Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

ABSTRACT

Bacillus sphaericus AND 303, a Cr(VI)-resistant and reducing bacterium reported from serpentine outcrops of Andaman was evaluated for Cr(VI) reduction using immobilized cells under batch culture. Screening of inert matrices for entrapment of whole cells indicated that polyvinyl alchohol-alginate was the most effective one reducing 87.5% of 20 µM Cr(VI) in 24 h. The rate of chromate reduction was dependent on initial Cr(VI) and biomass concentrations. The PVA cell beads were recycled three times without cell leakage and disintegration. The reduction efficiency was improved in the presence of glucose and glycerol as electron donors leading to complete reduction. However, the presence of additional metal ions was inhibitory to Cr(VI) reduction. It could be emphasized that PVA-alginate immobilized cells of B. sphaericus AND 303 could be used as a continuous bioprocess in treating Cr(VI) contaminated effluents.