Immobilization of the Proteolytic Fraction P1G10 from Vasconcellea pubescens in Alginate–Chitosan Complex and Enzyme Activity Release

The proteolytic fraction (P1G10) from <i>Vasconcellea pubescens</i> displays pharmacological activity in diverse therapeutic settings. It is responsible for antifungal activity against <i>Botrytis cinerea</i>, impairing its germination and the integrity of the plasma membrane. The application of P1G10 is limited by stability in aqueous environments, where proteases lose activity. In this study, we aim to stabilize the proteolytic fraction, by complexation, to preserve the enzymatic activity ensued by controlled release. The proportion of each polymer, and the established reaction sequence, is chitosan (CS) plus P1G10 and alginate (ALG) using ALG:CS mass ratio = 1.0. Scanning electron microscopy (SEM) of the product shows the ALG-CS-P1G10 complex displaying a rough surface contrasting with the smoother surface of the ALG-CS complex, likely induced by interactions between the protein and ALG-CS complex. The optimal amount of protein taken up by the complex under this condition was 13 mg, and the incorporation yield was 72%. The melting temperature (Tm) determined by differential scanning calorimetry (DSC) in ALG-CS increased from 80 °C to 86 °C for the biocatalyst ALG-CS-P1G10; this difference was probably induced by the interactions between P1G10 and ALG-CS. Fourier transform infrared spectrometry (FTIR) comparison between ALG-CS and ALG-CS-P1G10 shows two bands in the biocatalyst at 1601 and 1523 cm^-1, suggesting the presence of amine residues from P1G10 which is rich in lysine residues. The release of P1G10 from the complex was assessed by increasing the ionic strength in the media between 0.1 and 0.4 M NaCl. The results show that, at 0.3 M NaCl, the protein released after 8 h attained 70% and expressed enzymatic activity of 0.90 × 10^-3 U/mg protein compared to the enzymatic activity from free P1G10 protein, which was 5.55 × 10^-4 U/mg protein.