Biosynthesis of the fatty acid isopropyl esters by engineered Escherichia coli

The fatty acid methyl esters and fatty acid ethyl esters are known as biodiesels which are considered to be renewable, nontoxic and biodegradable biofuels. However, the conventional biodiesels show a high crystallization temperature which is one of the most critical obstacles against the widespread biodiesel usage. The high crystallization temperature of biodiesel can be reduced by replacing the methyl or ethyl ester with an isopropyl moiety. Here we report on a strategy to establish biosynthesis of the fatty acid isopropyl esters(FAIPEs) from the simple substrate glucose in Escherichia coli with heterologous coexpression of atoB encoded acetyl-CoA acetyltransferase and atoAD encode acetoacetyl-CoA transferase from E. coli, ADC encode acetoacetate decarboxylase from Clostridium acetobutylicum, ADH encoded NADP-dependent alcohol dehydrogenase from Clostridium beijerinckii, 'TesA encoded a truncated fatty acyl-ACP thioesterase and FadD encoded fatty acyl-CoA synthetase from E. coli, and the WS/DGAT encoded acyltransferase from Acinetobacter baylyi strain ADP1. It was found that the yield of FAIPEs was up to 203.4mg/L and accounted for around 6.4% (wt/wt) of the dry cell weight. Our results indicates that it is a feasible strategy to improve the yield of FAIPEs by increasing fatty acyl-CoA availability in biosynthetic pathway and exhibit a promising method for production of biodiesels with good low-temperature flow properties.