Screening for rhodanese producing Bacterium in freshly pressed Cassava effluents of a Cassava processing industry channeled to Odo-Oba Stream in Ogbomoso-Nigeria

Abstract

Rhodanese is a key enzyme that plays an important role in cyanide detoxification. The enzyme was extracted, purified and physico-chemically characterised from Bacillus licheniformis which demonstrated the highest efficacy compared to the seven isolates of bacteria of the cassava processing industry effluent morpholologically and biochemically characterised.  Statistical analysis was performed using one-way ANOVA and values were considered significant at p<0.05. This study showed that the optimum growth temperature was 350C at a pH 9.0. The highest duration time for the synthesis of rhodanese was at 40 hours. Potassium cyanide (KCN) and casein were the best carbon and nitrogen sources. The enzyme has a specific activity of 10.99 RU/mg, with a purification fold of 4.38, a percentage yield of 15.96%. The apparent Km for KCN and Sodium thiosulphate (Na2S2O3) were determined to be 30.24mM and 24.93mM respectively while their Vmax were 5.40 RU /ml/min and 5.07 RU /ml/min respectively.  The optimum pH and temperature were 8.0 and 50 0C respectively. The enzyme showed a high stability at 500C. The enzyme showed specificity at 6.78 RU/ml/min for Na2S2O3 while it was inhibited by other sulphur containing substrates namely 2-mercaptoethanol, ammonium persulphate, and sodium metabisulphite The enzyme activity was not inhibited by metal ions such as (K+, Mg2+, Ba2+, Ni2+, Sn2+ and Na+) at 1mM and 10mM and was not significant (p>0.05). Therefore, B. licheniformis have the potentials of reducing cyanide pollution thereby enhancing effective management of cassava mill effluent before eventual discharge into the environment and this may be developed into a more effective tool for bioremediation.