Feasible Analytical Protocol of Residual polymers in Culture Medium after Biodegradation Testing

The development of biodegradable polymers and their certification require an analytical method that is both reliable and practical. Although biochemical oxygen demand (BOD) testing remains a robust method for confirming polymer metabolism, it does not provide precise information about the residual compounds during and after biodegradation. Moreover, direct analysis these residues is challenging, particularly when seawater interferes with analysis. In this study, we propose an extraction/chemical-structure-analysis/molecular-mass-analysis protocol as an enhanced analytical approach for investigating the culture medium post-BOD biodegradation testing in seawater. We conducted BOD biodegradation test of poly(3-hydroxybutyrate- co -3-hydroxyvalerate), poly( ε -caprolactone), and poly(butylene succinate) in seawater. Following testing, ¹ H NMR analysis of the extracts identified the chemical structures of the residual polymers and enabled the assessment of NMR degradability, which aligned well with the BOD biodegradability trend. Additionally, molecular-mass-analysis revealed changes in the molecular mass, supporting evaluation of the chain scission of polymer. This study advances analytical methods in the field of biodegradable polymers.