cell biosorbents for removing heavy metals from industrial effluents.

Horizon scanning of potential environmental applications of terrestrial animals, fish, algae and microorganisms produced by genetic modification, including the use of new genomic techniques

“…Organic pollutants targeted include pesticides ( Gong et al, 2016 ; Yi et al, 2016 ; Xu et al, 2022 ), antibiotics stemming from industrial and agricultural sources ( Liu et al, 2020 ), and persistent organic pollutants like toluene ( Ishikawa et al, 2021 ), nitrobenzene ( Deng et al, 2022 ), and para-nitrophenol ( Huo et al, 2022 ). Anorganic pollutants targeted include mercury ( Priyadarshanee et al, 2022 ), chrome ( Zhou et al, 2020 ), and arsenic ( Maleki and Shahpiri, 2022 ). Also, fungal species and yeasts are developed, e.g., for waste water treatment ( Görner et al, 2016 ), accumulation of different heavy metals, such as cadmium ( Zhang et al, 2021 ), or to aid the volatilization of arsenic from contaminated soils ( Verma et al, 2019 ; Verma et al, 2021 ).…”

Determinantes Genéticos Y Sus Mecanismos De Acción Implicados en La Resistencia Bacteriana a Metales Pesados: Una Revisión.

“…La concentración detectable más baja del biosensor a 37 °C fue 1 mmol/L, disminuyendo a 1 μmol/L a 25 °C y 10 nmol/L a 15 °C. Una de las ventajas de este biosensor es la mejora de la sensibilidad a baja temperatura, así como la respuesta selectiva y dependiente de la dosis de Cd 2+ .Zhou et al(85) construyeron cepas de E. coli BL21 (DE3) que expresan el gen chrB de O. tritici 5bvl1. La expresión de chrB la realizaron intracelular y en superficie y compararon la capacidad de adsorción de Cr 6+ .…”

Table3.docx

“…Organic pollutants targeted include pesticides (Gong et al, 2016;Yi et al, 2016;Xu et al, 2022), antibiotics stemming from industrial and agricultural sources (Liu et al, 2020), and persistent organic pollutants like toluene (Ishikawa et al, 2021), nitrobenzene (Deng et al, 2022), and para-nitrophenol (Huo et al, 2022). Anorganic pollutants targeted include mercury (Priyadarshanee et al, 2022), chrome (Zhou et al, 2020), and arsenic (Maleki and Shahpiri, 2022). Also, fungal species and yeasts are developed, e.g., for waste water treatment (Görner et al, 2016), accumulation of different heavy metals, such as cadmium (Zhang et al, 2021), or to aid the volatilization of arsenic from contaminated soils (Verma et al, 2019;Verma et al, 2021).…”