Purification and characterization of an intracellular β-glucosidase from a new strain of Leuconostoc mesenteroides isolated from cassava

Abstract

The lactic acid bacterium, Leuconostoc mesenteroides, when grown on an arbutin-containing medium, was found to produce an intracellular β-glucosidase. The enzyme was purified by chromatofocusing, ion-exchange chromatography and gel filtration. The molecular mass of the purified intracellular β-glucosidase, as estimated by gel filtration, was 36O kDa. The tetrameric structure of the β-glucosidase was determined following treatment of the purified enzyme with dodecyl sulphate (SDS). The intracellular β-glucosidase exhibited optimum catalytic activity at 50°C and pH 6 with citrate-phosphate buffer, and 5.5 with phosphate buffer. The enzyme was active against glycosides with (1→4)-β, (1→4)-α and (1→6)-α(linkage configuration. From Lineweaver-Burk plots, K(m) values of 0.07 mmol l-1 and 3.7 mmol l-1 were found for p-nitrophenyl-β-glucopyranoside and linamarin, respectively. The β-glucosidase was competitively inhibited by glucose and by D-gluconic acid-lactone and a glucosyl transferase activity was observed in the presence of ethanol. The β-glucosidase of Leuconostoc mesenteroides, with cyanogenic activity, could be of potential interest in cassava detoxification, by hydrolysing the cyanogenic glucosides present in cassava pulp.