Enhanced Fatty Acid Production in Escherichia coli by Over-Expression of NADPH Generating Enzymes

Abstract

NADPH is an essential factor for Fatty Acid (FA) biosynthesis. The effect of NADPH generating enzymes [NADP⁺-dependent malic enzyme (NADP-ME), NADP⁺-dependent isocitrate dehydrogenase (NADP-IDH), Glucose 6-Phosphate Dehydrogenase (GPD) and 6-Phosphogluconate Dehydrogenase (PGD)] on FA biosynthesis was investigated in an engineered Escherichia coli BL21 △fadE/pTE. Among NADPH-generating enzymes, GPD and ICD increased total FA production by 60 and 16% respectively. Especially medium-chain FA production was increased up to 4.2 and 2.5 folds respectively. In addition, over-expression of the endogenous Thioesterase (TE) reduced Cyclopropane Fatty Acid (CFA) production by 40% and over-expressing of GPD and ICD further decreased CFA production by 23 and 30%, respectively compared to the TE over-expressed strain. Over-expression of TE appeared to be a good strategy to produce high quality biodiesel with medium-chain FAs as major Component (62%) and with Minimal Amount of CFA (4%). This study reveals that NADPH-generating enzyme GPD is associated with FA biosynthesis in E. coli, but not all reducing power generating enzymes, are involved in FA biosynthesis in bacteria.