title: Improvement of aromatic thiol release through the selection of yeasts with increased β-lyase activity.
abstract: The development of a selective medium for the rapid differentiation of yeast species with increased aromatic thiol release activity has been achieved. The selective medium was based on the addition of S-methyl-l-cysteine (SMC) as β-lyase substrate. In this study, a panel of 245 strains of Saccharomyces cerevisiae strains was tested for their ability to grow on YCB-SMC medium. Yeast strains with an increased β-lyase activity grew rapidly because of their ability to release ammonium from SMC in comparison to others, and allowed for the easy isolation and differentiation of yeasts with promising properties in oenology, or another field, for aromatic thiol release. The selective medium was also helpful for the discrimination between those S. cerevisiae strains, which present a common 38-bp deletion in the IRC7 sequence (present in around 88% of the wild strains tested and are likely to be less functional for 4-mercapto-4-methylpentan-2-one (4MMP) production), and those S. cerevisiae strains homozygous for the full-length IRC7 allele. The medium was also helpful for the selection of non-Saccharomyces yeasts with increased β-lyase activity. Based on the same medium, a highly sensitive, reproducible and non-expensive GC-MS method for the evaluation of the potential volatile thiol release by different yeast isolates was developed.
authors.affiliation: Department of Microbiology, Biology Faculty, Complutense University of Madrid, 28040 Madrid, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Belda
authors.affiliation: Department of Microbiology, Biology Faculty, Complutense University of Madrid, 28040 Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Ruiz
authors.affiliation: Agrovin, S.A., Alcázar de San Juan, 13600 Ciudad Real, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Navascués
authors.affiliation: Department of Microbiology, Biology Faculty, Complutense University of Madrid, 28040 Madrid, Spain.
authors.forename: Domingo
authors.initials: D
authors.lastname: Marquina
authors.affiliation: Department of Microbiology, Biology Faculty, Complutense University of Madrid, 28040 Madrid, Spain. Electronic address: ansantos@ucm.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Santos
mesh_terms: D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D003545:Cysteine / Q000378:metabolism; D005285:Fermentation; D005516:Food Microbiology / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D008190:Lyases / Q000235:genetics / Q000378:metabolism*; D016533:Mycological Typing Techniques; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014920:Wine / Q000382:microbiology
chemical_list: D003470:Culture Media; D029701:Saccharomyces cerevisiae Proteins; D013438:Sulfhydryl Compounds; D008190:Lyases; D013437:Carbon-Sulfur Lyases; C000607133:Irc7 protein, S cerevisiae; D003545:Cysteine
keywords: Aromatic thiols; Selective medium; Wine fermentation; β-lyase activity