A Novel application of Heyndrickxia coagulans in low-salt fish sauce: monoculture and co-culture evaluation with Lactiplantibacillus plantarum

This study reports the first isolation and characterization of Heyndrickxia (H.) coagulans from traditional fish sauce and evaluates its application as a starter culture for low-salt fermentation, as a monoculture, and in co-culture with Lactiplantibacillus (L.) plantarum . The strain, identified by 16 S rDNA sequencing (99.3% similarity to H. coagulans DSM 1), exhibited strong proteolytic and lipolytic activities with a favourable safety profile. Response surface methodology was used to establish optimal growth conditions for H. coagulans monoculture (30–34 °C, pH 6.0-6.7, up to 12% NaCl) and co-culture with L. plantarum (20–31 °C, pH 6.0-6.5, up to 6% NaCl). Fish sauces were produced over 90 days using traditional high-salt fermentation (20% NaCl), H. coagulans monoculture (10% NaCl), and H. coagulans - L. plantarum co-culture (5% NaCl). Starter inoculation significantly accelerated acidification and enhanced microbial safety, with complete suppression of Enterobacteriaceae and pathogenic microorganisms. Total biogenic amine contents remained below 57 mg/kg, with histamine levels < 5.9 mg/kg. Starter culture fermentations exhibited superior oxidative stability (0.18–0.22 mg MDA/kg) compared to traditional fermentation. Multivariate analysis identified starter culture selection as the primary driver of fermentation outcomes. H. coagulans , alone or in combination with L. plantarum , achieved up to 75% salt reduction while maintaining microbial safety and product quality, offering a viable approach to healthier fish sauce production.