Genomic and metabolic insights into solvent production by Thermoanaerobacterium thermosaccharolyticum GSU5

Abstract

Thermoanaerobacterium thermosaccharolyticum GSU5 was isolated from animal dung collected in a pasture plain in Buenos Aires, Argentina. This thermophilic and anaerobic microorganism was able to produce butanol and ethanol, but not acetone, using sugars such as xylose, arabinose, glucose, galactose, fructose, sucrose, and cellobiose. Key metabolic enzymes leading to solvent production were identified in its genome. A detailed analysis of the solvent and organic acid biosynthetic pathway genes of sequenced strains revealed new insights into the unique metabolic features of this species. Genes required for the synthesis of acetone are absent in the genomes of all sequenced Thermoanaerobacterium, suggesting that it is a general trait of the genus. Strains able to produce butanol synthesize butyrate through the one step pathway catalyzed by the butyryl-CoA:acetate-CoA transferase (But). The large range of fermentable substrates and the ability to produce both ethanol and butanol without acetone makes this species an interesting candidate for second generation biofuel production.