Profiling of autochthonous microbiota and characterization of the dominant lactic acid bacteria occurring in fermented fish sausages

The use of fish flesh to produce fermented sausages is uncommon, especially in European countries where fermentedsausages are mainly obtained using mammalian meat. In the present study, the microbiota naturallyoccurring in novel fermented fish sausages, handcrafted using marine fish species caught in the MediterraneanSea, was studied. To this end, fish sausages were subjected to physico-chemical analyses (including histaminequantification). Microbiological traits of sausages were studied via viable counting and metataxonomic analysis.Sausages were also subjected to the detection of genes encoding histidine decarboxylase of both Gram-positive(hdcA) and -negative (hdc) bacteria.The results of histamine quantification showed different contents among fish sausage samples. Moreover, thepresence of the hdcA gene was below the detection limit in all the samples, whereas the hdc gene was detectedonly in samples from batch 2, characterized by high levels of Enterobacteriaceae.In the analysed samples, viable lactic acid bacteria, coagulase-negative staphylococci, and eumycetes weredetected. Bacterial composition displayed the highest frequency of Latilactobacillus sakei, whereas eumyceticcomposition displayed the highest frequency of Kurtzmaniella zeylanoides.In order to select potential adjunct cultures for product improvement, 60 lactic acid bacteria (22 isolates ofL. sakei and 38 of Latilactobacillus curvatus) were isolated from sausage samples and characterized for: i) thepresence of the hdcA gene; ii) the production of exopolysaccharides (EPS); iii) the presence of genes involved inthe production of EPS; iv) the production of bacteriocins against Listeria innocua.None of the isolates tested positive for the presence of the hdcA gene. Moreover, 39 out of 60 isolates showedthe formation of mucoid colonies, thus attesting the production of EPS. Interestingly, 56 out of 60 isolates werepositive for the gene epsD/E, whereas 37 out of 60 isolates were positive for the gene epsA, all these genesencoding the production of heteropolysaccharides. Of note, the EPS production capability and the absence ofhdcA gene could represent a starting point for future selection of the isolates as autochthonous adjunct cultures toimprove texture, sensory traits and safety of the fermented fish sausages under study. None of the L. sakei orL. curvatus isolates exerted a bactericidal effect against L. innocua.