Enhancing Plant Protein-Based Bioplastics with Natural Additives: A Comprehensive Study by Experimental and Computational Approaches

Motivated by earlier discoveries, this study aims to enhance the properties of bioplastic films from two combined plant proteins (proteoposites) by incorporating natural additives, microfibrillated cellulose (MFC), and olive stone powder (OSP). To demonstrate the effect of the protein structure on interactions with additives, binding affinities of corn (zein) and soy proteins with MFC/OSP lignocellulosic constituents were investigated using computational protein-ligand docking. The obtained results indicate favorable interactions of zein macromolecules with lignin, while soy proteins interact more readily with cellulose and hemicellulose. Computational findings were validated by mechanical testing of the modified OSP and MFC proteoposites, where most property (tensile stress) improvements are revealed for the films where lignin-containing OSP is incorporated into zein. Furthermore, a reliable machine-learning-based quantitative structure-activity relationship model to predict the tensile stress of MFC-modified proteoposites was established to effectively predict experimental outcomes [>70% accuracy (R-2)]. As a result, adding MFC into the soy protein fraction of proteoposites enhances mechanical performance and barrier properties. Overall, this study provides valuable knowledge on a sustainable approach to making bioplastics from combined zein and soy proteins modified with natural lignocellulosic additives.