Fermentation of crystalline cellulose to ethanol by Klebsiella oxytoca containing chromosomally integrated zymomonas mobilis genes
- Univ. of Florida, Gainesville, FL (United States)
Complete enzymatic hydrolysis of cellulose to glucose is generally required for efficient fermentation to ethanol. This hydrolysis requires endoglucanase, exoglucanase, and cellobiase. The Gram-negative bacterium, Klebsiella oxytoca, contains the native ability to transport and metabolize cellobiose, minimizing the need for extracellular cellobiase. Strain P2 is a recombinant derivative in which the Zymomonas mobilis pdc and adhB genes have been integrated into the chromosome and expressed, directing the metabolism of pyruvate to ethanol. This organism has been evaluated in simultaneous saccharification and fermentation (SSF) experiments to determine optimal conditions and limits of performance. The temperature was varied between 32 and 40{degree}C over a pH range of 5.0-5.8 with 100 g/L crystalline cellulose (Sigmacell 50, Sigma Chemical Company, St. Louis, MO) as the substrate and commercial cellulase (Spezyme CE, South San Francisco, CA). A broad optimum for SSF was observed, with a pH of 5.2-5.5 and temperatures of 32-35{degree}C, which allowed the production of over 44 g of ethanol/L (81-86% of the maximum theoretical yield). Although the rate of ethanol production increased with cellulase, diminishing improvements were observed at enzyme loadings above 10 filter paper units/g of cellulose. 34 refs., 5 figs., 2 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 174271
- Journal Information:
- Biotechnology Progress, Vol. 9, Issue 5; Other Information: PBD: Sep-Oct 1993
- Country of Publication:
- United States
- Language:
- English
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