Bacterial Diversity and Antibiotic-Producing Bacillus spp. in Ogiri-egusi: Potential for Biocontrol and Industrial Applications

Abstract

Ogiri-egusi, a traditional alkaline-fermented condiment derived from Citrullus vulgaris seeds, is produced through spontaneous fermentation, resulting in diverse microbial communities that influence its quality and safety. This study investigated the microbial diversity, fermentation dynamics, and antimicrobial potential of Bacillus spp. isolated from Ogiri-egusi. Samples were collected from four major markets in Makurdi metropolis, and bacterial isolates were identified based on cultural, morphological, and biochemical characteristics. The microbial analysis revealed that Bacillus spp. were the predominant fermentative bacteria (62.5%), alongside Leuconostoc spp., Micrococcus spp., Proteus spp., and Lactobacillus spp., indicating a diverse microbial community. The pH of the fermenting substrate increased from 6.3 to 7.9 over four days, consistent with proteolytic ammonia production, a hallmark of alkaline fermentation. Antimicrobial screening of Bacillus spp. crude extracts against bacterial pathogens using the agar well diffusion method revealed significant inhibitory effects on Staphylococcus spp. (8.00 ± 0.58 mm) and moderate inhibition against Pseudomonas spp. (4.67 ± 2.40 mm) and Salmonella spp. (3.33 ± 1.76 mm). However, Proteus spp., Klebsiella spp., and Escherichia coli exhibited resistance to the crude extracts. Nutrient composition influenced antimicrobial activity, with sucrose-based extracts exhibiting higher inhibition against Staphylococcus spp. and Pseudomonas spp., while nitrogen-based extracts showed enhanced activity against Salmonella spp. The absence of inhibition against Proteus and Bacillus spp. suggests intrinsic resistance mechanisms. These findings highlight the role of Bacillus spp. in Ogiri-egusi fermentation and their potential as natural biocontrol agents. Optimizing fermentation conditions could enhance antibiotic yield and efficacy, while further purification and molecular characterization of bioactive compounds are necessary. Harnessing beneficial microbes from traditional fermented foods may offer sustainable solutions for antibiotic production, food preservation, and biopharmaceutical applications.