Analysis of Metabolic Pathways and Fluxes in a Newly Discovered Thermophilic and Ethanol-Tolerant Geobacillus Strain
A recently discovered thermophilic bacterium, Geobacillus thermoglucosidasius M10EXG, ferments a range of C5 (e.g., xylose) and C6 sugars (e.g., glucose) and istolerant to high ethanol concentrations (10percent, v/v). We have investigated the central metabolism of this bacterium using both in vitro enzyme assays and 13C-based flux analysis to provide insights into the physiological properties of this extremophile and explore its metabolism for bio-ethanol or other bioprocess applications. Our findings show that glucose metabolism in G. thermoglucosidasius M10EXG proceeds via glycolysis, the pentose phosphate pathway, and the TCA cycle; the Entner?Doudoroff pathway and transhydrogenase activity were not detected. Anaplerotic reactions (including the glyoxylate shunt, pyruvate carboxylase, and phosphoenolpyruvate carboxykinase) were active, but fluxes through those pathways could not be accuratelydetermined using amino acid labeling. When growth conditions were switched from aerobic to micro-aerobic conditions, fluxes (based on a normalized glucose uptake rate of 100 units (g DCW)-1 h-1) through the TCA cycle and oxidative pentose phosphate pathway were reduced from 64+-3 to 25+-2 and from 30+-2 to 19+-2, respectively. The carbon flux under micro-aerobic growth was directed formate. Under fully anerobic conditions, G. thermoglucosidasius M10EXG used a mixed acid fermentation process and exhibited a maximum ethanol yield of 0.38+-0.07 mol mol-1 glucose. In silico flux balance modeling demonstrates that lactate and acetate production from G. thermoglucosidasius M10EXG reduces the maximum ethanol yieldby approximately threefold, thus indicating that both pathways should be modified to maximize ethanol production.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Physical Biosciences Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 948038
- Report Number(s):
- LBNL-1442E; BIBIAU; TRN: US200905%%137
- Journal Information:
- Biotechnology and Bioengineering, Journal Name: Biotechnology and Bioengineering; ISSN 0006-3592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACETATES
AMINO ACIDS
ANAEROBIC CONDITIONS
BIOLOGICAL PATHWAYS
CARBON
CARBOXYLASE
ENZYMES
ETHANOL
FERMENTATION
GLUCOSE
GLYCOLYSIS
IN VITRO
LACTATES
METABOLISM
PENTOSES
PHOSPHATES
PHOSPHOENOLPYRUVATE
SACCHARIDES
SILICA
STRAINS
XYLOSE
C5 sugar
micro-aerobic
TCA cycle
anaplerotic pathway
flux balance model