Degradation of plastics in natural and technical systems and the development of new solutions
C01: Formation and degradation of microplastics under simulated environmental conditions: Mechanical and UV stress
C01 investigates within the CRC 1357 the influence of anisotropic geometries such as fibres (1D) and films (2D) as well as added commercial additives on the ageing of the plastics PS, PE, PP and PA6 when exposed to weathering under environmentally relevant conditions. The combination of complementary analytical methods allows changes in the ageing mechanism to be elucidated and the degradation, migration and leaching of the additives or additive fragments. This is central, as the chemical changes influence the toxicity of microplastic (MP). Based on this, monomaterial and multimaterial multilayer films are developed that have a lower environmental impact while maintaining the functional properties. A central control parameter is the additivation of individual layers and their arrangement in the laminate. In this way, we expect to understand synergies or inhibitions in the ageing of the individual film layers compared to the homogeneous film and ultimately to be able to use them. The solution approaches for reducing MP through process engineering, and material design will be consistently supplemented in the 3rd FP by new materials and findings from the other sub-projects.
Principal Investigators: Prof. Dr.-Ing. Holger Ruckdäschel, Prof. Jürgen Senker
C02: Degradation of biodegradable polymers and their clay nanocomposites under environmentally relevant conditions
Packaging films made of PLA or PBAT, marked as "biodegradable," do not degrade fast in many environmental compartments and technical systems. In addition, neither the mechanical characteristics nor the gas barrier properties are adequate for applications in the food industry. In the 2nd funding period oft he CRC 1357, the C02 project wants to develop new polyesters and composites whose degradation is promoted by anoxic/oxic redox cycles, which are often encountered in the environment in addition to the enzymatically catalysed hydrolysis. The expectation is that the new biodegradable packaging materials developed by C02 will, on the one hand, meet the requirements for the property profile, and on the other hand, no persistent MP particles will form due to their rapid degradation.
Principal Investigators: Prof. Seema Agarwal, Prof. Josef Breu
C03: Enzymatic degradation of synthetic polymers
C03 focuses within the CRC 1357 on the degradation of microplastic (MP) through direct interaction with enzymes. A series of PET-degrading hydrolases show the potential of natural enzymes to degrade synthetic polymers. Degradation rates and selectivity of the enzymes can be tailored to related polymer species through rational design and directed evolution. The aim is to better understand and optimise the interaction of the enzymes with different polymer surfaces as well as the specific substrate recognition. Enzymes developed in this way can form the basis for large-scale biorecycling or the degradation of MP from PET and other aromatic polyesters in technical systems.
Principal Investigators: Prof. Birte Höcker
C04: Influence of microbial diversity and biofilm formation on degradation mechanisms of microplastic particles in the environmentCO
Microorganisms (MOs, prokaryotes and fungi) play a central role in the mineralisation of microplastics (MP) in the environment and represent a huge unrecognised genetic and metabolic degradation potential. It is therefore the aim of C04 to identify new MP-degrading MOs, elucidate their MP degradation pathways, and map key enzyme-encoding genes of MP degradation and biological degradation mechanisms in the environment. Pure culture screening, degradation experiments with environmental samples and identification of key organisms, stable isotope sampling with 13C-labelled MP to track MP-13C flux and obtain metagenomes of 13C-MP degrading MOs, directed isolation, genomics and transcriptomics of pure cultures and environmental samples, and gene expression studies will provide enzyme-encoding genes and MOs involved in MP degradation. Accelerated evolution will be used to obtain highly efficient MP-degrading MOs. Furthermore, it will be investigated whether biofilms, through UV-absorbing properties, can inhibit UV-dependent plastic oxidation and how microbial colonisation affects the mechanical stability as well as the surface properties of plastics. The knowledge gained here is central to SFB 1357 and will make a significant contribution to understanding the role of microorganisms in the fate of MP in the environment, enable the identification of microbial 'hot spots' of MP degrading MOs in the environment, and provide a basis for the development of MP degradation-accelerating additives and environmentally friendly plastics.
Principal Investigators: Prof. Gerhard Rambold, Prof. Marcus Horn, Prof. Martin Obst
C06: Enzymatically induced fragmentation of weathered polyolefin microparticles
C06 investigates within the CRC 1357 the enzymatic degradation of weathered polyolefin microparticles (POMP), compared to unweathered particles. It is expected that during the enzymatic degradation of POMP, bioavailable oligomers form, which could then be metabolized by microorganisms, and thus MP is degraded. Besides oxygenases, the enzyme selection mainly focuses on enzymes that generate radicals in the presence of other factors. In addition to peroxidases, which form radicals with the help of chemical mediators, modified light-oxygen-voltage (LOV) proteins will as well be used, which under blue light form singlet oxygen, other reactive oxygen species and radicals with high efficiency.
Principal Investigators: Prof. Andreas Greiner, Prof. Andreas Möglich