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Thursday, 01 October 2020

Bio-based coatings: Anything else but cheesy

Thursday, 30 July 2015 | Posted by: Michael Richter, European Coatings Journal

Adopting renewable innovations is often a challenging task and current percentage ratios of sustainable components remain quite low. So what about a totally bio-based and fully controllable deposition process for the formation of biological coatings? How does that sound to you?

The enzymatic autodeposition process uses an enzymatic reaction for a controlled deposition of biological particles, e.g. from a colloidal dispersion. The enzymatic reaction triggers a solubility change of particles in close proximity to a support surface and initiates deposition and coagulation of the particles.

Just think of tacos and salsa dip

To ensure this, the enzyme is immobilised onto the support surface and destabilises particles only closely to the given surface. Thus, as a convenient advantage of this method, the actual coating procedure is realised by a simple dipping process, like you are dipping a taco into salsa sauce. The use of the enzymatic reaction as a "trigger” offers a very high control over the film formation and important parameters such as film thickness can easily be adjusted.

How coatings can prevent milk wasting

The first investigated system was inspired by the enzymatic reaction present in cheese making, which is also naturally occurring in the stomachs of nursing young mammals. Casein, the major milk protein is cleaved and precipitated by the aspartic protease chymosin. Casein is a protein with well-known physical and chemical properties and has a very long tradition in coating applications, which reach back into the times of ancient Egypt. Casein is a low cost renewable raw material and readily accessible. Since raw milk is subjected to strict governmental regulations, an enormous amount of milk is discarded every day, for example due to a varying amount of bacteria. Using potential waste milk for coating applications, would have no influence on any food issues. Also chymosin is low-priced, as it is commonly available and frequently used in the cheese industry.

Problems, potentials and solutions

Nowadays, casein coatings and adhesives are replaced with synthetic polymers in many coating applications, but exhibit a promising potential for medical and packaging applications. As a big advantage, enzymatically deposited casein coatings show an increased water stability compared to conventionally processed casein films.
From my point of view, it makes them, in connection with the site-specificity of the method and their intrinsic biocompatibility and biodegradability, an interesting material for the coating of medical implants.
According to the researchers, the concept of the enzymatic autodeposition process is not restricted to the system casein/chymosin, but is transferable to other biological systems, where an enzymatic reaction results in a solubility change and specific deposition of biological particles.

Now it is your turn!

What do you think about this new concept for the formation of biological coatings and its meaning for coating technology? Can you imagine reasonable applications? Just leave me a message!

O.I. Strube, A. A. Rüdiger, W. Bremser, J. Biotechnol., 2015, 201, 69-74.
O.I. Strube, A. Büngeler, W. Bremser, Biomacromolecules, 2015, 16, 1608-1613.

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Michael Richter
European Coatings Journal
Michael Richter
Scientific Consultant
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