Sunday, April 29, 2007

Fermentation of acid pretreated corn stover to ethanol without detoxification using Pichia stipitis

Frank Agbogbo, Frank Haagensen, and Kevin Wenger. Fuel Research & Development, Novozymes North America, 77 Perry Chapel Church Road, Franklinton, NC 27525

Economically feasible process for biomass conversion to ethanol requires the fermentation of the sugars generated in the pretreatment and hydrolysis steps. In agricultural residues and hardwoods, xylose constitutes about 45% of the total sugars and therefore xylose conversion to ethanol is important for high yields. Dilute acid hydrolysis of cellulosic biomass generates inhibitory compounds such as furfural, hydroxymethyl furfural, and acetic acid. These inhibitors affect the ability of yeasts to ferment the hydrolyzates and therefore a detoxification step is usually included in fermenting acid hydrolyzates. Detoxification may include the use of chemicals and may require additional process steps, which adds up to the total process costs.

 In this work, the effect of adaptation on P. stipitis fermentation using acid pretreated corn stover hydrolyzates without detoxification was examined. Two different types of adaptation were employed, liquid hydrolyzate and solid agar adaptation. Fermentation results were compared between the wild strains and the adapted strains.