Response-surface optimization of anti-pathogenic activity of metabolic extracts obtained from rhizobacteria of Parthenium hysterophorus

Abstract The anti-pathogenic activity (APA) of the metabolic extracts obtained from rhizobacteria of Parthenium hysterophorus was optimized by constructing a tri-factorial central composited design in the response surface methodology. The colonies of the rhizobacteria isolated from the rhizospheric soil of P. hysterophorus were identified microscopically. The pink and yellow-colored colonies were cultured at five levels of three culture variables including pH (5, 6, 7, 8, and 9), incubation temperature (IT: 24, 28, 32, 36, and 40°C), and incubation time (It: 24, 48, 72, 96, and 120 h). The bacterial metabolites were extracted in methanol and analyzed for their APA against Pseudomonas aeruginosa and Escherichia coli. A statistically significant linear positive effect of pH was observed on the APA of both of the bacterial extracts and quadratic negative effect on APA of yellow-colored extracts against each of the selected pathogens. The It showed a significant linear positive effect on APA of the pink-colored extract against E. coli and that of the yellow-colored extract against the selected pathogens. It also showed quadratic negative effects on the APA of both of the bacterial extracts against the selected pathogens. However, the IT in the selected range showed no significant effect on the APA of the selected bacterial metabolites against the selected pathogens.