A Thermostable Glucoamylase from Bispora sp MEY-1 with Stability over a Broad pH Range and Significant Starch Hydrolysis Capacity

文献类型： 外文期刊

第一作者： Hua, Huifang

作者： Hua, Huifang;Luo, Huiying;Bai, Yingguo;Wang, Kun;Niu, Canfang;Huang, Huoqing;Shi, Pengjun;Wang, Caihong;Yang, Peilong;Yao, Bin;Yang, Peilong

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期刊名称：PLOS ONE （ 影响因子：3.24； 五年影响因子：3.788 ）

ISSN： 1932-6203

年卷期： 2014 年 9 卷 11 期

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收录情况： SCI

摘要： Background: Glucoamylase is an exo-type enzyme that converts starch completely into glucose from the non-reducing ends. To meet the industrial requirements for starch processing, a glucoamylase with excellent thermostability, raw-starch degradation ability and high glucose yield is much needed. In the present study we selected the excellent Carbohydrate-Activity Enzyme (CAZyme) producer, Bispora sp. MEY-1, as the microbial source for glucoamylase gene exploitation. Methodology/Principal Findings: A glucoamylase gene (gla15) was cloned from Bispora sp. MEY-1 and successfully expressed in Pichia pastoris with a high yield of 34.1 U/ml. Deduced GLA15 exhibits the highest identity of 64.2% to the glucoamylase from Talaromyces (Rasamsonia) emersonii. Purified recombinant GLA15 was thermophilic and showed the maximum activity at 70 degrees C. The enzyme was stable over a broad pH range (2.2-11.0) and at high temperature up to 70 degrees C. It hydrolyzed the breakages of both alpha-1,4- and alpha-1,6-glycosidic linkages in amylopectin, soluble starch, amylose, and maltooligosaccharides, and had capacity to degrade raw starch. TLC and H-1-NMR analysis showed that GLA15 is a typical glucoamylase of GH family 15 that releases glucose units from the non-reducing ends of alpha-glucans. The combination of Bacillus licheniformis amylase and GLA15 hydrolyzed 96.14% of gelatinized maize starch after 6 h incubation, which was about 9% higher than that of the combination with a commercial glucoamylase from Aspergillus niger. Conclusion/Significance: GLA15 has a broad pH stability range, high-temperature thermostability, high starch hydrolysis capacity and high expression yield. In comparison with the commercial glucoamylase from A. niger, GLA15 represents a better candidate for application in the food industry including production of glucose, glucose syrups, and high-fructose corn syrups.

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