Antagonistic effects of Bacillus species against bacterial multi-drug resistant (MDR) food-borne pathogens and aflatoxigenic fungi

Abstract

Study’s Novelty/Excerpt • This study is novel as it offers a comprehensive evaluation of the antagonistic capabilities and technological properties of various Bacillus species, particularly against multidrug-resistant (MDR) bacterial food-borne pathogens and aflatoxigenic fungi. • By integrating morphological, biochemical, enzymatic, and HP-TLC analyses, this research uniquely identifies B. subtilis OKOI7.12ia as a standout strain with superior inhibitory activity, robust growth under diverse conditions, and high enzymatic production. • These findings underscore the potential of B. subtilis OKOI7.12ia as an effective starter culture for enhancing food safety, representing a significant advancement in the application of Bacillus species in food microbiology. Full Abstract This study was designed to investigate the antagonistic pattern of Bacillus species against MDR bacterial food-borne pathogens and aflatoxigenic fungi and evaluate their technological properties. Morphological and biochemical characterizations were done using standard methods. Production of cell-free metabolites, agar well diffusion, optimization of Bacillus growth rates, and enzymatic assays were also carried out using standard techniques, while aflatoxin quantification and qualification were done using high-performance thin-layer chromatography (HP-TLC). Results revealed that B. subtilis OKOI7.12ia had the highest inhibitory activity against S. enteritidis ATCC 13875 (27mm), while B. paralicheniformis had the least inhibitory activity against A. niger (7mm). B. subtilis OKOI7.12ia also had the highest growth rate at 30oC, followed by B. subtilis IPOI3.12ia and B. paralicheniformis OKAO4.12ia. However, there was no significant difference in the growth rates of B. subtilis IPOI3.12ia at 30oC and 40oC (p < 0.05). Furthermore, B. subtilis OKOI7.12ia and B. subtilis IPOI3.12ia had the highest growth rate at pH 8, while a lower growth rate was observed at pH6 (p < 0.05) in all five Bacillus sp. In addition, B. subtilis OKOI7.12ia and B. subtilis IPOI5.10ia had the highest growth rates using glucose and galactose as carbon sources, respectively. Growth in nitrogen sources showed that B. subtilis OKOI7.12ia had the highest growth rate, while B. subtilis IPOI5.10ia and B. subtilis OGOA10.7ii growths were not significantly different at p < 0.05. More so, B. subtilis IPOI3.12i had the least growth in peptone. In addition, B. subtilis OKOI7.12ia also produced the highest amounts of protease, amylase, and lipase enzymes, while B. subtilis IPOI3.12ia produced the least. Therefore, from the results obtained in this study, it can be concluded that B. subtilis OKOI7.12ia can be employed as a potential starter culture for producing microbiologically safe foods.

Keywords

• enzymes
• spectrophotometer
• antimicrobial metabolites
• agar well diffusion
• high-performance thin-layer chromatography