Studies On Optimization Of Fermentation Process Of Streptomyces Lavendulae Xjy Strain And The Control Effect Of Tomato Leaf Mould

The plant diseases impacted the production and quality of crops, and restricts the development of agriculture. Agricultural chemicals are presently employed to prevent and treat some plant diseases, but the frequently using of chemicals produces "3R" problems, and the human health and the environment was damaged. Using bio-control microorganisms to control plant diseases have characteristics as follows: low-toxic, efficient and environmentally friendly etc. Streptomyces spp. can produce various bioactive substances, such as enzymes, antibiotics etc. About half of antibiotics are produced by Streptomyces. The antibiotics were studied widely. These antibiotics can control fungi, bacteria and some insects. But some of the Streptomyces show a low level of active substances in fermentation process. So the optimization of the fermentation process(fermentation medium and conditions) is necessary and important.The strain Xjy was isolated from cotton field in Xinjiang,and was identified as Streptomyces lavendulae. It was found that the fermentation filtrate of strain Xjy had a broad-spectrum activity. The fermentation filtrate have control effects on tomato leaf mould in greenhouse and field. In this reaserch, Fulvia fulva was used as the target pathogen to study the optimization of the fermentation process of strain Xjy by cylinder plate method, using response surface methodology(RSM). The effectiveness of tomato leaf mould was studied as well.The results as follows:1. The fermentation medium of strain Xjy was optimized in shaking flask. The effects of different carbon and nitrogen sources and inorganic salts were investigated by one-factor-at-one-time experiments. The results showed that the optimum medium was soybean meal 1%, NaCl 1.8% and (NH4)2SO4 2%.2. Then the central composition design was used to investigate the concentratin combination of three variables (soybean meal, NaCl and (NH4)2SO4). The result showed that the optimum medium was soybean meal 1.46%, NaCl 2.25% and (NH4)2SO4 1.26%. Four unnecessary components were removed, and the production of active components in fermentation was improved.3. After the optimization of medinm, central composition design was used to optimized the fermentation conditions. The result showed that the maximum diameter of inhibition zone was obtained on the condition : tempreture 30℃, rotary speed of 200 rpm, initial pH 5, medium volume of 25 ml in 250 ml flasks and inoculation volume of 10 %. Maximum diameter of inhibition zone of 30mm was achieved under this condition and was improved by 20%.4. In three fields of different degree of the prevalence of tomato leaf mould, the control experiments were carried out.The percentage of diseased leaf and disease index decreased after treating by the fermentation filtrate and organism suspension of strain Xjy. The control effect were about 50%.In this research, the fermentation process of the strain Xjy were optimized by response surface methodology, the production of active components was mproved. The fermentation filtrate and organism suspension of strain Xjy also showed the control effects in field. All the results could be the theoretical foundation of strain Xjy in practical application.