Optimization of Pseudomonas aurantiaca ST-TJ4 Fermentation Medium and Its Control Effect on Phytophthora cinnamomi

Abstract

Previous research has indicated that Pseudomonas aurantiaca ST-TJ4 possesses a notable antagonistic impact on Phytophthora cinnamomi and holds promising potential for biocontrol. In this study, a combination of a single-factor experiment, a Plackett–Burman design and a response surface approach was employed to investigate the optimal formula of ST-TJ4 fermentation medium. Furthermore, the stability of ST-TJ4 fermentation filtrate and its biocontrol effect on Ph. cinnamomi in vivo were also evaluated. The results revealed that the optimal culture conditions for ST-TJ4 involved the use of 20.59 g/L of glucose and 18.76 g/L of yeast extract powder. Following optimization, the fermentation filtrate of ST-TJ4 exhibited an inhibition rate of 76.5%, representing a 15% increase compared to previous levels. Additionally, phzA, phzB, phzD, phzE, phzF and phzO genes involved in the synthesis of phenazine-1-carboxylic acid (PCA) and 2-hydroxyphenazine (2-OH-PHZ) were also upregulated. The ST-TJ4 fermentation filtrate demonstrated strong alkali resistance, weak acid resistance and favorable temperature and UV light stability. Furthermore, in vitro inoculation experiments confirmed that optimizing the fermentation medium reduced Ps. cinnamomi’s ability to infect the leaves of Rhododendron pulchrum.