Effect of environmental factors on biological reduction of hexavalent chromium by Pseudomonas mendocina

Abstract

In this study, the effects of pH, initial chromium concentrations, organic acids (alginic acid, galacturonic acid, glucuronic acid and citric acid) and their binary combinations on the bacterial chromium reduction were investigated. The results revealed that the Cr(VI) reduction for Pseudomonas mendocina was high at optimum pH value (6). The Cr(VI) reduction rate of P. mendocina decreased with the increase in initial chromium concentration. The Cr(VI) reduction ability of the bacterium increased in the presence of organic acids especially galactronic acid and glucuronic acid. Binary combinations of galactronic acid and glucuronic acid caused a dramatic increase in the rate of chromate reduction. Experiments with heat-inactivated cells indicated that biosorption onto cell material had a negligible impact for the loss of Cr(VI) from the solution. As a result of SDS-PAGE analysis, it was observed a protein band approximately 31 kDa in periplasmic extracts of P. mendocina cells.