초록
<P>Production of biofuels derived from microbial fatty acids has attracted great attention in recent years owing to their potential to replace petroleum-derived fuels. To be cost competitive with current petroleum fuel, flux toward the direct precursor fatty acids needs to be enhanced to approach high yields. Herein, fatty acyl-CoA metabolism in Saccharomyces cerevisiae was engineered to accumulate more free fatty acids (FFA). For this purpose, firstly, haploid S. cerevisiae double deletion strain faa1faa4 was constructed, in which the genes FAA1 and FAA4 encoding two acyl-CoA synthetases were deleted. Then the truncated version of acyl-CoA thioesterase ACOT5 (Acot5s) encoding Mus musculus peroxisomal acyl-CoA thioesterase 5 was expressed in the cytoplasm of the strain faa1faa4. The resulting strain faa1faa4 [Acot5s] accumulated more extracellular FFA with higher unsaturated fatty acid (UFA) ratio as compared to the wild-type strain and double deletion strain faa1faa4. The extracellular total fatty acids (TFA) in the strain faa1faa4 [Acot5s] increased to 6.43-fold as compared to the wild-type strain during the stationary phase. UFA accounted for 42 % of TFA in the strain faa1faa4 [Acot5s], while no UFA was detected in the wild-type strain. In addition, the expression of Acot5s in faa1faa4 restored the growth, which indicates that FFA may not be the reason for growth inhibition in the strain faa1faa4. RT-PCR results demonstrated that the de-repression of fatty acid synthesis genes led to the increase of extracellular fatty acids. The study presented here showed that through control of the acyl-CoA metabolism by deleting acyl-CoA synthetase and expressing thioesterase, more FFA could be produced in S. cerevisiae, demonstrating great potential for exploitation in the platform of microbial fatty acid-derived biofuels.</P>