Production of 1, 3- medium chain-2-long chain (MLM) triacylglycerols by metabolically engineered Escherichia coli

Abstract

As an ideal diet food and clinical nutrient, 1, 3- medium chain-2-long chain triacylglycerols (MLM-TAGs) are currently synthesized by enzymatic catalysis. However, high processing cost constrains the widespread use of MLM-TAGs. In this study, we proposed a novel approach for MLM-TAGs production by engineered Escherichia coli. Medium-chain fatty acids (MCFAs, C6-C14) were first synthesized by expressing UcFatB and the titer of MCFAs reached 114 mg/L in flask culture. Co-expression of RnACSM4 and UcFatB further augmented the synthesis of MCFAs and raised MCFAs titer up to 201 mg/L. Incremental introduction of CnGPAT9, AtPAP2 and CnDGAT1 made the recombinant successfully produce MLM-TAGs with a content of 7.15% (wt). Under the optimized conditions, a highest MLM-TAGs content of 20.31% (wt) was finally obtained in a 5-L bioreactor, which is an 88-fold increase over the original strain. These findings demonstrate the feasibility of using acyltransferases to alter the stereochemical composition of TAGs and provide a novel alternative for sustainable production of MLM-TAGs.