Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
Thayer School of Engineering, Dartmouth College, Hanover, NH 03755, USA; Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
Metab Eng. 2017 Jul;42:175-184. doi: 10.1016/j.ymben.2017.06.011. Epub 2017 Jun 27.
Clostridium thermocellum ferments cellulose, is a promising candidate for ethanol production from cellulosic biomass, and has been the focus of studies aimed at improving ethanol yield. Thermoanaerobacterium saccharolyticum ferments hemicellulose, but not cellulose, and has been engineered to produce ethanol at high yield and titer. Recent research has led to the identification of four genes in T. saccharolyticum involved in ethanol production: adhE, nfnA, nfnB and adhA. We introduced these genes into C. thermocellum and observed significant improvements to ethanol yield, titer, and productivity. The four genes alone, however, were insufficient to achieve in C. thermocellum the ethanol yields and titers observed in engineered T. saccharolyticum strains, even when combined with gene deletions targeting hydrogen production. This suggests that other parts of T. saccharolyticum metabolism may also be necessary to reproduce the high ethanol yield and titer phenotype in C. thermocellum.
热纤梭菌能够发酵纤维素，是一种很有前途的从纤维素生物质生产乙醇的候选生物，并且一直是旨在提高乙醇产率的研究的重点。产酸热丝菌能够发酵半纤维素，但不能发酵纤维素，并且已经被工程化改造以高产率和高浓度生产乙醇。最近的研究确定了产酸热丝菌中与乙醇生产有关的四个基因：adhE、nfnA、nfnB 和 adhA。我们将这些基因引入热纤梭菌中，观察到乙醇产率、浓度和生产效率有了显著提高。然而，仅这四个基因本身不足以实现在热纤梭菌中达到与工程化产酸热丝菌菌株中相同的乙醇产率和浓度，即使与针对氢气生成的基因缺失相结合也是如此。这表明产酸热丝菌代谢的其他部分可能也有必要在热纤梭菌中重现高乙醇产率和浓度表型。
