Break it down now: stubborn plastics broken down by microbes

Plastic pollution continues to threaten ecosystems worldwide and effective solutions to break down stubborn plastics are needed. In the meantime, nature has evolved to benefit from the surplus of plastic available to it. Particular microbes have developed ways to benefit from the waste plastic and turn it into products that can be used for energy. This means that one potential solution to the problem of plastic pollution is the use of plastic “eating” bacteria.   

It has been known for some years that plastics, such as polyethylene terephthalate (PET), with hetero-functionality in the backbone (in the case of PET, ester-containing backbones) can be degraded by a variety of species of fungi and bacteria.  

Some plastics, like polyethylene (PE), have backbones made up of carbon-carbon bonds.  These are far more difficult to break down. However, it has more recently been discovered that particular bacteria can do just that.

While PE is resistant to most forms of natural decomposition, under certain environmental conditions, such as exposure to sunlight, it is degraded by a bacterium known as Rhodococcus ruber  (R. ruber). This is achieved by the bacterium producing enzymes that attack the plastic's molecular structure, fragmenting it into smaller pieces. Degradation of PE by R. ruber has been exemplified in laboratory experiments replicating natural conditions, by Maaike Goudriaan at the Royal Netherlands Institute for Sea Research (NIOZ) (see here).

Although the degradation process is slow and not yet fully understood, it represents a significant step forward in understanding how nature is dealing with plastic waste, particularly in marine environments where R. ruber has been found.

Research by the scientific community into R. ruber is ongoing, with a focus on exploring ways to enhance its plastic-degrading abilities and better understand the mechanisms involved. Perhaps harnessing the mechanisms used by such bacteria to degrade PE will provide more solutions to the problem of how to break down stubborn plastic waste.