The concentration of thehydrolysis product, i.e. p-nitrophenol (pNP) was measured usinga spectrophotometric method (Spectrophotometer T80+, PG Com-pany) at 410 nm. In these experiments, the substrate solution wasadded to the immobilized lipases at 40◦C on a reciprocal shakerat 110 rpm for 10 min. After collecting nanoparticles with a mag-net, the supernatant was removed to measure the amount of pNP.For the free lipase, the same amount of lipase was mixed with thesubstrate solution.