Studies on the growth of magnetospirillum gryphiswaldense under several conditions and its influence on the production of magnetosomes

Abstract

In recent years, Magnetospirillum gryphiswaldense has called attention because it is a bacteria capable of producing magnetic nanoparticles (magnetosomes) that can be used in a variety of applications, such as directed therapies for drug delivery. The production of magnetosomes has not reach threshole concentration to ensure feasible for industrial applications. Thus, it is of high importance to increase the magnetosome production. This research evaluated the effect of stirring rate (100, 200, 400 and 600 rpm) and hydrodinamic conditions based on Reynolds number for the grwoth and production of M. gryphiswaldense. Overall, the better results were obtained at 200 rpm, with correspond to higher biomass and oxygen transfer coeficient (KLA). Optimal impeler stirring rate was selected to grow bacteria, followed by an anaerobic stage with feeding, to induce the production of magnetosomes. The best magnetosome yield obtained was 18.79 mg/mL*day in a fed-batch culture, 11.78 in continuous culture and 1.4 in batch culture. Their respective specific growth (μ) and generation time (min) were 0.083 and 8.31, 0.022 and 31.38, 0.02 and 34.65. Three different pellets were obtained and their magnetosome content was extracted to be analyzed in Z-sizer, resulting in an average size of 100 nm. Also aggregates of magnetosomes were found. The findings reported here could serve as a basis for the future scaling up of a biological factory for nanocarriers for multiple research and/or medical applications.