产蛋白酶海洋细菌的筛选、鉴定及发酵培养基的研究

采用酪蛋白培养基,对来源于中国南海的深海海泥进行微生物的富集与筛选,分离出18株产蛋白酶海洋细菌,从中筛选出一株产蛋白酶活力最高的菌株C-7,结合生理生化实验及16S rDNA基因序列鉴定为苏云金芽孢杆菌（Bacillus thuringiensis）。该菌株所产蛋白酶的最适反应温度为50℃,最适pH7,属于中温中性蛋白酶,该蛋白酶在15%NaCl条件下仍能保持原有酶活的43%,具有良好的耐盐性。优化后该菌株产蛋白酶培养基为:葡萄糖5.0g,蛋白胨10.0g,KH2PO40.5g,MgSO4·7H2O 0.3g,NaCl 10.0g,CaCl20.5g,吐温-80 1.5g,蒸馏水1L,pH7.2。 

Study on isolation and identification of protease-producing marine bacteria and optimization of fermentation medium

18 strains of protease-producing marine bacteria were isolated from the South China deep sea mud by casein medium.Among them, C-7 was selected based on its higher protease activity and it was identified as Bacillus thuringiensis strain by morphological observation, physiological and biochemical experiments and 16S rDNA sequence analysis.The optimal reaction temperature of the protease was 50℃ and the optimal reaction pH was 7, which showed that it was mesophilic neutral protease.The protease had good salt- tolerance, 43% protease activity was still remained in 15% NaCl.The culture medium was as follows:5.0g glucose, 10.0g peptone, 0.5g KH2 PO4, 0.3g MgSO4 ·7H2 O, 1.0g CaCl2, 1.5g Tween-80, 1L distilled water, pH7.2.