(390g) Effect of Surfactants On Lignin Toxicity in One-Step Ethanol Production

One-step ethanol production involves the use of an ethanologenic microorganism that can produce different cellulases (a whole-cell biocatalyst) on the cell surface to convert the cellulose to sugar, and at the same time convert the pentose and hexose sugars to ethanol. In previous work by the group, Escherichia coli LY01 was used as a host for expressing cellulase genes from Clostridium cellulolyticum. We have successfully produced ethanol from the solid fraction of acid pretreated corn stover at low substrate loading in flask cultures. Commercial viability of the process would require scale-up of this process. The scale-up of such a system would require an understanding of transport phenomena in the heterogeneous hydrolysis of cellulose by cell surface cellulases. The hydrolysis of cellulose proceeds by the interaction of the cell surface enzymes and the cellulose particle. Surface area plays a key role in rate of hydrolysis. Lignin is hypothesized to reduce the hydrolysis rate by physical blockage, and non-productive enzyme binding. In one-step ethanol production, lignin may prove toxic to cells. There is evidence that surfactants may provide beneficial protection against lignin inhibition. This presentation will discuss these issues giving quantitative results on scale-up, specific ethanol production rate, specific growth rate, and surfactant concentration effects on growth rates at various shear rates.