Isolation, identification, and tolerance analysis of yeast during the natural fermentation process of Sidamo coffee beans.

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 ℃), 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.

Photoaffinity Labeling-Based Chemoproteomic Strategy Reveals RBBP4 as a Cellular Target of Protopanaxadiol against Colorectal Cancer Cells.

Protopanaxadiol (PPD), a main ginseng metabolite, exerts powerful anticancer effects against multiple types of cancer; however, its cellular targets remain elusive. Here, we synthesized a cell-permeable PPD probe via introducing a bifunctional alkyne-containing diazirine photo-crosslinker and performed a photoaffinity labeling-based chemoproteomic study. We identified retinoblastoma binding protein 4 (RBBP4), a chromatin remodeling factor, as an essential cellular target of PPD in HCT116 colorectal cancer cells. PPD significantly decreased RBBP4-dependent trimethylation at lysine 27 of histone H3 (H3K27me3), a crucial epigenetic marker that correlates with histologic signs of colorectal cancer aggressiveness, and PPD inhibition of proliferation and migration of HCT116 cells was antagonized by RBBP4 RNA silencing. Collectively, our study highlights a previously undisclosed anti-colorectal cancer cellular target of the ginseng metabolite and advances the fundamental understanding of RBBP4 functions via a chemical biology strategy.