Use of Nisin-Producing Starter Cultures of Lactococcus lactis subsp. lactis on Cereal Based-Matrix to Optimize Preservative Factors over Fish Fermentation at 30°C Typical to Senegal

This study describes an application of bacteriocinogenic lactic acid bacteria to improve preservative factors over fish fermentation based on the most frequently used technique in Senegal. Traditional fish fermentation performed by immersion in salted sea water and incubation at 30°C for 24 to 48h to develop flavor, is characterized by a pH value around 7. The process led to the growth of Enterobacteriaceae to reach 9 log CFU/g. Four bacteriocinogenic lactic acid bacteria characterized in previous works were screened for decarboxylation activities. Only cultures of two Lactoccus lactis subsp. lactis (CWBI-B1410 and CWBI-B1426) producing nisin, a heat stable antibacterial peptide, did not produce histamine and tyrosine regarded as undesirable compounds on seafood products. The two lactococcal starter cultures grew well on a substrate based on millet, a local cereal. The AU/ml minimum inhibitory concentration of the antibacterial neutralized supernatant of the bacteriocinogenic starter cultures against Listeria monocytogenes was lower to those of many food poisoning or spoilage bacteria. Then, pieces of lean (Podamassys jubelini) and fat (Arius heudelottii) fish inoculated with 104-5 CFU/g of Listeriamonocytogenes, were immersed in the millet flour based substrate seeded with 105-6 CFU/g pure cultures of the nisinogenic bacteria to evaluate the control of the fermentation at 30°C. Listeria monocytogenes contaminated fish samples immersed in the millet-based substrate without starter cultures addition were used as negative controls.