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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.    Supplementary Information  The online version contains supplementary material available at 10.1186/s13068-021-02052-3.

biotechnology for biofuels

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