PRODUCTION OF ANTIBIOTICS BY Bacillus subtilis M10 IN UREA-SORBITOL MEDIUM. Infection diseases still become the main health problems that suffered by people in Indonesia. Besides, there were many pathogen bacteria found to be resistant to the some antibiotics. Therefore, the efforts to get a new antibiotic require to be done continuously. A new local strain of Bacillus subtilis BAC4 has been known producing an antibiotic that inhibit Serratia marcescens ATCC 27117 growth. To make efficient the local strain, mutation on Bacillus subtilis BAC4 was done by using acridine orange and a mutant cell of Bacillus subtilis M10 that overproduction for producing antibiotic was obtained. Nevertheless, the production kinetics of antibiotic by this mutant has not been reported. The objective of this research was to study the production kinetics of antibiotic by Bacillus subtilis M10 mutant. The production of antibiotic was conducted using batch fermentation and antibiotic assay was performed with agar absorption method using Serratia marcescens ATCC 27117 as bacteria assay. Research result provided that Bacillus subtilis M10 mutant with overproduction of antibiotic produced an antibiotic since 8^th hour’s fermentation and optimum of it production was at 14^th hours after inoculation.