Transcriptomic Analysis of Cell Stress Response in Wickerhamomyces anomalus H4 Under Octanoic Acid Stress

The purified yeast strain H4, identified as W. anomalus through morphological, genetic, and phylogenetic analyses, was characterized and compared to a commercial Saccharomyces cerevisiae strain X16. W. anomalus H4 exhibited distinct morphological features. It demonstrated notable tolerance to 11% ethanol, 220 g/L glucose, and 200 mg/L octanoic acid, similar to X16, except for having a lower tolerance to SO2. Survival analysis under various stress conditions revealed that ethanol and octanoic acid had the most detrimental effects, with 56% cell mortality at 13% ethanol and 400 mg/L octanoic acid. Transcriptomic analysis under octanoic acid stress showed that at 200 mg/L, 3369 differentially expressed genes (DEGs) were induced, with 1609 being upregulated and 1760 downregulated, indicating broad transcriptional reprogramming. At 400 mg/L, only 130 DEGs were detected, suggesting a more limited response. KEGG pathway analysis indicated that most DEGs at 200 mg/L were associated with the “ribosome” and “proteasome” pathways, reflecting disruptions in protein synthesis and turnover. At 400 mg/L, the DEGs were primarily related to “DNA replication” and “pyruvate metabolism”. These findings highlight the adaptive mechanisms of W. anomalus H4 to environmental stresses, particularly octanoic acid, and its potential for use in brewing and fermentation processes.