Variation in α‐acetolactate production within the hybrid lager yeast group Saccharomyces pastorianus and affirmation of the central role of the ILV6 gene. Issue 1 (6th August 2014)

• Record Type: Journal Article
• Authors: Gibson, Brian; Krogerus, Kristoffer; Ekberg, Jukka; Monroux, Adrien; Mattinen, Laura; Rautio, Jari; Vidgren, Virve
• Is Part Of: Yeast. Volume 32:Issue 1(2015:Jan.)
• Page Start: 301
• Page End: 316
• Publication Date: 2014-08-06
• Subjects: Yeast -- Periodicals; Yeasts -- Periodicals; Yeasts -- genetics -- Periodicals; Electronic journals; 547
• DOI: 10.1002/yea.3026
• Languages: English
• ISSNs: 0749-503X

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>A screen of 14 <italic>S. pastorianus</italic> lager‐brewing strains showed as much as a nine‐fold difference in wort total diacetyl concentration at equivalent stages of fermentation of 15°Plato brewer's wort. Two strains (A153 and W34), with relatively low and high diacetyl production, respectively, but which did not otherwise differ in fermentation performance, growth or flavour production, were selected for further investigation. Transcriptional analysis of key genes involved in valine biosynthesis showed differences between the two strains that were consistent with the differences in wort diacetyl concentration. In particular, the <italic>ILV6</italic> gene, encoding a regulatory subunit of acetohydroxy acid synthase, showed early transcription (only 6 h after inoculation) and up to five‐fold greater expression in W34 compared to A153. This earlier transcription was observed for both orthologues of <italic>ILV6</italic> in the <italic>S. pastorianus</italic> hybrid (<italic>S. cerevisiae</italic> × <italic>S. eubayanus</italic>), although the <italic>S. cerevisiae</italic> form of <italic>ILV6</italic> in W34 also showed a consistently higher transcript level throughout fermentation relative to the same gene in A153. Overexpression of either form of <italic>ILV6</italic> (by placing it under the control of the <italic>PGK1</italic> promoter) resulted in an identical two‐fold increase in wort total diacetyl concentration relative to a control. The results confirm the role of the <italic>Ilv6</italic> subunit in controlling <italic>α</italic>‐acetolactate/diacetyl concentration and indicate no functional divergence between the two forms of <italic>Ilv6</italic>. The greater contribution of the <italic>S. cerevisiae ILV6</italic> to acetolactate production in natural brewing yeast hybrids appears rather to be due to higher levels of transcription relative to the <italic>S. eubayanus</italic> form. Copyright © 2014 John Wiley & Sons, Ltd.</p> </abstract>