Surfactin production in the bioreactor: Emphasis on magnetic nanoparticles application

Surfactin is one of the main lipopeptide biosurfactants produced by different species of Bacillus subtilis. This study aims to analyze the effect of starch-coated Fe⁰ and Fe³⁺ nanoparticles on the biomass and biosurfactant production of Bacillus subtilis. Out of 70 soil samples, 20 Bacillus were isolated and genome sequenced by biochemical methods and 16S rRNA gene. Quantitative and qualitative screening methods were used to isolate and detect biosurfactant production. For the aim of this study, 61 and 63 (Bacillus subtilis subsp. Inaquosorum) were selected. Then, hemolytic activity, biomass amount, surfactant production, and reduction of surface tension in Minimal Salt Medium containing Fe⁰ and Fe³⁺ nanoparticles were examined after 48, 72, and 96 h of culture. Strain 61 was the best bacterium and Fe³⁺ was the best nanoparticle. The results were compared with the results of non-nanoparticle bioreactor. The results showed the amount of biomass, surfactin, and surface tension decrease, 72 h after growth in 61 strain containing Fe³⁺ reached the highest values. Surfactin from strain 61 culture in the Fe³⁺nanoparticle bioreactor after 72 h of growth showed higher production than the same strain culture after 72 h without Fe³⁺, if continuing the research, this strain can be commercialized in the future.