Effects of expressing exogenous microalgal DGAT genes on the growth and lipids of Saccharomyces cerevisiae

The H1246 mutant of Saccharomyces cerevisiae, which is deficient in triacylglycerol (TAG) synthesis, is often used to identify the function of exogenous genes encoding diacylglycerol acyltransferase (DGAT). In order to understand the effects of exogenous DGATs on the lipid synthesis and growth of the yeast cells; one type Ⅰ (DGAT1) and three type Ⅱ DGAT (DGAT2a, DGAT2b, DGAT2c) genes of Myrmecia incisa were transformed into H1246 strain respectively, and four transgenic yeast strains were obtained by screening, The morphology and lipid droplet formation, cell density, biomass, total lipids, total fatty acids and TAG content of S. cerevisiae were detected by microscopic observation, spectrophotometry, gravimetry, Rod thin layer chromatography and gas chromatography-mass spectrometry; oil droplets were observed in all the four transgenic yeasts during the stable growth period under microscopic observation, which illustrated that the four exogenous genes could lead to the synthesis and storage of TAG. Lipid component analysis showed that the contents of TAG and fatty acid of tDGAT1 strain were the highest among all the transgenic strains and the wild-type Scy62. The growth performance analysis showed that densities of the cells transformed with the four exogenous genes could reach the level of Scy62 yeast, which might be owing to the consumption of free fatty acids in the synthesis of TAG to reduce its damage to cells. However, as a result of the significantly prolonged period of growth retardation, the growth of tDGAT1 strain was the lowest. It was supposed that differences of growth performances and lip components among the four transgenic strains might be due to the special domains of the four DGATs. The results of this study laid a foundation for producing the desired lipids by using genetically engineered yeast strains.