Second-generation ethanol from sugarcane and sweet sorghum bagasses using the yeast Dekkera bruxellensis

• Sugarcane (SCB) and sweet sorghum (SSB) bagasses were analysed and compared.
• SSB contained less lignin than SCB and released more sugars upon hydrolysis.
• Dekkera bruxellensis GDB248 produced ethanol at 0.42–0.44 g/g for both substrates.
• Cellobiose and glucose were co-consumed by the yeast cells, but not xylose.
• A yeast consortium was proposed for second generation ethanol production.

In previous work we showed that the yeast Dekkera bruxellensis (strain GDB 248) is capable of assimilating cellobiose and converting this sugar to ethanol, a characteristic that may help in reducing the cost of biomass hydrolysis with commercial enzyme. In the present work we tested the efficiency of ethanol production by this yeast from bagasse of sugarcane (SCB) and sweet sorghum (SSB) after alkaline H2O2 pretreatment and enzymatic hydrolysis treatment. SSB contained less lignin and ashes and more waxes than SCB, resulting in more efficient pretreatment and enzyme hydrolysis, as evidenced by chemical and physical analysis. Glucose and cellobiose were released from cellulose, as well as xylose from the remaining hemicellulose. The hexoses were completely consumed with final yields of 0.42 (±0.04) g/g for SCB and 0.44 (±0.03) g/g for SSB. Acetate was not produced, which indicated that the fermentations were carried out under anaerobic condition. This yeast was capable of metabolising cellobiose for ethanol production, which therefore proves to be a promising industrial microorganism for the production of second-generation ethanol.