Process development of nattokinase microcapsules based on a novel sodium alginate-gelatin-chitosan composite material

Nattokinase, an alkaline serine protease produced by Bacillus subtilis natto during natto fermentation, exhibits potent thrombolytic activity and is considered a promising next generation thrombolytic agent. Currently, most commercially available nattokinase is formulated as oral health supplements. However, unencapsulated nattokinase is rapidly inactivated due to the highly acidic gastric environment pH of approximately 1.2. Therefore, developing formulations that enhance enzymatic stability and bioavailability is crucial for its successful industrialization. In this study, we developed nattokinase microcapsules using a novel ternary composite embedding system composed of sodium alginate, gelatin, and chitosan. The optimal formulation prepared with a sodium alginate-gelatin mass ratio of 3:1, a total polymer concentration of 3%, and a chitosan concentration of 0.8%, achieved an enzyme activity recovery rate of 96.54%. Release studies in simulated gastrointestinal fluids demonstrated excellent gastric stability, with only 4.47% of nattokinase released over 2.5 h, which was 5-35% lower than that of single or binary encapsulation systems, significantly minimizing acid-induced inactivation. In contrast, sustained intestinal release was observed, reaching 91.58% at 48 h. This biphasic release profile ensures targeted intestinal delivery, where nattokinase can exert its therapeutic effects, while enabling acid resistance and controlled release.