Extracellular transglucosylase and alpha-amylase of Streptococcus equinus.

Culture filtrates of Streptococcus equinus 1091 contained alpha-amylase and transglucosylase. The effects of calcium carbonate, age of inoculum, concentration of maltose, and duration of the fermentation on alpha-amylase and transglucosylase production were determined. The extracellular alpha-amylase was purified 48-fold and was free of transglucosylase activity. The alpha-amylase (amylose substrate) required Cl(-) for maximum activity; ethylenediaminetetraacetic acid (EDTA) partially inhibited activity, but CaCl(2) prevented EDTA inhibition. The temperature optimum was 38 C at pH 7.0, and the pH optimum was 7.0 at 37 C in the presence of CaCl(2). Predominant final products of amylose hydrolysis, in order of decreasing prevalence, were maltose, maltotriose, maltotetraose, and glucose. The alpha-amylase showed no evidence of multiple attack. The extracellular transglucosylase was purified 27-fold, but a small amount of alpha-amylase remained. Transglucosylase activity (amylose substrate) was not increased in the presence of CaCl(2). The temperature optimum was 37 C at pH 6.5, and the pH optimum was 6.0 at 37 C. Carbohydrates that served as acceptors for the transglucosylase to degrade amylose were, in order of decreasing acceptor efficiency: d-glucose, d-mannose, l-sorbose, maltose, sucrose, and trehalose. The extracellular transglucosylase of S. equinus 1091 synthesized higher maltodextrins in the medium when the cells were grown in the presence of maltose.