Spoilage phenotypic characterization and identification of Aeromonas isolated from spoiled Larimichthys crocea

To identify the spoilage potential of two Aeromonas strains isolated from the spoiled Larimichthys crocea, we identified the isolates that did not produce H₂S by biochemical characterization and 16S rRNA. All of the isolates were able to grow aerobically from 4 °C to 37 °C, survived below 60 salinity, and could reduce trimethylamine N-Oxide to trimethylamine (TMA). Biochemical characterization and phylogenetic tree analysis of 16S rRNA gene showed that AE03 and AE04 belonged to A. salmonicida and A. molluscorum, repectively. The isolate AE03 showed the faster growth rate than AE04 on the growth curves at 4 °C and 25 °C, and exhibited the higher production of biogenic amine, TMA, and extracellular enzyme activity in vitro. In sterile fish juice, the total volatile basic nitrogen (TVB-N) value of AE03 was also significantly higher than that of AE04. Furthermore, two isolates could produce AHLs by C. violaceum CV026 and A. tumefaciens A136 biosensor detecting system, and AHLs activity in AE03 was higher than that in AE04.Thus, it was found that AE03 (A. salmonicida) was a strong spoiler in deterioration of L. crocea at refrigerated storage, and produced higher AHLs activtiy. The present study provided a good foundation to clarify the mechanism of spoilage of Aeromonas from the point of quorum sensing.