Bacteria Produce Polymers and Intermediate Products

Biotechnologically produced building blocks for chemistry and biodegradable synthetics

polymers
Casing cover made from a blend of Polyhxdroxybutyric acid and polypropylen carbonate – Photo: Andreas Battenberg / TUM

In July 2015, the Bavarian Ministry of the Environment and Consumer Protection set up the project group “Resource-friendly Biotechnology in Bavaria – BayBiotech.” The aim is to contribute to resource-friendliness through application specific research projects in the field of biotechnology and to support the transition to a sustainable bio-economy. Today scientists at the Technical University of Munich (TUM) and the University of Bayreuth presented the results of their research in Erlangen.

Considering the limited supply of oil and natural gas there is a clear development towards resource friendly and sustainable production of synthetics and intermediate chemical products using biotechnological processes. To this end, the Bavarian Ministry of the Environment and Consumer Protection has initiated the project group “Resource-friendly Biotechnology in Bavaria – BayBiotech.”

“We want to build on our previous successes in environmental protection on the road to a sustainable bio-economy. The project group utilizes biotechnology to advance innovative and environmentally friendly manufacturing processes. With nature’s toolbox we could produce future products using plants and bacteria. Today’s wool sweater might be tomorrow’s car tire made of botanical materials. Our goal is a sustainable bio-economy that combines ecology and economics through the responsible use of biological resources,” says Ulrike Scharf, the Bavarian Minister for the Environment and Consumer Protection, whose Ministry funds the project group to the tune of 2 million euro.

Bespoke Biopolymers

A key focus of the project lies on the biotechnological production of bespoke synthetics made of polyhydroxybutyric acid (PHB). Bacteria produce this biopolymer as a storage substance. PHB has properties like propylene, which is produced from petroleum but is significantly more brittle and thus more difficult to process.

The bacteria always combine the individual building blocks in the same manner. The material thus forms crystalline regions, making it brittle. In the context of the project, teams at the Chair of Chemistry of Biogenic Resources and the Professorship of Biogenic Polymers in Straubing demonstrated how mechanical properties of the biopolymer can be improved by adding other synthetics, such as polylactides.

Separating the production of individual building blocks and the polymerization opens the door to new processing options. Therefore the team led by Thomas Brück, Professor of Industrial Biocatalysis, has developed a resource-friendly production methodology of PHB monomers from bran, a cheap by-product of flour production.

Mixing these monomers with others made from beta-butyrolactone, researchers at the TUM Chairs of Macromolecular Chemistry and Chemistry of Biogenic Resources introduces specific irregularities into the polymer, thereby custom-tailoring the material properties for given applications. The research also develops improved metallic and biogenic catalysts opening the butyrolactone ring.

Biotechnological Production of Chemical Intermediates

Many biotechnological processes make use of spontaneously formed biofilms. However, these are often quite sensitive and therefore cannot be adapted to all desired reactions. That is why teams at the Chairs of Process Biotechnology and Macromolecular Chemistry II of the University of Bayreuth developed artificial biofilms in which microorganisms are embedded into a bespoke synthetic polymer matrix. This makes the bacteria significantly more robust and allows them to be exploited for a wide variety of cases.

Acetic acid bacteria are already being deployed in the production of vitamin C. Since the bacterium must react to myriad environmental stimuli, it has a variety of enzymes on its exterior. Using newly developed biomolecular methodologies, the researchers at the Chair of Microbiology on the TUM Weihenstephan campus and the Institute of Biochemical Engineering in Garching succeeded in removing the unneeded enzymes. The energy of the bacteria is thus concentrated on the biotechnological production of the desired enzymes. This rsults in increased activity and inhibition of undesired secondary reactions.

Compounds that behave in a mirror-like fashion to one another are important building blocks in the synthesis of pharmaceutical products. So-called enoate reductases can accumulate hydrogen at double bonds, thereby producing this property of chirality, as it is called. In this way, for example, carvon, a component of cumin oil, can be converted into the chiral dihydrocarvon. Using various protein engineering techniques, scientists at the TU Munich Institute of Biochemical Engineering have altered the enzyme to increase its activity more than fourfold.

Synergy of Group Research

“The successful work of this research group demonstrates the great benefit of interdisciplinary collaboration even if distributed over different locations,” says Thomas Brück, Professor of Industrial Biocatalysis at TU München. “Bringing together the three TUM locations Straubing, Weihenstephan and Garching, spans the arch from basic research to application development and greatly accelerates the path to actual implementation.

”Contributors from the Technical University of Munich were the Chair of Chemistry of Biogenic Resources and the Professorship of Biogenic Polymers in Straubing, the Chair of Microbiology in Weihenstephan and the Institute of Biochemical Engineering, the Wacker-Chair of Macromolecular Chemistry and the Professorship of Industrial Biocatalysis in Garching. Further members of the group were the Chairs of Process Biotechnology and Macromelecular Chemistry II at the University of Bayreuth and the Institute of Bioprocess Engineering at the University of Erlangen, which coordinates the project group funded by the Bavarian Ministry for the Environment and Consumer Protection.