γ-CGTase突变体制备及其产γ-CD条件优化

采用定点突变法将来自Bacillus sp.G-825-6的γ-CGTase的211位的酪氨酸突变为亮氨酸，并利用突变体Y211L催化淀粉制备γ-CD，分别研究了底物种类、底物质量分数、反应时间、反应温度、加酶量对γ-CD产率的影响，并在单因素的基础上进行了正交优化，优化后的反应条件为：木薯淀粉质量分数为6%，加酶量为4 U/g，反应温度50 ℃，反应时间为24 h，在此条件下催化产生γ-CD的产率可达到14%，以总环糊精质量分数为100%计，催化产γ-CD的比率为97%。
In this thesis，tyrosine 211 of γ-CGTase from Bacillus sp. G-825-6 changed into leucine based on site-directed mutagenesis. The influences of substrate type，concentration，time，temperature，and enzyme concentration on the mutant Y211L catalyticed starch to produced γ-CD were evaluated. On the basis of single of factor experiments，orthogonal design method was used to optimize the condition for production of γ-CD. As a result，the best condition was：cassava starch 6%，enzyme concentration 4 u/g，temperature 50 ℃，time 24 h. Under thses conditions，the production of γ-CD can reach 14%. If the total cyclodextrin content is 100%，the catalytic production ratio of γ-CD is 97%