Enzyme-Induced “Sea–Island” Structure Reinforced Bio-Based Adhesive: Toward High Bonding Strength, Toughness, and Bacterial Resistance

Soy meal (SM), a plant-derived feedstock, has garnered increased attention as a potential substitute for formaldehyde-based adhesives. However, SM-based adhesives do not exhibit a superior bonding performance. Herein, a strong, tough, and multifunctional SM-based adhesive was prepared using keratinase (Ker) and thiolated lanthanum alginate (La@TSA) microspheres to create “sea–island” structure. This design involved Ker unraveling the deeply embedded disulfide bonds (S–S) within soy globulin, facilitating the formation of a uniform matrix, while the La@TSA microspheres acted as “island” integrated into the unfolded SM matrix “sea”, establishing a S–S bonds “bridge” that dissipated energy and increased cross-linking density. The SM/Ker/La@TSA adhesive showed that the dry/wet shear strengths for plywood reached 2.49/1.47 MPa. Notably, the adhesive exhibited effective mold inhibition and resistance to Escherichia coli due to the bactericidal property of lanthanum ion. Overall, the adhesive produced through this readily available and practical approach offers a compelling combination of cost-effectiveness and excellent overall performance.