Biosynthesis of Antibiotic Bacitracin by Bacillus Licheniformis as Supplement in Poultry Feed

Abstract

The present study is concerned with the synthesis of antibiotic bacitracin in shake flasks and stirred fermenters by “Bacillus” species, isolated from milk samples and also obtained from foreign culture collections. Of all the cultures tested “Bacillus Licheniformis” PCSIR-88 gave maximum antibiotic titre (270.0 i. u/m1) in the fermented broth. Different defined as well as natural media such as defatted melas of soyabeans, sunflower and cotton seed (phamacolia), were evaluated for antibiotic formation. Soyabean and sunflower meals were found to be ideal substrates for the production of bacitracin. Effect of the addition of various carbohydrates such as glucose, sucrose, mannose or lactose on the bacitracin formation was also investigated. The other parameters such as size of the inoculum, pH and the rate of aeration were optimized. The antibiotic formation reached maximum 44hrs. after inoculation. The incubation temperature was 37oC. The antibiotic fermentation was also carried out by solid substrate fermentation using a mixture of wheat bran and soyabean meal. The antibiotic activity, 48 hrs. after inoculation, was 2670 units/g. The culture of “Bacillus Licheniformis” PCSIR-88 was improved by UV irradiation and the antibiotic activity was 346.0 i. u/ml in stirred fermenter. The conditions for the recovery of antibiotic as Zn- Bacitracin were also optimized. The evaluation of Zn- Bacitracin after its incorporation in poultry feed, in parallel with the imported stuff, was also investigated and the results were found encouraging.