Bioreduction based Bioremediation of Hexavalent Chromium Cr (VI) through Potential Indigenous Microbes

Abstract

Sukinda Valley, of Orissa, contains 97% of India’s chromite ore deposits and one of the prime open cast chromite ore mines in the world. (ENVIS Newsletter, 2007). Hexavalent
chromium pollution in this area has caused a major health hazard affecting 2,600,000 people in this area (Blacksmith Institute report, 2007). Our investigation involved biological treatment of Cr (VI) without producing any byproduct. Bacterial cultures tolerating high concentrations of chromium were isolated from the soil sample collected from the chromite contaminated sites of
Sukinda chromite mines and their bioaccumulation properties are investigated. Strains capable of growing at 300 mg/l of Cr (VI) are considered as chromium resistant. The mentioned stain was capable of resisting Cr (VI) up to 500 mg/l. Its resistance to different metals such as Ni, Zn, Cu,
Cd and Fe were also investigated. The effects of different operating parameters such as initial pH, temperature and initial Cr (VI) concentrations on bioaccumulation of Cr (VI) by enriched cultures were studied in a batch system. The experimental investigation showed the maximum
specific chromium uptake at pH 7 and temperature 300C. With increasing initial Cr (VI)concentration from 5 mg/l to 50 mg/l showed increase in Cr (VI) uptake. At about 50 mg l−1
initial Cr (VI) concentrations, uptake of the selected potential strain exceeded 98% within 12 hours of incubation. The bacterial isolate is identified by 16S rRNA sequencing as Brevebacterium casei. Data indicated that isolate culture can be utilized to improve efficiency of
biological treatment processes for effluents containing higher levels of Cr (VI).