Improvement of thermostability and catalytic efficiency of glucoamylase from Talaromyces leycettanus JCM12802 via site-directed mutagenesis to enhance industrial saccharification applications

• Published in: Biotechnology for biofuels Vol. 14; no. 1; pp. 1 - 202
• Main Authors: Tong, Lige, Zheng, Jie, Wang, Xiao, Wang, Xiaolu, Huang, Huoqing, Yang, Haomeng, Tu, Tao, Wang, Yuan, Bai, Yingguo, Yao, Bin, Luo, Huiying, Qin, Xing
• Format: Journal Article
• Language: English
• Published: London BioMed Central Ltd 16.10.2021; BioMed Central; BMC
• Subjects: Amino acids; Amylases; Biochemical engineering; Catalysis; Catalytic efficiency; Chemical engineering; Chemical engineering research; Chemical properties; Correlation analysis; Cross correlation; Disulfide bonds; Efficiency; Engineering; Enzymes; Fungi; Genetic aspects; Glucoamylase; Industrial application; Industrial microorganisms; Melt temperature; Methods; Microbial enzymes; Molecular dynamics; Molecular weight; Mutagenesis; Optimization; Physiological aspects; Proteins; Saccharification; Site-directed mutagenesis; Starch; Talaromyces; Thermal equilibrium; Thermal properties; Thermal stability; Thermophilic fungi; Thermostability; China
• ISSN: 1754-6834; 1754-6834
• DOI: 10.1186/s13068-021-02052-3

Abstract Background Glucoamylase is an important industrial enzyme in the saccharification of starch into glucose. However, its poor thermostability and low catalytic efficiency limit its industrial saccharification applications. Therefore, improving these properties of glucoamylase is of great significance for saccharification in the starch industry. Results In this study, a novel glucoamylase-encoding gene TlGa15B from the thermophilic fungus Talaromyces leycettanus JCM12802 was cloned and expressed in Pichia pastoris . The optimal temperature and pH of recombinant Tl Ga15B were 65 ℃ and 4.5, respectively. Tl Ga15B exhibited excellent thermostability at 60 ℃. To further improve thermostability without losing catalytic efficiency, Tl Ga15B-GA1 and Tl Ga15B-GA2 were designed by introducing disulfide bonds and optimizing residual charge–charge interactions in a region distant from the catalytic center. Compared with Tl Ga15B, mutants showed improved optimal temperature, melting temperature, specific activity, and catalytic efficiency. The mechanism underlying these improvements was elucidated through molecular dynamics simulation and dynamics cross-correlation matrices analysis. Besides, the performance of Tl Ga15B-GA2 was the same as that of the commercial glucoamylase during saccharification. Conclusions We provide an effective strategy to simultaneously improve both thermostability and catalytic efficiency of glucoamylase. The excellent thermostability and high catalytic efficiency of Tl Ga15B-GA2 make it a good candidate for industrial saccharification applications.