ABSTRACT
Yeast, which plays a pivotal role in the brewing, food, and medical industries, exhibits a close relationship with human beings. In this study, we isolated and purified 60 yeast strains from the natural fermentation broth of Sidamo coffee beans to screen for indigenous beneficial yeasts. Among them, 25 strains were obtained through morphological characterization on nutritional agar medium from Wallerstein Laboratory (WL), with molecular biology identifying Saccharomyces cerevisiae strain YBB-47 and the remaining 24 yeast strains identified as Pichia kudriavzevii. We investigated the fermentation performance, alcohol tolerance, SO2 tolerance, pH tolerance, sugar tolerance, temperature tolerance, ester production capacity, ethanol production capacity, H2S production capacity, and other brewing characteristics of YBB-33 and YBB-47. The results demonstrated that both strains could tolerate up to 3% alcohol by volume at a high sucrose mass concentration (400 g/L) under elevated temperature conditions (40 â), while also exhibiting a remarkable ability to withstand an SO2 mass concentration of 300 g/L at pH 3.2. Moreover, S. cerevisiae YBB-47 displayed a rapid gas production rate and strong ethanol productivity. whereas P. kudriavzevii YBB-33 exhibited excellent alcohol tolerance. Furthermore, this systematic classification and characterization of coffee bean yeast strains from the Sidamo region can potentially uncover additional yeasts that offer high-quality resources for industrial-scale coffee bean production.
Subject(s)
Ethanol , Fermentation , Pichia , Saccharomyces cerevisiae , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/isolation & purification , Pichia/metabolism , Pichia/isolation & purification , Pichia/genetics , Pichia/classification , Ethanol/metabolism , Hydrogen-Ion Concentration , Coffee/microbiology , Coffea/microbiology , Temperature , Seeds/microbiology , Hydrogen Sulfide/metabolismABSTRACT
A simple and mild protocol for copper catalyzed halogenation of quinoline at C5 and C7 positions was developed, affording the desired remote C-H activation products in moderate to good yields. This reaction proceeds with low-cost sodium halides (NaX, X = Cl, Br, I) and features excellent substrate tolerance. A series of control experiments were carried out to illustrate a single-electron-transfer process which plays a vital role in the halogenation.
