Effects of acetic acid on the kinetics of xylose fermentation by an engineered, xylose-isomerase-based Saccharomyces cerevisiae strain

• Published in: FEMS yeast research Vol. 9; no. 3; pp. 358 - 364
• Main Authors: Bellissimi, Eleonora, van Dijken, Johannes P, Pronk, Jack T, van Maris, Antonius J.A
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.05.2009; Blackwell Publishing Ltd; Oxford University Press
• Subjects: Acetic acid; Acetic Acid - pharmacology; Acids; Aldose-Ketose Isomerases - analysis; Aldose-Ketose Isomerases - genetics; Culture Media - chemistry; Enzyme Inhibitors - pharmacology; Fermentation; Glucose; Glucose - metabolism; Hydrogen-Ion Concentration; lignocellulose; pH effects; Piromyces - enzymology; Piromyces - genetics; Recombinant Proteins - antagonists & inhibitors; Recombinant Proteins - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - drug effects; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Stoichiometry; stress; Xylitol; Xylose; Xylose - metabolism; Xylose isomerase; Yeast; stress; xylose isomerase; xylose; acetic acid; lignocellulose
• ISSN: 1567-1356; 1567-1364
• DOI: 10.1111/j.1567-1364.2009.00487.x

Acetic acid, an inhibitor released during hydrolysis of lignocellulosic feedstocks, has previously been shown to negatively affect the kinetics and stoichiometry of sugar fermentation by (engineered) Saccharomyces cerevisiae strains. This study investigates the effects of acetic acid on S. cerevisiae RWB 218, an engineered xylose-fermenting strain based on the Piromyces XylA (xylose isomerase) gene. Anaerobic batch cultures on synthetic medium supplemented with glucose-xylose mixtures were grown at pH 5 and 3.5, with and without addition of 3 g L⁻¹ acetic acid. In these cultures, consumption of the sugar mixtures followed a diauxic pattern. At pH 5, acetic acid addition caused increased glucose consumption rates, whereas specific xylose consumption rates were not significantly affected. In contrast, at pH 3.5 acetic acid had a strong and specific negative impact on xylose consumption rates, which, after glucose depletion, slowed down dramatically, leaving 50% of the xylose unused after 48 h of fermentation. Xylitol production was absent (<0.10 g L⁻¹) in all cultures. Xylose fermentation in acetic -acid-stressed cultures at pH 3.5 could be restored by applying a continuous, limiting glucose feed, consistent with a key role of ATP regeneration in acetic acid tolerance.