Chromate Reduction by Allochromatium sp. Isolated from the Coastal Area of Visakhapatnam

Abstract

A phototrophic purple bacterium Allochromatium sp. strain GSKRLMBKU–01 was used in this study for the reduction of hexavalent chromium. This phototrophic bacterium was isolated from samples collected from the coastal area of Visakhapatnam, India. Both the cells (free (FC) and alginate entrapped immobilized (IC)) are used for the reduction of chromate. Among them, chromate reduction was increased using immobilized cells. Immobilized cells entrapped in sodium alginate reduced the chromate up to 33 ± 3.0 μM on the 8th day of incubation by Allochromatium sp., incubated in presence of light (2000 lx) under the strictly anaerobic conditions, while a chromate reduction up to 26 ± 0.20 μM was recorded by FC of Allochromatium sp. Chromate reduction can be recorded even up to the 20th day by both FC and IC. An incubation period of 8 days was found to be optimum for its growth and chromate reduction. The maximum growth in terms of dry cell weight (DCW) of FC is recorded up to 1.7 ± 0.20 g.L-1 and IC is 2.0 ± 0.30 g.L-1. The growth was recorded even on complete chromate reduction. The final pH of the FC was recorded at pH 8.5 ± 0.10, while the final pH of 8.6 ± 0.20 was recorded for the IC of Allochromatium sp. in the growth medium. The obtained results were mentioned in terms of mean and standard deviation which are statistically significant at P ≤ 0.001 level. The detoxification of chromium in the large-scale systems by employing a purple phototrophic bacteria Allochromatium sp., is proposed.

Keywords

• allochromatium sp., chromate reduction, free cells, immobilized cells, incubation period