No abstract

This study aimed to economically develop the yeast whole-cell biocatalyst from the lipase-secreting Magnusiomyces spicifer SPB2 to serve green biodiesel production. The scaled-up productions of lipases were optimized using a 5-L stirred-tank bioreactor. The maximum extracellular lipase and cell-bound lipase (CBL) yields of 1189.65 U/L and 5603.74 U/L were achieved at 24 h and 60 h, respectively, in the modified IMY medium (pH 5.0) containing 2% of soybean oil as a carbon source and 0.2% Gum Arabic as an emulsifying agent. The optimized cultivation was initiated with an inoculum size of 1 × 107 cells/mL and conducted under an aeration rate of 0.75 vvm with an agitation speed of 400 rpm. The obtained whole-cell biocatalyst of M. spicifer SPB2 was applied to catalyze the transesterification reaction using palm oil and methanol as substrates. The greatest yield of 97.93% fatty acid methyl ester (FAME) was reached at 72 h using a palm oil/methanol ratio of 1:7, indicating high methanol stability of the biocatalyst. Moreover, substrate homogenization accelerated the reaction to achieve FAME production of 97.01% at 48 h and remained stable afterwards. Without homogenization, the highest FAME of 98.20% was obtained at 60 h. The whole-cell biocatalyst prepared from lipase-secreting M. spicifer SPB2 at an up-scaled level greatly enhanced efficiency and feasibility for commercial biodiesel production through a green conversion process.

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

No abstract