Cocktail biosynthesis of triacylglycerol by rational modulation of diacylglycerol acyltransferases in industrial oleaginous Aurantiochytrium

Abstract

Abstract Background Triacylglycerol (TAG) is an important storage lipid in organisms, depending on the degree of unsaturation of fatty acid molecules attached to glycerol; it is usually used as the feedstock for nutrition or biodiesel. However, the mechanism of assembly of saturated fatty acids (SFAs) or polyunsaturated fatty acids (PUFAs) into TAGs remains unclear for industrial oleaginous microorganism. Results Diacylglycerol acyltransferase (DGAT) is a key enzyme for TAG synthesis. Hence, ex vivo (in yeast), and in vivo functions of four DGAT2s (DGAT2A, DGAT2B, DGAT2C, and DGAT2D) in industrial oleaginous thraustochytrid Aurantiochytrium sp. SD116 were analyzed. Results revealed that DGAT2C was mainly responsible for connecting PUFA to the sn-3 position of TAG molecules. However, DGAT2A and DGAT2D target SFA and/or MUFA. Conclusions There are two specific TAG assembly routes in Aurantiochytrium. The “saturated fatty acid (SFA) TAG lane” primarily produces SFA-TAGs mainly mediated by DGAT2D whose function is complemented by DGAT2A. And, the “polyunsaturated fatty acid (PUFA) TAG lane” primarily produces PUFA-TAGs via DGAT2C. In this study, we demonstrated the functional distribution pattern of four DGAT2s in oleaginous thraustochytrid Aurantiochytrium, and provided a promising target to rationally design TAG molecular with the desired characteristics.