Studies on some physicochemical properties of Rhodanese synthesized by Bacillus cereus isolated from the effluents of iron and steel smelting industry

Abstract

The study purified and investigated the physicochemical properties of rhodanese (a cyanide detoxifying enzyme) synthesized by Bacillus cereus. This was with a view to producing an industrially important enzyme. The bacterial strain was identified as B. cereus by sequencing of its 16SrRNA gene. B. cereus rhodanese was purified with a fold of 3.53, yield of 36.80% and specific activity of 25.30 µmol/min/mg protein. The molecular weight determined on SDS-PAGE was 33.800 kDa. The enzyme exhibited maximum activity at 9.0 pH and 50°C. The Kms of B. cereus rhodanese for sodium thiosulphate and potassium cyanide were 19.9 ± 1.05 and 31.4 ± 1.55 mM respectively, while Vmax were 6.19 ± 0.40 and 4.83 ± 0.93 RU/ml respectively. The substrate specificity study using different sulphur compounds showed that the enzyme prefers sodium thiosulphate. The enzyme showed stability at a temperature range of 40-50°C. At 10 mM concentration, metals such as (BaCl2, CaCl2, MnCl2, and SnCl2) had little influence on the enzyme activity while NaCl and HgCl2 inhibited enzyme activity. The presence and biochemical properties of B. cereus rhodanese suggest its possible application in cyanide detoxification.   Key words: Bacillus cereus, isolate, cyanide, purification, rhodanese, kinetics.