Engineering microbial consortia capable of efficient ethanolic fermentation of cellulose is a strategy for
the development of consolidated bioprocessing for bioethanol production. Co-cultures of cellulolytic Clostridium
thermocellum with non-cellulolytic Thermoanaerobacter strains (X514 and 39E) significantly
improved ethanol production by 194–440%. Strain X514 enhanced ethanolic fermentation much more
effectively than strain 39E in co-cultivation, with ethanol production in X514 co-cultures at least 62%
higher than that of 39E co-cultures. Comparative genome sequence analysis revealed that the higher ethanolic
fermentation efficiency in strain X514 was associated with the presence of a complete vitamin B12
biosynthesis pathway, which is incomplete in strain 39E. The significance of the vitamin B12 de novo biosynthesis
capacity was further supported by the observation of improved ethanol production in strain
39E by 203% following the addition of exogenous vitamin B12. The vitamin B12 biosynthesis pathway provides
a valuable biomarker for selecting metabolically robust strains for bioethanol production