Abstract:

Bacillus velezensis SD23LJ1314 is a biocontrol strain that has excellent efficacy against Phytophthoracapsici， and its fermentation level directly affects the field control effect. To enhance the fermentation level of this strain， this study used the bacterial quantity as the core evaluation index. Firstly， the fermentation bacterial quantity of 8 commonly used industrial culture media was compared using the plate counting method， and the most suitable basic culture medium for SD23LJ1314 fermentation was selected. On this basis， through single-factor experiments， 11 commonly used industrial fermentation carbon sources and 9 nitrogen sources were optimized to determine the optimal carbon and nitrogen sources. Subsequently， the Plackett-Burman experimental design was further adopted， combined with the Box-Behnken design and response surface analysis method， to precisely optimize the addition concentration of the optimal carbon and nitrogen sources. The experimental results showed that fructose and yeast powder were the optimal carbon source and nitrogen source combinations， respectively. After optimization by the above methods， the final optimized culture medium formula was determined as follows， 10.75 g·L^-1 fructose， 21.48 g·L^-1 yeast extract， 5.65 g·L^-1 NaCl， and 0.71 g·L^-1 MnSO₄·7H₂O. Under this optimized condition， the fermentation bacterial quantity of this strain reached 9.32×10⁹ CFU·mL^-1， and the bacterial yield was significantly increased by 31.6% compared to the basic culture medium. This study through a series of experiments clarified the efficient fermentation process of Bacillus velezensis SD23LJ1314. The optimized culture medium formula and related technical parameters obtained have laid a solid foundation for the large-scale production of this biocontrol strain and have significant value for promoting its application in the development of biological control agents for Phytophthora capsici.

Key words: Bacillus velezensis, fermentation broth, biomass, medium optimization, response surface analysis

摘要：

贝莱斯芽孢杆菌（Bacillus velezensis）SD23LJ1314是一株对辣椒疫病（Phytophthora capsici）具有很好防效的生防菌，其发酵水平的高低直接影响田间防治效果。为提升该菌株的发酵水平，以菌体量为核心评价指标，采用平板计数法对8种常用工业培养基的发酵菌量进行比较，筛选出了SD23LJ1314发酵的最适基础培养基。在此基础上，通过单因素实验对11种工业发酵常用碳源和9种氮源进行优化，确定最优碳氮源；进一步采用Plackett-Burman实验设计，并结合Box-Behnken设计与响应面分析法，对最优碳氮源的添加浓度进行了精确优化。结果表明，果糖与酵母粉分别为最优碳源和氮源组合，最终确定的发酵培养基配方为果糖10.75 g·L^-1、酵母粉21.48 g·L^-1、NaCl 5.65 g·L^-1、MnSO₄·7H₂O 0.71 g·L^-1。在此优化条件下，该菌株的发酵菌量达到9.32×10⁹ CFU·mL^-1，与基础培养基相比，菌体产量显著提高了31.6%。通过系列实验，明确了贝莱斯芽孢杆菌SD23LJ1314的高效发酵工艺，所获得的优化培养基配方及相关技术参数，为该生防菌的规模化生产奠定了坚实基础，对推动其应用于辣椒疫病的生物防治制剂开发具有重要价值。

关键词: 贝莱斯芽孢杆菌, 发酵液, 菌体量, 培养基优化, 响应面分析