Construction of polylactic acid plastisphere microbiota for enhancing nitrate reduction in denitrification biofilters.

Developing methods for reusing biodegradable plastics, like polylactic acid (PLA) straws, is highly needed. Here, PLAs were applied to substitute traditional commercial ceramic media (CCM) in denitrification biofilters. During long-term operation, replacing CCM with PLA significantly enhanced nitrate removal efficiency from 32.68-54.39 % to 41.64-66.26 %. Ammonia nitrogen effluent maintained below 0.5 mg/L in all reactors. PLA plastisphere shaped unique microbial communities, i.e., denitrifying bacteria Bacillus, Pseudomonas and Acidovorax preferred to inhabit or degrade PLA. Compared to CCM biofilms, PLA diminished the importance of stochastic process in biofilm assembly of PLA plastisphere. Metagenomic sequencing suggested that PLA biofilms possessed greater metabolic capabilities of denitrification and glycolysis compared to CCM. Additionally, Bacillus strain P01 isolated from PLA plastisphere demonstrated strong PLA depolymerization. Overall, this study revealed that PLA serves as carbon source and biofilm carrier, offering a promising approach to integrating plastic reuse with wastewater treatment.