Low Cost Medium for Ethanol Production Using Novel Moderately Alkaliphilic Alkalibaculum bacchi CP15

Cellulosic ethanol can be made through fermentation of syngas (CO, H2 and CO2) produced from gasifying biomass. The use of low cost medium is critical to improve the feasibility of syngas fermentation. Alkalibaculum bacchi CP15 was found to be the most promising among three strains discovered recently in our laboratories for ethanol production. To reduce the cost of production medium, yeast extract (YE), minerals and vitamins were replaced with corn steep liquor (CSL). In addition, N-[Tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS) buffer previously identified as being important for a better pH control during growth phase, was removed. Syngas fermentation was conducted with CP15 in 250-mL fermentation bottles with 20% CO, 15% CO2, 5% H2 and 60% N2 gas mixture. Treatments containing YE and various concentrations of CSL were investigated. The results showed that CP15 produced two times more ethanol using CSL than in the YE medium. In addition, over 94% of the medium cost was eliminated by replacing YE with CSL and elimination of TAPS. These results showed that using CSL enables the removal of TAPS, YE, minerals and vitamins.