极长链霉菌SL01菌株抑菌活性物质的发酵条件优化和稳定性研究

为了获得极长链霉菌Streptomyces longissimus SL01菌株发酵的最佳培养基配方和发酵条件，采用单因素和正交试验法对SL01菌株的发酵液配方进行了优化，采用离体枝条和果实病斑抑制试验检测了其配方优化效果，并测定了SL01抑菌活性物质对温度、酸碱度和紫外光照射的稳定性。最终获得最佳发酵液的配方（质量分数）为:小米粉2%、酵母粉1%和MgSO4·7H2O 0.15%。以在28℃、初始pH 7.0、接种量2%、装液量50 mL/250 mL和转速180 r/min的条件下培养7 d得到的发酵液抑菌活性最强。采用优化的培养基配方发酵所得的SL01发酵液对苹果枝条和果实上的苹果树腐烂病的防效，分别比对照提高了39.86%和10.15%。所得发酵液在低于40℃、pH在6~10或紫外光照射12 h时，抑菌活性仍较为稳定。研究表明，通过培养基优化，可以显著提高SL01发酵产物的抑菌活性。

Optimization of fermentation conditions for antifungal substance production of Streptomyces longissimus SL01 and its stability evaluation

Medium and conditions for the fermentation of Streptomyces longissimus SL01 (CGMCC No.9543) were optimized, and the stability of the antifungal substance was investigated. The single factor experiment and orthogonal experiment were used to optimize the ingredients of medium and suitable fermentation conditions in shake flask. To evaluate the results of optimization, the methods of disease extension inhibition on the branches and apple fruits in vitro was used. The stability of the active substance in SL01 was measured under the condition of different temperatures, pH values and ultraviolet radiation. The optimum ingredients of fermentation broth were 2% millet powder, 1% yeast extract and 0.15% MgSO₄·7H₂O. The optimal conditions were 28, initial medium pH=7.0, inoculum volume 2%, liquid volume 50 mL/250 mL, and rotation speed 180 r/min. By using the optimized formula, the control effect of the SL01 fermentation filtrate against Valsa mali on branches and apple fruits had increased by 39.86% and 10.15%, respectively. The inhibitroy activity of fermentation broth was stable under 40, it was also relative stable when pH values ranged from 6 to 10, and it was almost not affected after exposed to UV irradiation for 12 h. This study proves that the inhibitory activity of SL01 fermentation broth was significantly improved by media optimization.