Dimethyl trisulfide (DMTS) is one of the main components responsible for hineka, the aroma associated with deteriorated Japanese sake during storage. The molecule 1,2-dihydroxy-5-(methylsulfinyl)pentan-3-one (DMTS-P1) has been previously identified as a major precursor compound of DMTS. Furthermore, it had been suggested that the yeast methionine salvage pathway is involved in the production of DMTS-P1. In sake brewing tests, DMTS-P1 and the DMTS producing potential (DMTS-pp; DMTS amount of sake after accelerated storage) were significantly reduced in mde1 or mri1 strain, which lack genes of the methionine salvage pathway. Industrial use of the gene-disrupting strains may not be accepted in the Japanese food industry. In order to obtain mde1 or mri1 mutants, we established a method to screen 5′-methylthioadenosine (MTA) non-utilizing strains using minimum culture medium containing methionine or MTA by ethyl methanesulfonate (EMS) mutagenesis with methionine-auxotrophic sake yeast haploid. As expected, mde1 and mri1 mutants were identified among the obtained mutants by an established screening method. The obtained strains had poor fermentation ability in sake brewing tests, so back-crossing was performed on the mutants to obtain mde1 or mri1 homozygous mutants. These strains had improved brewing characteristics, and DMTS-P1 and the DMTS-pp of the produced sake were significantly lower than those of the parent strains. These strains are expected to contribute to improving the maintenance of sake quality during storage.

二甲基三硫化物（DMTS）是负责hineka的主要成分之一，hineka是与日本清酒在储存过程中变质相关的香气。分子1,2-二羟基-5-（甲基亚磺酰基）戊-3-酮（DMTS-P1）先前已被确定为DMTS的主要前体化合物。此外，已经提出酵母蛋氨酸的挽救途径与DMTS-P1的产生有关。在清酒酿造测试中，在缺少蛋氨酸挽救途径基因的mde1或mri1菌株中，DMTS-P1和DMTS产生潜力（DMTS-pp；加速储存后的DMTS量）显着降低。在日本食品工业中可能不接受破坏基因的菌株的工业用途。为了获得mde1或mri1突变体，我们建立了一种方法，使用含有蛋氨酸或MTA的最低培养基，通过甲磺酸乙酯（EMS）诱变与蛋氨酸营养缺陷型清酒酵母单倍体，筛选5'-甲基硫代腺苷（MTA）非利用菌株。如所期望的，通过建立的筛选方法在获得的突变体中鉴定出mde1和mri1突变体。在清酒酿造试验中，所获得的菌株发酵能力较弱，因此对这些突变体进行回交以获得mde1或mri1。纯合突变体。这些菌株具有改善的酿造特性，并且所生产的清酒的DMTS-P1和DMTS-pp显着低于亲本菌株。预计这些菌株将有助于改善贮藏期间清酒品质的维持。