[Objective] The aim of this study was to purify an antimicrobial protein from a biocontrol bacterium strain K2-1 and analyze its antimicrobial activity in vitro against some typical aquatic pathogens. [Method] The antimicrobial protein was ob- tained by using ammonium sulfate precipitation and Sephadex chromatography combined with hot water bath. The antimicrobial assay was conducted by means of agar diffusion technique, using Vibrio alginolyticus, Aeromonas hydrophila, Aeromonas. Sobria, Pseudomonas fluorescens, Vibrio Parahaemolyticus, Vibrio har- veyi and Vibrio anguillarum as test bacteria. [Result] Antimicrobial protein APK2 can be derived from fermentation broth of strain K2-1 and purified to the chromatogra- phy pure level by the methods provided, the final yield of the antimicrobial compo- nent is approximately 0.08%. This antimicrobial protein had a strong antimicrobial activity against the growth of most those bacteria. [Conclusion] The results show that APK2 could be a potential alternative to replace chemical antimicrobial agent in the control and prevention of aquatic diseases.
A strain LHB02 with strong antibacterial activity against some aquatic pathogens was screened from the coastal marine sediment in Fujian province, China. LHB02 was identified as Bacillus subtilis, based on its 16S rRNA sequence, together with the morphological, physiological and biochemical characteristics. The antagonistic activity of strain LHB02 and its optimal fermentation conditions were also investigated. The results showed that LHB02 had strong antagonistic activity against 3 species of vibrios： Vibrio harveyi,Vibrio alginolyticus and Vibrio anguillarum, and the optimum fermentation conditions for the strain LHB02 were as follows： KB culture medium （peptone 20 g, glycerol 10 mL, K2HPO4 1.5 g, MgSO 4 .7H2O 1.5 g, H2O 1 000 mL）; temperature, 28 ℃; pH ,7.0; culture time, 36 h; and inoculation amount, 1.5% （v/v）.
