Expression levels of the yeast alcohol acetyltransferase genes ATF1, Lg-ATF1, and ATF2 control the formation of a broad range of volatile esters

Volatile aroma-active esters are responsible for the fruity character of fermented alcoholic beverages such as beer and wine. Esters are produced by fermenting yeast cells in an enzyme-catalyzed intracellular reaction. In order to investigate and compare the roles of the known Saccharomyces cerevisi...

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Published in:	Applied and Environmental Microbiology Vol. 69; no. 9; pp. 5228 - 5237
Main Authors:	Verstrepen, K.J, Laere, S.D.M. van, Vanderhaegen, B.M.P, Derdelinckx, G, Dufour, J.P, Pretorius, I.S, Winderickx, J, Thevelein, J.M, Delvaux, F.R
Format:	Journal Article
Language:	English
Published:	Washington, DC American Society for Microbiology 01-09-2003
Subjects:	Acetyltransferases - genetics Acetyltransferases - metabolism acyltransferases Alcoholic beverages alcoholic fermentation alleles beers Biological and medical sciences biosynthesis brewers yeast esters Esters - classification Esters - metabolism Fermentation Fermentation - physiology flavor compounds Fundamental and applied biological sciences. Psychology Gene Deletion gene expression gene overexpression Genes, Fungal Kinetics messenger RNA Microbiology Mycology Plasmids Proteins Saccharomyces cerevisiae Saccharomyces cerevisiae - enzymology Saccharomyces cerevisiae - genetics Saccharomyces cerevisiae Proteins - genetics Saccharomyces cerevisiae Proteins - metabolism structural genes Substrate Specificity transcription (genetics) volatile organic compounds Yeast Volatile compound Acyltransferases Ester Alcohol O-acetyltransferase Yeast Gene Enzyme Transferases
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Summary:	Volatile aroma-active esters are responsible for the fruity character of fermented alcoholic beverages such as beer and wine. Esters are produced by fermenting yeast cells in an enzyme-catalyzed intracellular reaction. In order to investigate and compare the roles of the known Saccharomyces cerevisiae alcohol acetyltransferases, Atf1p, Atf2p and Lg-Atf1p, in volatile ester production, the respective genes were either deleted or overexpressed in a laboratory strain and a commercial brewing strain. Subsequently, the ester formation of the transformants was monitored by headspace gas chromatography and gas chromatography combined with mass spectroscopy (GC-MS). Analysis of the fermentation products confirmed that the expression levels of ATF1 and ATF2 greatly affect the production of ethyl acetate and isoamyl acetate. GC-MS analysis revealed that Atf1p and Atf2p are also responsible for the formation of a broad range of less volatile esters, such as propyl acetate, isobutyl acetate, pentyl acetate, hexyl acetate, heptyl acetate, octyl acetate, and phenyl ethyl acetate. With respect to the esters analyzed in this study, Atf2p seemed to play only a minor role compared to Atf1p. The atf1delta atf2delta double deletion strain did not form any isoamyl acetate, showing that together, Atf1p and Atf2p are responsible for the total cellular isoamyl alcohol acetyltransferase activity. However, the double deletion strain still produced considerable amounts of certain other esters, such as ethyl acetate (50% of the wild-type strain), propyl acetate (50%), and isobutyl acetate (40%), which provides evidence for the existence of additional, as-yet-unknown ester synthases in the yeast proteome. Interestingly, overexpression of different alleles of ATF1 and ATF2 led to different ester production rates, indicating that differences in the aroma profiles of yeast strains may be partially due to mutations in their ATF genes.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 Corresponding author. Mailing address: Centre for Malting and Brewing Science, Department of Food and Microbial Technology, K.U.Leuven, Kasteelpark Arenberg 22, B-3001 Louvain (Heverlee), Belgium. Phone: 32-(0)16-329627. Fax: 32-(0)16-321576. E-mail: Kevin.Verstrepen@agr.kuleuven.ac.be.
ISSN:	0099-2240 1098-5336
DOI:	10.1128/AEM.69.9.5228-5237.2003