Effect of culture conditions on growth and esterase production by the moderate thermophile Bacillus circulans MAS2

Growth and esterase production (activity on p-nitrophenyl caprylate) by the newly isolated Bacillus circulans MAS2 bacterial strain were studied. The growth rate at 50 degrees C was high (0.9 h(-1)) on LB medium with glucose added. Esterase production followed growth with the majority of activity be ing intracellular during exponential growth phase. During stationary phase, the esterase activity was released in We culture medium. The strain was ab le to grow at 35-55 degrees C with maximum growth rate at 50 degrees C, sho wing a pattern typical of a moderate thermophile. Growth occurred at pH 6-9 with a maximum at 8, with a similar pattern for the esterase production. A ddition of glucose, fructose, sucrose or sodium acetate greatly promoted bo th growth and esterase production while starch, inulin, tributyrin or glyce rol showed no effect. Complex nitrogen sources such as tryptone or yeast ex tract Increased growth and esterase production while mineral sources (ammon ium chloride or sulfate), glycine or glutamate showed no effect. An increas e of tryptone plus yeast extract and glucose concentrations stimulated grow th and esterase production which reached 160 U L-1.