<p>This study represents the first report on applying chitosan nanoparticles for the encapsulation and controlled release of trypsin enzyme specifically in Persian sturgeon feed, offering a promising strategy for aquafeed formulation. Trypsin enzyme was encapsulated at concentrations of 5, 10, and 20&#xa0;mg through the ionic gelation method using chitosan and the cross-linking agent sodium tripolyphosphate (TPP). The results indicated that as enzyme concentration increased, the encapsulation efficiency and nanoparticle size increased. However, the best encapsulation sample in terms of encapsulation efficiency, zeta potential, and particle size distribution was obtained in nanoparticles loaded with 10&#xa0;mg of trypsin enzyme. In addition, the scanning electron microscopy (SEM) images revealed that as the enzyme concentration increased, the nanoparticles transitioned from a spherical and smooth morphology to an asymmetric form. The examination of Fourier transform infrared (FTIR) spectra and the appearance of new peaks confirmed the encapsulation of the trypsin enzyme. The shelf life of the encapsulated enzyme in the feed was maintained at 95% during 20&#xa0;days of storage. Finally, in vitro observations reported pH-dependent and sustained enzyme release. It was concluded from this study that chitosan nanoparticles have the potential to serve as encapsulating materials, capable of transporting biological substances and protecting them from unfavorable conditions, while also facilitating their release at the appropriate time and location.</p> Graphical abstract <p></p>