Five strains of Lactococcus, including L. garviae K2, L. piscium SU4, L. lactis subsp. cremoris E22, L. plantarum L7 and L. lactis subsp. hordinae E91 were screened for production of antimicrobial agents. The strains were also analysed for antimicrobial activities against spoilage and pathogenic organisms, including Staphylococcus aureus, Salmonella Typhimurium, Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa, Klebsiella pneumoniae, Listeria monocytogenes, Bacillus cereus and Pseudomonas fluorescens. Result revealed that L. piscium SU4, L. plantarum L7 and L. lactis subsp. cremoris E22 had lactic acid production (g/107 colony forming units, CFU) of 7.23, 7.20 and 7.19. The value of 6.83 recorded as lactic acid produced by L. garviae K2 was significantly different from those obtained for others. The highest acetic acid production (3.55 g/107 CFU) was recorded for L. garviae K2 while L. piscium SU4 had the lowest (2.99 g/107 CFU). L. lactis subsp. hordinae E91 had diacetyl production of 71.99 (µg/107 CFU), which was higher than those recorded for other Lactococcus strains. Test for antimicrobial activities showed that Escherichia coli NCTC 86, Yersinia enterocolitica NCTC 10460, Pseudomonas aeruginosa NCIMB 10848, Bacillus cereus NCTC 21113 and Pseudomonas flourescens recorded higher susceptibilities to the antimicrobial action of the Lactococcus strains than others; zones of inhibition of 5 mm and above were recorded for the indicator organisms compared to lower values (

Dahi is a fermented milk product containing probiotic lactic acid bacteria. This study aimed to isolate, identify, and characterize lactic acid-producing bacteria from native Dahi and evaluate their viability in orange juice using natural prebiotics. Dahi samples were obtained from local shops in Chattogram and Bogura, Bangladesh. Lactic acid-producing bacteria were isolated using MRS (de Mann Rogosa and Sharpe) medium. The isolated bacteria were identified through colony morphology, biochemical tests, and probiotic characteristics. Molecular identification was performed using polymerase chain reaction (PCR) targeting conserved 16S rDNA regions. Isolates of the genus Lactobacillus and Lactococcus lactis sp. Lactis were confirmed and used to develop probiotic orange juice. Prebiotics (Asparagus falcatus and Zingiber officinale) were added to the juice to support probiotic growth. The inoculated cell’s viability and the juice’s physicochemical parameters were evaluated during fermentation (48 hours) and storage (28 days). All fruit juice samples showed a mean number of viable cells of at least 1×105 CFU/mL during the 48-hour fermentation and 28-day storage in the refrigerator. Using natural prebiotics positively affected the survival of lactic acid bacteria, as demonstrated by bacterial colony growth on Petri dishes. Developing probiotic fruit juice enriched with prebiotics could be an effective alternative for individuals allergic or intolerant to milk-based products. Incorporating lactic acid bacteria from native Dahi into orange juice, combined with natural prebiotics, resulted in viable probiotic cells throughout fermentation and storage.