Team:PuiChing Macau/Proof Of Concept


In our project, our Food waste-PLA system is composed of Breaking down (glucose test), Fermentation (Acid tolerant) and PLA production system+phasin.
To confirm our concepts, we did food waste analyzing (pH tests) on the food waste, an acid challenge to our acid tolerant system.

Figure 1. Concept of our system

Acid Tolerant

We have known that e-coli cannot grow well in an acidic environment where food waste contributes to a low pH environment while we are generating lactic acid. (Lactic Acidosis Fermentation) That’s why we transformed the fabB gene to the e-coli to change fatty acids to unsaturated fatty acids to produce a persistent decrease in intracellular pH, eventually helping it grow better in a low pH environment.

Total colonies(CFU/mL) =
No. of colonies *Total dilution factor/Volume of the culture plate in mL

Figure 2a. Number of E.coli colonies (WT: BL21 control, FabB: E.coli with acid tolerant gene) in pH 4 (N=4, error bar: SEM)

Figure 2b. Number of E.coli colonies (WT: BL21 control, FabB: E.coli with acid tolerant gene) in pH 7 (N=4, error bar: SEM)

Figure 3. (1) flow chart of breaking down part

Figure 4. (2) flow chart of acid tolerant system

Figure 5. (3) flow chart of PLA-PHA production system.

PLA production system

For the final step, we transformed the PHAC and PCT gene to the bacteria to polymerase the lactic acid. We also added phasin, which could affect Phac on the polymer-elongating, similar to the prepolymerization PhaC. [1]
We did IR test and melting point testing on the PLA powder we made to ensure that it is the PLA we want.

Figure 6a. IR test result of PHA in and PHA un, to validate the molecules are PLA or PHA.

Figure 6b. IR test result of Phac in and Phac un

Figure 7c: IR test result of Phasin in and Phasin un

Figure 7d: IR test result of Control in and Control un


With the three parts validating our concept of our system, we are able to produce PLA and PHA. We made tests and experiments to improve our system and verify our products. However, our system is still not perfect, and we will make it better by doing more testing and studying more about PLA and PHA.


1. Phasin Proteins Activate Aeromonas caviae Polyhydroxyalkanoate (PHA) Synthase but Not Ralstonia eutropha PHA Synthase, NCBI, 2014, (