Wu Hui, Karanjikar Mukund, San Ka-Yiu
Department of Bioengineering, Rice University, Houston, TX, USA.
Technology Holding, Salt Lake City, UT, USA.
Metab Eng. 2014 Sep;25:82-91. doi: 10.1016/j.ymben.2014.06.009. Epub 2014 Jul 8.
Crude glycerol, generated as waste by-product in biodiesel production process, has been considered as an important carbon source for converting to value-added bioproducts recently. Free fatty acids (FFAs) can be used as precursors for the production of biofuels or biochemicals. Microbial biosynthesis of FFAs can be achieved by introducing an acyl-acyl carrier protein thioesterase into Escherichia coli. In this study, the effect of metabolic manipulation of FFAs synthesis cycle, host genetic background and cofactor engineering on FFAs production using glycerol as feed stocks was investigated. The highest concentration of FFAs produced by the engineered stain reached 4.82g/L with the yield of 29.55% (g FFAs/g glycerol), about 83% of the maximum theoretical pathway value by the type II fatty acid synthesis pathway. In addition, crude glycerol from biodiesel plant was also used as feedstock in this study. The FFA production was 3.53g/L with a yield of 24.13%. The yield dropped slightly when crude glycerol was used as a carbon source instead of pure glycerol, while it still can reach about 68% of the maximum theoretical pathway yield.
粗甘油是生物柴油生产过程中产生的废弃副产物，近来被视作一种用于转化为高附加值生物产品的重要碳源。游离脂肪酸（FFAs）可用作生物燃料或生物化学品生产的前体。通过将酰基-酰基载体蛋白硫酯酶导入大肠杆菌，可实现FFAs的微生物生物合成。在本研究中，考察了FFAs合成循环的代谢调控、宿主遗传背景及辅因子工程对以甘油为原料生产FFAs的影响。工程菌株产生的最高FFAs浓度达到4.82g/L，产率为29.55%（g FFAs/g甘油），约为II型脂肪酸合成途径最大理论途径值的83%。此外，本研究还使用生物柴油厂的粗甘油作为原料。FFAs产量为3.53g/L时，产率为24.13%。当使用粗甘油而非纯甘油作为碳源时，产率略有下降，但仍可达到最大理论途径产率的约68%。
