Impact of Temperature Variations on Bacteriocin Activity Against Spoilage Bacteria in Melon and Its Fermented Product 'Ogiri'

Abstract

The efficacy of bacteriocins produced by Lactobacillus plantarum NRIC 0383 against spoilage bacteria isolated from melon seeds and their fermented product, Ogiri, was evaluated under various storage temperatures. Traditional fermented foods, such as Ogiri made from melon seeds (Citrullus lanatus), are significant protein sources in rural African communities but are susceptible to microbial contamination, posing public health risks. The study aimed to assess the antimicrobial activity of L. plantarum bacteriocins against identified spoilage bacteria: Escherichia coli 2013C-3342, Staphylococcus aureus CIP 9973, and Enterobacter cloacae AS10. Isolation and identification of these bacteria were performed using serial dilution and molecular techniques, respectively. Bacteriocin production by L. plantarum NRIC 0383 was confirmed via 16S rDNA sequencing and PCR amplification of bacteriocin genes. Partially purified bacteriocins, obtained through ammonium sulfate precipitation and dialysis, demonstrated significant inhibitory effects against the test microorganism, with inhibition zones ranging from 10-20 mm. Stability tests revealed that the bacteriocins retained more than 80% of their activity at temperatures between 30°C and 70°C, but activity declined at 90°C and was almost entirely lost at 121°C. These findings suggest that L. plantarum NRIC 0383 bacteriocins are potent bio-preservatives that could enhance the safety and shelf-life of melon seed-based fermented products, offering a natural alternative to chemical preservatives.