Compost microbiomes as reservoirs of cellulolytic microorganisms for cellulosic textile degradation.

Cellulosic textiles, constituting over 30% of global fibre production, are biodegradable but remain challenging to recycle at scale owing to their high crystallinity, chemical finishes, and heterogeneous waste streams. Although microorganisms drive cellulose turnover in natural ecosystems, their potential for transforming anthropogenic cellulosic waste remains largely unexplored. In this study, composting was evaluated both as a sustainable approach to textile biodegradation and a reservoir of cellulolytic microorganisms with biotechnological potential. Biodegradation assays of cotton and lyocell were integrated with shotgun metagenomics and targeted cultivation to identify microbial taxa and enzymes involved in cellulose degradation. Composting trials showed that degradation was strongly influenced by both composting system and fibre composition. Community composting achieved near-complete textile disintegration, while shredded textiles exhibited the highest degradation rates, reaching up to 97%. Shotgun metagenomic revealed a bacterial-dominated community enriched in Actinomycetota and Bacillota and characterised by an abundance of glycoside hydrolases. Culture-based screening recovered 62 microbial isolates, of which Neurospora and Aspergillus exhibited the highest cellulolytic activity (>60%). In vitro assays further showed that cotton was more readily degraded than lyocell, with several isolates achieving >70% mass loss. Metagenomic approach revealed a predominantly bacterial composting community at the sampled stage, whereas cultivation preferentially recovered fungi that, despite their low relative abundance in situ, exhibited strong cellulolytic potential. These findings highlight the potential of composting as a sustainable end-of-life strategy for cellulosic textiles and identify compost microbiomes as valuable reservoirs of cellulolytic microorganisms for the development of sustainable bioprocesses for textile waste treatment.