Purification and characterization of an intracellular beta-glucosidase from lactobacillus casei ATCC 393

The lactic acid bacterium, Lactobacillus casei, produces an intracellular b eta-glucosidase when grown on Man-Rogosa-Sharpe (MRS) medium with cellobios e as carbon source. The beta-glucosidase activity is produced intracellular y, and no extracellulary activity was detected. The enzyme was purified by ion-exchange chromatography and gel filtration. The molecular mass of the p urified intracellular beta-glucosidase as estimated by gel filtration was 4 80 kDa, consisting of six probably identical subunits. The enzyme exhibited optimum activity at 35 degrees C and pH 6.3 with citrate-phosphate buffer. The enzyme was active against soluble glycosides with (1-->4)-beta configu ration and from Linesweaver Burk plots, K-m value of 16 mmol/L was found fo r beta-pNPG. The beta-glucosidase was competitively inhibited by glucose, a nd no glycosyl transferase activity was observed in the presence of ethanol .