A reliable methodology to determine biotransformation of PBAT in anaerobic conditions

Anaerobic digestion (AD) units from wastewater treatment plants (WWTPs) constantly receive plastics at the end of the urban water cycle while their fate is poorly understood. The first biotransformation step is hydrolysis, and its quantification it's a technical challenge in the AD matrix. Previous research has applied differential methane production, calorimetry, or FTIR for this purpose. However, the results reported in the literature are not consistent. Here, we propose to track plastic biotransformation by 1H-NMR-assisted quantification of the derived monomers. We used polybutylene adipate co-terephthalate (PBAT) in thermophilic AD (55ºC) as a model. One of its monomers was rapidly depleted (1,4-butanediol), while adipic (AA) and terephthalic acid (TPA) accumulated over time serving as monitors. Based on TPA concentrations detected, a 11.1±1.9 % of PBAT was biotransformed, while based on AA a 10.1±2.3 %. The core microbial community was stable indicating its intrinsic hydrolytic capacities . The workflow presented here represent a reliable methodology that could be transferred to assess the biotransformation of other types of plastics.