Optimization of biosurfactant production by Pseudomonas aeruginosa using rice water and its competence in controlling Fusarium wilt of Abelmoschus esculentus

Biosurfactants, in comparison to chemical surfactants, have a greater impact on various applications due to their stability, degradability, and other physicochemical characteristics. Increasing yield and lowering production costs are critical to enhancing biosurfactant efficiency. Because biosurfactant production costs are determined by the least expensive substrate, agro-based industrial waste is one of the most promising economic strategies. Therefore, in this study we aimed to achieve the biosurfactant production in Pseudomonas aeruginosa by low cost rice medium using Response surface methodology (RSM) and assessed their competence in controlling the Fusarium wilt of Abelmoschus esculentus. Initially, the selected strain P. aeruginosa PBS29 was confirmed using 16S rRNA sequencing. Then, the 20% (v/v) of rice water was chosen as the cheapest carbon source for formulating rice water medium to optimize biosurfactant production using Central Composite Design. Enhanced biosurfactant yield of 9.35 g/l was attained through RSM by 0.59 fold higher than preliminary analysis. The model was significant with a regression coefficient of 0.98. The optimal condition was identified as 1.18% (w/v) nitrogen source [glutamic acid], pH 6.8, temperature at 37.4 °C, 2.5% (v/v) inoculum size, and 167.9 rpm agitation. In-vitro antifungal activity and biocontrol strategy of the biosurfactant demonstrated against Fusarium wilt of Abelmoschus esculentus at 100 μg/ml concentration by both soil drenching and foliar spray by pot trial. Furthermore, the detection of rhl gene, TLC, FT-IR, HPLC and GC–MS analyses suggested that the biosurfactant is rhamnolipid. Overall, in this study, the biosurfactant was synthesized using inexpensive rice water and substantiated its safe use as a biocontrol agent, which will help large-scale commercialization and interchange chemical surfactant used in agricultural wastes.