Production of Methanol Tolerant Cell-bound Lipase of Magnusiomyces spicifer SPB2 and Application as Whole-cell Biocatalyst in Transesterification Reaction

Abstract

Cell-bound lipase (CBL) is a potential biocatalyst for production of fatty acid alkyl ester (FAAE), which is feasible replacement for diesel fuel. This study aimed to improve both hydrolysis and transesterification activities of CBL from the yeast Magnusiomyces spicifer SPB2, which could be employed as whole-cell biocatalyst for transesterification reactions through optimizing the growth medium using Taguchi orthogonal array experimental method (L9). The optimized medium, resulting the highest CBL transesterification activity, consisted of soybean oil, peptone, Gum Arabic and an initial pH of 5. Interestingly, the fatty acid methyl ester (FAME) yield increased up to 33.28 times when compared with non-optimized medium. Moreover, cell morphology of M. spicifer SPB2 varied depending on the culture medium component. The single cell was more active to be used as the whole-cell biocatalyst than the pseudomycelial form for transesterification reaction. The highest FAME yield was 93.86 % when refined palm oil to methanol molar ratio of 1:8 was used as substrates. Whole-cell lipase from M. spicifer showed favorable activity to iso-butanol as an acyl accepter, resulting in fatty acid butyl ester (FABE) yield of 86.80 % at 1:3 molar ratio of palm oil to iso-butanol. The FAME and FABE yields dramatically decreased from 93.86 and 86.80 % to 57.02 and 4.48 %, respectively after the reuse of the enzyme to the second batch of reaction. These results indicated that the whole-cell biocatalyst developed from M. spicifer was an efficient and economical approach to improve enzyme activity and stability in the transesterification reaction. HIGHLIGHTS Methanol tolerant cell-bound lipase and extracellular lipase of spicifer SPB2 were produced The whole-cell biocatalyst of spicifer SPB2 was developed for FAME production The optimized medium was developed to prepare whole-cell lipases from spicifer SPB2 Gum Arabic was the most influencing factor for synthetic activity of whole-cell CBL from yeast Single cell morphology exhibited higher transesterification activity than pseudomycelial form GRAPHICAL ABSTRACT