Isolation and process parameter optimization of Brevibacterium casei for simultaneous bioremediation of hexavalent chromium and pentachlorophenol.

Chromate and pentachlorophenol are major pollutants discharged through tanneries. Three bacteria resistant to high Cr(6+) and PCP concentrations simultaneously were isolated. The TVS-3 strain was tolerant to highest 850 mg l(-1) Cr(6+) and 1000 mg l(-1) PCP concentration and concomitantly reduced 69% Cr(6+) and degraded 72% PCP within 168 h at pH 7.5, 35 ± 1°C temperature, was selected and identified as Brevibacterium casei. At 168 h of growth, bacterium showed maximum PCP utilization of 720 mg l(-1) and released 900 mg l(-1) chloride ion. The bacterium exhibited remarkable ability to significantly reduce Cr(6+) and degrade PCP in presence of other metals, between 100-120 rpm aeration and over broad pH (6.5-10.0) and temperature (30-40°C) range. Maximum 78% Cr(6+) reduction and 82% PCP degradation was observed at pH 8.0, 35 ± 1°C within 168 h of incubation, 120 rpm and initial concentration of 850 mg l(-1) Cr(6+) and 1000 mg l(-1) PCP. This is the first study reporting 78% Cr(6+) reduction and 82% PCP degradation simultaneously by single native bacteria under wide growth conditions utilizing PCP as sole carbon source. This bacterium may potentially be useful for simultaneous bioremediation of Cr(6+) and PCP containing wastes in the environment.