Influence of nitrogen source on formation of chloramphenicol in cultures of Streptomyces sp. 3022a

Abstract

The rate of growth and chloramphenicol production of Streptomyces sp. 3022a can be controlled by varying the nitrogen source used in the medium. Sources such as peptone and nitrate support rapid growth but the high initial rate of antibiotic production was not sustained. Nitrogen sources which resulted in slow, controlled growth supported the highest yields of chloramphenicol. DL-Serine was the most suitable nitrogen source to use in this synthetic medium as good yields of chloramphenicol were obtained within a reasonable incubation period, e.g. 7 days.The substitution of part of the nitrogen supplied as DL-serine as nitrate (e.g. up to 2% of the total nitrogen supplied) decreased the fermentation time required without affecting the total amount of chloramphenicol produced. Nitrate at higher concentrations inhibited both chloramphenicol and mycelial production whereas the complete elimination of DL-serine from the medium restored mycelial production but not chloramphenicol production. Studies with ¹⁵N-nitrate showed that the nitro group of chloramphenicol does not originate from a biological nitration reaction but rather that both nitrogen atoms are derived from a common pool.The low dilution of radioactivity obtained from ¹⁴C-glycerol as compared with serine-1,3-¹⁴C indicates that serine does not have a special role as a precursor of chloramphenicol. Rather its value lies in its ability to control the growth rate of Streptomyces sp. 3022a, maintaining physiological conditions suitable for the formation of chloramphenicol.