Lignin-Zein Composite: Synthesis, Three-Dimensional Printing, and Microbial Degradation

Abstract

Worldwide use and disposal of plastics have reached a dramatic saturation point, polluting lands, oceans, and air across the globe. Responding to such a challenge requires, among other environmental remediation measures, the manufacture of alternative sustainable plastics. Recent studies in the area have enabled the development of degradable plastics; however, the rate and conditions required for the degradation of such materials remains under scrutiny. Here, we introduce a new class of fully plant-based, rapidly degradable lignin and zein composite blend that can be transformed into macroscopic structures using extrusion three-dimensional (3D) printing. Corn-derived zein forms the polymeric solution, while insoluble lignin granules act as a binder for enhanced printability and facile degradation. The blend showcases a shear-thinning behavior that is ideal for rapid extrusion printing into desired 3D structures, from cuvette caps to circuit boards. Biodegradation studies show that common bacteria readily found in soil and compost are able to decompose structures made with the lignin-zein composite in shorter time frames compared to a known biodegradable plastic, viz., polylactic acid. The rapid biodegradability and enhanced processability highlight the potential of lignin-zein composites to decrease our dependence on petroleum oil-based plastics.