| Iturin A has a strong antifungal properties,low toxicity,low residue,wide antimicrobial spectrum,and so on.It has a very good antagonism effect to the majority of plant pathogen,is a kind of potential biological pesticide with application value.In recent years,the microcapsule technology develops rapidly,combines with the biological pesticide to prepare biological pesticide microcapsule which has such characteristic as low toxicity,low residue,sustained-release property,long effective,safe and convenient.The biological pesticide microcapsule can be used to control multi pest of agriculture and forestry,instead of the chemical pesticides with high toxicity and high residue,and protect the ecological environment.Prospectively,the pesticide microcapsule will replace the traditional pesticide,whose vigorous development has a great of social and economic benefits.Presently,there is no report about iturin A microcapsule.We optimize the fermentation medium of Bacillus subtilis X-01 to reduce the production cost of iturin A,prepare the iturin A microcapsule by spray drying,study about its preparation method,surface morphology,sustained-release,ultraviolet resistance and storage stability mainly.This article designed the experimental method of optimizing the fermentation medium of Bacillus subtilis X-01 by Taguchi Robust Design,and analyzed the experimental results by the Minitab software.The study shows that the sort of situation of various factors effecting on the signal-to-noise ratio and the mean is: glucose > soybean meal powder > p H > sodium chloride > ammonium chloride > corn flour,the optimal fermentation medium of Bacillus subtilis X-01 is 4 g/L of corn flour,16 g/L of glucose,12 g/L of soybean meal powder,6 g/L of ammonium chloride,1 g/L of potassium dihydrogen phosphate,1 g/L of sodium chloride,8.0 of initial p H.We prepared the iturin A microcapsule by spray drying,optimized and determined the technical parameters.The optimal technical parameters were determined to be sodium alginate and poly(γ-glutamic acid)as wall material,a wall/wall ratio of 1:1(M: M),an inlet air temperature of 180℃,a stirring speed of 495 r/min and a core/wall ratio(V: M,m L/g)of 5:1.Finally,the encapsulation yield was 42.80%,the encapsulation efficiency was 73.97%,and the effective load of itruin A in microcapsule was 475 μg/g wall materials.The surface morphology of iturin A microcapsule was observed by scanning electron microscopy(SEM),the particles showed a spherical shape and similar sizes with no apparent cracks or fissures.There were fewer teeth or roughness on the surface of microcapsule.The results of studying the sustained-release of iturin A microcapsule showed that the iturin A in microcapsule released very fast and the release rate was around 70% at first day,subsequently released relative slower until the iturin A was released completely.Iturin A microcapsule could release for 6 days,its release mechanism is Fickan diffusion and it has a good sustained-release property.The results of studying the ultraviolet resistance of iturin A microcapsule showed that the retention percentage was over 90% when microcapsule was irradiated by ultraviolet(30 cm,30 W)for 36 h.It indicated that wall shell could protect core material from the influence of the ultraviolet effectively.Thus iturin A microcapsule has a good ultraviolet resistance.The results of studying the storage stability of iturin A microcapsule showed that the retention percentage was over 98% after microcapsule was stored for 3 months at normal pressure and temperature.The amount of iturin A in microcapsule had no obvious change.The iturin A microcapsule has good storage stability. |
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