Using silk woven fabric as support for lipase immobilization: The effect of surface hydrophilicity/hydrophobicity on enzymatic activity and stability

Silk fibers in the form of woven fabric were used as a novel and inexpensive carrier for the immobilization of lipase from Candida sp.99–125. In this study, the activity and stability of lipases adsorbed on two silk fabrics with different hydrophilic/hydrophobic properties were compared. Hydrophobic silk fibers functionalized with methyl groups were prepared by treatment with amino-functional polydimethylsiloxane (PDMS). The lipase immobilized on PDMS-treated fiber exhibited an over 2-fold increase in both hydrolysis and esterification activity due to the interfacial activation as compared to its immobilization on a hydrophilic support (native fiber). To characterize the properties of different immobilized derivatives, the effects of pH and temperature were investigated in the hydrolysis of olive oil. The esterification behavior in organic media with variable water contents and operational stability of immobilized derivatives were also compared. The lipase immobilized on the hydrophobic fibers could maintain a constantly high activity at a water content range from 1 to 10% (v/v), while the activity of lipase immobilized on native fibers showed a clear dependence on water content in organic media and decreased rapidly at high water content (> 2%). Furthermore, lipase immobilization on the hydrophobic support exhibited a significantly improved operational stability in esterification reaction system. After 27 batches were recycled, a high esterification yield (97%) was maintained. The results in this work indicate that a hydrophobic surface of fabric fiber promotes the interfacial activation of lipase and that woven silk could be a potential material as an immobilization matrix for industrial process.