Production of biopolymers and biobased polymers

Synthetic or petroleum-based polymers offer significant advantages that have benefited mankind for more than a century. It is therefore hardly surprising that more than 90 percent of the polymers produced worldwide are based on crude oil. However, in addition to the advantages they offer, their disadvantages are now becoming increasingly apparent, including the depletion of fossil resources, pollution of the world's oceans and increased CO₂ emissions caused by the combustion of non-degradable plastics.

New approaches therefore aim to significantly increase recyclability, for example through the increased use of monomaterials. Despite these efforts, however, alternative and complementary approaches are also required to meet the aforementioned challenges. This circumstance, as well as climate change and increased environmental awareness, has directed the focus towards plastics made from biogenic raw materials. Biobased plastics are mostly biodegradable, biocompatible and can be produced CO₂-neutrally.

Biodegradable polymers are in particular high demand when plastics are required for direct use in the environment, for example in agricultural films. These simply decompose over time and leave no traces of microplastics. The aspect of biocompatibility plays a part especially in medical and cosmetic applications.

At Fraunhofer IGB, we contribute significantly to the development of novel biobased plastics by designing and optimizing processes for the production or purification of various biobased polymers and biopolymers.

Native biopolymers (lignin, cellulose, hemicellulose, latex, inulin or chitin) are obtained at the IGB after purification and extraction from renewable raw materials or waste streams.

Another option is using these material flows after appropriate conversion:

• Microbially produced polymers, e.g. polyhydroxyalkanoates (PHA)
  We use waste streams such as used cooking oils, lignocellulose fractions or volatile fatty acids from wastewater treatment for the production of various PHAs.
• Biobased monomers (hydroxycarboxylic acids and dicarboxylic acids)
  We produce biobased monomers biotechnologically by fermentation from waste streams. These can subsequently be chemically polymerized into polymers (polyesters, polyamides, polyurethanes) with the desired properties. Our portfolio includes malic acid, itaconic acid, xylonic acid, long-chain dicarboxylic acids (lc-DCA) and lactic acid. 

Based on underlying thermodynamic-mechanical data, biopolymers can replace fossil-based polymers or even open up new fields of application. 

We will gladly investigate the processing of native biopolymers and the microbial production of PHA, hydroxycarboxylic acids and dicarboxylic acids as well as the purification of polymers based on your individual waste streams.

Chitin – after cellulose – is the second most common natural polymer on earth and is formed as a structural component by fungi, insects and crabs. Cellulose is the main component of plant cell walls. Lignocellulose is the structural material in the cell wall of all woody plants and the main component of residues such as straw or wood.

After purification and extraction, we obtain native biopolymers such as lignin, cellulose, hemicellulose, chitin, latex or inulin from renewable raw materials or waste streams at Fraunhofer IGB. For instance, we purify residual materials containing chitin (insect skins, waste from fishing and mushroom cultivation) to extract the chitin and subsequently convert it into chitosan.

We also fractionate lignocellulosic biomass from agricultural and forestry waste streams into the fractions cellulose, hemicellulose and lignin. Due to our expertise in the enzymatic hydrolysis of the individual polymers, we are able to open them up for further applications.

We have also been working on the extraction of latex and inulin from Russian dandelions.

Polyhydroxyalkanoates (PHA) – biodegradable and biocompatible

Polyhydroxyalkanoates (PHA) are bacterial storage polymers whose production is induced by nutrient limitation and excess carbon. The best-known representative of PHA is polyhydroxybutyrate (PHB) and its copolymers – above all PHBV (polyhydroxybutyrate-co-hydroxyvalerate) – are of major importance for the production of bioplastics.

The microbial synthesis of PHA offers the advantage of producing biopolymers with the desired thermal and mechanical properties (e.g. glass transition and melting temperature) by selecting the microorganisms and substrates and by optimizing the bioprocess itself.

Regardless of their composition, PHAs are characterized by biocompatibility and biodegradability. This means that they can be used in packaging, e.g. as disposable plastic bottles for non-food applications, for medical implants and agricultural films to replace various fossil-based polymers (e.g. polyethylene).

In our process optimization, the microorganism is able to accumulate more than 90 percent PHA in the cell. A purification process is therefore potentially no longer necessary but is already established for the production of high-purity PHA.

We produce different variants of PHA and copolymers of PHBV with varying valerate content according to the requirements for various applications. For this, we use waste cooking oil, volatile fatty acids (from wastewater treatment), crude glycerine and other suitable waste  

At Fraunhofer IGB, we produce hydroxycarboxylic acids and dicarboxylic acids from biogenic waste streams using various fermentative processes. Our portfolio includes malic acid, itaconic acid, xylonic acid, long-chain dicarboxylic acids (lc-DCA) and lactic acid, which can be polymerized in downstream processes.

When using biobased carboxylic acids, the desired polymer properties can be achieved not only via the monomer itself, but also via the polymerization conditions

Although the process development, taking into account the substrate, its feed or the microorganism, has no influence on the properties of the target molecule, it is nevertheless crucial for product concentration and conversion efficiency. In the case of xylonic acid, we were able to achieve titres of over 300 g/L.

Polymalate – as a laminating adhesive?

Polymalates are polymers of the dicarboxylic acid malic acid. The consortium of the Malum project is concerned with the fermentative production of enantiomerically pure malic acid, further purification and the subsequent production of polymers. While the IGB is involved in the scale-up of fermentation and downstream processing in this project, one of our project partners, HPX Polymers GmbH, is responsible for the polymerization of L-malic acid.

Homopolymers of racemic malic acid are water-soluble, biocompatible and biodegradable, but too hard and brittle for the intended applications.

Initial tests were carried out with commercially available DL-malic acid. In the project, novel biopolymers with higher elasticity and durability were produced by functionalization or copolymerization with other monomers. Initial application tests have shown that these polymers can be used as laminating adhesives.

• Qualitative and quantitative analysis of the chemical composition of the raw or waste stream (chitin, lignin, cellulose, hemicellulose, ash, fat, protein)
• Fractionation / purification of various raw and waste streams
• Screening for microbial polyhydroxyalkanoate producers
• Qualitative and quantitative analysis of polyhydroxyalkanoates
• Optimization of the fermentative production of hydroxy- and dicarboxylic acids
• Development of purification strategies for biobased carboxylic acids and microbial polymers
• The respective processes can be scaled up at our institute branch in Leuna, Fraunhofer CBP..
• In-house post-modification of various polymers

We will gladly investigate the microbial production or purification of biobased polymers or biopolymers from your waste streams on your behalf.