Effect of magnetite nanoparticles addition on modification of cobalamins production via Propionibacterium freudenreichii PTCC۱۶۷۴ using oily sludge of lubricant industry as the carbon source

Cobalamins are one of the most complicated cofactors produced by the microorganisms. Propionibacterium freudenreichii has to follow the anaerobic and aerobic conditions respectively during a course of batch fermentation, for the production of the biologically active form of cobalamins. Magnetite (Fe۳O۴) nanoparticles can modify gas-liquid volumetric mass transfer coefficient in the fermentation system to create more efficient aeration step. Initially, the modified production of Fe۳O۴ nanoparticle through coprecipitation method was investigated, and the smallest size of nanoparticles optimized to ۱۳.۸۶ nm via Box-Behnken design of response to surface methodology (RSM). The optimum condition was at the synthesis temperature of ۶۰ °C, reaction duration of ۱۰ minutes, and the medium agitation speed of ۷۰۰ rpm. Synthesized nanoparticles characterized by SEM images, PXRD and EDS analysis while EDS spectrum reflects ۳۹.۳۳% of Fe and ۵۱.۸% of oxygen atomic distribution, which confirms Fe۳O۴ nanoparticles synthesis. Magnetite nanoparticle suspension added to the fermentation medium to compare the effect of nanoparticles incorporation and dimethylbenzimidazole addition on the cobalamin production via Propionibacterium freudenreichii. NPs incorporation in the fermentation broth was able to increase cyanocobalamin production by ۲۰%, while there was no incorporation of external DMBI in the medium. Finally, by the central composite design analysis, cyanocobalamin production from Propionibacterium freudenreichii fermentation was optimized to ۱.۵۴۸ mg.L-۱. Oily sludge (as a new carbon source) of ۴ %w/v, magnetite nanoparticles suspension of ۷.۵ %v/v, and the fermentation temperature of ۳۷ °C caused to CCD optimum condition.

Keywords:

Cobalamins biosynthesis , Magnetite nanoparticles , RSM Optimization , Propionibacterium freudenreichii