Streptomyces venezuelae GY1产聚乙烯醇降解酶的培养条件

EFFECT OF CULTURE CONDITIONS ON POLY(VINYLALCOHOL)-DEGRADING ENZYME PRODUCTION BY STREPTOMYCES VENEZUELAE GY1

放线菌StreptomycesvenezuelaeGY1产生的聚乙烯醇(PVA)降解酶是一种诱导酶.以4种不同类型的PVA为唯一碳源时,该菌株单位质量细胞产酶能力比以糖类物质为唯一碳源时提高10倍以上.聚合度和醇解度最高的PVA1799是该菌株产生PVA降解酶的适宜底物,其浓度为1gL-1时,PVA降解酶的产量为120u/g(细胞).培养基中PVA1799浓度由1gL-1上升到5gL-1时,该菌株单位质量细胞产酶能力下降73%,表明PVA1799浓度过高会抑制产酶.GY1菌株产酶的最适温度和pH分别为30℃和7.0.在GY1菌株生长过程中控制以下条件有利于产生PVA降解酶:(1)保持培养体系中较高的溶氧水平;(2)在氮源中补充NO-3;(3)在一定浓度范围内添加MgSO4·7H2O、CaCl2、MnSO4、BaCl2、ZnSO4、FeSO4·7H2O和CuSO4等金属盐.Pseudomonassp.产生的PVA降解酶能够作用伯醇或仲醇类化合物,以这些伯醇或仲醇类化合物代替培养基中的PVA,不能诱导GY1菌株产生PVA降解酶;而在培养基中有PVA存在时,再添加0.5gL-1的3戊醇和环己醇能够明显促进PVA降解酶的产生(单位质量细胞产酶能力分别提高了21%和32%).

The poly （vinyl alcohol） （PVA）-degrading enzyme produced by a newly isolated strain, Streptomyces venezuelae GY1, was inducible and substrate-dependent. With each of the four different PVA as a sole carbon source, the PVA-degrading enzyme producing capability （units per gram dry cell weight） of strain GY1 increased up to 10 folds compared with that of the cells grown on glucose, starch, maltose or lactose. The highest specific enzyme activity （ 120 u/g） was achieved when the strain was cultivated in medium containing PVA1799, the polymerization and saponification degree of which were the highest among the four PVA tested. The optimal temperature and initial pH for strain GY1 to produce PVA-degrading enzyme were 30℃ and 7.0, respectively. The production of PVA-degrading enzyme could be further improved by ： （ 1 ） controlling the dissolved oxygen concentration at a higher level; （2） providing NOr as an additional nitrogen source; and （3） supplementing suitable concentrations of MgSO4 · 7H2O, MnSO4 , BaC12 , ZnSO4, FeSO4 · 7H20, CaC12 and CuSO4. When PVA was used as a sole carbon source, the specific enzyme activity was increased by 21% and 32%, respectively, upon addition of 0.5 g L^-1 3-pentanol and cyclohexanol. However, the addition of 3-pentanol and cyclohexanol to the medium free of PVA did not induce the pro- duction of PVA-degrading enzyme by the strain. Fig 8, Tab 1, Ref 11