BACKGROUNDIn this work, fumed nano-silica (FNS) was chemically modified to amino (AFNS) and subsequently to cyanuric chloride (CCAFNS) modified silica and tested for the immobilization of lipase from Candida rugosa (CRL). The effects of the initial enzyme concentration, immobilization time and buffer ionic strength on immobilization were investigated in order to optimize utilization of the support and determine the mechanism of immobilization. The most active preparations were used to examine thermal and operational stability. RESULTSThe amount of immobilized enzyme increased with increasing enzyme concentration, achieving loadings of 121.3, 104.8 and 61.2mg per g of FNS, CCAFNS and AFNS, respectively. Lipase immobilized on CCAFNS carrier in 0.1molL(-1) buffer expressed the highest lipolytic activity (1320 IU g(-1) support), while more stable preparations were obtained in 1molL(-1) buffer. CONCLUSIONSuccessful modification of silica was confirmed with Fourier transform infrared spectroscopy and thermogravimetric analysis. Activity results showed that, depending on the support, immobilization was governed by different interactions. On FNS and AFNS immobilization was exclusively by adsorption, while on CCAFNS after the initial adsorption lipase molecules reoriented and amino groups of the enzyme formed a covalent bond with the chlorine atom of the modified carrier. Improved thermal and operational stability of lipase immobilized on CCAFNS in 1molL(-1) buffer led to the conclusion that electrostatic interactions have a great role in the immobilization. (c) 2014 Society of Chemical Industry