Metabolic footprint analysis of metabolites that discriminate single and mixed yeast cultures at two key time-points during mixed culture alcoholic fermentations.

Introduction: There has been a growing interest towards creating defined mixed starter cultures for alcoholic fermentations. Previously, metabolite differences between single and mixed cultures have been explored at the endpoint of fermentations rather than during fermentations.

Objectives: To create metabolic footprints of metabolites that discriminate single and mixed yeast cultures at two key time-points during mixed culture alcoholic fermentations.

Methods: H NMR- and GC-MS-based metabolomics was used to identify metabolites that discriminate single and mixed cultures of Lachancea thermotolerans (LT) and Saccharomyces cerevisiae (SC) during alcoholic fermentations.

Results: Twenty-two metabolites were found when comparing single LT and mixed cultures, including both non-volatiles (carbohydrate, amino acid and acids) and volatiles (higher alcohols, esters, ketones and aldehydes). Fifteen of these compounds were discriminatory only at the death phase initiation (T1) and fifteen were discriminatory only at the death phase termination (T2) of LT in mixed cultures. Eight metabolites were discriminatory at both T1 and T2. These results indicate that specific metabolic changes may be descriptive of different LT growth behaviors. Fifteen discriminatory metabolites were found when comparing single SC and mixed cultures. These metabolites were all volatiles, and twelve metabolites were discriminatory only at T2, indicating that LT-induced changes in volatiles occur during the death phase of LT in mixed cultures and not during their initial growth stage.

Conclusions: This work provides a detailed insight into yeast metabolites that differ between single and mixed cultures, and these data may be used for understanding and eventually predicting yeast metabolic changes in wine fermentations.