Previous work has demonstrated the feasibility of in vivo biodiesel synthesis in Escherichia coli, however, ethyl ester formation was dependent on an external fatty acid feedstock. In contrast to E. coli, actinomycetes may be ideal organisms for direct biodiesel synthesis because of their capacity to synthesize high levels of triacylglcerides (TAGs). In this study, we investigated the physiology and associated TAG accumulation along with the in vivo ability to catalyze ester formation from exogenous short chain alcohol sources in Gordonia sp. KTR9, a strain that possesses a large number of genes dedicated to fatty acid and lipid biosynthesis. Total lipid fatty acids content increased by 75 % and TAG content increased by 50 % under nitrogen starvation conditions in strain KTR9. Strain KTR9 tolerated the exogenous addition of up to 4 % methanol, 4 % ethanol and 2 % propanol in the media. Increasing alcohol concentrations resulted in a decrease in the degree of saturation of recovered fatty acid alcohol esters and a slight increase in the fatty acid chain length. A linear dose dependency in fatty alcohol ester synthesis was observed in the presence of 0.5-2 % methanol and ethanol compared to control KTR9 strains grown in the absence of alcohols. An inspection of the KTR9 genome revealed the presence of several putative wax ester synthase/acyl-coenzyme A : diacylglycerol acyltransferase (WS/DGAT) enzymes, encoded by atf gene homologs, that may catalyze the in vivo synthesis of fatty acid esters from short chain alcohols. Collectively, these results indicate that Gordonia sp. KTR9 may be a suitable actinomycete host strain for in vivo biodiesel synthesis.

译文

:先前的工作证明了在大肠杆菌中体内生物柴油合成的可行性,但是,乙酯的形成取决于外部脂肪酸原料。与大肠杆菌相反,放线菌可能是直接生物柴油合成的理想生物,因为它们能够合成高含量的三酰基甘油(TAGs)。在这项研究中,我们调查了生理和相关的TAG积累以及体内催化Gordonia sp。中外源短链醇源形成酯的能力。 KTR9,具有大量致力于脂肪酸和脂质生物合成的基因的菌株。在氮饥饿条件下,菌株KTR9的总脂质脂肪酸含量增加了75%,TAG含量增加了50%。菌株KTR9耐受培养基中外源添加多达4%的甲醇,4%的乙醇和2%的丙醇。醇浓度的增加导致回收的脂肪酸醇酯的饱和度降低,并且脂肪酸链长度略微增加。与在不存在醇的情况下生长的对照KTR9菌株相比,在存在0.5-2%的甲醇和乙醇的条件下观察到脂肪醇酯合成的线性剂量依赖性。对KTR9基因组的检查发现存在一些推定的蜡酯合酶/酰基辅酶A:二酰基甘油酰基转移酶(WS / DGAT)酶,这些酶由atf基因同源物编码,可能催化体内短链脂肪酸酯的合成酒精。总的来说,这些结果表明Gordonia sp。 KTR9可能是适合体内生物柴油合成的放线菌宿主菌株。

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