β-葡聚糖酶产生菌的选育及培养基初步优化

摘要

In the husk and aleurone layer of malt, there is some β-glucan which could not be degraded completely by endogenous enzymes.The existence of β-glucan affects extraction efficiency, wort viscosity, filtration and beer colloid stability.The problem could be solved effectively by the addition of exogenous β-glucanase during beer production.In this study, 3 microbial strains, which had relatively high β-glucanase activities, were isolated from Hengshui Laobaigan and Laolongkou Daqu by GCN plate method and were coded as 4#, 8# and 12# respectively.Their β-glucanase activities were detected to be 0.362U/mi, 0.542U/mi and 0.511U/mi respectively.By the optimization of fermentation medium, the β-glucanase activity of 8# strain was improved as 0.55U/mi.Furthermore, a mutant of 8# strain was achieved by UV treatment, whose β-glucanase activity reached 0.879U/ml.%麦芽的皮层和胚乳糊粉层中都残存有内源酶无法完全降解的β-葡聚糖,进而影响浸出率和麦汁粘度、过滤难度和啤酒胶体稳定性.在啤酒生产中,添加外源β-葡聚糖酶可以有效解决这些问题.采用刚果红营养平板法(GCN平板法)从衡水老白干和老龙口酒曲中筛选了3株β-葡聚糖酶活力较高且生产周期短的菌株(分别标记为4#、8#、12#),通过液态发酵,测得酶活分别为0.362U/mL、0.542U/mL、0.511U/mL.并对发酵培养基进行了优化,得到8#初始菌株最佳酶活为0.556U/mL.对该菌株进行紫外诱变,得到突变株酶活为:0.879U/mL.