Your compost bin could be a plastic factory

Here is something that has been thoroughly categorized by scientists all over the world, and has been used in a variety of applications: bacteria.

Here are two problems: food waste and plastic pollution.

Here is a solution: Bacteria that feed on food waste and have a product of usable plastic.

It may seem like a fantasy, but scientists have been developing sustainable methods of using endogenous pathways inside bacteria that produce plastics from carbon sources. With food waste being well documented as a significant portion of all landfill waste, and plastic production contributing largely to global greenhouse gas (GHG) emissions, diverting food waste to controlled microbial processing facilities will address two problems at once.

Some bacteria can produce a diverse group of plastics known as Polyhydroxyalkanoates (PHA) as a by-product of their regular metabolism (Nielson et al. 2017). This plastic is bridgeable, can be easily moulded into different products, and is a thermoplastic, which means it does not interfere with the recycling process if it is thrown into a blue bin rather than a green bin (Campbell 2019). Luna Yu is a researcher at the University of Toronto who is working to perfect this technique. She specializes in creating PHAs through her start-up Genecis that are used for high-end products such as 3D printing filament, flexible packaging, and medical equipment.

Current hindrances of this process have included the cost of viable carbon sources, which compromised 28-50% of the total production process (Nielson et al. 2017). Although food waste may intuitively be the best carbon source, its composition is often too impure to feed to the PHA-producing bacteria directly (Nielson et al. 2017). Straight food waste must first be pre-treated and processed into basic compounds like simple sugars and fatty acids, which can then be used by bacteria to produce PHAs (Nielson et al. 2017). This process, however, can also be done through genetically engineered bacteria as opposed to using laboratory chemicals (Campbell 2019).

Stressors such as nitrogen and phosphorus starvation are often needed to induce the PHA-producing mechanisms, which adds layers to the work needed for this process to work (Nielson et al. 2017). Using synthetic biology and engineering, however, this system can be hijacked so that the bacteria can constantly produce PHAs (Nielson et al. 2017). A specific strain of Escherichia Coli, the standard organism used in genetic engineering, has been modified to contain A. latus genes that create PHA (Nielson et al. 2017). This strain of E. Coli can produce a dry weight of 80.5% PHA to the weight of a single cell, which means 1kg of dry bacteria would yield 805g of plastic, for example (Nielson et al. 2017). In their paper, Nielson et al. (2017) present a table outlining various combinations of food waste categories, kinds of PHAs that are produced, and the bacterial genes responsible for them.

With future advancements, it could be possible that the technique of converting food waste into plastic could be integrated into modern households. Plastics are a commodity that has become abused and overused to the point where today people cannot envision a world without a plastic grocery bag or disposable utensils. Not only do plastics often pollute our environment and oceans, but their production also involves using oils and natural resources that pollute the earth even more. Investing in synthetic biology to produce bridgeable plastics can change resource use in more ways than one.

References:

Campbell, D. U of T startup that turns food waste into high-quality bio-plastic eyes next phase of growth. University of Toronto News. Posted 24 September 2018. Accessed 12 June 2019. Available from: https://www.utoronto.ca/news/u-t-startup-turns-food-waste-high-quality-bio-plastic-eyes-next-phase-growth

Nielsen, C., Rahman, A., Rehman, Rehman, A. U., Walsh, M. K., Miller, C. D. Food waste conversion to microbial polyhydroxyalkanoates. Microbial Technology. 10(6), (2017).

 

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