Comparative behavior of two gram positive Cr(6+) resistant bacterial strains Bacillus aerius S1 and Brevibacterium iodinum S2 under hexavalent chromium stress

Bacillus aerius S1 and Brevibacterium iodinum S2 showed maximum growth at 37 °C and pH 8. B. aerius and B. iodinum could resist Cr(6+) upto 30 and 35 mM and biosorption proficiency (q) of B. aerius S1 was 19, 27, 52 and 34 mM/g while for B. iodinum S2, it was 39, 50, 23 and 16 mM/g mM/g after 2, 4, 6 and 8 days of incubation. A pronounced rise in antioxidant enzymes activities was determined in B. aerius S1 i.e. POX (963%), CAT (717%), APOX (699%), SOD (683%), and GST (792%). However, in B. iodinum S2, relatively a minor increase was estimated. A significant GSH increase was determined in B. aerius S1 (364%) and B. iodinum S2 (663%) cultures under 2 mM Cr(6+) stress. Pilot scale study demonstrated that both strains could reduce Cr(6+) into Cr(3+) within 6 days from the original tannery effluent with efficiency of 99%.