INRA, UMR1131, F-68021 Colmar, France.
Food Microbiol. 2013 Apr;33(2):228-34. doi: 10.1016/j.fm.2012.09.021. Epub 2012 Oct 11.
Geraniol produced by grape is the main precursor of terpenols which play a key role in the floral aroma of white wines. We investigated the fate of geraniol during wine fermentation by Saccharomyces cerevisiae. The volatile compounds produced during fermentation of a medium enriched with geraniol were extracted by Stir-bar sorptive extraction and analysed by GC-MS. We were able to detect and quantify geranyl acetate but also citronellyl- and neryl-acetate. The presence of these compounds partly explains the disparition of geraniol. The amounts of terpenyl esters are strain dependant. We demonstrated both by gene overexpression and gene-deletion the involvement of ATF1 enzyme but not ATF2 in the acetylation of terpenols. The affinity of ATF1 enzyme for several terpenols and for isoamyl alcohol was compared. We also demonstrated that OYE2 is the enzyme involved in geraniol to citronellol reduction. Fermenting strain deleted from OYE2 gene produces far less citronellol than wild type strain. Moreover lab strain over-expressing OYE2 allows 87% geraniol to citronellol reduction in bioconversion experiment compared to about 50% conversion with control strain.
葡萄产生的香叶醇是萜醇的主要前体，萜醇在白葡萄酒的花香中起着关键作用。我们研究了葡萄酒发酵过程中酵母对香叶醇的命运。通过搅拌棒吸附萃取法提取富含香叶醇培养基发酵过程中产生的挥发性化合物，并通过 GC-MS 进行分析。我们能够检测和定量乙酸香叶酯，但也能检测到香茅基和橙花基乙酸酯。这些化合物的存在部分解释了香叶醇的消失。萜烯酯的含量取决于菌株。我们通过基因过表达和基因缺失证明了 ATF1 酶而不是 ATF2 酶参与了萜醇的乙酰化。比较了 ATF1 酶对几种萜醇和异戊醇的亲和力。我们还证明了 OYE2 酶是参与香叶醇还原为香茅醇的酶。从 OYE2 基因缺失的发酵菌株比野生型菌株产生的香茅醇少得多。此外，过表达 OYE2 的实验室菌株在生物转化实验中允许 87%的香叶醇转化为香茅醇，而对照菌株的转化率约为 50%。
