Does poly-3-hydroxybutyrate biodegradation affect the quality of soil organic matter?

The search for eco-friendly substitutes for traditional plastics has led to the production of biodegradable bioplastics. However, concerns have been raised about the impact of bioplastic biodegradation on soil health. Despite these concerns, the potential negative consequences of bioplastics during various stages of biodegradation remain underexplored. Therefore, this study aims to investigate the impact of micro-bioplastics made of poly-3-hydroxybutyrate (P3HB) on the properties of three different soils. This investigation revealed changes in soil organic matter (SOM), microbial activity, and the contents of carbon, nitrogen, sulphur, and phosphorus. These changes were particularly notable following the introduction of P3HB into soils at varying concentrations, leading to an accelerated degradation of SOM. The thermogravimetric analysis confirmed the presence of residual P3HB and underscored the heightened biodegradation of SOM, especially in the more stable SOM fractions. This was notably evident in Phaeozem soils, where even the stable SOM pool was affected. Elemental analysis showed an increase in soil organic carbon content following P3HB degradation, although nitrogen levels remained constant. Enzymatic activity was found to vary with soil type and responded differently across P3HB concentration levels. Our findings suggest that P3HB acts as a bioavailable carbon source. Its biodegradation stimulates the production of enzymes, which in turn affects various soil elements, indicating complex interactions within the soil ecosystem.