Computation-aided engineering of starch-debranching pullulanase from Bacillus thermoleovorans for enhanced thermostability.

TitleComputation-aided engineering of starch-debranching pullulanase from Bacillus thermoleovorans for enhanced thermostability.
Publication TypeJournal Article
Year of Publication2020
AuthorsBi J, Chen S, Zhao X, Nie Y, Xu Y
JournalAppl Microbiol Biotechnol
Date Published2020 Sep

Pullulanases are widely used in food, medicine, and other industries because they specifically hydrolyze α-1,6-glycosidic linkages in starch and oligosaccharides. In addition, high-temperature thermostable pullulanase has multiple advantages, including decreasing saccharification solution viscosity accompanied with enhanced mass transfer and reducing microbial contamination in starch hydrolysis. However, thermophilic pullulanase availability remains limited. Additionally, most do not meet starch-manufacturing requirements due to weak thermostability. Here, we developed a computation-aided strategy to engineer the thermophilic pullulanase from Bacillus thermoleovorans. First, three computational design predictors (FoldX, I-Mutant 3.0, and dDFIRE) were combined to predict stability changes introduced by mutations. After excluding conserved and catalytic sites, 17 mutants were identified. After further experimental verification, we confirmed six positive mutants. Among them, the G692M mutant had the highest thermostability improvement, with 3.8 °C increased T and 2.1-fold longer half-life than the wild type at 70 °C. We then characterized the mechanism underlying increased thermostability, such as rigidity enhancement, closer conformation, and strengthened motion correlation using root mean square fluctuation (RMSF), principal component analysis (PCA), dynamic cross-correlation map (DCCM), and free energy landscape (FEL) analysis. KEY POINTS: • A computation-aided strategy was developed to engineer pullulanase thermostability. • Seventeen mutants were identified by combining three computational design predictors. • The G692M mutant was obtained with increased Tand half-life at 70 °C.

Alternate JournalAppl Microbiol Biotechnol
PubMed ID32632476
Grant List31872891 / / National Natural Science Foundation of China /
G20190010083 / / High-End Foreign Experts Recruitment Program /
2015-NY-007 / / Program for Advanced Talents within Six Industries of Jiangsu Province /
M201803 / / Program for the Key Laboratory of Enzymes of Suqian /
LITE2018-09 / / National First-Class Discipline Program of Light Industry Technology and Engineering /