The applicability of Impranil®DLN for gauging the biodegradation of polyurethanes

Polyurethane-based polymers and their eventual degradation products pervade modern society. One common method for determining whether a microorganism or protein can degrade this class of polymer is to qualitatively assess its ability to “clear” a polyester-polyurethane colloid branded Impranil®DLN (Impranil), whose formulation is proprietary. However, its colloidal state has ultimately made Impranil a precarious choice for determining if an organism or enzyme can degrade polyurethanes. In this work, the chemical hydrolysis products from Impranil using 0.1 M HCl or 0.1 M NaOH were identified and compared to the concentration of hydrolysis products formed using three commercial enzymes by proton nuclear magnetic spectroscopy (1H NMR) and Fourier-transform infrared spectroscopy (FT-IR). The differences in the integrated signal intensities from key 1H NMR signals were used to calculate the amount of Impranil that was hydrolyzed. These data were then correlated with the change in optical density of colloid containing reaction mixtures (termed as “clearing”). The enzymes (a Pseudomonas fluorescens recombinant esterase, Pseudomonas sp. lipase, and Bacillus sp. protease) showed significant esterase activities and partially-cleared, completely-cleared, or aggregated Impranil, respectively. However, only the Pseudomonas sp. lipase significantly degraded Impranil based on NMR and IR data. This study illustrates how Impranil can be used to quantitatively assess biodegradation rather than just be a qualitative “clearing” indicator of biodegradation.