Microencapsulation Of Bacillus Subtilis TP-2 And Its Pilot Scale Experiment

Chemical pesticides cause environmental pollution; therefore, biological control is a promising approach to protecting plants from disease. Bacillus subtilis has been widely used in agriculture for promoting plant growth and biocontrol, since it has a broad-spectrum resistance to various pathogens. B. subtilis B99-2 strongly inhibits Rhizoctonia solani and Fusarium oxysporum isolated from tomato rhizosphere in China. However, no information regarding its formulation for commercial use is available.The carrier and B. subtilis were used as core materials of microcapsules; the maltodextrin was viewed as wall material. The optimal processing technology of microencapsulation was established through single factor and orthogonal experimental:m(white carbon black):m(corn starch):v(fermentation broth)=1:3:5, inlet temperature 165℃, feed flow rate 550 mL/h, spray pressure 0.20 Mpa. Meanwhile, the pilot scale experiment at the optimum condition was carried out with fluidized-bed dryer. The optimal processing technology of microencapsulation was established through single factor and orthogonal experimental: m(white carbon black):m(corn starch):v(fermentation broth)=1:1:2, inlet temperature 80℃.The thallus was used as core material; the maltodextrin was viewed as wall material; microencapsulation of Bacillus subtilis was made by spray-drying to determine the spray-drying conditions by single factor experiment; The best condition of microencapsulation was as follows:m(corn starch):v(fermentation broth)=1:1, inlet temperature 145℃, feed flow rate 550 mL/h, spray pressure 0.15 Mpa. The pilot scale experiment at the optimum condition was carried out with air-stream and centrifugal spray drier. The best condition of microencapsulation was as follows:m(corn starch):v(fermentation broth)=2:1, inlet temperature 145℃.While Bacillus subtilis microcapsules’survival rate was 87.53% after storage of 540 days, significantly higher than wettable powders.And to assess Bacillus subtilis microcapsule biocontrol efficiency against Rhizoctonia solani in tomato under field conditions in this study. Bacillus subtilis TP-2 microcapsules biocontrol efficacy could reach to 71.85% when a dosage of 30 mg/m2 was used, characteristics that indicate their potential to become a successful biocontrol product. Nowadays, there is no report indicate that microencapsulation of microorganism was used in biological control; our research effectively pushed the application of microbial pesticide.