Biomacromolecules Biomacromolecules Carrier-Free Immobilization of Lipase from <i>Candida rugosa</i> with Polyethyleneimines by Carboxyl-Activated Cross-Linking Velasco-Lozano Susana López-Gallego Fernando Vázquez-Duhalt Rafael Mateos-Díaz Juan C. Guisán José M. Favela-Torres Ernesto 2014 research-article