Team:PuiChing Macau/Design

The overall goal of this project is to develop a bioplastic production system using food waste as raw material to produce PLA and PHA. We aim to achieve this through developing an engineered recombinant E.coli strain, given that this would allow more easy and less polluted mass production.


1. Breaking down polysaccharides in food waste

In order to facilitate the production of lactic acid from food waste fermentation, the macromolecules in food waste need to convert to monosaccharides. To achieve this, we first break down polysaccharides in food waste into monosaccharides through amylase and glucoamylase (BBa_K3863006). The monosaccharides produced are then fermented to produce lactic acid for further steps.

2. Engineering Success: Acid Tolerant System

Considering food waste contains different types, including Fruit & vegetables, Meat, Carbohydrates, etc., we have analyzed the pH value of different food waste and discovered that their pH is lower than 7 which will inhibit the growth of E.coli indicated in Engineering success. Moreover, the fermentation process of monosaccharides will produce lactic acid and lower its pH. In such a case, we employed acid-tolerant gene fabB, which has been proved to resist acid to protect E.coli through increasing the production of unsaturated fatty acid on bacteria’s membrane [1], to ensure the growth and efficiency of the system.

3. Bioplastic Production system

In the hope of producing copolymer, we have selected two genes PhaC and PCT gene, which has been approved for their ability on producing bioplastic using lactic acid and polyhydroxybutyrate(PHB) as a single unit, from the previous iGEM team as the basis of the production system. To increase the overall efficiency of bioplastic production, we fused the PhaC and PCT genes with phasin, a gene proved to promote the production of plastic by iGEM 2014 Yale.

4. Future: Cotransformation

The primary goal of the system is to develop a step-approach system to convert food waste to bioplastic. Therefore, we would like to perform cotransformation by inserting multiple plasmids in E.coli, so the bacteria could have multiple functions in the process of production.


[1]Xu, Y., Zhao, Z., Tong, W., Ding, Y., Liu, B., Shi, Y., ... & Zhao, G. (2020). An acid-tolerance response system protecting exponentially growing Escherichia coli. Nature communications, 11(1), 1-13.