Synergistic Effect of Bacillus and Chitosan: From Flocculation to Enhanced Antimicrobial Activity

Eco-friendly pest management solutions are acknowledged as a crucial element in shaping the future of agriculture through sustainable practices. Achieving the maximum viable cell concentration while being cost-effective is the main goal of the downstream processing for efficient biomass-based microbial biopesticide production. The purpose of this study was to determine the effectiveness of chitosan flocculation in recovering bacterial Bacillus sp. BioSol021 biomass from broth cultivated using fruit juice industrial effluent as a medium, with the hypothesis of the synergistic effect of microbial and biopolymer components in phytopathogen suppression. Second-order polynomial models were used to calculate the influence of chitosan concentration and mixing speed on flocculation efficiency, settling velocity, and antibacterial activity against Aspergillus flavus (i.e., the inhibition zone diameter). The response surface approach, followed by desirability function optimization and the genetic algorithm were applied. The optimal values achieved in this study were 97.18%, 0.0369 mm/s, and 74.00 mm for flocculation efficiency, settling velocity, and inhibition zone diameter, respectively. The obtained results suggest that chitosan can be used as a flocculation agent for effective downstream processing, but also has a positive effect on the final product antimicrobial activity.