Study Group: Biopolymers

1. Polyhydroxyalkanoates (PHA)

Group Leader: Dr. Gisela Mothes

Polyhydroxyalkanoates (PHA) are biodegradable thermoplastic polymers, accumulated by bacteria of different taxonomic classification. In contrast to petrochemically synthesized polymers they can be produced from renewable carbon resources. The best known and most wide spread example is poly(3-hydroxybutyric acid) (PHB). It is of special commercial interest due to its thermoplastic properties, its biocompatibility, biodegradability, hydrophobicity and relatively low oxygen permeability. The mechanical properties can be modified by blending with other materials or by the synthesis of copolymers, allowing a wide range of applications e.g. industrial plastic materials or in the field of medicine.

We have developed effective methods of biotechnological production of PHA using different bacterial strains and carbon substrates. The synthesis of tailor made copolymers of 3-hydroxybutyric acid and 3-hydroxyvaleric acid or 3-hydroxybutyric acid and 4-hydroxybutyric acid allows the creation of materials with specific mechanical properties which can be provided as a sample. As well fed-batch as continuous operational modes of fermentation have been developed and scaled up to the 500 L mark.

Projects:

Developement of applicable materials made from PHA for the coating of natural materials
LfUG

Autologous tissue reconstructions from mesenchymal stem cells and biofunctionalized polymer scaffolds
SMWK

Biotechnological production of copolymers with target composition
UFZ

Characterization and optimization of two-stage continuous product synthesis with heterogeneous cell populations
UFZ

Microbial product synthesis
SMWK

Biopolymers on the basis of polyhydroxyalkanoates (PHA)- Synthesis of PHB from crude glycerol- a by product of biodiesel production
BASF

2. Chitosan

Group Leader: Dr. Jelka Ondruschka

Chitosan is a natural occurring polysaccharide – it is biodegradable, biocompatible, non toxic and possesses good film forming properties. Because of its solubility in aqueous solutions chitosan can be chemically modified and a variety of materials can be prepared from it (fibres, films, semi-permeable membranes, micro- and nanocapsules). Numerous applications have been suggested (waste-water engineering, textiles, paper technology, medicine and healthcare).

Currently, the world wide technical production is based mostly on the processing of chitinous resources from the shells of shrimps by deacetylation. Alternatively, the recovery of chitosan from the cell wall of fungi is becoming more and more commercially relevant. Up to 45% of the organic fraction of the cell wall of deuteromycetes consists of chitin. The fungi can be grown in bioreactors and the chitin can be extracted and chemically or enzymatically deacetylated to yield chitosan. The taxon of deuteromycetes includes nearly all industrial used fungal producers of antibiotics and enzymes. In these processes the fungal cell wall remains as a waste product which should allow an economic efficient production of chitosan from fungi. Additionally, the use of cheap carbon substrates (for instant stillage from distillery or spent sulphite liquor) should be investigated for further reduction of fermentation costs.

Projects:

Recovery of chitosan from fungal mycelia used for enzyme production (FNR)
FNR

Production of fungal-chitosan for the compoundation of new materials (FNR/ BMVEL)
FNR/ BMVEL

Investigation for elimination of 17ß-estradiol from water by fungal-chitosan (SAB)
SAB