Yuan Jifeng, Mishra Pranjul, Ching Chi Bun
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore; Temasek Laboratories, National University of Singapore, T-Lab Building 5A, Singapore 117411, Singapore; Present address: Biotransformation Innovation Platform, Agency for Science, Technology and Research (A*STAR), Singapore 138673, Singapore.
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585, Singapore.
J Biotechnol. 2016 Dec 10;239:90-97. doi: 10.1016/j.jbiotec.2016.10.013. Epub 2016 Oct 13.
Medium branched-chain esters can be used not only as a biofuel but are also useful chemicals with various industrial applications. The development of economically feasible and environment friendly bio-based fuels requires efficient cell factories capable of producing desired products in high yield. Herein, we sought to use a number of strategies to engineer Saccharomyces cerevisiae for high-level production of branched-chain esters. Mitochondrion-based expression of ATF1 gene in a base strain with an overexpressed valine biosynthetic pathway together with expression of mitochondrion-relocalized α-ketoacid decarboxylase (encoded by ARO10) and alcohol dehydrogenase (encoded by ADH7) not only produced isobutyl acetate, but also 3-methyl-1-butyl acetate and 2-methyl-1-butyl acetate. Further segmentation of the downstream esterification step into the cytosol to utilize the cytosolic acetyl-CoA pool for acetyltransferase (ATF)-mediated condensation enabled an additional fold improvement of ester productions. The best titre attained in the present study is 260.2mg/L isobutyl acetate, 296.1mg/L 3-methyl-1-butyl acetate and 289.6mg/L 2-methyl-1-butyl acetate.
中等支链酯不仅可以用作生物燃料，还是具有各种工业应用的有用化学品。开发经济可行且环境友好的生物基燃料需要能够高产所需产品的高效细胞工厂。在此，我们试图采用多种策略对酿酒酵母进行工程改造，以实现支链酯的高水平生产。在具有过表达缬氨酸生物合成途径的基础菌株中基于线粒体表达ATF1基因，同时表达线粒体重新定位的α-酮酸脱羧酶（由ARO10编码）和醇脱氢酶（由ADH7编码），不仅产生了乙酸异丁酯，还产生了乙酸3-甲基-1-丁酯和乙酸2-甲基-1-丁酯。将下游酯化步骤进一步分割到细胞质中，以利用细胞质中的乙酰辅酶A库进行乙酰转移酶（ATF）介导的缩合反应，能够使酯产量再提高一倍。本研究中获得的最佳产量为乙酸异丁酯260.2mg/L、乙酸3-甲基-1-丁酯296.1mg/L和乙酸2-甲基-1-丁酯289.6mg/L。
