Survey of enzyme activity responsible for phenolic off-flavour production by Dekkera and Brettanomyces yeast.
Volatile phenols are produced by Dekkera yeasts and are of organoleptic importance in alcoholic beverages. The key compound in this respect is 4-ethylphenol, responsible for the medicinal and phenolic aromas in spoiled wines. The microbial synthesis of volatile phenols is thought to occur in two steps, beginning with naturally occurring hydroxycinnamic acids (HCAs). The enzyme phenolic acid decarboxylase (PAD) converts HCAs to vinyl derivatives, which are the substrates of a second enzyme, postulated to be a vinylphenol reductase (VPR), whose activity results in the formation of ethylphenols. Here, both steps of the pathway are investigated, using cell extracts from a number of Dekkera and Brettanomyces species. Dekkera species catabolise ferulic, caffeic and p-coumaric acids and possess inducible enzymes with similar pH and temperature optima. Brettanomyces does not decarboxylate HCAs but does metabolise vinylphenols. Dekkera species form ethylphenols but the VPR enzyme appears to be highly unstable in cell extracts. A partial protein sequence for PAD was determined from Dekkera anomala and may indicate the presence of a novel enzyme in this genus.
School of Agriculture, Food and Wine, The University of Adelaide, PMB1, Glen Osmond 5064, Adelaide, South Australia, Australia.
Victoria
V
Harris
Christopher M
CM
Ford
Vladimir
V
Jiranek
Paul R
PR
Grbin
D000595:Amino Acid Sequence; D055168:Brettanomyces / Q000201:enzymology* / Q000378:metabolism*; D002109:Caffeic Acids / Q000378:metabolism; D002262:Carboxy-Lyases / Q000378:metabolism; D003373:Coumaric Acids / Q000378:metabolism; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D055167:Dekkera / Q000201:enzymology* / Q000378:metabolism*; D005421:Flavoring Agents / Q000378:metabolism*; D008969:Molecular Sequence Data; D010636:Phenols / Q000378:metabolism*; D011422:Propionates; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D055549:Volatile Organic Compounds / Q000378:metabolism
D002109:Caffeic Acids; D003373:Coumaric Acids; D004271:DNA, Fungal; D005421:Flavoring Agents; D010636:Phenols; D011422:Propionates; D055549:Volatile Organic Compounds; C004999:ferulic acid; D002262:Carboxy-Lyases; C417714:phenolic acid decarboxylase; C495469:p-coumaric acid; C040048:caffeic acid