Fungal Biodegradation of a Hybrid Adhesive Polymer Containing High-Biomass Content

Water-based acrylic pressure-sensitive adhesives (PSA) are a common component of disposable products such as tapes, labels, and packaging. Such adhesives are generated from fossil-derived monomers and additives and persist in the environment due to their low biodegradability. Furthermore, they can interfere with the recycling and remediation of products they interact with, such as plastic and paper products. Although touted as a promising remedy to these issues, adhesive polymers generated using renewable and degradable monomers tend to fall short regarding performance and cost. This study reports on the fungal degradation behaviors of hybrid PSAs copolymerized mainly from traditional acrylics and lactide-based macromonomers. These structures provide high performance at a reasonable cost and represent an alternative approach to addressing environmental concerns. Evaluating the biodegradability of these hybrid PSAs involved solid and liquid cultures using 53 unique fungal species. Nearly 50% (n = 23) of the screened species showed PSA-degrading capacities of varying degrees, including Trametes versicolor and Pestalotiopsis microspora, providing roughly complete (> 96%) polymer removal in liquid cultures. Fungal degradation of cast adhesive films was monitored using evolved CO₂ and mass loss and confirmed through scanning electron microscopy and spectral analysis (FTIR). Enzyme assays, namely laccases, lipases, and proteases, showed a high correlation with the observed biodegradation rates, suggesting that hydrolytic and oxidative enzymes were likely factors driving latex degradation. These results demonstrate that the high-performing hybrid formulation is degradable by fungi. While a portion of the studied adhesive was synthesized using petroleum-derived monomers, this could serve as a bridge technology, helping to usher in more sustainable disposable consumer products until a time comes when all components are renewably sourced.