Synthesis of Metal Oxide Microcapsules Using Metal-Reducing Bacteria

Begin by inoculating a suspension of metal-reducing bacteria into a culture medium with metal ions.

Incubate with rotation to promote growth and facilitate the uptake of metal ions.

The metal ions diffuse into the cells and are enzymatically reduced to insoluble metal oxides.

These oxides are excreted and nucleate near the bacterial membrane, where they self-assemble into rigid metal oxide microcapsules outside the cells.

After incubation, ultrasonicate the suspension to dissociate the bacteria from the microcapsules.

Centrifuge the mixture to pellet the dense microcapsules and discard the supernatant.

Wash the pellet with water, then ultrasonicate. Centrifuge again to separate the bacteria from the microcapsules.

Next, add ethanol to reduce surface tension.

Ultrasonicate again to dislodge any remaining bacteria and to disperse the microcapsules.

Centrifuge again and discard the supernatant.

Repeat the ethanol wash.

Finally, seal the tubes to prevent the drying and deformation of the purified microcapsules.

Retrieve the culture containing the monoclonal bacteria and add 50 microliters of it into each of the ten 50-milliliter centrifuge tubes containing the sodium tungstate media.

Incubate the ten tubes in a 37 degrees Celsius incubator for 120 hours. Following the incubation, place each of the tubes in an ultrasonicator and sonicate the cells at 20 kilohertz with 150 watts for one hour.

Centrifuge the tubes and then remove the clear liquid with a pipette.

Next, add water and then sonicate and centrifuge the tubes one more time.

After the second centrifugation, remove the clear liquid in the tubes with a pipette.

Then add 35 milliliters of 99.8% Ethanol and ultrasonicate the samples again.

Rinse the minerals by centrifuging them, adding alcohol, and sonicating the sample one more time.

Then, remove the clear liquid in the tubes with a pipette and immediately cap the tubes without drying out the sample.