Abstract:Objective: Strains for antifungal peptides production were screened and isolation from soil, and then the antifungal peptides yield was improved by optimizing its fermentation conditions. Methods: Agar plate dilution and agar diffusion method were used for the strain isolation. Morphological, physiological and biochemical characteristics and 16S rDNA sequence of the strain were used for the strain analysis and identification. The antifungal properties of antifungal substances were determined by protease treatment, ammonium sulfate precipitation, membrane dialysis and thermal stability study. The fermentation medium and conditions for antifungal peptides production were optimized by single factor and orthogonal tests, and then the fermentation amplification was carried out in the fermenter. Results: An antifungal peptides-producing strain was screened and identified as Paenibacillus ehimensis. The strain was named as Paenibacillus ehimensis HD. The antifungal substances produced by P. ehimensis HD was verified as small molecular polypeptides with the molecular weight of about 1 ku. The antifungal peptides had a broad spectrum of antimicrobial activity, which could not only inhibit the spoilage fungi, but also inhibit the pathogenic bacteria. The optimum conditions for antifungal peptides production by P. ehimensis HD were as follows: mannitol 2.5 g/L, MgSO4 3.0 g/L, fish peptone 10 g/L, initial pH 7.5, liquid volume 40 mL/250 mL, inoculation amount 1×108 CFU/mL, shaker speed 220 r/min, fermentation temperature 32 ℃, fermentation time 32 h. Under the optimal conditions, the titer of antifungal peptides was 324.92 AU/mL, which was 3.63-fold compared to the initial medium. Scale-up of antifungal peptides fermentation from shaking flask to 5 L and 30 L fermenters, the titers of antifungal peptides were 371.01 AU/mL and 364.05 AU/mL, respectively, moreover, the fermentation time was forward to 20 h. Conclusion: The antifungal peptides produced by P. ehimensis HD had good antifungal activity, and the yield of antifungal peptides was stable after fermentation optimization and amplification.