Introduction and Approaches for Improvement in Antibiotic Production Aminoglycosides Template-Biosynthesized Peptide and b-Lactam Antibiotics Ribosomally Synthesized Peptide Antibiotics Polyketide Antibiotics Produced by Type-I Multifunctional Enzymes Polyketide Antibiotics Produced by Type-II Polyketide Synthase Systems Peptydil Nucleoside Antibiotics Recombinant Bioconversions of Bioactive Molecules