In situ growth of β-galactosidase-manganese hybrid nanoflower on polycaprolactone/ xanthan electrospun nanofibers: A novel nanobiocatalyst for efficient lactose hydrolysis

Hydrolysis by β-galactosidase enzyme is an efficient and eco-friendly way to solve the problem of people with lactose intolerance. However, the activity reduction, instability, and high cost of β-galactosidase become the main limiting step for the practical application. In this study, a novel strategy was suggested to improve this condition. For this purpose, the β-galactosidase/manganese hybrid nanoflower was successfully grown on the polycaprolactone (PCL)/xanthan electrospun nanofiber scaffold to achieve a highly active nanocomposite for lactose hydrolysis. To optimize the immobilization efficiency and find the optimal enzymatic conditions, the effect of four independent variables: enzyme concentration (0.1–0.9 mg/mL), manganese concentration (0.2–0.8 M), incubation time (2–18 h), and incubation temperature (5–39 °C) were investigated using a central composite design. The optimal conditions were determined as a manganese concentration of 0.63 M, β-galactosidase concentration of 0.57 mg/mL, incubation time of 12.6 h, and an incubation temperature of 23.5 °C, which resulted in an immobilization efficiency of 94.87 % and enzymatic activity of 60.23 mM. FESEM, EDS, FTIR, XRD, and TGA results confirmed the successful construction of manganese-based β-galactosidase hybrid nanoflowers on polycaprolactone/xanthan nanofibers. The optimum temperature and pH of the free enzyme were changed after immobilization. Immobilization caused a decrease in the K_m and an increase in the V_max. Also, nanoflower exhibited good stability and high reusability. Thus, the manganese hybrid nanoflowers on nanofibers are expected to be a promising support for biological molecule immobilization because of their hierarchical structures, high surface-to-volume ratio, easy separating, and excellent performance.