Abstract
To prevent the loss of raw material in ethanol production by anaerobic yeast cultures, glycerol formation has to be reduced. In theory, this may be done by providing the yeast with amino acids, since the de novo cell synthesis of amino acids from glucose and ammonia gives rise to a surplus of NADH, which has to be reoxidized by the formation of glycerol. An industrial strain of Saccharomyces cerevisiae was cultivated in batch cultures with different nitrogen sources, i.e., ammonium salt, glutamic acid, and a mixture of amino acids, with 20 g of glucose per liter as the carbon and energy source. The effects of the nitrogen source on metabolite formation, growth, and cell composition were measured. The glycerol yields obtained with glutamic acid (0.17 mol/mol of glucose) or with the mixture of amino acids (0.10 mol/mol) as a nitrogen source were clearly lower than those for ammonium-grown cultures (0.21 mol/mol). In addition, the ethanol yield increased for growth on both glutamic acid (by 9%) and the mixture of amino acids (by 14%). Glutamic acid has a large influence on the formation of products; the production of, for example, alpha-ketoglutaric acid, succinic acid, and acetic acid, increased compared with their production with the other nitrogen sources. Cultures grown on amino acids have a higher specific growth rate (0.52 h-1) than cultures of both ammonium-grown (0.45 h-1) and glutamic acid-grown (0.33 h-1) cells. Although the product yields differed, similar compositions of the cells were attained. The NADH produced in the amino acid, RNA, and extracellular metabolite syntheses was calculated together with the corresponding glycerol formation. The lower-range values of the theoretically calculated yields of glycerol were in good agreement with the experimental yields, which may indicate that the regulation of metabolism succeeds in the most efficient balancing of the redox potential.
Full Text
The Full Text of this article is available as a PDF (289.7 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Blomberg A., Adler L. Physiology of osmotolerance in fungi. Adv Microb Physiol. 1992;33:145–212. doi: 10.1016/s0065-2911(08)60217-9. [DOI] [PubMed] [Google Scholar]
- Casey G. P., Ingledew W. M. Ethanol tolerance in yeasts. Crit Rev Microbiol. 1986;13(3):219–280. doi: 10.3109/10408418609108739. [DOI] [PubMed] [Google Scholar]
- Horák J. Amino acid transport in eucaryotic microorganisms. Biochim Biophys Acta. 1986 Dec 22;864(3-4):223–256. doi: 10.1016/0304-4157(86)90001-8. [DOI] [PubMed] [Google Scholar]
- Lagunas R., Gancedo J. M. Reduced pyridine-nucleotides balance in glucose-growing Saccharomyces cerevisiae. Eur J Biochem. 1973 Aug 1;37(1):90–94. doi: 10.1111/j.1432-1033.1973.tb02961.x. [DOI] [PubMed] [Google Scholar]
- MOORE S., STEIN W. H. A modified ninhydrin reagent for the photometric determination of amino acids and related compounds. J Biol Chem. 1954 Dec;211(2):907–913. [PubMed] [Google Scholar]
- Peña A., Pardo J. P., Ramírez J. Early metabolic effects and mechanism of ammonium transport in yeast. Arch Biochem Biophys. 1987 Mar;253(2):431–438. doi: 10.1016/0003-9861(87)90196-2. [DOI] [PubMed] [Google Scholar]
- Schulze U., Larsen M. E., Villadsen J. Determination of intracellular trehalose and glycogen in Saccharomyces cerevisiae. Anal Biochem. 1995 Jun 10;228(1):143–149. doi: 10.1006/abio.1995.1325. [DOI] [PubMed] [Google Scholar]
- Thomas K. C., Ingledew W. M. Fuel alcohol production: effects of free amino nitrogen on fermentation of very-high-gravity wheat mashes. Appl Environ Microbiol. 1990 Jul;56(7):2046–2050. doi: 10.1128/aem.56.7.2046-2050.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Thomas K. C., Ingledew W. M. Relationship of low lysine and high arginine concentrations to efficient ethanolic fermentation of wheat mash. Can J Microbiol. 1992 Jul;38(7):626–634. doi: 10.1139/m92-103. [DOI] [PubMed] [Google Scholar]
- Verduyn C., Postma E., Scheffers W. A., van Dijken J. P. Physiology of Saccharomyces cerevisiae in anaerobic glucose-limited chemostat cultures. J Gen Microbiol. 1990 Mar;136(3):395–403. doi: 10.1099/00221287-136-3-395. [DOI] [PubMed] [Google Scholar]
- Verduyn C., Stouthamer A. H., Scheffers W. A., van Dijken J. P. A theoretical evaluation of growth yields of yeasts. Antonie Van Leeuwenhoek. 1991 Jan;59(1):49–63. doi: 10.1007/BF00582119. [DOI] [PubMed] [Google Scholar]
- Watson T. G. Amino-acid pool composition of Saccharomyces cerevisiae as a function of growth rate and amino-acid nitrogen source. J Gen Microbiol. 1976 Oct;96(2):263–268. doi: 10.1099/00221287-96-2-263. [DOI] [PubMed] [Google Scholar]
- Wiame J. M., Grenson M., Arst H. N., Jr Nitrogen catabolite repression in yeasts and filamentous fungi. Adv Microb Physiol. 1985;26:1–88. doi: 10.1016/s0065-2911(08)60394-x. [DOI] [PubMed] [Google Scholar]
- van der Rest M. E., Kamminga A. H., Nakano A., Anraku Y., Poolman B., Konings W. N. The plasma membrane of Saccharomyces cerevisiae: structure, function, and biogenesis. Microbiol Rev. 1995 Jun;59(2):304–322. doi: 10.1128/mr.59.2.304-322.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]