New Antifungal Bacteriocin-Synthesizing Strains of Lactococcus lactis ssp. lactis as the Perspective Biopreservatives for Protection of Raw Smoked Sausages

Abstract

Problem statement: Screening for the effective bacteriocin-synthesizing strains of Lactococcus lactis as the perspective biopreservatives was performed. We used a raw milk and dairy products from different climatic regions as well as from powerful drinks of mixed lactic acid and alcoholic fermentation: kurunga, kumiss and Iranian “Dough”, that were widely used by local population to prevent diseases. Approach: The special interest was paid to isolates of lactococci with antagonistic activity. According to their morphological, cultural, physiological, biochemical properties and sequence of 16S rRNA gene they were identified as Lactococcus lactis ssp. lactis. Only nine from the selected 94 strains expressed a broad spectrum of activity against Gram-positive and Gramnegative bacteria including pathogens (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella gallinarum), moulds (Aspergillus, Fusarium, Penicillium genera), as well as yeasts (Rhodotorula, Candida). Results: It reveals the unique biological properties for isolated natural strains of Lactococcus lactis species. Most effective new bacteriocin-synthesizing strains 194 and K-205 were isolated from raw cow milk and kurunga from Buryatia. These strains had high antibiotic activity up to 3600 and 2700 IU mL^-1 as compared to nisin and up to 2500-1700 IU mL^-1 as compared to fungicidal antibiotic nistatin. In our experiments we used raw smoked sausages that were infected with fungi. The identification of this infection showed the presence of Eurotium repens de Bary on the sausages. Treatment of the raw smoked sausages with cultural broth of L.lactis ssp. lactis 194 and K-205 inhibited growth of these microorganisms. After treatment the sausages had longer shelf-life and was in accordance with basal production data (Russian State Standard Specification 16131-86). Conclusion: The results of this study indicated that the treatment with lactococci strains can prevent a contamination of raw smoked sausages by potential food-borne pathogens.