AbstractThe effect of penicillin‐G on the production of the potential microbial insecticide thuringiensin byBacillus thuringiensissp.darmstadiensiswas studied. Shake flask and 3‐L jar fermentor studies showed that the addition of 360 units/mL penicillin‐G at 9 h, when the fermentable sugar in the medium was about to be mostly consumed, improved thuringiensin production by more than 1‐fold relative to the control. The dosage of 360 units/mL penicillin‐G had only a modest effect on the growth of the microorganism. However, cell growth was inhibited at higher dosages of the antibiotic. Since penicillin‐G could interfere with cell wall synthesis, which facilitated the release of thuringiensin, a high thuringiensin productivity of 2600 mg/L was attained in this study, which is about 2–10‐fold higher than those values reported in
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