长野芽胞杆菌普鲁兰酶(PulA)是我国实现规模化生产的淀粉脱支酶,但因其酶学属性与现有葡糖淀粉酶的淀粉糖化pH的不一致性,影响到淀粉制葡萄糖的转化率。该文研究了PulA酸性突变体LoPulA的酶学性质和其在淀粉制葡萄糖中的应用价值,结果显示,LoPulA在pH 4.5和60 ℃下表现出最高酶活力,在pH 4.3下的酶活力是其最高酶活力的96.40%,此酶活性特征与葡糖淀粉酶的最适作用条件十分吻合。使用突变体LoPulA与葡糖淀粉酶一起进行淀粉制糖试验,结果显示,经LoPulA与葡糖淀粉酶协同作用后,淀粉糖液的葡萄糖当量(dextrose equivalent,DE值)最高可达到96.66%,较PulA和葡糖淀粉酶协同作用后的糖液DX值提高了1.40%,显示普鲁兰酶突变体LoPulA在淀粉制葡萄糖中具有重大应用潜力。
Bacillus naganoesis pullulanase (PulA) is a starch debranching enzyme that has achieved large-scale production in China.However, its enzymatic properties (especially saccharification pH) are inconsistency with that of glucoamylase in starch saccharification, which effects on the conversion rate of starch to glucose.The characteristics of an acidic mutant, LoPulA, from PulA, and its application value in the production of glucose from starch were studied.The results showed that the maximal activity of LoPulA was at pH 4.5 and 60 ℃ and kept 96.40% of the maximal activity at pH 4.3, which was greatly consistent with the optimal saccharification pH with glucoamylase.In starch saccharification experiments, the DX value of the sugar solution could reach 96.66% with the synergistic hydrolysis of LoPulA and glucoamylase, which was 1.40% higher than that of PulA (wild type) and glucoamylase, thereby indicating LoPulA of great application potential in high glucose syrup preparation from starch.
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