Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology & Business University , Beijing 100048, China.
Beijing Engineering and Technology Research Center of Food Additives, Beijing Technology & Business University , Beijing 100048, China.
J Agric Food Chem. 2017 Jul 12;65(27):5503-5511. doi: 10.1021/acs.jafc.7b01359. Epub 2017 Jun 27.
2-Furfurylthiol is an important aroma compound with characteristic sesame flavor. It was recently identified as the representative aroma compound of Chinese sesame-flavored Baijiu. But its formation mechanism is unclear. In this study, the dominant yeast species Saccharomyces cerevisiae, Pichia kudriavzevii, and Wickerhamomyces anomalus were isolated from samples of Chinese sesame-flavored fermentation and were screened for the capacity of 2-furfurylthiol biosynthesis. Some isolates were found to be capable of generating 2-furfurylthiol using furfural and l-cysteine as precursors, among which S. cerevisiae G20 exhibited the strongest capacity with a yield of 3.03 mg/L. Furthermore, the genes STR3 and CYS3 from S. cerevisiae were cloned and overexpressed in the reference strain S. cerevisiae S288c and the isolate strain G20, respectively, which resulted in a significant increase in 2-furfurylthiol release in the two strains. Moreover, inactivation of STR3 gene in S288c and G20 led to obvious reduction in 2-furfurylthiol production, demonstrating that STR3 got involved in 2-furfurylthiol biosynthesis in S. cerevisiae. It is the first time that the yeast isolates with high capacity of 2-furfurylthiol biosynthesis were found during Chinese sesame-flavored Baijiu fermentation and confirmed that the genes STR3 and CYS3 were closely relevant to 2-furfurylthiol biosynthesis.
2-糠硫醇是一种具有特征芝麻风味的重要香气化合物。它最近被确定为中国芝麻香型白酒的代表性香气化合物。但它的形成机制尚不清楚。在这项研究中，从中国芝麻香型发酵样品中分离出优势酵母物种酿酒酵母、毕赤酵母和异常威克汉姆酵母，并筛选其 2-糠硫醇生物合成能力。一些分离株被发现能够使用糠醛和 l-半胱氨酸作为前体生成 2-糠硫醇，其中酿酒酵母 G20 的生成能力最强，产量为 3.03mg/L。此外，酿酒酵母 STR3 和 CYS3 基因从酿酒酵母中被克隆并在参考菌株酿酒酵母 S288c 和分离株 G20 中过表达，这导致在这两个菌株中 2-糠硫醇的释放显著增加。此外，STR3 基因在 S288c 和 G20 中的失活导致 2-糠硫醇产量明显减少，表明 STR3 参与了酿酒酵母中 2-糠硫醇的生物合成。这是首次在中国芝麻香型白酒发酵过程中发现具有高 2-糠硫醇生物合成能力的酵母分离株，并证实 STR3 和 CYS3 基因与 2-糠硫醇生物合成密切相关。
