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zwei Männer in Laborkittel vor einem Computer, der Mann im Vordergrund notiert auf seinem Klemmbrett, der Mann im Hintergrund füllt ein Reagenzglas
Mikrobiologie, Foto: Colourbox

In the area of polymer biotechnology, the application of biocatalysis for the modification and degradation of synthetic polymers is investigated. Enzymes are playing a growing role in polymer processing. Recent progress has demonstrated the biocatalytic functionalization of polymers with applications in textile or electronic industries and the enzymatic hydrolysis of post-consumer plastic waste for novel environmentally benign recycling processes.

While chemical synthesis of carbohydrates is often hampered by their intrinsic structural complexity, enzymes can be employed as efficient and powerful tools for the synthesis and modification of carbohydrates. By carbohydrate bioengineering, we are aiming at the identification of oligosaccharides and carbohydrate-derived products with industrial application value.

Biocatalytic functionalization and degradation of synthetic polymers

Identification and engineering of novel polyester hydrolases

In ongoing programs, metagenomic libraries obtained from diverse environment samples are screened for novel polyester hydrolases active against the synthetic polymers polyethylene terephthalate (PET) and polyurethane (PU). 

To improve the degradation of PET at elevated temperatures, molecular dynamics simulations are performed based on the crystal structure of the enzymes. The optimization of the protein stability is addressed by rational protein design and directed evolution strategies.

Docking studies of a PET dimer with polyester hydrolases were used as a tool to predict the ligand orientation as well as the binding affinity between ligand and receptor. This data can be used for the understanding of activation and/or inhibition effects caused by molecules. It can also be used as a guide for the designing of more active or selective proteins.

  • Adv Appl Microbiol 89:267–305 (2014) 
  • Appl Microbiol Biotechnol 98:7815–7823 (2014)
  • Biotechnol J 10:592–598 (2015)

Polyester hydrolases for the functionali-zation of PET surfaces

Biocatalysts active on synthetic polymers can be used to modify the properties of synthetic textiles and to produce new multi-functional materials for applications in the textile, electronic, and biomedical industry.

  • Adv Biochem Engin/Biotechnol 125:97–120 (2011)
  • Biocat Biotrans 22:347–351 (2004)
  • Biotechnol Lett 28:681–685 (2006)

Biocatalytic recycling of plastic waste

The contamination of the environment by plastic wastes has become a global issue. Applying biotechnlogy to recycle this material by biocatalysis is a novel approach to mitigate this problem. The enzymatic hydrolysis of synthetic polymers such as polyethylene terephthalate (PET) and polyurethane (PU) by enzymes still remains a challange due to the high recalcitrance of their structures against biological attack.

The enzymatic hydrolysis of post-consumer PET materials to their monomeric building blocks is investigated as an alternative to chemical recycling processes.

An ultrafiltration membrane reactor for the heterogeneous hydrolysis of insoluble PET is developed to remove the inhibition of the biocatalyst by intermediate products.

  • J Membrane Science 494:182–187 (2015)

Carbohydrate Bioengineering

Cyclic oligosaccharides such as cyclodextrins with molecular recognition properties are becoming important tools as drug delivery systems, in biomaterial science and in nanobiotechnology. They find applications in the pharmaceutical, food, and chemical industry sectors. Other carbohydrate-derived products such as biosurfactants can be utilized as components of food, health, and cosmetic products. This group of compounds can be produced from renewable biomass such as sugars and starches, offering environmental advantage over petrochemical-based products.

Cyclodextrin technology

Biosynthetic cyclic oligosaccharides such as cyclodextrins are becoming important tools in drug delivery and controlled release systems. Due to their molecular recognition properties, cyclodextrins can be used as building blocks for nanoscale structures with applications in biomaterial science and as functional units such as sensors in nanobiotechnology. We have developed methods for the analysis of cyclodextrins and have identified a range of bacterial cyclic oligosaccharide-producing glucanotransferases. The ability of these enzymes to synthesize novel cyclodextrins, cyclic alpha-1,4-glucans composed of eight to more than several hundred glucopyranose units is investigated. This work involves the engineering of their cyclization activity and product specificity by site directed mutagenesis and directed evolution, the application of molecular imprinting techniques, and the development of enzymatic bioprocesses for their production.

  • FEBS Journal 274:1001–1010 (2007)
  • J Mol Recog 23:480–485 (2010)
  • Appl Microbiol Biotechnol 66:475–485 (2005)
  • Appl Environ Microbiol 78:7223–7228 (2012)
  • FEBS Open Bio 5:528–534 (2015)


Carbohydrate fatty acid esters are composed of mono- or oligosaccharides esterified with fatty acids of various chain lengths. These non-ionic biosurfactants are non-toxic, non-allergenic and biodegradable. Biosurfactants can be employed in foods, detergents and cosmetics as well as in the pharmaceutical and biomedical industries. We are presently studying the synthesis of these compounds by employing bacterial polyester hydrolases and acetylesterases.

In collaboration with ICES, A-Star Singapore the microbial production of rhamnolipids, glycolipid biosurfactants with a wide range of industrial applications, is investigated.

  • Biotechn Lett 21:275–280 (1999)
  • Carbohydrate Research 329:57–63 (2000)
  • Biotechnol Bioeng 74:483–491 (2001)
  • Appl Biochem Biotechnol 166:1969–1982 (2012)

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