Optimized Bioconversion of Soybean Meal Waste to Valued Biosurfactant by Pseudomonas Aeruginosa (PTCC 1074)

Recently, microbial surface-active molecules called biosurfactants, have gained significant attention due to their structural diversity, biodegradability, low toxicity, and several environmental and industrial applications. However, despite their advantages, they are not widely used because of high production costs, which can be overcome by bioconversion of agro-industrial wastes as low-cost substrates. The current study aimed to overcome the challenges of biosurfactant production by bioconversion of soybean meal, as a low-cost renewable substrate, and to optimize the significant parameters. Rhamnolipid biosurfactant was produced by Pseudomonas aeruginosa (PTCC 1074) using soybean meal under solid-state fermentation and Response Surface Methodology (RSM) by Central Composite Design (CCD) was employed to optimize the significant parameters. The experimental value of biosurfactant production and Emulsification Index were 17.05 (g/kg dry substrate) and 54 % respectively under the optimal conditions (temperature 33 °C, Initial substrate moisture 80%, and carbon-to-nitrogen ratio (C/N ratio) 54). Regression analysis with RSM resulted in quadratic models and the coefficient of determination (R²), adjusted R², and predicted R² were respectively calculated as 0.9767, 0.9557, and 0.9088, indicating that the model fitted the experimental data well. An increase in temperature from 25 to 34°C led to a rise in rhamnolipid production, which implies the significant influence of temperature. The results demonstrated that the production of biosurfactants increased with increasing the initial moisture content at high temperatures and also at low C/N ratios. The current study confirmed the considerable potential of soybean meal for biosurfactant production and also enhanced the production yield by optimizing the significant process parameters.