Creating Optimal Conditions for Bacteriocin Production from Lactiplantibacillus plantarum Isolated from Traditionally Fermented Fruits and Vegetables

Lactic acid bacteria produce a large number of antimicrobial metabolites which are effective against pathogenic microorganisms. Amongst LAB’s antimicrobial agents, bacteriocins have been found as potentially safe biopreservatives. In this research, LAB isolates from less studied non-dairy fermented products were screened for simultaneous production of bacteriocins. Among 253 dominant isolates from 48 types of fruit and vegetable fermented products, strains which found to be potent bacteriocin producers were selected. Further, DNA of the strains was evaluated by the 16S rRNA sequencing. Five isolates identified as Lactiplantibacillus plantarum (10A, V3, S6, Sa, and Ab), showed the highest inhibitory effect against the growth of pathogenic indicators Listeria monocytogenes PTCC 1165, Escherichia coli ATCC 25923, Salmonella enterica serovar typhimurium PTCC 1609 and Staphylococcus aureus ATCC 25922. Response surface methodology was used to optimize the culture conditions based on various carbon/nitrogen sources in different temperatures (30, 32, 35, and 37 ºC) and incubation periods. This led to an increase in efficiency of bacteriocin production by 70%. The bacteriocin production curve was plotted within 58 hours showing that the maximum production and activity happened at 35 °C/48 h in culture containing peptone, yeast extract, tween 80 and glucose. Inhibitory effect of bacteriocins was significantly reduced when treated with proteolytic enzymes. Among the 5 isolated strains, 10A with an activity of 64000 Au/mL exhibited the highest inhibitory effect, even more than nisin. This study successfully recommends the selective potential of bacteriocin 10A as a candidate food biopreservative to control the growth of food pathogenic and spoiling bacteria.