Abstract

Lactic acid bacteria (LAB) responsible for spontaneous fermentation of cucumber were isolated and their antimicrobial producing potentials were screened against 10 indicator strains. 65% of the isolated LAB produced antimicrobial activities against at least two indicator strains. The indicator strains used were: Escherichia coli, Bacillus licheniformis, B. cereus, Proteus species, Staphylococcus aureus, Salmonella species, Pseudomonas flourescence, P. aeruginosa, Serratia species and Pediococcus  acidilactici. Of the 42 antimicrobial producing isolates characterized, 16, 12, 6 and 8 were identified as Lactobacillus plantarum, L. fermentum, L. acidophilus and Leuconostoc mesenteroides, respectively. Highest lactic acid producers DW7, DT6, DH13 and DF12 were selected for further investigations and were identified as L. plantarum. None of the selected L. plantarum isolates had antagonistic activity against S. aureus, Salmolnella species and P. acidilactici. The effect of pH and temperature on the antimicrobial activity of selected isolates showed that pH 5.5 and temperature 30°C were the optimum pH and temperature respectively. Thus, the selected L. plantarum isolates are good producers of antimicrobial compounds and could be suitable for application in food industry in preservation of vegetables so as to increase their shelf life.

Key words: Cucumber, fermentation, antimicrobial activity, indicator strains, lactic acid bacteria.