TECHNOLOGICAL CHARACTERISTICS AND ANTIBACTERIAL ACTIVITIES OF Lactococcus lactis subsp. Lactis ISOLATES RECOVERED FROM LABAN RAYEB AND KARIESH CHEESE

Lactococcus lactis subsp. lactis is widely used as a starter in the preparation of fermented dairy products. Extensive amounts of commercial starters containing this organism are annually imported from Western countries, which represents a burden on the national dairy industries and retards its development. This study aimed to isolate the organism from Laban Rayeb and Kariesh cheese, which are locally available traditional fermented dairy products that contain diverse bacterial floras. The study also considered characterizing the technological characteristics and antibacterial activities of the resultant isolates. Thirty Lactococcus spp isolates could be recovered from 68 samples of Laban Rayeb and Kariesh cheese and identified as Lac. lactis subsp. lactis. Three isolates of the same organism were also recovered from commercial starters and compared with those cultured from Laban Rayeb and Kariesh cheese. The total of the 33 isolates were assessed for their technological characteristics and antibacterial activities. Results showed that there were isolates of Lac. lactis subsp. lactis recovered  from Laban Rayeb and Karieshcheesethat produced titratable acidity and expressed proteolytic activities significantly higher (P<0.05) than isolates obtained from commercial starters. Some of the isolates were also able to produce exopolysaccharides, but produced less acidity. The isolates were further found to show antibacterial activities against Staphylococcus aureus and Salmonella ser. Typhimurium. Together, these results show that it is possible to select isolates of Lac. lactis subsp. lactis recovered from Laban Rayeb and Kariesh cheese and use them in the preparation of dairy products instead of imported starter cultures.