Continuous Production of Biogenic Magnetite Nanoparticles by the Marine Bacterium Strain MV-1 with a Nitrous Oxide Injection Strategy.

Magnetotactic bacteria (MTB) produce magnetosomes, which are membrane-embedded magnetic nanoparticles. Despite their technological applicability, the production of magnetite magnetosomes depends on the cultivation of MTB, which results in low yields. Thus, strategies for the large-scale cultivation of MTB need to be improved. Here, we describe a new approach for bioreactor cultivation of strain MV-1. Firstly, a fed-batch with a supplementation of iron source and NO injection in 24-h pulses was established. After 120 h of cultivation, the production of magnetite reached 24.5 mg∙L. The maximum productivity (16.8 mg∙L∙day) was reached between 48 and 72 h. However, the productivity and mean number of magnetosomes per cell decreased after 72 h. Therefore, continuous culture in the chemostat was established. In the continuous process, magnetite production and productivity were 27.1 mg∙L and 22.7 mg∙L∙day, respectively, at 120 h. This new approach prevented a decrease in magnetite production in comparison to the fed-batch strategy.