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ARRS project J4-50148

MicroBeast: Understanding microbial degradation for advanced sustainable materials and biodegradation techniques for tackling plastic pollution

Principal investigator: dr. Miša Mojca Cajnko


Content description of the project

The production of plastic materials has been increasing globally since the 1950s due to their wide range of applications in sectors like packaging, agriculture, construction, electronics etc. The annual global production of plastics is >380 million tonnes and this number is increasing by 4% every year. The high production rates and, even more so, the improper waste management, have resulted in accumulation of plastics and their biodegradation products like microplastics in the environment causing extensive damage to numerous ecosystems. Plastics are chemically inert and hydrophobic, therefore are not easily bio-degradable which enables them to persist in the environment for long periods of time. The fact that micro/nanoplastics have a high sorption potential for a wide range of persistent pollutants only increases their possible ecotoxicological concern. There are several waste management scheme options such as recycling, incineration and biodegradation by microorganisms. However, most of these systems, including biodegradation, are environmentally unfriendly, produce toxic compounds and are time consuming. Thus, considering the huge burden plastic waste has on our environment globally, the development of (i) biodegradable alternatives to oil-based plastics, (ii) exploring the factors (biotic and abiotic) that facilitate their biodegradation, next to (iii) developing an efficient recycling system, are of utmost importance. Such tripartite system would not only reduce the amount of plastic waste (that is not readily biodegradable in natural environments) and cease to leach toxic compounds upon degradation, but would also reduce the amount of resources needed to produce new materials, leading to the desired state of a zero-waste circular economy.

In the MicroBeast project we will start by designing natural biopolymer-based biocomposite films that would be biodegradable in natural environments, e.g. soil. The materials will be formed from natural biopolymers like alginate, cellulose, starch, agar-agar and chitosan, which will be chemically modified to tailor their chemical and physical properties as well as their biodegradation potential. The applicability of the materials will be mostly focused on food packaging since, according to UNEP, single use plastic packaging alone accounts for about half of all the plastic waste generated every year.

Our starting biodegradation protocols will be performed utilizing soil from well characterized long-term ecological site with one of the highest microbial diversity, which will be analysed for its capacity to degrade the produced biocomposite films. Enzyme activity of a number of enzyme groups will be determined under soil physical-chemical conditions in order to elucidate the dominant enzyme (sub)groups involved in the biodegradation process and their distribution over time. The microbiome will be analysed by utilizing high-resolution shot-gun metagenomics to identify responsive part of microbiome at the level of species and strains covering bacteria, archaea, fungi, protozoa and their functional genes involved in biocomposite biodegradation process in soil, including its exploration in other relevant environments subsequently (marine and freshwater, anaerobic digestion).

Commercially available enzymes (lipase, esterase, oxidoreductase) will be explored in the degradation process of produced biocomposite films as well to provide the baseline of existing enzyme toolbox, selected from the enzyme (sub)groups determined in the previous steps, and their biodegradation potential determined. Lastly, based on the shortcomings of the commercial enzymes, new versions and novel enzymes with targeted activity will be engineered in order to reach utmost/complete degradation of newly developed biocomposite films. Directed enzyme evolution (ProSAR) will be employed in order to engineer novel enzymes with high specific depolymerizing activity and a wide range of usable substrates. This way catalytic functions of enzymes of interest are improved and progressively redesigned in laboratory evolution under controlled conditions enabling fast learning curves and achievement of highly functional mutants of original enzymes to be produced in large quantities in artificial hosts. Protein Sequence Activity Relationship (ProSAR) is one of the approaches enabling rational design utilizing machine learning guided evolution in protein engineering.


Basic information on funding

The project is co-financed by ARRS with 2017 annual hours of price class C for a period from 1.10.2023 to 30.9.2026


Work plan and implementation


  • Development of new and improved biocomposite films based on natural mono-polymers;
  • Determination of the percentage of biodegradability of the biocomposite films;
  • Identification of the structural and chemical changes within the biocomposite film during the degradation process;
  • Evaluation of the potential toxicity of the degradation products.


  • Determination of the major microbial species, diversity and functional genes involved in the biodegradation process;
  • Determination of the changes in microbiome during the biodegradation process;
  • Confirmation by isolation of specific microbial constituents effectively degrading biocomposite films;
  • Identification of the correlation between microbial consortia and physio-chemical parameters during soil biodegradation process


  • Identification of the major enzyme classes involved in biocomposite film degradation;
  • Development of an enzymatic degradation protocol based on commercially available enzymes;
  • Production of engineered enzymes capable of complete biocomposite film degradation;
  • Identification of the most suitable conditions within the reaction space for future safe disposal and degradation in addition to controlled degradation and reuse of the same building blocks to produce new series of materials


  • Management
  • Communication
  • Dissemination


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