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Technical note: the influence of controlled thermophilic composting of PLA bio-composites on bacterial community
Summary
This technical note examined how controlled thermophilic composting conditions affect polylactic acid (PLA) bio-cutlery, measuring mass loss, molecular weight changes, and physical fragmentation over the composting period. PLA degraded substantially under industrial composting conditions but incomplete degradation left residual fragments, raising concerns about microplastic formation in finished compost.
Polylactic acid (PLA) is one of the most widespread industrial-scale products of biodegradable polymers with fast growing commercial applications. In this study, we assessed the biodegradation of PLA and modified PLA films with eco-friendly plasticizers acetyl tributyl citrate (PLA-ATBC), calcium carbonate (CaCO 3 , i.e., PLA-ATBC@CaCO 3 ), and lignin-coated cellulose nanocrystals (LCNC, PLA-ATBC@LCNC) under controlled thermophilic aerobic conditions. The biodegradation of PLA films was evaluated according to the standard method by analysis of evolved carbon dioxide. The bacterial communities attached on different PLA films were characterized by 16S rRNA sequencing. After two months, the PLA-ATBC@CaCO 3 film was 100% degraded, which corresponded to the highest bacterial abundance in bioreactors compared to PLA, PLA-ATBC and PLA-ATBC@LCNC films. The abundance of bacterial populations (0.01) showed minor changes over 3 months, whereas Thermogemmatispora, Thermoflavifilum and Acidicaldus (not in PLA-ATBC-CaCO 3 ) were highly abundant in all treatments. The bacterial populations of low-abundance (0.001) dynamically changed in PLA-ATBC@CaCO 3 samples, Geobacillus found potential PLA degrader and others, Thermobispora, Rhodoplanes, Thermoleophilum, Filomicrobium and Roseisolibacter.
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