Department of Microbiology, Biology Faculty, Complutense University of Madrid, 28040 Madrid, Spain.
Agrovin, S.A., Alcázar de San Juan, 13600 Ciudad Real, Spain.
Int J Food Microbiol. 2016 May 16;225:1-8. doi: 10.1016/j.ijfoodmicro.2016.03.001. Epub 2016 Mar 3.
The development of a selective medium for the rapid differentiation of yeast species with increased aromatic thiol release activity has been achieved. The selective medium was based on the addition of S-methyl-l-cysteine (SMC) as β-lyase substrate. In this study, a panel of 245 strains of Saccharomyces cerevisiae strains was tested for their ability to grow on YCB-SMC medium. Yeast strains with an increased β-lyase activity grew rapidly because of their ability to release ammonium from SMC in comparison to others, and allowed for the easy isolation and differentiation of yeasts with promising properties in oenology, or another field, for aromatic thiol release. The selective medium was also helpful for the discrimination between those S. cerevisiae strains, which present a common 38-bp deletion in the IRC7 sequence (present in around 88% of the wild strains tested and are likely to be less functional for 4-mercapto-4-methylpentan-2-one (4MMP) production), and those S. cerevisiae strains homozygous for the full-length IRC7 allele. The medium was also helpful for the selection of non-Saccharomyces yeasts with increased β-lyase activity. Based on the same medium, a highly sensitive, reproducible and non-expensive GC-MS method for the evaluation of the potential volatile thiol release by different yeast isolates was developed.
已经开发出一种用于快速区分具有增加的芳香硫醇释放活性的酵母物种的选择性培养基。该选择性培养基基于添加 S-甲基-L-半胱氨酸 (SMC) 作为 β-裂合酶底物。在这项研究中，测试了 245 株酿酒酵母菌株在 YCB-SMC 培养基上生长的能力。由于其能够将 SMC 中的铵释放出来，具有增加的 β-裂合酶活性的酵母菌株生长迅速，这使得能够轻松分离和区分在酿酒或其他领域具有芳香硫醇释放前景的酵母。该选择性培养基还有助于区分那些在 IRC7 序列中存在常见 38-bp 缺失的酿酒酵母菌株（存在于大约 88%的测试野生菌株中，并且可能对 4-巯基-4-甲基戊烷-2-酮 (4MMP) 的生产功能较低），以及那些 IRC7 等位基因完全纯合的酿酒酵母菌株。该培养基还有助于选择具有增加的 β-裂合酶活性的非酿酒酵母。基于相同的培养基，开发了一种高度敏感、可重复且经济实惠的 GC-MS 方法，用于评估不同酵母分离物潜在的挥发性硫醇释放。
