Bioremediation potential of hexavalent chromium by a novel bacterium Stenotrophomonas acidaminiphila 4-1

A gram-negative bacterial strain capable of resisting hexavalent chromium was isolated and evaluated for its characteristics. The strain was designated as Stenotrophomonas acidaminiphila 4-1 according to the 16S rDNA sequence and phylogenic analysis. It was founded that sufficient nutrients were more suitable for intracellular enrichment of chromium, such as LB medium. Extracellular polymeric substances were observed as binding sites for chromium entering bacterial cells by transmission electron microscopy (TEM) and scanning transmission electron microscope-energy dispersive spectroscopy (STEM-EDS) analysis. Two sharp peaks at 577.18 eV and 578.24 eV were assigned to Cr 2p3/2 in X-ray photoelectron spectroscopy (XPS) spectra, illustrating only Cr(III) and Cr(VI) forms existed in stain 4-1. Possible removal mechanisms of chromium were also described. The removal rate of Cr(VI) was 75.69% with initial substrate concentration of 15 mg L-1 after 7d incubation. The microbial biomasses which cultured below Cr(VI) of 100 mg L-1 were varied slightly. And strain 4-1 could tolerate high concentration of Cr(VI) up to 1000 mg L-1. Removal rate of Cr(VI) was not obviously affected with diesel. The results showed that Stenotrophomonas acidaminiphila 4-1 is an excellent bacterial candidate for the bioremediation of chromium or combined with diesel contaminated sites. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The gram-negative bacterial strain Stenotrophomonas acidaminiphila 4-1 was isolated for its ability to resist hexavalent chromium and showed promising potential for chromium removal. Results indicated a removal rate of 75.69% for Cr(VI) with an initial substrate concentration of 15 mg L-1.