Optimization of degradation conditions and mitigation the stress effect of p-hydroxybenzoic acid in cucumber rhizosphere by a strain of p-hydroxybenzoic acid degrading bacteria

Abstract:

Phenolic acids autotoxic substances secreted by plant roots, such as p-hydroxybenzoic acid (PHBA), are the main factors causing continuous cropping obstacles in plants. [Objective] In order to obtain PHBA degrading bacteria and improve its degradation efficiency. [Methods] a PHBA-degrading strain was isolated by screening medium and inorganic salt medium, and it was identified as Microbacterium aurantiacum. The initial content of PHBA, culture temperature, pH and nitrogen source were optimized by single factor experiment and response surface methodology. [Results] The highest degradation rate was obtained when the PHBA content was 0.4 g/L, the temperature was 30 ℃, the pH was 8.0, and the nitrogen source was ammonium sulfate. The optimal degradation conditions were temperature 30.2 ℃, pH 8.3, and PHBA concentration 0.18 g/L, and the degradation rate reached 100%. Combined with pot experiments and high performance liquid chromatography, the results showed that the strain could effectively mitigate the PHBA stress effect in cucumber rhizosphere. [Conclusion] The strain of Microbacterium aurantiacum screened in this study has a high ability to degrade PHBA, and has the potential value in continuous cropping obstacles.