Bioaugmentation influences PBAT biodegradation patterns during composting through associated shifts in plastisphere...

The plastisphere microbiome plays a critical yet incompletely resolved role in the biodegradation of bioplastics during aerobic composting. Here, we investigated the degradation of poly(butylene adipate-co-terephthalate) (PBAT) by integrating surface physicochemical characterization with high-throughput microbial profiling under simulated industrial composting conditions. Inoculant amendment significantly enhanced PBAT degradation, yielding a 12.7 % carbon loss compared with 3.2 % in the control. Gel permeation chromatography further confirmed polymer depolymerization, showing pronounced declines in molecular weight (particularly Mz). These structural changes were accompanied by accelerated ester bond hydrolysis, reflected by reduced water contact angle and attenuation of the CO stretching peak. Plastisphere succession revealed that inoculants reshaped surface-associated communities, increasing α-diversity and selectively enriching thermophilic taxa. Temporal community shifts suggested stage-dependent contributions, with hydrolytic genera (Bacillus, Lactobacillus) dominating the thermophilic phase, whereas oxidative taxa (Pseudomonas) became more prominent during maturation. Neutral community model analysis indicated that plastisphere assembly followed a largely deterministic pattern linked to compost stabilization parameters. Although direct functional validation was not performed, the study reveals correlated changes among PBAT depolymerization, surface hydrolysis/oxidation, and plastisphere restructuring. On this basis, we propose a conceptual degradation framework while emphasizing that specific enzymatic pathways and microbial functions require future confirmation. These findings advance understanding of biopolymer-microbe interactions and provide guidance for optimizing inoculant-assisted composting of biodegradable plastics.