Brief Summary
The video discusses the global issue of plastic pollution and the potential of using microbes to biodegrade plastics. It highlights the challenges in breaking down plastics due to their man-made polymers and the high temperatures required for degradation. The discovery of plastic-digesting enzymes in bacteria like Ideonella sakaiensis and Leaf Branch Compost Cutinases offers hope for improved recycling. However, the video emphasizes the need for a comprehensive approach, including reducing plastic production, improving recycling processes, and designing more biodegradable polymers.
- Microbes can break down organic material, but most can't biodegrade plastics.
- Plastics are made from man-made polymers that are difficult for microbes to digest.
- Some microbes and enzymes have been discovered that can break down certain plastics like PET.
- More research is needed to find microbes that can break down other types of plastics.
- Reducing plastic production and designing more biodegradable polymers are also important.
The Problem with Plastics
Microbes are everywhere, constantly breaking down organic material. However, most microbes cannot biodegrade plastics. Plastics are made from molecules refined from oil, gas, and coal, which are turned into long, repeating chains called polymers. This process requires high temperatures and pressures, resulting in man-made polymers that are very different from natural polymers. Because plastics have only been around since the 1950s, most microbes haven't had time to evolve enzymes to digest them. Breaking the chemical bonds in most plastics requires high temperatures that are deadly to microbes. As a result, most plastics never biologically degrade and instead turn into tiny, indigestible pieces.
The Scale of Plastic Waste
The most common plastics, such as Polyethylene, Polypropylene, and Polyester-terephthalate, have been accumulating for decades. Each year, humanity produces approximately 400 million tons of plastic, with 80% being discarded as trash. Only 10% of this plastic waste is recycled, while 60% is incinerated or sent to landfills, and 30% leaks into the environment, polluting natural ecosystems for centuries. An estimated 10 million tons of plastic waste end up in the ocean each year, primarily as microplastic fragments that contaminate the food chain.
Microbial Solutions for PET
In 2016, Japanese researchers discovered Ideonella sakaiensis 201-F6, a bacterium capable of slowly breaking down PET polymers at relatively low temperatures. This bacterium contains two enzymes that facilitate this process. Researchers isolated the genes coding for these plastic-digesting enzymes, enabling bioengineers to combine and improve them, creating super-enzymes that can break down PET up to six times faster. However, even these enhanced enzymes still take weeks to degrade a thin film of PET and operate best at temperatures below 40°C.
High-Temperature Enzymes
Another group of scientists in Japan researched bacterial enzymes adapted to high-temperature environments, such as compost piles. They found gene sequences for powerful degrading enzymes known as Leaf Branch Compost Cutinases in a warm pile of rotting leaves and branches. Researchers genetically engineered fast-growing microorganisms to produce high quantities of these enzymes. They then enhanced and selected special variants of the Cutinases that could degrade PET plastic in environments reaching 70°C, a high temperature that can weaken PET polymers and make them digestible.
The Future of Plastic Degradation
While the future of PET recycling looks promising with the help of these microbes, PET is just one type of plastic. There is still a need to find ways to biologically degrade other types of plastics, including abundant PEs and PPs, which only begin breaking down at temperatures well above 130°C. Currently, researchers are unaware of any microbes or enzymes tough enough to tolerate such temperatures. The primary methods for dealing with these plastics involve energy-intensive physical and chemical processes.
Rethinking Our Relationship with Plastics
Currently, only a small fraction of plastic waste can be biologically degraded by microbes. Researchers are searching for more heat-tolerant plastivores in the planet’s most hostile environments and engineering better plastivorous enzymes in the lab. However, we cannot rely solely on these tiny helpers to clean up our enormous mess. We need to completely rethink our relationship with plastics, make better use of existing plastics, and stop producing more of the same. It is crucial to design more environmentally friendly types of polymers that our growing entourage of plastivores can easily break down.
