Optimization of extracellular chromate reductase production by Bacillus amyloliquefaciens (CSB 9) isolated from chromite mine environment

Chromate reductase production by a bacterial isolate CSB 9 has been optimized to a high titer in the present investigation. The bacterium isolated previously from a chromium contaminated site and identified as Bacillus amyloliquefaciens following biochemical and 16S rRNA gene sequencing, was evaluated for chromate reductase production. Chromate reductase activity of B. amyloliquefaciens (CSB 9) was associated with the contribution of extracellular enzymes under the influence of various physico-chemical parameters. In presence of 50 µM of Cr(VI) concentration, the bacterial growth exhibited 8 h of lag phase, 8–32 h of log phase and stationary phase upto 48 h. The maximum chromate reductase production was achieved in the presence of 50 µM of Cr(VI); 0.5% (w/v) of glucose; 1% (w/v) of trypton; 0.5% (w/v) of Na2HPO4; 0.5% (w/v) KNO3; 0.5% (w/v) KCl and 0.5% (w/v) thiamine as source of vitamin with the initial medium pH of 7.0 and incubation at 35 °C under shaking condition (100 rpm). In optimized conditions, the chromate reductase production was enhanced to a significant level of 3.67±0.014 U ml−1 as compared to unoptimized condition (2.37±0.029 U ml−1) with decrease in time from 20 h (late log phase) under unoptimized condition to 16 h under optimized condition. This communication elucidates the enhanced production of extracellular chromate reductase from a newly isolated bacterium B. amyloliquefaciens from chromite mine soil under optimized conditions which can be potentially exploited for biotechnological application.