Purification and properties of endo-β-glucanase in the yeast Hanseniaspora valbyensis

Endo-β-glucanase was detected in Hanseniaspora valbyensis and Hanseniaspora uvarum. The extracellular enzyme activity of H. valbyensis was maximal with vigorous aeration at 30 C in a complete mineral medium with glucose and 0.2 M Na-succinate buffer. The enzyme concentration was lower when the buffer was 0.05 M Na-succinate. The use of a variety of carbon sources, including yeast cell walls, failed to induce higher enzyme activities. The enzyme was purified 34-fold from the culture fluid of H. valbyensis. The purified enzyme had a broad pH optimum between pH 3.5 and 4.5. Among the known β-glucan homopolymers, only laminarin (β-1 → 3 bonds) was hydrolyzed by the enzyme. The Km for laminarin was 0.11 mg/ml and the Vmax was 0.835 μmoles glucose equivalents/min mg protein. No action was detected with laminaribiose, laminaritriose, or oat glucan. Laminaritetraose, however, was hydrolyzed slowly in a random pattern. These results suggest the requirement for three consecutive β-1 → 3 bonds for activity.