IMPROVING BIOCHEMICAL PROCESSES FOR THE PRODUCTION OF SUSTAINABLE FUELS AND CHEMICALS
Location: Renewable Product Technology Research Unit
Title: Evaluation of Engineered Pichia stipitis Strains for Ethanol Production
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 2, 2010
Publication Date: October 2, 2010
Citation: Gibbons, J.L., Geiger, W.R., Gibbons, W.R., Hughes, S.R. 2010. Evaluation of Engineered Pichia stipitis Strains for Ethanol Production [abstract]. American Society for Microbiology. Abstract #35. p. 4.
We evaluated the fermentation capabilities of five strains of Pichia stipitis that had been engineered for xylose fermentation to ethanol by USDA, ARS, National Center for Agricultural Utilization Research. The strains tested were P. stipitis WT-1-11, WT-1-2, 14-2-6, 22-1-1, and 22-1-12. Strains were incubated under both facultative and anaerobic conditions to evaluate ethanol production on glucose, xylose, cellobiose, and a combination of all three sugars. The total sugar concentration was 50 g/L, and the medium also included 5 g/L yeast extract. The strains performed significantly better under facultative compared to anaerobic conditions. As expected, glucose was the most readily fermented sugar with complete utilization under facultative conditions, but only 8 g/L used anaerobically. Xylose utilization was only 10 g/L under facultative conditions, and only 7 g/L anaerobically. Cellobiose was the least fermented sugar, with only 5-7 g/L used under either condition. Similar sugar utilization trends occurred in the sugar mixtures. Under facultative conditions strain WT-1-2 yielded 19.1 g/L ethanol on glucose and 0.9 g/L on cellobiose, but strain 14-2-6 performed best on xylose (3.3 g/L ethanol) and the sugar combination (8.0 g/L ethanol). Ethanol titers under anaerobic conditions ranged from 0.7 g/L on cellobiose to 4.5 g/L on the sugar combination (strain WT-1-2). Future trials will evaluate addition of specific nutrients to boost xylose fermentation.