Optimization of antibiotic production against Bacillus cereus by a mutant strain of Bacillus licheniformis isolated from Egyptian Hamam Pharaon hot springs

Background The growing threat of multidrug-resistant bacteria necessitates the development of new and effective antibiotics for pathogen control. Bacteria are widely distributed in nature and have a wide applied biotechnological potential for cleaning up the environment. They have been demonstrated by their ability to produce thousands of novel bioactive metabolites with many potential applications in agriculture, medical, pharmaceutical industries, and bioremediation. The nature and yield of the secondary metabolites produced by the bacteria are greatly influenced by nutrition factors and fermentation conditions. So, the bioactive metabolites can be increased by several folds by applying optimization studies of the factors affecting the production process. Objective To optimize antibiotic production against Bacillus cereus by a potent bacterial strain isolated from hot springs and identification of the antibiotic compounds produced by such a bacterial strain. Materials and methods Bacillus licheniformis mutant (M15/Amo) obtained by ethyl methane sulfonate treatment was optimized for antibiotic production. A Plackett–Burman Design was employed to determine the influence of independent variables on the antibiotic production by the B. licheniformis mutant strain. Response surface methodology was further used by applying a Box–Behnken Design to optimize the more effective variables. Supernatants were extracted using ethyl acetate as a solvent. The crude compounds were assayed to confirm the presence of antibacterial bioactive metabolites. The analysis of the target antimicrobial metabolites was performed using liquid chromatography–electrospray ionization–tandem mass spectrometry. Results and conclusion The study is a trail to find microorganisms capable of producing antibiotics against B. cereus and optimize the conditions of antibiotic production by the isolated bacteria from hot springs. The highest antibiotic production was achieved in the presence of glucose and peptone as optimum carbon and nitrogen sources, respectively. The optimization of medium composition and fermentation conditions to produce antibiotics by the B. licheniformis mutant strain was studied. The effect of seven factors on antibiotic production was investigated. Optimization of antibiotic production by the B. licheniformis mutant strain using statistical modeling revealed that the mutant (M15/Amo) gave the highest antibiotic production using 3% glucose, 2.5% peptone, incubation time of 60 h at pH 7.5. The analysis of the extracts using liquid chromatography–electrospray ionization–tandem mass spectrometry showed the presence of seven compounds that have antipathogenic activity.