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Applied and Environmental Microbiology, April 2002, p. 1616-1623, Vol. 68, No. 4
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.4.1616-1623.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Influence of Medium Buffering Capacity on Inhibition of Saccharomyces cerevisiae Growth by Acetic and Lactic Acids

K. C. Thomas, S. H. Hynes, and W. M. Ingledew*

Department of Applied Microbiology and Food Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5A8

Received 6 July 2001/ Accepted 10 January 2002

Acetic acid (167 mM) and lactic acid (548 mM) completely inhibited growth of Saccharomyces cerevisiae both in minimal medium and in media which contained supplements, such as yeast extract, corn steep powder, or a mixture of amino acids. However, the yeast grew when the pH of the medium containing acetic acid or lactic acid was adjusted to 4.5, even though the medium still contained the undissociated form of either acid at a concentration of 102 mM. The results indicated that the buffer pair formed when the pH was adjusted to 4.5 stabilized the pH of the medium by sequestering protons and by lessening the negative impact of the pH drop on yeast growth, and it also decreased the difference between the extracellular and intracellular pH values ({Delta}pH), the driving force for the intracellular accumulation of acid. Increasing the undissociated acetic acid concentration at pH 4.5 to 163 mM by raising the concentration of the total acid to 267 mM did not increase inhibition. It is suggested that this may be the direct result of decreased acidification of the cytosol because of the intracellular buffering by the buffer pair formed from the acid already accumulated. At a concentration of 102 mM undissociated acetic acid, the yeast grew to higher cell density at pH 3.0 than at pH 4.5, suggesting that it is the total concentration of acetic acid (104 mM at pH 3.0 and 167 mM at pH 4.5) that determines the extent of growth inhibition, not the concentration of undissociated acid alone.

* Corresponding author. Mailing address: Department of Applied Microbiology and Food Science, Agriculture 3E08, University of Saskatchewan, 51 Campus Dr., Saskatoon, Saskatchewan, Canada S7N 5A8. Phone: (306) 966-5028. Fax: (306) 966-8898. E-mail: ingledew{at}sask.usask.ca.

Applied and Environmental Microbiology, April 2002, p. 1616-1623, Vol. 68, No. 4
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.4.1616-1623.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Narendranath, N. V., Power, R. (2005). Relationship between pH and Medium Dissolved Solids in Terms of Growth and Metabolism of Lactobacilli and Saccharomyces cerevisiae during Ethanol Production. Appl. Environ. Microbiol. 71: 2239-2243 [Abstract] [Full Text]  


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