Investigation of microbial biocontrol agents and essential oils synergism in suppression of Aflatoxigenic Aspergillus flavus

Abstract

Confectionery industry wastewater contains substantial amounts of organic and inorganic matter, posing a significant environmental burden. Microbial bioconversion offers a promising solution by utilizing these nutrients to produce value-added products, such as microbial biocontrol agents. Bacillus spp. in combination with essential oils, are particularly promising for fungicidal applications. The aim of this study was to investigate the potential of confectionery industry wastewater as a medium for producing the Bacillus sp. BioSol021-based biocontrol agent and to assess the effects of incorporating essential oils into the cultivation medium on bacterial growth and antimicrobial activity against the aflatoxigenic fungal pathogen Aspergillus flavus. Biomass content of Bacillus sp. BioSol021 was measured using the plate count method, while antifungal activity was evaluated using the well-diffusion method. The biomass content of Bacillus sp. BioSol021 during cultivation suggests the potential for utilizing this waste as suitable substrate for microbial growth, as no inhibition was observed. However, the addition of essential nutrients' sources could be considered to enhance bio-mass proliferation. The applied essential oils did not inhibit bacterial growth; rather, thyme and fennel oils increased biomass content compared to medium without essential oils. The highest antimicrobial activity against Aspergillus flavus was observed using oregano oil, followed by basil oil, with maximum activity at 72 hours of cultivation, which also corresponded with the highest biomass content. Future research should focus on further investigating wastewater seasonal characteristics, optimizing bioprocess parameters, and exploring the specific mechanisms of biocontrol action of both the Bacillus isolate and essential oils, as well as their interactions.