Abstract

Bacitracin is a potent antibiotic which is used in combination with other antimicrobial agents. Bacitracin in the form of its zinc salt is used as feed additive, growth promoter and for reduction of diseases in poultry. In the present study, twenty five bacterial strains capable of producing bacitracin were isolated from milk samples by heat shock method. Among all bacterial strains, the isolate no. 21 was found to be the most potential strain; it was identified and designated as Bacillus licheniformisBCL-21. Different fermentation media were evaluated for antibiotic production under submerged fermentation in shake flasks. The medium M1 gave higher antibiotic production (245.5 IU/ml) than M2(186.0 IU/ml) and M3(202.2 IU/ml). Different parameters were optimized in shake flask studies. The antibiotic production was 271.2±1.51 IU/ml by using 24 h old inoculum. Inoculum size was optimized to be 6.0 % ((274.0±1.89 IU/ml). The optimum pH was found to be 8.0 and bacitracin production was 245.5±0.58 IU/ml. At 37oCtemperature, production was295.0±1.34 IU/ml. Antibiotic activity was observed to be 283.9±1.43 IU/mlafter 48 h of incubation. The optimum agitation speed and working volume were observed to be 150 rpm(207.0±0.85 IU/ml) and 100 mL(232±1.29 IU/ml) respectively. Partial purification of bacitracin from fermentation broth was successfully done by precipitation method.