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.
Highlights
To meet the increasing fuel demand and to provide an alternative source to the limited fossil fuel supply, the development of renewable energy has become increasingly urgent
To construct the strains with over expressed reducing power generating enzyme and a Fatty Acid (FA) metabolic sink, the E. coli BL21 △fadE competent cells were co-transformed by pTE with each of the plasmids designated YS2YS5 respectively (Table 2)
The pET28a and pTE plasmids were co-transformed into E. coli BL21 △fadE competent cells and the resulting strain was used as a control (YS1)
Summary
To meet the increasing fuel demand and to provide an alternative source to the limited fossil fuel supply, the development of renewable energy has become increasingly urgent. Biodiesel such as Fatty Acid Ethyl Ester (FAEE) and Fatty Acid Methyl Ester (FAME), which has high energy density and low water solubility (Bharathiraja et al, 2017), is rapidly moving toward the mainstream of alternative energy sources of fossil diesel. Biodiesel is usually derived from animal fats or plant oils (triacylglycerides, TAGs), which is accompanied by high cost and inadequate supply. This limited the development of biodiesel production. Escherichia coli has become an alternative Fatty Acid (FA) producer because it possesses several attractive advantages such as a known genomic sequence, available genetic tools and a rapid growth rate
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