Location: Renewable Product Technology ResearchTitle: Automated UV-C mutagenesis of Kluyveromyces marxianus NRRL Y-1109 and selection for microaerophilic growth and ethanol production at elevated temperature on biomass sugars Author
|Cote, Gregory - Greg|
Submitted to: Journal of Laboratory Automation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2013
Publication Date: 3/18/2013
Publication URL: http://handle.nal.usda.gov/10113/61970
Citation: Hughes, S.R., Bang, S.S., Cox, E.J., Schoepke, A., Ochwat, K., Pinkelman, R., Nelson, D., Qureshi, N., Gibbons, W.R., Kurtzman, C.P., Bischoff, K.M., Liu, S., Cote, G.L., Rich, J.O., Jones, M.A., Cedeno, D., Doran-Peterson, J., Riano, N.M. 2013. Automated UV-C mutagenesis of Kluyveromyces marxianus NRRL Y-1109 and selection for microaerophilic growth and ethanol production at elevated temperature on biomass sugars. Journal of Laboratory Automation. 18(4):276-290. Interpretive Summary: More robust industrial yeast strains are needed for conversion of lignocellulosic materials to fuel ethanol. Two novel Kluyveromyces marxianus strains have been obtained by irradiation that are able to grow anaerobically at elevated temperatures on glucose, mannose, xylose, and arabinose. These strains grew with higher ethanol production at high temperature than a Saccharomyces cerevisiae yeast at low temperature fed glucose. These two mutant strains were also able to grow well on polymeric sugars, such as guar and pectin making them useful for ethanol production on a variety of agricultural waste streams.
Technical Abstract: The yeast Kluyveromyces marxianus is a potential microbial catalyst for producing ethanol from lignocellulosic substrates at elevated temperatures. To improve its growth and ethanol yield under anaerobic conditions, K. marxianus NRRL Y-1109 was irradiated with UV-C, and surviving cells were grown anaerobically on xylose or glucose for 5 months at 46°C. Two K. marxianus mutant strains that grew anaerobically at 46°C on glucose, galacturonic acid, pectin, and YM medium were isolated from the glucose plates. The mutant strains (designated 7-1 and 8-1) but not the wild-type strain grew aerobically on glucose at 47°C. Strains 7-1 and 8-1 also grew better than the wild-type strain on xylose and arabinose. In contrast, Saccharomyces cerevisiae NRRL Y-2403 did not grow at 46°C on any of these substrates. On glucose, both strains 7-1 and 8-1 gave higher ethanol yields after 3 days at 46°C than wild-type (0.56, 0.51, and 0.43 g ethanol/ g glucose, respectively). Similarly, on galacturonic acid, strains 7-1 and 8-1 gave higher ethanol yields after 7 days at 46°C than wild type (0.50, 0.36, and 0.35 g ethanol/ g galacturonic acid, respectively). Variable number tandem repeat analysis indicated mutations had occurred in the genomes of strains 7-1 and 8-1. The robust thermotolerant K. marxianus mutant strains resulting from this intense multigene mutagenesis strategy have potential application in industrial fuel ethanol production at elevated temperature from starch, sucrose, pectins, and cellulosic biomass.