Hexavalent Chromium (Cr(VI)) is a human carcinogen and has been found in drinking water, industrial wastewater and groundwater throughout the United States. It has been reported as a co-occurring contaminant at many sites contaminated with 1,4-dioxane. In this study, 1,4-dioxane degrader Mycobacterium austroafricanum JOB5 (JOB5) was discovered to produce soluble extracellular polymeric substances (EPS) biosorping Cr(VI) simultaneously. Several cell treatments including EPS free cells, EPS containing cells, dry cells, permeabilized cells and dead cells were examined to illustrate the Cr(VI) removal mechanism. Approximately 78%-99% of 10 mg/L Cr(VI) was removed by 166 mg/L soluble polysaccharides, which was the major component of EPS. To determine EPS mitigating Cr(VI), propane metabolism and 1,4-dioxane cometabolism processes were examined in Cr(VI) exposed JOB5 culture. Little effect of Cr(VI) was observed at below 10 mg/L in EPS containing culture; stronger inhibition was showed in EPS free culture. Additionally, the alkane monooxygenase (alkb1& alkb2) gene expression was down regulated during exposure of Cr(VI) at 10 mg/L in EPS containing culture. However, little influence on monooxygenase gene expression was observed in EPS containing culture which confirmed the role of soluble EPS to prevent Cr(VI) directly attack. Fourier Transform Infrared spectroscopy (FTIR) was performed to identify the function group which is responsible for Cr(VI) biosorption. Our results support the possibility of simultaneous remediation of Cr(VI) as well as 1,4-dioxane in the contaminated environments.

Bioprocesses for simultaneously removing hexavalent chromium and 1,4-dioxane

251st National Meeting (2016)

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