The Influence of Acetic and Other Weak Carboxylic Acids on Growth and Cellular Death of the Yeast Yarrowia lipolytica
Georgina Rodrigues and Célia Pais*
Centro de Ciências do Ambiente – Departamento de Biologia, Universidade do Minho, 4710–57 Braga, Portugal
Article history:
Received November 10, 1999
Accepted January 21, 2000
Key words:
Yarrowia lipolytica, carboxylic acids, weak acids toxicity, cell death
Summary:
Acetic, lactic, propionic, malic, succinic, citric and oleic acids were used by Yarrowia lipolytica as the sole carbon and energy source, this capacity being, in most cases, independent of the pH of the culture media. When the yeast was grown in a mixed medium with glucose 0.1 % (w/v) and a volume ratio of acetic, succinic, propionic or malic acid 0,1 %, pH= 3.0 and 5.0, the acid was used simultaneously with the glucose. Diauxic growth was observed when the yeast was grown in glucose and citric or lactic acid. These results suggest that the utilisation of these two acids, is subjected to glucose repression. Presence of acetic acid in the extracellular medium decreased the specific growth rate of the yeast grown in glucose medium at 26 °C, pH=3.0. Propionic, butyric and sorbic acids also had inhibitory effects on yeast growth. The effects of acetic, propionic, butyric and sorbic acids on the kinetics of cell death in glucose-grown cells, were studied as well. For each one of these compounds, and under isothermic conditions, cell death was exponentially stimulated in the presence of increasing extracellular acid concentrations; the toxic effects induced by the acids were higher for sorbic and butyric acids. In terms of acetic acid resistance this strain seems to be qualitatively more resistant than Saccharomyces cerevisiae and is closer to Zygosaccharomyces bailli, one of the most important food spoilage yeasts.
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