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The characteristics of growth and esterase activity of bacterial strains isolated from acid hydrolysed soybean protein were examined. All the isolated strains having decomposition activity of p-hydroxybenzoic acid butyl ester and esterase producing activity were identified as Bacillus sp. by morphological and biochemical methods. The specific growth rates, esterase activities and p-hydroxybenzoic acid butyl ester decomposition activities of isolated strains were 0.844∼1.213h^(-1), 21∼222 mU/㎖ and 5.4∼8.1 mU/㎖, respectively. In the fermentation of Bacillus sp. KB8 strain which had the highest esterase producing activity, growth, extracellular excretion and intracellular synthesis of esterase were inhibited by adding NaCl in the culture broth. Esterase producing activity gradually increased after late exponential growth phase, until maximum value of 420 mU/㎖ reached after 64 hours culture period. Esterase of Bacillus sp. KB8 strain was stable up to 50℃ for 30 minutes, but was inactivated by heating for 30 minutes at 70℃. The enzyme activity exponentially decreased during the incubation time at the temperatures of 60 and 65℃.
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