Optimization of Growth Conditions for Magnetospirillum magnetotacticum and Green Synthesis of Metallic Nanoparticles

Nanotechnology is especially useful in biotechnological and biomedical applications as nanomaterials have unique physicochemical properties. Current physical and chemical techniques used for the production of nanoparticles have various disadvantages that has led to the evaluation of biological strategies. This study focused on the use of a bacterial species known as Magnetospirillum magnetotacticum for the production of metallic nanoparticles. The cultivation of MTB is known to be tedious and time-consuming using the current standardized magnetic spirillum growth media (MSGM). This study explored the optimization of MSGM for improved growth and nanoparticle yield. It was found that glucose significantly improved and sustained the growth of M. magnetotacticum compared to other sole carbon sources having a sustainable OD of ~1.15. However, use of a higher concentration of sodium nitrate (40 mM) as a nitrogen source was able to significantly improve iron-containing nanoparticle yield by 1.6× with a final yield of 22 mg/50 mL when compared to the yield obtained from the MSGM original media. Growth media with a combination of glucose, sodium nitrate, ammonium sulphate and yeast extract showed the highest exponential growth of Magnetospirillum magnetotacticum compared to all other MSGM modifications with the highest OD being 1.7. Silver and gold nanoparticles were also successfully produced in addition to iron-containing nanoparticles. Overall, no direct correlation between growth and nanoparticle yield was found.