Antibacterial Activity of Crude Bacteriocins Produced by Lactobacillus Species Isolated from Nono (Fermented Milk)

Abstract

Bacteriocins are newly discovered exometabolites of lactic acid bacteria (LAB) with antimicrobial activity and biopreservative potential; however, studies investigating the potential of LAB from locally fermented milk (Nono) in Northern Nigeria for bacteriocin production and their antimicrobial effects on foodborne pathogenic bacteria are still insufficient. The present study aims to evaluate the antibacterial activity of bacteriocins produced by Lactobacillus spp isolated from Nono against foodborne pathogens. A total of 30 samples of Nono were purchased from Bayero University Kano old campus and K/Wambai market Kano State. Nono’s physicochemical parameters (pH and Titratable acidity) and Lactic acid Bacteria (LAB) counts were determined according to standard methods. The samples were further screened for Lactobacillus spp based on routine cultural characteristics, general morphological, biochemical tests and API 50CHL techniques. Crude bacteriocins were extracted and evaluated for antibacterial activity by Agar well diffusion method. The analyses revealed that Nono had pH values ranging from 2.84- 4.08, titratable acidity (1.16- 1.34%) and LAB counts ranged from 8.60x106 – 3.00x108. Thirty – eight (38) Lactobacillus spp based on distinct morphology were isolated from Nono.  The different species of the genus Lactobacillus were identified phenotypically based on their carbohydrates fermentation profiles (API 50 CHL) as Lactobacillus plantarum 1, Lactobacillus fermentum 1 , Lactobacillus pentosus, Lactobacillus fermentum 2  and Lactobacillus delbrueckii ssp lactis 1. Ten (10) out of the 38 isolates were potential bacteriocin producers. Extracted crude bacteriocins exhibited broad-spectrum activity against E. coli (9.5+0.3 – 20 +0.8mm) and S. aureus (9.47+0.6 -18.3 + 0.6mm). Bacteriocins produced by Lactobacillus spp isolated from Nono could be used to solve the problem of contaminating microorganisms in food industries.