LAUSR

Abstract 3‐(methylthio)‐1‐propanol (methionol), produced by yeast as an end‐product of L‐methionine (L‐Met) catabolism, imparts off‐odours reminiscent of cauliflower and potato to wine. Saccharomyces cerevisiae ARO genes, including transaminases Aro8p and Aro9p, and decarboxylase Aro10p, catalyse two key steps forming methionol via the Ehrlich pathway. We compared methionol concentrations in wines fermented by single &Dgr;aro8, &Dgr;aro9 and &Dgr;aro10 deletants in lab strain BY4743 versus wine strain Zymaflore F15, and F15 double‐ and triple‐aro deletants versus single‐aro deletants, using headspace‐solid phase microextraction coupled with gas chromatography‐mass spectrometry. Deletion of two or more aro genes increased growth lag phase, with the greatest delay exhibited by F15 &Dgr;aro8 &Dgr;aro9. The single &Dgr;aro8 deletion decreased methionol by 44% in BY4743 and 92% in F15, while the &Dgr;aro9 deletion increased methionol by 46% in F15 but not BY4743. Single deletion of &Dgr;aro10 had no effect on methionol. Unexpectedly, F15 &Dgr;aro8 &Dgr;aro9 and F15 &Dgr;aro8 &Dgr;aro9 &Dgr;aro10 produced more methionol than F15 &Dgr;aro8. In the absence of Aro8p and Aro9p, other transaminases may compensate or an alternative pathway may convert methanethiol to methionol. Our results confirm that Ehrlich pathway genes differ greatly between lab and wine yeast strains, impacting downstream products such as methionol.