Raman Spectroscopy Enables Real-Time Identification and Monitoring of Plastic Biodegradation Metabolites

Abstract

Managing plastic pollution is challenging because current physical and chemical recycling methods are inefficient and environmentally intensive. Biological recycling approaches have been framed as sustainable alternatives but are challenging to optimize due to a lack of process analytical technologies that provide real time data on microbial plastic metabolism. In this study we used Piscinibacter sakaiensis 201-F6, a model bacterium with a well-studied polyethylene terephthalate (PET) metabolism, to validate non-destructive Raman spectroscopy methods to monitor plastic biodegradation by tracking metabolite production. Cells were grown on PET and known metabolites stemming from PET metabolism. Raman spectroscopy was used alongside destructive mass spectrometry techniques to monitor PET metabolite production and uptake under different growth conditions. Although cells grew effectively using PET, Raman spectroscopy did not detect the known PET metabolite terephthalic acid during growth assays. Instead, Raman detected isophthalic acid (IPA), a metabolite not previously associated with PET metabolism whose identity was confirmed with LC-HRMS. Raman spectroscopy was also used alongside thermoanalytical techniques to predict the biodegradability of PET at different crystallinities through the release of IPA. This study frames Raman spectroscopy as a promising tool to study metabolic pathways for plastic recycling and optimize their application in situ.