# Influence of Inoculating Saccharomyces cerevisiae and Levilactobacillus brevis on the Quality of Fermented Large Yellow Croaker (Larimichthys crocea): Biogenic Amines, Volatile Components, and Microbial Communities Changes

## TL;DR

This study shows that adding specific yeast and bacteria improves the safety and flavor of fermented fish.

## Contribution

The novel contribution is demonstrating how S. cerevisiae and L. brevis affect biogenic amines, flavor compounds, and microbial communities in fermented fish.

## Key findings

- Combined inoculation reduced biogenic amines and nitrite, improving safety.
- S. cerevisiae increased ester compounds linked to flavor.
- L. brevis suppressed harmful bacteria and correlated with specific volatile flavor compounds.

## Abstract

As a representative of traditional Chinese fermented fish, fermented large yellow croaker (Larimichthys crocea) is characterized by its rich aroma, appealing color, distinctive flavor, and long shelf life. In this study, Saccharomyces cerevisiae (S. cerevisiae) and Levilactobacillus brevis (L. brevis) were inoculated to enhance fermentation, and their effects on biogenic amine (BA) formation, volatile flavor compounds (VFCs), and microbial community composition were investigated. Combined inoculation significantly reduced most BAs and nitrite levels, thereby improving the safety of fermented large yellow croaker. The S. cerevisiae-inoculated group exhibited higher contents of ester compounds such as 3-methylbutyl acetate, 2-methylpropyl acetate, and ethyl 2-methylbutanoate. L. brevis effectively suppressed spoilage and amine-producing bacteria, including Aeromonas, Shewanella, and Morganella. Pearson’s correlation analysis revealed that Levilactobacillus was positively correlated with butyl 2-methylbutanoate, (Z)-4-heptenal, pentyl acetate, 2-ethyl-3-methylpyrazine, 3-methylbutyl acetate, 4-methyl-2-pentanone, 3-pentanone, and propanal, while Saccharomyces showed positive correlations with propionaldehyde, 1-penten-3-ol, 4-methyl-3-penten-2-one, (E)-2-pentenal, and 2-hexenal. In contrast, BAs were negatively correlated with Levilactobacillus and Saccharomycopsis, but positively correlated with Aeromonas, Shewanella, Photobacterium, Vagococcus, Vibrio, Morganella, Lactococcus, Apiotrichum, and Cutaneotrichosporon. Overall, these findings demonstrate that L. brevis and S. cerevisiae improve both the flavor and safety of fermented large yellow croaker. This study offers a theoretical basis for advancing industrial production of fermented fish products.