Influence of acid-reducing Saccharomyces cerevisiae on the microbial communities and metabolites of Suanyu.

The inoculation of S. cerevisiae can address the excessive acidity in Suanyu, but its influence on the microbial community structure has not been documented. In this study, the microbiota succession, and metabolites of Suanyu with the inoculation of acid-reducing S. cerevisiae L7 were explored. The findings revealed that the addition of S. cerevisiae L7 elevated the pH, and decreased the microbial α-diversity. In Suanyu, the dominant bacterial genera were Lactiplantibacillus and Bacillus, while the dominant fungal genera were Meyerozyma and Saccharomyces. Following the inoculation of S. cerevisiae L7, the relative abundance of Lactiplantibacillus decreased from 21 % to 13 %. Meanwhile, the growth of fungi such as Meyerozyma and Candida was suppressed. The rise in Saccharomyces had a significant impact on various pathways related to amino acid and carbohydrate metabolism, causing the accumulation of flavor compounds. This study sheds more lights on the methods for manipulating microbial community structure in fermented food.

Multi-omics analysis reveals the microbial interactions of S. cerevisiae and L. plantarum on Suanyu, Chinese traditional fermented fish.

S. cerevisiae and L. plantarum play important roles in Suanyu fermentation. This study investigated the interaction between S. cerevisiae and L. plantarum during fermentation and its impact on metabolic pathways. Co-culturing S. cerevisiae and L. plantarum increased pH to 5.72, reduced TVB-N to 9.47 mg/mL, and achieved high utilization rates of sugars (98.9%) and proteins (73.7%). During microbial interactions, S. cerevisiae and L. plantarum produced antibiotics, including phenyllactate and Gentamicin C1a, inhibiting the growth of each other. S. cerevisiae used S-adenosyl-l-methionine to counteract acid production of L. plantarum, establishing dominance in Suanyu fermentation. Microbial interactions influenced carbohydrate and energy metabolism pathways, such as nicotinate and nicotinamide metabolism and purine metabolism. S. cerevisiae significantly impacted gene expression in protein synthesis and cell growth pathways, including ribosome, SNARE interactions, basal transcription factors, and MAPK signaling. These findings offer insights into microbial interactions and metabolic processes during Suanyu fermentation.