Screening of Wild Lactobacillus Plantarum Found in Brine Solution of Naturally Fermented Cucumbers

Fermentation has been used as a simple technique for preserving vegetables since ancient days. This research work aimed to isolate, characterize, and identify wild Lactobacillus plantarum found in a brine solution (8% w/v NaCl) of naturally fermented cucumber. Cucumber samples were naturally fermented at ambient temperature for 14 days in a brine solution, in which lactic acid bacteria (LAB) were then cultured (37℃, 48 h) within 24 h for 3, 5, 7, 10, and 14 days. Seventeen different LAB strains were isolated and identified within the different time intervals of fermentation using morphological, biochemical API 50 CHL, PCR verification using Lactobacillus subspecies-specific genes primer, and 16S rRNA gene sequencing. The API confirmed strains were further verified by PCR to be L. plantarum subsp. plantarum M23 based on the amplified gene fragment separation by gel electrophoresis and gene sequencing. After 24 h of fermentation, the most dominant LAB-identified strains were Leuconostoc mesenteroides, Tetragenococcus halophilus, and L. plantarum M23, respectively. Starting from the fifth day of fermentation, L. plantarum M23 controlled the fermentation process as the dominant LAB. The drop in the pH value was significant (from 6.8 to 3.18) due to the variations in the LAB strains throughout the 14 days of fermentation. Further investigation will be carried out to study the production of plantaricin, which has great importance in food biopreservation.