Assessing the impact of agrifood byproduct-based bioplastics on soil microbial communities and functioning

The environmental burden of plastic pollution has driven the search for sustainable alternatives, such as biodegradable bioplastics derived from agrifood byproducts, which hold the potential for addressing global waste management challenges. Given the close relationship between the biodegradability of biopolymers and soil microbial activities, it is vital to understand how the presence of novel bioplastics affects their function and structure. This study assessed microbial responses to different plastics: potato starch-based bioplastic, locust bean-based bioplastic, and non-biodegradable polyamide-polyethylene plastic in natural sandy-loam soil (LUFA 2.2). Soil without any (bio)plastics was used as a control. Despite initial pronounced differences in defragmentation rates between the two types of bioplastics, only 10 and 20 % w/w of the fragments were recovered after 17 weeks. The type of bioplastic influenced the fungal colonization pattern, with potato starch-based bioplastic resulting in more isolated fungal species than locust bean-based bioplastic. The soil dehydrogenase response was inconsistent, while β-glucosidase activity showed an initial increase in both bioplastic treatments, with a sustained stimulation only in potato starch-based bioplastic. β-glucosidase activity coincided with higher carbon substrate consumption maintained by the end of the 17 weeks of exposure, indicating more dynamic changes in microbial functions in potato starch-based bioplastic. Decreased carbon substrate consumption was observed in non-biodegradable polyamide-polyethylene plastic. The current study represents a first screening approach for the impact of applying agrifood byproducts as novel biopolymers directly in the soil, demonstrating their distinct effects without any pronounced adverse effects on soil microbiota compared to conventional polyamide-polyethylene plastic. • Bioplastics from agrifood byproducts influenced soil microbial dynamics. • Potato starch-based bioplastic supported more isolated fungal species. • Bioplastics stimulated microbial activity and promoted soil multifunctionality. • Carbon substrate utilization increased in bioplastic-treated soils. • Synthetic plastic exhibited lower carbon consumption compared to bioplastics.