Primary Study On Fermentation Of S15, Isolation Of Its Antibiotics,and Biocontrol Of Black Spot Of Cabbage

Optimum fermentation medium of antagonistic Streptomyces strain 15 was screened on the base of NMM, and it was composed of glucose 2%, starch 1%, peanut powder 2%, peptone 0.3%, ammonia sulfate 0.5%, CaCO3 0.4%, KH2PO4 0.02% ,NaCI 0.3%, FeSO4 0.01%, MgSO4 0.02%. Optimum fermentation condition of strain 15 was also determined , which indicated that antibiotics of strain 15 had strong inhibition activity with 28h seed age, 4% inoculation volume (v/v) , 80m1 medium volume , 200 r/min rotatory velocity , 26~C temperature and pH 7. Culture filtrate of 515 mixed with 1% surface active agent had protection effect against black spot of cabbage in green house. Spraying the culture filtrate, its five-fold dilution and Duojunhing (check) 24 hours before inoculation of the pathogen on cabbage had strong control efficacy , which was 93.2% , 91.5% , and 93.0% respectively, Carrying the treatments 48 hours after the inoculation almost had no any control efficacy. It was shown that the antibiotics of strain IS was sensitive to heating in alkline situation, while stable in neutral and acid situations. They were water dissolvable and composed of 6 components at least. The culture filtrate was absorbed by active carbon, then active fractions were eluted by 0.5 N H2S04: acetone(l :3,v/v) . Such active fractions were further isolated through D155 and CG-50 columns eluted by 2% ammonia water. The fourth active fraction above was isolated through HPLC (Sephadex-LH-20), then was scanned by UVI000. And it was found that there was no UV spectrum absorption during wavelength of 200 nm to 400 nrn.