Abstract
Two new derivatives of Zymomonas mobilis CP4 were isolated from enrichment cultures after 18 months of serial transfers. These new strains were selected for the ability to grow and produce ethanol rapidly on transfer into fresh broth containing ethanol and allyl alcohol. Ethanol production by these strains was examined in batch fermentations under three sets of conditions. Both new derivatives were found to be superior to the parent strain CP4 with respect to the speed and completeness of glucose conversion to ethanol. The best of these, strain YO2, produced 9.5% ethanol (by weight; 11.9% by volume) after 17.4 h compared with 31.8 h for the parent strain CP4. The addition of 1 mM magnesium sulfate improved ethanol production in all three strains. Two factors contributed to the decrease in fermentation time required by the mutants: more rapid growth with minimal lag on subculturing and the retention of higher rates of ethanol production as fermentation proceeded. Alcohol dehydrogenase isozymes were altered in both new strains and no longer catalyzed the oxidation of allyl alcohol into the toxic product acrolein. This loss of allyl alcohol-oxidizing capacity is proposed as a primary factor contributing to increased allyl alcohol resistance, although it is likely that other mutations affecting glycolysis also contribute to the improvement in ethanol production.
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- Fowler P. W., Ball A. J., Griffiths D. E. The control of alcohol dehydrogenase isozyme synthesis in Saccharomyces cerevisiae. Can J Biochem. 1972 Jan;50(1):35–43. doi: 10.1139/o72-007. [DOI] [PubMed] [Google Scholar]
- Ingram L. O., Buttke T. M. Effects of alcohols on micro-organisms. Adv Microb Physiol. 1984;25:253–300. doi: 10.1016/s0065-2911(08)60294-5. [DOI] [PubMed] [Google Scholar]
- Karp M. T., Raunio R. P., Lövgren T. N. Simultaneous extraction and combined bioluminescent assay of NAD+ and NADH. Anal Biochem. 1983 Jan;128(1):175–180. doi: 10.1016/0003-2697(83)90359-7. [DOI] [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Neale A. D., Scopes R. K., Kelly J. M., Wettenhall R. E. The two alcohol dehydrogenases of Zymomonas mobilis. Purification by differential dye ligand chromatography, molecular characterisation and physiological roles. Eur J Biochem. 1986 Jan 2;154(1):119–124. doi: 10.1111/j.1432-1033.1986.tb09366.x. [DOI] [PubMed] [Google Scholar]
- Osman Y. A., Ingram L. O. Mechanism of ethanol inhibition of fermentation in Zymomonas mobilis CP4. J Bacteriol. 1985 Oct;164(1):173–180. doi: 10.1128/jb.164.1.173-180.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Williamson V. M., Bennetzen J., Young E. T., Nasmyth K., Hall B. D. Isolation of the structural gene for alcohol dehydrogenase by genetic complementation in yeast. Nature. 1980 Jan 10;283(5743):214–216. doi: 10.1038/283214a0. [DOI] [PubMed] [Google Scholar]
- Wills C., Kratofil P., Londo D., Martin T. Characterization of the two alcohol dehydrogenases of Zymomonas mobilis. Arch Biochem Biophys. 1981 Sep;210(2):775–785. doi: 10.1016/0003-9861(81)90245-9. [DOI] [PubMed] [Google Scholar]
- Wills C., Kratofil P., Martin T. Functional mutants of yeast alcohol dehydrogenase. Basic Life Sci. 1982;19:305–329. doi: 10.1007/978-1-4684-4142-0_24. [DOI] [PubMed] [Google Scholar]
- Wills C., Phelps J. Functional mutants of yeast alcohol dehydrogenase affecting kinetics, cellular redox balance, and electrophoretic mobility. Biochem Genet. 1978 Jun;16(5-6):415–432. doi: 10.1007/BF00484208. [DOI] [PubMed] [Google Scholar]
- Wills C. Production of yeast alcohol dehydrogenase isoenzymes by selection. Nature. 1976 May 6;261(5555):26–29. doi: 10.1038/261026a0. [DOI] [PubMed] [Google Scholar]