A Study On Biocontrol And Flocculation Activity Of Paenibacillus Elgii F53

Paenibacillus elgii F53 was obtained from eggplant rhizosphere, which has proved with better inhibiting activity to the pathogenic fungus verticillium dahliae. In order to obtain the F53 solid preparation for field used, a series work was developed, involving with optimizing solid fermentation experiment, testing the safety for germination of vegetables, promoting growth effects and controlling infection and its colonizating ability in the plant roots, and so on. The strain F53 could produce extracellular polysaccharide and had higher flocculating activity. Thus, the component and flocculating activity of its extracellular polysaccharide had also been analysed.The solid substrates of F53 were primarily selected from 5 kinds of single substrate and combination solid substrates by an orthogonal test. The results showed that in the best direction of solid substrate, weight ratio of bran, grain pieces and cornmeal was 2:1:1. The effects of ferment temperature, ratio of solid materials and water, pH and inoculum concentration on endospore yield and inhibiting compounds were studied. Accumulation of antifungal compound was directly correlative with the quantities of endosporulation in the solid fermentation. The solid ferment conditions were optimized as follows: temperature 35℃, ratio of solid substrate and water 1:1.4, pH 7.0, 10% inoculum.The effects of solid fermentation preparation on the seed germination of tomato, cucumber, eggplant and rape were carried out. It was indicated that F53 resulted in different germination percentages with different vegetables. When the solid ferment preparation reached 10% in soil, the germination of tomato, eggplant and rape was remarkably inhibited. There was no effect on the germination of all 4 tested kinds of vegetables when the solid ferment preparation was 1% in soil.While the content of solid ferment preparation between 2%-5% in soil, F53 restrained the seeding ,growth of eggplant and rape. While the solid fermentation preparation reached 1% in soil, not only the negative effect had been removed, but also F53 promoted the seeding growth of eggplant and rape. Comparing the CK, the height, root length and fresh weight of eggplant respectively increased by 31.14%, 11.94%, 30.36%, rape increased by 10.91%, 3.26%, 21.55%.In comparison with the liquid ferment preparation, the solid ferment preparation had better control efficacy on Verticillium dahliae. The control efficacy of 10% liquid ferment preparation was only 56.04%. However, the control efficacy of 2% solid ferment preparation was much higher, reached 78.01%.Colonization experiments showed that F53 could colonize on rhizosphere of eggplant for 40d at 3.51×10~8cfu/g. This showed that the species of antagonistic bacterium had better colonizing ability in the soil. In comparison with inoculation of antagonistic bacteria F53 only, pre-inoculation of F53 had a negative effect on colonization of the antagonist, which meaned that the F53 was better in prevention against Verticillium dahliae.In addition, F53 could produce extracellular polysaccharide and thus had a high flocculating activity on kaolin, reaching 72.3%. The extracellular polysaccharide was extracted and purificated. It was mainly composed of D-glucose, which was confirmed by IR technique and TLC analysis of the acid hydrolyzed product.