Adaptive Evolution for Increased Biomass and Magnetic Nanoparticle Productivity of Magnetotactic Bacteria

Large magnetic nanoparticles (over 25 nm diameter) are a valuable commodity but remain difficult to synthesize using traditional chemical synthesis methods. Magnetotactic bacteria (MTBs) have evolved mechanisms to produce monodisperse, protected magnetic nanostructures within organelles (magnetosomes). Genomic diversity of MTB species result in unique particle properties that vary in shape and size ranging from 30 nm to 150 nm based on the genetic background. Culturing and engineering MTBs for the production of magnetic nanoparticles carries tremendous potential but is underdeveloped. This primarily because MTBs are difficult to culture and genetically manipulate, limitations that could be alleviated with adaptive evolution. We propose the magnetotrophic reactor, a novel bioreactor system for adaptively evolving MTBs for better growth and magnetosome production. This platform is projected to be superior to the traditional evolution methods since robust growth phenotypes can be selected for while maintaining selective pressure for magnetotaxis. We provide, herein, a quantitative basis for our platform including considerations of continuous evolution, sizing, and magnetic field pulsing. Our proposed fermentation process anticipates scalable production of 1 g/L per day of monodisperse magnetic nanoparticles to enable industrial applications.