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

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 360 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, Km values of 0·07 mmol l−1 and 3·7 mmol l−1 were found for p‐nitrophenyl‐β‐D‐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.