Fermentative and physiological responses of Saccharomyces cerevisiae LMQA SRC-143 and PE-2 in co-culture with Lactobacillus fermentum: Insights with flow cytometry in the Melle-Boinot process

The presence of multiple microbial species during the fermentation process remains a major challenge for controlled and high-yield ethanol production. Therefore, it is essential to select strains capable of maintaining or enhancing their biotechnological activity when involved in interspecies interactions. This study aimed to assess the impact of microbial competition, mediated by Lactobacillus fermentum CCT 1668, along with cell recycling and acid washing, on the fermentative performance and physiological responses of Saccharomyces cerevisiae strains LMQA SRC-143 and PE-2. Flow cytometry was employed to assess cell vitality, viability, and intracellular carbohydrate reserves throughout the fermentation cycles. The results challenge the conventional notion that lactic acid bacteria co-culture is universally detrimental during fermentation. Interestingly, while PE-2 exhibited higher resilience when isolated, the presence of L. fermentum significantly enhanced the performance and vitality of LMQA SRC-143. This research underscores the potential of exploiting microbial interactions to optimize fermentation processes, using as an example the bioethanol production, suggesting that certain non-commercial yeast strains may not only withstand bacterial co-culture but also be benefited under specific conditions. These insights carry significant implications for the fermentation industry, as they could reduce dependency on chemical interventions for bacterial control, promoting more sustainable approaches aligned with SDG 7 - affordable and clean energy.