Title: Evaluation of UV-C mutagenized Scheffersomyces stipitis strains for ethanol production Authors
|Geiger, Melanie -|
|Gibbons, Jaimie -|
|West, Thomas -|
|Gibbons, William -|
Submitted to: Journal of Laboratory Automation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2012
Publication Date: August 10, 2012
Citation: Geiger, M., Gibbons, J., West, T., Hughes, S.R., Gibbons, W. 2012. Evaluation of UV-C mutagenized Scheffersomyces stipitis strains for ethanol production. Journal of Laboratory Automation. 17(6):417-424. Interpretive Summary: Yeast strains for anaerobic conversion of five- and six-carbon sugars to ethanol were produced from Scheffersomyces (formerly Pichia) stipitis NRRL Y-7124 using UV-C irradiation to produce mutations in the genome and generate unique strains of Scheffersomyces stipitis (WT-2-1, WT-1-11, 14-2-6, 22-1-1, and 22-1-12). They were incubated under conditions with and without oxygen to evaluate ethanol production on glucose, xylose, cellobiose, and a combination of all three sugars. These new strains have potential application in industrial high-yield fuel ethanol production from plant biomass.
Technical Abstract: We evaluated fermentation capabilities of five strains of Scheffersomyces stipitis (WT-2-1, WT-1-11, 14-2-6, 22-1-1, and 22-1-12) that had been produced by UV-C mutagenesis and selection for improved xylose fermentation to ethanol using an integrated automated robotic work cell. They were incubated under both facultative and anaerobic conditions to evaluate ethanol production on glucose, xylose, cellobiose, and a combination of all three sugars. The medium contained 50 g/L total sugar and 5 g/L yeast extract. The strains performed significantly better under facultative compared with anaerobic conditions. As expected, glucose was the most readily fermented sugar with ~100% fermentation efficiency (FE)under facultative conditions but only 5% to 16% FE anaerobically. Xylose utilization was 20% to 40% FE under facultative conditions but 9% to 25% FE anaerobically. Cellobiose was the least fermented sugar, at 18% to 27% FE facultatively and 8% to 11% anaerobically. Similar trends occurred in the sugar mixture. Under facultative conditions, strain 22-1-12 produced 19.6 g/L ethanol on glucose, but strain 14-2-6 performed best on xylose (4.5 g/L ethanol) and the sugar combination (8.0 g/L ethanol). Ethanol titers from glucose under anaerobic conditions were again highest with strain 22-1-12, but none of the strains produced ethanol from xylose. Future trials will evaluate nutrient addition to boost microaerophilic xylose fermentation.