一株能产生聚乙烯醇降解酶的委内瑞拉链霉菌

以聚乙烯醇(PVA)为唯一碳源,从土壤中筛选到1株能产生胞外PVA降解酶的放线菌GY1.根据扩增出的该菌株的16SrDNA全序列在GenBank中的比较结果,结合生理生化实验、细胞化学成分及菌落形态分析,确定该菌为委内瑞拉链霉菌(Stretopmycesvenezuelae).GY1菌株以PVA为唯一碳源时,产生的PVA降解酶活性达到120UL-1,是以葡萄糖或可溶性淀粉为唯一碳源时的10倍.当在PVA培养基中添加1gL-1至3gL-1的葡萄糖时,该菌株细胞量和PVA降解酶总酶活随着葡萄糖添加量的增加而增加,最大细胞量是未添加葡萄糖时的2.4倍,最高总酶活是未添加葡萄糖时的2.6倍,而单位质量细胞产生PVA降解酶的能力提高不大.但当添加的葡萄糖浓度从3gL-1增至10gL-1时,总酶活随着细胞量的增加出现下降趋势,同时单位质量细胞产生PVA降解酶的能力也大大降低.在相同PVA聚合度下,高醇解度PVA比低醇解度PVA更有利于GY1菌株的生长及产生PVA降解酶.图5表1参16

Isolation of a Streptomyces venezuelae Strain Producing Polyvinyl Alcohol Degrading Enzyme

With polyvinyl alcohol (PVA) as sole carbon source, an actinomyces strain GY1 that produces extracellular PVA degrading enzyme was isolated from soil sample of a PVA plant. The strain was identified as Streptomyces venezuelae according to the whole nucleotide sequence analysis of 16S ribosomal DNA, physiological characteristics and chemical component analysis of its whole cell. S. venezuelae GY1 could produce 120 U L -1 PVA degrading enzyme when PVA was used as sole carbon source, and the yield was 10 times higher than that when glucose or soluble starch was used as sole carbon source. Supplement of glucose in PVA medium would affect biomass and enzyme yield. Biomass and PVA degrading enzyme activity of the strain increased with the increasing of initial glucose concentration in the PVA medium if the concentration of glucose was less than 3 g L -1. When 3 g L -1 glucose was supplemented in the medium, the dry cell weight and PVA degrading enzyme activity were 2.4 fold and 2.6 fold of those without glucose in medium. However, the specific enzyme activity (PVA degrading enzyme activity per dry cell weight) was enhanced very little. When the initial glucose concentration in PVA medium continued to increase, the PVA degrading enzyme activity and specific enzyme activity decreased though the biomass concentration continuously increased. In addition, PVA with lower saponification inhibited the growth of S. venezuelae GY1 and the production of PVA degrading enzyme. This strain is different from other bacteria that produce PVA degrading enzyme, which might be partially due to that S. venezuelae GY1 lacks esterase. Fig 5, Tab 1, Ref 16