Microbial lipase obtained from the fermentation of pumpkin seeds: immobilization potential of hydrophobic matrices

Abstract

Immobilization potential of lipase from Aspergillus niger on sol-gel matrix was evaluated by physical adsorption and covalent binding and the biochemical characterization of free and immobilized enzyme was performed. Lipase was produced by solid state fermentation of pumpkin seed flour with 30% moisture, at 30°C for 120h. The enzyme was pre-purified with ammonium sulfate and immobilized in the sol-gel matrix by covalent attachment and physical adsorption. A higher yield of immobilization (81.88%) was obtained in the latter. The free enzyme presented higher hydrolytic activity with pH 4.0, at 37°C; moreover, it was more stable with pH between 6.0 and 7.0, at 35°C. The immobilized lipase showed maximum hydrolytic activity with pH 11.0, at 50°C; it was more stable with pH 11.0, at 37°C. Parameters K_m and V_max were best determined by Hanes-Woolf linearization.