Paenibacillus polymyxa Antagonism towards Fusarium: Identification and Optimisation of Antibiotic Production

Abstract

An antibiotic produced by <i>Paenibacillus polymyxa</i> 7F1 was studied. The 7F1 strain was isolated from the rhizosphere of a wheat field. Response surface methodology was used to optimize the physicochemical parameters. The strain showed broad-spectrum activity against several plant pathogens. Identification of the strain was realized based on 16s rRNA gene and <i>gyrB</i> gene sequencing. The antibiotic was optimized by one-factor-at-a-time (OFAT) and response surface methodology (RSM) approaches. The suitable antibiotic production conditions were optimized using the one-factor-at-a-time method. The individual and interaction effects of three independent variables: culture temperature, initial pH, and culture time, were optimized by Box-Behnken design. The 16SrRNA gene sequence (1239 nucleotides) and <i>gyrB</i> gene (1111 nucleotides) were determined for strain 7F1 and shared the highest identities to those of <i>Paenibacillus polymyxa</i>. The results showed the optimal fermentation conditions for antibiotics produced by <i>Paenibacillus polymyxa</i> 7F1 were a culture temperature of 38 °C, initial pH of 8.0, and culture time of 8 h. The antibiotics produced by <i>Paenibacillus polymyxa</i> 7F1 include lipopeptides such as iturin A and surfactin. The results provide a theoretical basis for the development of bacteriostatic biological agents and the control of mycotoxins.