Abstract
Halotolerant Cr (VI) reducing bacteria (VITP21) was isolated from kumta coastal region, India and was identified by biochemical methods and 16S rRNA analysis as Planococcus maritimus. The halotolerant bacteria exhibited complete reduction of 100 and 200 mg/L of Cr (VI) within 24 and 28 h, respectively and greater than 90% reduction was observed for higher concentration of Cr (VI) in the range of 300 to 500 mg/L (pH 7, 35°C, and 4% NaCl). The optimum parameters for chromium reduction was found to be pH 7.0, 35°C and 4% NaCl with an agitation rate of 140 rpm under aerobic condition. The isolate was capable to grow and reduce chromate even in the presence of different divalent metal ions (50 mg/L of Pb2+, Co2+, Cd2+, Ni2+, Zn2+, Cu2+ and Mn2+) under saline conditions. Experiments with resting cells, permeabilized cells, sonicated cells and cytosolic fractions demonstrated that the chromium reduction is mainly associated with the soluble cytosolic fraction of the cell. To our knowledge, this is the first detailed report on effective reduction of Cr (VI) by halotolerant bacteria P. maritimus VITP2l. The current investigation indicates that the isolated organism can promisingly contribute for the treatment of toxic hexavalent chromium present in saline industrial waste water.
Key words: Bioremediation, chromium reduction, chromium removal, halotolerant bacteria, Planococcus, saline wastewater.
