Cellulosic Ethanol Production Through Cocultivation of Thermoanaerobacter brockii subsp. finnii DSM 3389 and Acetivibrio thermocellus JYT01

Consolidated bioprocessing integrates enzyme production, cellulose hydrolysis, and fermentation in a single reactor; however, few naturally occurring microorganisms combine efficient cellulose degradation, broad sugar utilization, inhibitor tolerance, and ethanol production. In this study, seven thermophilic ethanologenic strains were compared for sugar utilization, ethanol production, and tolerance to furfural, p-hydroxybenzoic acid, ethanol, formate, acetate, and lactate. Four strains showed sugar-to-ethanol conversion ratios above 32% in a glucose and xylose mixture. Among them, Thermoanaerobacter brockii subsp. finnii DSM 3389 showed the highest conversion ratio of 35.7% and retained growth and ethanol production in the presence of 20 mM furfural or 20 mM p-hydroxybenzoic acid. DSM 3389 also grew in the presence of approximately 2.5% (v/v) exogenous ethanol and in media containing 100 mM sodium formate, sodium acetate, or sodium lactate. The strain was subsequently cocultivated with Acetivibrio thermocellus JYT01 in a single preliminary 2 L pH-controlled fermentation containing 40 g/L Avicel. In this run, the ethanol concentration at 72 h was 10.86 g/L, corresponding to a mass-based cellulose-to-ethanol conversion ratio of 27.2% based on the initial Avicel concentration. These results demonstrate ethanol production by the DSM 3389–JYT01 coculture and support further evaluation of DSM 3389 as an ethanologenic partner for thermophilic cellulose conversion.