Using a very common bacterium, researchers at KAIST have created a bio-based plastic that could replace PET bottles

Korean researchers have developed a bio-based plastic which could be used to replace PET in the production of plastic bottles. It is a pseudo-aromatic polyester, that is, a monomer that to some extent imitates the structure of the molecules that form plastic polymers, produced starting from glucose using five strains of Corynebacterium glutamicum, a bacterium that already finds wide application in the industrial field for the production of the amino acids lysine and glutamate.

Replacing plastic: a challenge for chemistry

The ever-increasing use of plastic is putting the health of the planet and its inhabitants to the test: according to the latest Earth Action Report, this year alone we have dispersed in nature approximately 70 million tons of plastic, 31,5% of the total waste produced, essentially due to the imbalance between the volumes of plastic consumed and the capacity to manage the material at the end of its life.

These huge amounts of waste abandoned in the environment they can pollute the soil and end up directly in the oceans, suffocating animals and entire marine ecosystems, and it is now proven that the degradation of plastic objects leads to the creation of microparticles capable of insinuating themselves in human blood and tissue. Concern for human health is thus added to the environmental issue, making the search for technologies and solutions capable of reversing this dangerous trend increasingly urgent.

Chemical research has long accepted this challenge, proposing solutions ranging fromupcycling of plastic materials to the creation of new materials capable of replacing those derived from petroleum. The latest news comes from Korea Advanced Institute of Science & Technology (KAIST): Researchers seem to have found a remarkable alternative to plastic. The research team, led by Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering, has succeeded in producing a microbial-based plastic biodegradable which would even be able to replace PET used for the production of bottles.

Bacteria as an alternative to plastic

Professor's research group Sang Yup Lee he succeeded in developing a microbial strain that efficiently produces a monomer of pseudoaromatic polyester which can be used to replace polyethylene terephthalate (PET).

Pseudo-aromatic dicarboxylic acids, the scientists explain, have better physical properties and greater biodegradability than an aromatic polyester such as PET when synthesized as polymers. For this reason, they are attracting the attention of researchers as eco-friendly monomers with which to attempt to build alternative polymers to plastics.

The production of pseudo-aromatic dicarboxylic acids through chemical methods, however, presents several problems: it is not very selective, has a low yield, requires very complex reaction conditions and produces hazardous waste.

To solve this problem, Professor Sang Yup Lee's research group used themetabolic engineering to develop a microbial strain that produces five types of pseudoaromatic dicarboxylic acids from glucose using five strains of Corynebacterium glutamicum engineered. As the study states, published on PNAS, "A base strain for the production of 2-pyrone-4,6-dicarboxylic acid was constructed, which was then further engineered and optimized to produce other pyridine dicarboxylic acids.".

An important step towards oil-free chemistry

The new production method has proven to be very efficient: The researchers were able to successfully produce 2,79 g/L of 2,3-pyridinic acid, 0,49 g/L of 2,4-pyridinic acid, 1,42 g/L of 2,5-pyridinic acid and 79 g/L of 2,3-pyridinic dicarboxylic acid. In addition, they obtained 0,49 g/L of 2,4-pyridinic dicarboxylic acid and 1,42 g/L of 2,5-pyridinic dicarboxylic acid, the highest high production concentrations recorded in the world. In particular, the researchers explain, 2,4-, 2,5-pyridinic dicarboxylic acid has reached a production on a g/L scale, where it had never been possible to exceed mg/L scales.

The methods used in this study will be useful in developing increasingly efficient cell factories to be used for the production of bio-based plastic monomers. The research results are expected to be applied in various industrial processes Polyester production, and which will be actively used in future research on the production of aromatic polyesters.

As Professor Sang Yup Lee stated,

“The importance of this research is that we have developed an environmentally friendly technology that efficiently produces similar aromatic polyester monomers based on microorganisms. This study will help the microorganism-based bio-monomer industry to replace the petroleum-based chemical industry in the future.”

Korean researchers have finally found a way to efficiently produce these compounds that could one day be replace the plastic, opening an important window of opportunity for future research on alternative monomers from bio-based sources.

Here are three insights that might interest you:

How much plastic is in the human body?
The world's first edible rechargeable battery
The Kenyan start-up that turns plastic waste into freezers