Enhancing the methanol tolerance of Candida antarctica lipase B by saturation mutagenesis for biodiesel preparation

Methanol tolerance of lipase is one of the important factors affecting its esterification ability in biodiesel preparation. By B factor indicated prediction of Candida antarctica lipase B (CalB) surface amino acids, eight sites (Val(139), Ala(146), Leu(147), Pro(218), Val(286), Ala(287), Val(306), and Gly(307)) with high B value indicating more flexibility were chosen to perform saturation mutagenesis. High-methanol-tolerant variants, CalB-P218W and -V306N, created larger haloes on emulsified tributyrin solid plate including 15% (v/v) methanol and showed 19% and 31% higher activity over wild-type CalB (CalB-WT), respectively. By modeling, a newly formed hydrogen bond in CalB-V306N and hydrophobic force in CalB-P218W contributing more stability in protein may have resulted in increased methanol tolerance. CalB-P218W and -V306N transesterified the soybean oil into biodiesel at 30 degrees C by 85% and 89% yield, respectively, over 82% by CalB-WT for 24 h reactions. These results may provide a basis for molecular engineering of CalB and expand its applications in fuel industries. The as-developed semi-rational method could be utilized to enhance the stabilities of many other industrial enzymes.

Automated summary

The methanol tolerance of lipase is an important factor affecting its esterification ability in biodiesel preparation. Through saturation mutagenesis, researchers identified two high-methanol-tolerant variants of lipase that showed increased activity and yield in transesterification reactions. Modeling analysis revealed the mechanisms behind the improved methanol tolerance. These findings provide a basis for molecular engineering of lipase and expand its applications in the fuel industry.