Studies On The Fermentation Condition And Antibitic Physicochemical Property For Two Biocontrol Streptomyces

Streptomyces are a kind of Gram-positive bacteria which exist in the soil.There are hundreds of genus heretofore.They are a kind of important microorganisms used in industrial porduction which produced half of antibiotics in the wold.Microorganisms in this genus can produce kinds many bioactive compounds most of which have been used in agriculture production widely.Thses antibiotics can control fungi,bacteria, nematode disease and a number of important pests,and some also have herbicidal activity.In this research,Pseudomonas syringae pv. Actinidiae and Bacillius subtilis were used as the target pathogen to study the culturing conditions for achieving higher productivity of strain Xjy and gCLA4 by cylinder plate method. Finally,the broth physical and chemical properties for strain gCLA4 and production of the extracellular enzyme were explored.The optimum fermentation conditions of strain xjy were optimized in the study, The results of single-factor experiment and the orthogonal test showed that the optimum medium was wheat bran 2 % , soybean meal 1%, NaCl 1.5%,CaCO3 0.6%,(NH4)2SO41%,K2HPO40.04% and FeSO₄·7H₂O 0.001%. The active components in fermentation production was increased by 36% when the strain xjy was cultivated in the optimum medium instead of the initial one.The higher yield of active components was obtained on the conditions that the temperature is at 20-35℃, the shaker rotation speed is at 150r/min, the medium capacity is 50mL in 250mL flask, the initial pH value is 5.5-8.0.The metabolizing parameters were tested at shake flask for the new medium.The result showed that the use of sugar and the nitrogen, pH value and active substance were increased to peak At 72 hours when the bacterial content was the highest. So the fermentation time can been shortened from the previous 120 hours to 72 hours. This will significantly reduce the fermentation period and the cost of fermentation.The optimum fermentation conditions of strain gCLA4 were optimized by the single-factor experiment and the orthogonal test, the results showed that the optimum medium was granulated sugar 1.5%, wheat bran 1.5%,NH₄NO₃ 1.5 %, NaCl 0.4%,CaCO3 0.2%, K2HPO4 0.05%. The higher yield of active components was obtained on the conditions that the initial pH value is 6.5, the medium capacity is 40mL in 250mL flask, the temperature is at 30℃, the shaker rotation speed is at 150r/min.The result of metabolizing parameters showed that reducing sugar content has been relatively low and becomes more and more scarce along with the fermentation, finally the fermentation the content is very weak.The use of total sugar and the nitrogen were increased to peak at 48 h when the bacterial content was the highest. Then the tolal sugar content kept reducing but the nitrogen level increased and kept stability. The pH value in the whole changed little in the fermentation process, increasing to 7.96 after a small decline, then gradually reduced to 7.71. Broth began to produce antibacterial substances around 36 hours and has the highest content at 96 hours. So the fermentation time can been shortened from to 96 hours.The results for antibiotic physicochemical property of strain gCLA4 showed that the active substance was stable to natural light and ultraviolet irradiation. It was also relatively stable to the hyperthermia around 90℃and acidic and neutral condition but not 120℃. Genetic tests show that this train degenerated seriously with the passage.Test by the clear zone method on colloidal chitin-containing agar plate,poria (including aniline blue)plate and screening protease plate indicated that both of Xjy and gCLA4 can produce protease andβ-1,3-glucanase.They cannot produce chitinase.