Low-Temperature Active Dry Yeast Rehydration: Nutrients for Enhanced Fermentation and Membrane Fluidity

Active dry yeasts (ADY) are vital in winemaking due to their durability, but successful rehydration—relying on optimal trehalose levels, time, temperature, pH, nutrients, and ergosterol—is essential for restoring function. Low rehydration temperatures, however, reduce membrane fluidity and may impair yeast performance. This study evaluated the effects of suboptimal rehydration temperatures on selected yeast strains of Saccharomyces cerevisiae and Torulaspora delbrueckii, preserved at the Unimore Microbial Culture Collection (UMCC), and assessed the efficacy of two rehydration nutrients—FERMOPLUS® Energy Glu 3.0 and FERMOPLUS® Energy Glu 4.0 (AEB S.p.A)—focusing on improving fermentation performance and stabilizing membrane fluidity. All tested strains, except for T. delbrueckii, exhibited enhanced initial fermentation performance upon treatment with both nutrients. Analyses of membrane fluidity revealed that yeast cells rehydrated at 20°C displayed reduced fluidity compared to those cultivated at 25°C for 24 hours, confirming a temperature-induced stiffening effect. Notably, cells treated with FERMOPLUS® Energy Glu 4.0 demonstrated less variation in membrane fluidity, suggesting a more effective stabilization of membrane properties under suboptimal conditions. Overall, this work provides valuable insights into optimizing ADY rehydration at low temperatures—conditions employed in the wine industry to save time and costs—and offers practical strategies to enhance fermentation performance, ultimately improving wine quality. This work was funded by the European Commission – NextGenerationEU (“Strengthening the MIRRI Italian Research Infrastructure for Sustainable Bioscience and Bioeconomy”, code IR0000005), by the European Union – NextGenerationEU (“National Biodiversity Future Center-NBFC”, CUP E93C22001090001), and by AEB S.p.A (“Studio di Ceppi di Lievito di Interesse in Campo Enologico e Mantenimento delle Colture presso la Collezione UMCC”, CUP E83C24002050007).