Poly(butylene adipate-co-terephthalate) biodegradable microplastics accelerated the decomposition of amino sugar in soil

Abstract Biodegradable microplastics (BMPs) are reported to have a priming effect on soil organic matter (SOM) decomposition. However, their impact on the turnover of specific SOM components, especially nitrogen (N)-containing ones, remains unclear. Given the wide use of poly(butylene adipate-co-terephthalate) (PBAT) in agricultural films and the crucial role of amino sugar N-acetylglucosamine (NAG) in microbial necromass, the effects of PBAT BMPs on NAG decomposition in soil were investigated. We found that PBAT accelerated the decomposition of NAG, with specific effects varying considerably in the two soils examined (Yingtan soil and Nanjing soil). Microbial biomass and metagenomic sequencing analyses revealed that, in Yingtan soil with low available N (6 mg kg -1 ), PBAT promoted the incorporation of NAG into living microbial biomass, and increased the abundance of NAG phosphorylation and isomerization genes ( amgK and glmM ). In Nanjing soil with high available N (127 mg kg -1 ), chitin synthase gene ( CHS1 ) abundance decreased and there was no significant change in microbial biomass, indicating the extra NAG decomposed in PBAT-treated soils might mainly enter the glycolysis pathway to generate energy rather than synthesizing new cells. Potential PBAT degraders enriched were also NAG degraders, suggesting carbon-rich PBAT selected for microbes that could obtain N from amino sugars.