Innovative lees-derived extracts as modulators of malolactic fermentation in model wine

Malolactic fermentation (MLF) is an important process affecting wine acidity, microbial stability, and sensory quality, but it can be challenging in certain wines due to low pH, high ethanol concentration, and low nutrient availability. This study evaluated the ability of yeast lees-derived extracts to modulate Oenococcus oeni growth and MLF performance in a model wine system. Two categories of yeast lees-derived products were investigated. The first consisted of extracts obtained from post-distillation wine lees using McIlvaine saline buffer or natural deep eutectic solvents based on citric, malic, or lactic acid. The second category consisted of purified peptide fractions obtained from yeast lees subjected to natural autolysis in synthetic wine and collected at different ageing times. The products were tested in synthetic wine at different dosages. Bacterial growth was monitored by flow cytometry, while malic acid degradation and related metabolites were analyzed by HPLC. Post-distillation lees extracts effects on O. oeni were generally positive, but product-, dose-, and strain-dependent. Among these extracts, the citric acid-based extract and the McIlvaine saline buffer extract generally promoted malic acid degradation more effectively. Conversely, the lactic acid-based extract showed weaker activity. Purified peptide fractions displayed a positive dose dependent effect, independently from the ageing time collection.ag Overall, yeast lees-derived extracts were able to modulate O. oeni growth and MLF performance in a model wine system, with specific products showing promising effects on bacterial growth and malic acid degradation. These findings support their potential application as targeted MLF modulators and highlight the possibility of valorizing post-distillation wine lees as a winery by-product. Further validation in real wine conditions is required to confirm their technological relevance and define their optimal conditions of use.