Sunday, May 3, 2009
2-38
Metabolic engineering of a novel thermophilic ethanologen Geobacillus thermoglucosidasius M10EXG for enhanced ethanol production
Carol L. Kozina1, Ashtamurthy S. Pawate1, Dominique Joyner2, Ken L. Sale1, David S. Reichmuth1, Terry C. Hazen3, and Rajat Sapra4. (1) Sandia National Laboratories, 7011 East Ave., Livermore, CA 94550, (2) Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720, (3) Lawrence Berkeley National Laboratory in conjunction with Joint BioEnergy Institute, 1 Cyclotron Road, MS 70A-3317, Berkeley, CA 94720, (4) Sandia National Laboratories in conjunction with Joint BioEnergy Institute, 7011 East Avenue, Livermore, CA 94550
The thermophilic bacterium Geobacillus thermoglucosidasius (Gth) M10EXG is a facultative anaerobe that has an optimal growth temperature of 60 oC. It can metabolize both C5 (xylose) and C6 (glucose) sugars and is tolerant to 10% ethanol, making it an attractive candidate for industrial bioethanol production from lignocellulosic biomass. However, in order to maximize the production of ethanol from the fermentative pathway, it is essential to understand the fermentative metabolism, operational pathways, and the flux through the different fermentative pathways. We have completed a metabolic analysis of the growth of Gth M10EXG using both xylose and glucose under varying concentrations of oxygen. As expected, ethanol production is detected only under anaerobic conditions using either xylose or glucose as the sole carbon source. Furthermore, metabolic flux analysis of the anaerobic and aerobic growth using glucose as the sole carbon source shows that 0.6 mol lactate, 0.9 mol acetate, 0.4 mol ethanol, and 1.0 mol formate are produced per mole of glucose metabolized. With recent genome sequencing and metabolic flux analysis completed, we have targeted both lactate and formate production pathways for modification to increase ethanol production. We present results from the metabolic engineering of the aforementioned pathways and the effect on ethanol production.