In the production of Victor the Vector, our team used a 3D printer to create parts for the device. This 3D printer used PLA (polylactic acid) plastic to print the parts.
PLA is a biodegradable polyester that is developed from various biological sources such as corn starch. PLA can be used for several plastic products such as cups, packaging material, and even as various parts of medical implants. It is a desirable replacement for several other plastics that may not be able to degrade.
Due to the fact that PLA is produced from biological sources, it is reasonable that it could be broken down and recycled into the environment. Since PLA is a polymer of lactic acid, hydrolysis of the polymer will degrade it back into lactic acid. Our team decided to use the scrap pieces of PLA from the 3D printing, and convert it back into lactate, which could then be used in the media for our E. coli cells.
This was done by a simple hydrolysis reaction, adding base to the polymer to break it down, then neutralizing the solution with acid and filtering. The reaction is shown below along with the protocols used to degrade and characterize the solution.
Protocols
To a 1 L Erlenmeyer flask add:
Stir reaction, heating to 50-60°C, overnight or until all plastic has visibly dissolved.
Neutralize with HCl to a pH of 5-6.
Vacuum filter solution 2-3 times, dispose of any solid collected.
Using a sterile syringe, filter solution into a jar to store until needed.
The filtered solution was measured in a polarimer. The optical rotation results are as follows.
| pH | Optical Rotation |
|---|---|
| 2.5 | .12 |
| 3.5 | -.13 |
| 4.21 | -.26 |
This suggests that the solution did in fact contain lactate because a pH change made a significant difference in the optical rotation of the solution.
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