Enhancing titre and production stability of paenibacillin from Paenibacillus polymyxa by sequential drug resistance screening

Aims Paenibacillin is a naturally biosynthesized antimicrobial lantibiotic peptide which is produced by wild‐type Paenibacillus polymyxa OSY‐DF in low but detectable levels. The aim was to increase paenibacillin titre and production consistency through sequential drug resistance screening. Methods and results Spontaneous mutants of P. polymyxa OSY‐DF were isolated by subjecting the bacterium to two rounds of screening for resistance to rifampicin, which targets RNA polymerase, and gentamicin, which targets ribosomes. Changes in antimicrobial production of the mutants were monitored using a bioassay method. A spontaneous mutant, P. polymyxa OSY‐EC, capable of producing high paenibacillin titre, was selected and compared phenotypically to the wild‐type strain. The mutant was found to produce paenibacillin at five‐fold higher titre than the wild type. The mutant constantly produced paenibacillin while the wild type produced the antimicrobial agent variably. Fourier transformation mid‐infrared spectroscopy revealed an interclass distance of 6·4 between the wild type and the mutant strain, suggesting significant phenotypic change during the mutation. Conclusions P. polymyxa OSY‐EC, a spontaneous mutant capable of consistent production of high paenibacillin titre, was isolated from the wild type after sequential screening on rationally selected antibiotics. Significance and Impact of the Study The study will help make paenibacillin available for large‐scale testing by interested researchers and industries seeking applications that improve food safety and quality.