Improved Thermostability of Lipase B from Candida antarctica by Directed Evolution and Display on Yeast Surface

To expand the functionality of lipase B from Candida antarctica (CALB), we used the multi-site saturation mutagenesis methods to create CALB mutants with improved thermal stability. The times of residual activity of the mutants mCALB168 and mCALB7 were 14 and 6 times higher than that of the displayed WT-CALB at 60 A degrees C. Amino acid substitutions at positions 218, 219, 220, and 221 in mCALB7 introduced two additional hydrogen bonds and altered part of the surface domain from 217 to 224. In mCALB168, we introduced mutations T57A/R168K, which formed three additional hydrogen bonds. The mutants displayed on yeast significantly increased the thermostability in an aqueous system at 60 A degrees C. These results indicate that yeast surface display technology could dramatically improve the stability of CALB.