Identification,Optimization Of Fermentation Conditions Of Bacillus Velezensis Strain S6 And Its Biocontrol Effect

In this experiment,the biocontrol bacteria strains S6 was isolated and screened from the horticultural greenhouse of tomatoes for many years by using Alternaria solani and Botrytis cinerea as target pathogens.16 SrDNA sequence was used to identify the bacteria,and the different culture conditions were screened by plate confrontation method.The isolation and purification of antagonistic substances and different culture conditions were carried out,and the results were as follows.1.Through the morphological observation of the S6,and the result of physiological and biochemical tests,combined with molecular biology analysis,the strain S6 was identified as Bacillus velezensis2.The growth curve of strain S6 showed that 8-16 h was the logarithmic growth period,culture 16 h was the most suitable for seed liquid for growth curve determination.The best carbon resource,nitrogen resource and inorganic salts resource were as follows: glucose 2%,yeast extract powder 0.5%,KCl 0.75%,distilled water 1000 mL;the best culture condition was culture time 3 d,culture temperature 30?,speed 210 r/min,3% inoculums,liquid volume 60 mL/250 mL,initial pH 7.23,.3.The optimum saturation of ammonium sulfate was 80%,and the crude protein solution after ammonium sulfate precipitation was purified by DEAE-SephroseTM Fast Flow anion exchange and SuperdexTM 75 to a single antibacterial protein.The molecular weight is 20.1 KDa determined by SDS-PAGE.A preliminary study showed antimicrobial agent can be determined as protein.crude extracts of antifungal protein was found to be thermostable,resistant to Ultraviolet irradiation,and sensitive to acid and alkali.4.The results showed that strain S6 has good inhibitory effect on the pathogen hyphal growth and growth rate,and produce the phenomenon of deformity,distort etc.for mycelium.It also has obvious inhibitory effect on spore growth and germination.,the hyphae became thinner,deformed,expanded and the cell wall ruptured.5.The results showed that the fermentation liquid of strain S6 had a bacteriostatic effect and did not infect to the host within a certain dose range.Field experiments showed that 500 times the fermentation broth and the solution had better control effect.