CAO Kai;DENG Guozhi;HU Xiaojie;ZHANG Jiasheng;WU Chao;School of Resources and Environmental Engineering, Anhui University;

Bacillus hwajinpoensis;;halotolerant bacteria;;protease;;optimal conditions

A halotolerant bacterium CK-1 was isolated form a saltworks of ZheJiang Zhoushan. The strain CK-1 was an undetermined species of Bacillus based on its 16 S rDNA sequence as well as physiological and biochemical analysis, and its systematic taxonomic relationship was closest to the species of Bacillus hwajinpoensis,and The Bacillus sp. CK-1 could grow at the concentration of 20% NaCl, indicating it as a halotolerant bacteria. The Na Cl concentration for the optimal growth of Bacillus sp. CK-1 was 4%. The Bacillus sp. CK-1 secreted proteases during growth. The proteases had the highest activity at pH 8.0 and 45℃, and remained 44.9% activity in the presence of 8% NaCl. Sucrose, starch and maltose significantly improved the production of proteases. The activity of proteases increased firstly and then decreased with the increase of NaCl concentration in the fermentation medium.The activity of proteases reached the maximum in the presence of 12% NaCl. The activity of proteases is significantly promoted by Ca~(2+), suggesting that they were calcium-dependent proteases.The maximal activity was obtained in the optimized medium(KCl 2.0 g·L~(-1),NaHCO_3 0.06 g·L~(-1),Fe Cl3 0.001 g·L~(-1), NaCl 120.0 g·L~(-1),CaCl_2·2 H_2O 1 mmol·L~(-1), maltose 10 g·L~(-1), tryptone 10 g·L~(-1), initial ph7.5) after fermentation at 40℃ for 5 h.