Imagine a plastic like this: tougher than ordinary plastic, non-flammable, and even self-healing. What's more, it can be produced in water at room temperature, is very energy efficient, and doesn't require toxic solvents. You can mold it into any shape before it hardens. After molding, you can also reshape it at any time by adding water and recycle it as needed.
In fact, back in 2016, a team of researchers led by Helmut Cölfen, a chemist in Constance, Germany, proposed such a material - mineral plastic. Although this plastic has attracted a great deal of industrial interest with its novel manufacturing process and excellent material properties, there is still one key drawback: due to its chemical composition, it is very difficult to be biodegraded.
Now, the team has finally solved this flaw, and the key is a different ingredient.
"Previously, we used polyacrylic acid to produce mineral plastics. Chemically, this acid has the same main chain as polyethylene, which can cause major problems for the environment because it is difficult to biodegrade," explains Cölfen.
So the research team, led by Cölfen, set out to find an alternative basic building block to develop an environmentally compatible mineral plastic that retains the fascinating properties of the original material. Now, they have found what they were looking for. The latest findings were recently published in the journal Small Methods.
They are now using polyglutamic acid instead of petroleum-based feedstocks such as polyacrylic acid. This natural biopolymer is readily available in large quantities and can even be sustainably obtained, for example by biotechnological production using microorganisms. Moreover, a wide range of microorganisms already present in the environment can degrade polyglutamic acid.
Polyglutamic acid (γ-PGA) is an environmentally friendly biopolymer material. Bio-polymer material polyglutamic acid (γ-PGA) is a biopolymer synthesized by fermentation of microorganisms using glutamic acid as the basic raw material and combining with organic carbon, nitrogen and minerals, which is one of only four polymer homopolymer amino acids synthesized by microorganisms. Each molecule of γ-PGA contains more than 1,000 super-strong water-locking groups (-COOH), which gives it multiple functions such as high water-absorbency, high viscosity, chelating of trace elements (metals), synergistic and slow-release, etc., and is 100% biodegradable under natural conditions. Therefore, γ-PGA can be widely used in agricultural production materials (fertilizers, pesticides), which can significantly retain water, chelate trace elements, and play a role in increasing efficiency and slow release to improve crop yield and quality.
Cölfen says: "Our new mineral plastic has the same positive properties as its predecessors, but with the decisive advantage that its basic component, polyglutamic acid, can be produced with the help of microorganisms and is completely biodegradable. "
In degradation experiments, biologists eventually demonstrated that microorganisms found in forest soils, for example, can begin to metabolize mineral plastics after just a few days. After just 32 days, the microbes completely degraded the plastic.
As a result, researchers have actually succeeded in making mineral plastics with all the positive material properties that are now also sustainable and biodegradable
