Selective response of soil bacterial and fungal taxa to biodegradable polymers

Biodegradable mulching films offer an eco-friendly alternative to petroleum-based plastics in agriculture, but their effects on soil parameters are not well understood. A microcosm experiment (20 °C, 75% field capacity) investigated the impact of two doses (0.021% and 1% w/w) of a biodegradable polymer on soil chemical and microbiological properties over a year. The 1% dose significantly (p < 0.05) increased CO₂ emissions, water-extractable organic C, and hydrolytic activity. A significant (p < 0.05) effect on microbial alpha- and beta-diversity was noted only during short- and medium-term incubations. In contrast, a taxon-related response was found for both bacterial and fungal taxa affecting the abundance of the genera Aquicella, Cellvibrio, Bacillus, Ramlibacter, and Saccharibacteria genera incertae sedis among bacteria, and Malassezia, Orbilia, and Rhodotorula among fungi (including both yeast and filamentous lifestyles). Microbial functions revealed a greater impact on fungal communities compared to bacterial ones. However, after one year of exposition, only a marginal effect on the abundance of both bacterial and fungal functional groups was found in the microcosms. A significantly higher concentration of tightly bound exopolysaccharides in the presence of 1% biodegradable polymer at the start of the experiment suggested their key role in microbial degradation of bioplastics via biofilm formation.