Studies On Medium Optimization And Wetting Powder Of Endophytic Breviacillus Subtilis Strain011

Currently, agronomic chemicals are still the major means for biological control. A fact is that people are being threatened by more and more adverse diseases accompanied with an increasing extent of pesticide residue and pathogen resistence. Eddophytes, a kind of microorganism that reside in the internal tissues of living plants, are potential sources of novel natural products for pathogen control in agriculture. In this study, endophytic Brevibacillus brevis strain011that had strong inhibitory effects on pathogens was selected to investigate the best medium and fermentation conditions using agricultural and sideline products. The wettable powder formula was also explored to determine its feasibility on biopesticides. The aim of this study was to lay a foundation for the development and application of novel antibiotics in medicine, agriculture and industry.1. In order to obtain the optimal antagonistic effect, the medium and cultural conditions of strain011were optimized by orthogonal design method and single factor tests in shake-flask. The optimal culture compositions of strain011were bran15g, bean pulp l0g, yeast extract3g, and NaCl7g in1L medium. The optimal cultural conditions were as follows: initial pH5.5, inoculum volume1%(v/v), temperature30℃, medium volume50%flask, and fermentation time60h. Under the conditions, the OD680value of011strain was0.584and the inhibitory diameter to Alternaria solani reached11.3mm, which was significantly improved.2. To obtain the optimal10L fermentation tank conditions (temperature, rotating speed, ventilation and pH) affecting the inhibitory effect of011strain, surface methodology based on single factor tests was used in this study. Through the model analysis of variance, P<0.0001, no significant loss in quasi items, the measured and predicted show the antimicrobial substance has a better fitting, test error is small, c.v%only5.05, R2Adj correlation coefficient was96.67%, the model can explain this model. Results showed that the optimal fermentation conditions were temperature32℃, rotating speed180r/min, ventilation145L/h, and pH5.5. Under the conditions, the inhibitory diameter to Alternaria solani reached16.8mm, which improved37.5%than flask fermentation. 3. Wettable powder of Brevibacillus brevis strain011. Through researching on the formulation of the wetting powder of Breviacillus subtilis strain011, the optimal formulation were confirmed as follows:10%filler talcum powder,7%dispersing agent calcium lignosulphonate,4%DBS,2%CMC-Na, and0.1%dextrin. Based on the national standard NY/Y2294.2-2012, the spores content, suspension rate, fineness rate and survival rate of Brevibacillus brevis strain011were1.8×1010CFU/g,76%,98%, and72%, respectively, under the conditions of temperature25℃, pH6.8, dispersion time52s and storage time100d, which met the national standard. The different concentration of Brevibacillus brevis strain011wettable powder act on the Alternaria solani spore germination, to some extent, is restrained. The regression analysis virulence equation: Y=3.872164+1.68346X, correlation index R is0.99197, MIC is25mg/mL and the EC50is4.68%.