Insight into broad substrate specificity and synergistic contribution of a fungal α-glucosidase in Chinese Nong-flavor daqu

Microbial Cell Factories

Research

Yao Xiao¹  Hai Zhao²  Yanling Jin²  Kaize He²  Yang Fang²  Zhuolin Yi²  Lanchai Chen³  Nian Liu⁴  Kui Peng⁴  Yi Shen⁵  Xi Wang⁵ 

[1] Analytical and Testing Center, Sichuan University of Science and Engineering, 643000, Zigong, China;CAS Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, No. 9 Section 4, Renmin Nan Road, 610041, Chengdu, Sichuan, P.R. China;School of Food and Bioengineering, Xihua University, 610039, Chengdu, Sichuan, China;Sichuan Food and Fermentation Industry Research & Design Institute, 611130, Chengdu, China;Sichuan Langjiu Co., Ltd, 646523, Gulin, China;

关键词: α-Glucosidase (AG);    Liquor starter;    Heterologous expression;    Glycoside hydrolase family 31 (GH31);    Metatranscriptomics;   

DOI  :  10.1186/s12934-023-02124-z

 received in 2023-02-02, accepted in 2023-06-07,  发布年份 2023

来源: Springer

【 摘 要 】

BackgroundChinese Nong-favor daqu, the presentative liquor starter of Baijiu, has been enriched with huge amounts of enzymes in degrading various biological macromolecules by openly man-made process for thousand years. According to previous metatranscriptomics analysis, plenty of α-glucosidases were identified to be active in NF daqu and played the key role in degrading starch under solid-state fermentation. However, none of α-glucosidases was characterized from NF daqu, and their actual functions in NF daqu were still unknown.ResultsAn α-glucosidase (NFAg31A, GH31-1 subfamily), the second highest expressed α-glucosidases in starch degradation of NF daqu, was directly obtained by heterologous expression in Escherichia coli BL21 (DE3). NFAg31A exhibited the highest sequence identities of 65.8% with α-glucosidase II from Chaetomium thermophilum, indicating its origin of fungal species, and it showed some similar features with homologous α-glucosidase IIs, i.e., optimal activity at pH ~ 7.0 and litter higher temperature of 45 ℃, well stability at 41.3 ℃ and a broad pH range of pH 6.0 to pH 10.0, and preference on hydrolyzing Glc-α1,3-Glc. Besides this preference, NFAg31A showed comparable activities on Glc-α1,2-Glc and Glc-α1,4-Glc, and low activity on Glc-α1,6-Glc, indicating its broad specificities on α-glycosidic substrates. Additionally, its activity was not stimulated by any of those detected metal ions and chemicals, and could be largely inhibited by glucose under solid-state fermentation. Most importantly, it exhibited competent and synergistic effects with two characterized α-amylases of NF daqu on hydrolyzing starch, i.e., all of them could efficiently degrade starch and malto-saccharides, two α-amylases showed advantage in degrading starch and long-chain malto-saccharides, and NFAg31A played the competent role with α-amylases in degrading short-chain malto-saccharides and the irreplaceable contribution in hydrolyzing maltose into glucose, thus alleviating the product inhibitions of α-amylases.ConclusionsThis study provides not only a suitable α-glucosidase in strengthening the quality of daqu, but also an efficient way to reveal roles of the complicated enzyme system in traditional solid-state fermentation. This study would further stimulate more enzyme mining from NF daqu, and promote their actual applications in solid-state fermentation of NF liquor brewing, as well as in other solid-state fermentation of starchy industry in the future.

【 授权许可】

CC BY   
© The Author(s) 2023

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