Palmitoleic Acid Enhances the Tolerance of Lager Yeast to Oxidation Stress by Regulating the Multilevel Defense System

Oxidative stress is a major physiological constraint on industrial lager yeast, compromising fermentation efficiency and flavor quality. Unsaturated fatty acids are known to influence membrane fluidity, but whether exogenous fatty acid supplementation can actively reprogram the yeast defense system, beyond serving as a passive membrane component, remains unclear. Here, we compared the effects of four fatty acids (palmitic, palmitoleic, oleic, and linoleic acid) on oxidative stress tolerance and fermentation performance in industrial lager yeast, under a defined chemical oxidative challenge (2.0 mM H2O2) in 15 °P wort, combining physiological assays with targeted gene-expression and untargeted metabolomic analyses; the dose was selected from a 0–2.0 mM gradient, with an ethanol-vehicle control included throughout. Among the fatty acids tested, palmitoleic acid (POA) most markedly enhanced oxidative stress tolerance, maintaining 91% cell viability, restoring intracellular pH to 6.1 by 24 h after transient acidification, and reducing ROS accumulation by 41.2%. Mechanistically, POA upregulated the antioxidant system, increasing catalase and glutathione peroxidase activities by 35.6% and 85.5%, respectively, and restoring glutathione levels by 35.5%. Metabolic profiling revealed a global reconfiguration, including a 2.6-fold increase in the stress-protectant proline and elevated pantothenate and coenzyme A levels, accompanied by a shift in the volatile profile toward esters, which rose from 26.1% to 60.3% of the total pool, alongside a 52.1% increase in total volatiles that did not reach significance after correction for multiple testing (q = 0.070); sensory evaluation confirmed higher fruity-estery intensity and lower soapy and staling notes in the POA beer. These findings identify POA as an active metabolic modulator, not merely a passive structural lipid, pointing to a non-transgenic nutritional strategy whose industrial value now requires validation under high-gravity, pilot-scale, and serial-repatching conditions.