摘 要：
This study focused on the optimization of the fermentation process of Bacillus amyloliquefaciens, the establishment of an electrochemical method for detecting indole-3-acetic acid (IAA) in the fermentation broth, and the growth-promoting effect of the optimized fermentation broth on pepper seedlings. The fermentation process was optimized in terms of inoculum size, seed age, and carbon source type and concentration. The determined optimal conditions were as follows: inoculum size of 2%, seed age of 4 h, and the addition of glucose at 8 g/L to the basal LB medium, while other conditions remained unchanged (temperature 37 ℃, rotation speed 180 r/min, pH 6.5). Differential pulse voltammetry with an electrochemical workstation was used for quantitative detection of IAA in the fermentation broth. The results showed that the IAA concentration in the optimized diluted fermentation broth used in the subsequent pot experiment (T1 group) was 43.8 mg/L, which was significantly higher than the 6.5 mg/L in the pre-optimization diluted fermentation broth (T2 group). In the pepper seedling root-drenching experiment, three groups were set up: T1 (irrigated with optimized diluted fermentation broth), T2 (irrigated with pre-optimization diluted fermentation broth), and CK (irrigated with distilled water). After 21 days of treatment, there were no significant differences in plant height and stem diameter changes among the three groups. However, the root length of the T1 group (9.70 cm) was significantly greater than that of the T2 (8.69 cm) and CK (7.43 cm) groups, and the fresh weight (3.69 g) was also higher than that of T2 (3.41 g) and CK (2.32 g). The chlorophyll increment was highest in the T1 group (25.55 SPAD). The results indicate that the optimized Bacillus amyloliquefaciens fermentation broth can effectively promote root growth and increase chlorophyll content in pepper seedlings, and the established differential pulse voltammetry method can be used for the detection of IAA content in the fermentation broth.This provides a feasible technical pathway for the dynamic monitoring and efficient fermentation of IAA production by Bacillus amyloliquefaciens, validates its growth-promoting effects, and demonstrates promising value for agricultural application and extension.
Keywords: Fermentation process optimization; IAA; Electrochemical detection; Differential pulse voltammetry
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