一株产聚乙烯醇降解酶的紫色杆菌的发酵条件研究

Optimization of Fermentation Conditions for a PVA-degrading Enzyme Producing Strain

从聚乙烯醇(PVA)污染环境中筛选出一株产聚乙烯醇降解酶活力较高的菌株WSH04-01,该菌株能够利用聚乙烯醇作为唯一碳源进行生长。通过一系列生理生化试验和16SrDNA序列分析结果,鉴定该菌株属于紫色杆菌属(Janthinobacteriumsp.),实验室编号WSH04-01。这是目前国内外有关紫色杆菌产生PVA降解酶的首例报道。首先对菌株合成PVA降解酶的营养条件进行了考察,通过单因素试验和正交试验确定了菌株最优培养条件为PVA10g·L-1,葡萄糖3g·L-1,酵母膏6g·L-1,K2HPO42g·L-1,KH2PO40.25g·L-1,MgSO40.05g·L-1,CaCl20.05g·L-1,FeSO4·7H2O0.02g·L-1,NaCl0.02g·L-1。最适发酵温度为30℃,培养基初始pH为7.2,装液量为30mL培养基·(250mL摇瓶)-1,接种量为8%。在最优条件下,PVA降解酶酶活可以达到4.94U·mL-1,略高于正交试验中的最高酶活(4.83U·mL-1)。同时利用凝胶渗透色谱得到分子量分布图,对最优发酵条件下发酵过程中聚乙烯醇的降解进行了验证。

A high-yield poly（vinyl alcohol）-degrading enzyme bacterium, which can use polyvinyl alcohol （PVA） as sole carbon source, was isolated from PVA- contaminated samples. The bacterium isolated was identified by cell morphology, physiology and biochemistry and 16S rDNA, and it is found that the bacterium isolated belongs to Janthinobacterium sp.. So far, this is the first time a strain of Janthinobacterium sp. can degrade PVA was reported. The effect of culture conditions on the production of polyvinyl alcohol-degrading enzyme was studied by both single-factor and orthogonal experiment methods. The optimal fermentation conditions were determined as follows： PVA 10 g·L^-1, glucose 3 g·L^-1, yeast-extract 6 g·L^-1, K2HPO4 2 g·L^-1, KH2PO4 0.25 g·L^-1, MgSO4 0.05 g·L^-1, CaCl2 0.05 g·L^-1 FeSO4-7H2O 0.02 g·L^-1, NaCl 0.02 g·L^-1. Besides, the optimum growth temperature is 30℃, the initial pH of fermentation is 7.2, the suitable volume size of medium in 250 mL flask is 30 mL and the inoculum size of 8% is used. Under the optimal conditions mentioned above, the PVA-degrading enzyme activity is 4.94 U.mL^-1, which is slightly higher than the best result of orthogonal experiment （4.83 U.mL^-1）. Molecular weight distributions of PVA in liquid culture were determined by gel penetration chromatography （GPC）. The resorts validate that PVA is degraded during culture course under the optimum fermentation conditions.