| As metabolite of microbe, agricultural antibiotics have been paid attention because of its characteristics such as low poison, high effect, strong selectivity, short-time remains and without pollution. Kaidmycin is systematically researched on following aspects: screening and evaluation of strains, optimum fermentation condition, separation, purification and analysis of its structure, its control effect in the field and so on.Screening biocontrol strains is necessary precondition to obtaining agricultural antibiotic.686 Streptomyces isolates was separated from 37 soil samples, 46 isolates showed antagonism to pathogenic fungus. Antifungal activities of fermentation was mensurated by method of cup-dish, There are 5 strains which diameter of inhibition is more than 15mm. SY20-2 and SY20-4 inhibiting rate is more than 90% against plant pathogenic fungus and bacterium such as Fulviafulva, Botrytis cinerea, Xanthomonas oryzae pv. oryzae and so on.Classification status of isolates SY20? and SY20? were definited by traditional classification. By studying their morphology, cultural characteristics, antagonism, physiological and biochemical properties and cultural condition, SY20-2 is Streptomyces chromogenes var. shandong and SY20-4 is Streptomyces rimosus var.Heilongjiang.Three recombinant progenies with high effect and extensive antibiotic spectrum were obtained by making use of protoplast fusion between isolates SY20-2 and SY20-4. Protoplast fusion rate is 1.24% in the first screening, and 0.124% in the second screening.The best optimal fermentation condition was researched. Influence of carbon sources on the antibiotic production of strain SY20-4 is different from single factor test. Maltose is the best carbon source, others are sucrose, dextrin, starch, glucose. Peanut pie flour and bean flour are the best nitrogen sources, others are corn flour, yeast flour, peptone, ammonia and (NH^SO^ Regression equation of fermentation condition is definited by uniform design experiment. The optimum culture medium direction includes: starch 3,36%, Peanut pie flour 1.733%,(NH4)2SO4 0.23 % , CaC03 0.175 % , NaC10.2%.The optimum fermentation condition includes: 25癈of culture, 150r/min of rotation, 10% of inoculation amount, the initial pH of 4.0,144hof culture time.Total carbon and total nitrogen drop off during fermentation process, but utilization rate of carbon source is higher than that of nitrogen.Pure crystal of Kaidimycin was isolated and its structure was defined, this proves that Kaidimycin is a new agricultural antibiotic. Kaidimycin is a neutral antibiotic by Doskochilova paper chromatography system, pH-PC and PaperElectrophoresis. The fermentation was filtered and extracted with n-butanol, marcroporus resin absorption,then obtained crude extract of Kaidimycin. The pure sample of Kaidmycin also obtained by silica gel separation. Analysis of HPLC showed that purity of Kaidimycin is 81%. Molecular formula and structure of Kaidimycin are respectively follows: Kaidimycin can keep activity at neutral, alkaline , light, 54 "C for 15d respectively, Kaidimycin loses activity when deposited for half of a year and its inhibition activity falls down to half when deposited for a year at normal condition. The estimate liter of fermentation is tested by method of spreading and colorimetry. The colorimetry is the best method of estimating titer.Studies on acting mechanisms of Kaidimycin showed that MIC and MBC of Kaidimycin against Fulvia fulva are lOug/ml and 25ug/ml respectively. Action spot of Kadimycin is cell membrane. Kaidimycin of 20ug/ml restrains germination of spores completely. ECso of Kaidimycin is 129.66ug/ml in PDA and 94.6ug/ml in tomato plant.Ultrastructure observation indicated that the electron-densed substance can be founded in the cells treated with Kaidimycin and Botrytis cinerea, but appearing time and amount of substance is earlier and more than that induced by single inoculated.The activities of the main defensive enzymes such as superoxide dismutase(SOD), catalase(CAT...
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