Abstract

In spite of overwhelming information about lactic acid bacteria (LAB), only a few studies are available for the LAB of marine environment. The purpose of the present study was the isolation and characterization of new strains of LAB from gastrointestinal tract of coastal fish: sardine (Sardina pilchardus) and bug (Boops boops). A total of 67 strains of LAB were isolated of which 16 strains displayed antibacterial activities againstStaphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiellapneumoniae, Bacillus cereus, Salmonella sp. and Enterococcus faecalis. Also anantifungal activity was detected against Fusarium oxysporum and Aspergillus sp. The strains selected for their antimicrobial activity were identified on the basis of phenotypic characters including API system as: Lactococcus lactis subsp. lactis, L. lactis subsp.diacetylactis, Leuconostoc sp. and Lactobacillus plantarum. Three strains were screened for the study of their antibacterial compounds: L. lactis subsp. lactis MT, L. lactis subsp. diacetylactis BT4 and L. lactis subsp. diacetylactis BL10. It was observed that inhibitory activities of all three LAB strains were due to bacteriocin-like substances. This antimicrobial activity was inactivated by the addition of proteinase K, α-chymotrypsin, but not by lipase. All strains were able to hydrolyze casein, majority showed amylolytic activity and produces biogenic amines. However,  they were non-hemolytic, showed no particular antibiotic resistance profile and none of them was found to possess lipolytic activity.

Key words: Marine fish, Lactococcus, Enterococcus, biogenic amines, antimicrobial activity.