Biotransformation of monoterpene alcohols by Saccharomyces cerevisiae, Torulaspora delbrueckii and Kluyveromyces lactis

Monoterpenoids are important flavor compounds produced by many plant specie s, including grapes (Vitis vinifera) and hops (Humulus lupulus). Biotransfo rmation reactions involving monoterpenoids have been characterized in filam entous fungi, but few examples have been observed in yeasts. As monoterpeno ids are in contact with yeasts during beer and wine production, biotransfor mation reactions may occur during the fermentation of these beverages. This paper describes the biotransformation of monoterpene alcohols, of signific ance in the alcoholic beverage industries, by three yeast species. All thre e species analysed had the ability to convert monoterpenoids. Saccharomyces cerevisiae and Kluyveromyces lactis reduced geraniol into citronellol, whi lst all three yeasts produced linalool from both geraniol and nerol. Monocy clic alpha-terpineol was formed from both linalool and nerol, by all three yeasts. alpha-Terpineol was then converted into the diol cisterpin hydrate. K. lactis and Toruldaspora delbrueckii also had the ability to form gerani ol from nerol. Finally, the stereospecificity of terpenoid formation was an alysed. Both (+) and (-) enantiomers of linalool and alpha-terpineol were f ormed in roughly equal quantities, from either geraniol or nerol. Copyright (C) 2000 John Wiley & Sons, Ltd.