Extraction and purification of antibiotic principles from the culture medium of selected microbial isolates from sea cucumber

Introduction: Three broad-spectrum antibiotic-producing microbes (named IF32, IF52, and CF42) were identified and isolated from intestinal region and coelomic fluids of sea cucumber species collected from Kanyakumari district, Tamil Nadu. Biochemical characterization of the isolated microbes and optimization of culture characteristic (for maximum antibiotic productivity) were performed. The present study focuses on extraction and purification of antibiotic principles from the culture medium of the selected isolates. Methodology: The antibiotic fermentation was carried out in the optimized fermentation medium under optimum conditions separately for the isolated species. After separation of the cells by filtration, the fermented culture media were subjected to solvent extraction using 1-butanol, chloroform, ethyl acetate, and hexane. Obtained residues were subjected to antibiotic screening against Staphylococcus aureus (MTCC 1430) by disc plate method. Purification of the selected residues which showed antibiotic activity was done by column chromatography using silica gel as packing material. Collected fractions of the three antibiotic residues were subjected to bioautography to ensure the purification of the antibiotics. Results: The results show that chloroform, 1-butanol, and ethyl acetate are found to be suitable solvents for the extraction of antibiotics from the fermented cultures of IF32, IF52, and CF42, respectively. Bioautography performed using fractions obtained from column chromatographic separation ensured the purification of the antibiotic principles.