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When gelification is performed by freezing-thawing repeated cycles, the resultant gel-like polymer systems are called cryogels. This work aims to assess the effect of the addition of glutaraldehyde and 18 Crown Ether-6 on surface properties and protein loading of dried chitosan cryogel films. Residual water content of treated chitosan membranes ranged between 11.93 and 13.86%, while their water activities vary from 0.5 to 0.7 (measured from 4 to 60 degrees C). Based on thermal data, water evaporation peak and degradation temperatures of chitosan membranes shifted to a higher temperature for crosslinked samples. X-ray diffractograms provide high values of crystallinity for all the samples (70.67-92.86%), the highest value being for the glutaraldehyde-treated membrane. Candida rugosa lipase can be immobilized successfully on chitosan membranes. Lipase immobilized on glutaraldehyde-crosslinked chitosan yielded the highest efficiency in terms of total coupled protein and protein loading efficiency.

The enzymatic synthesis of Ethyl esters from coconut oil ( Cocos nucifera ) and ethanol was evaluated in a bioreactor assisted by electromagnetic field, using lipase from Pseudomonas fluorescens immobilized on chitosan with magnetic properties as biocatalyst. Then, the magnetic, physicochemical and textural characteristics of the prepared biocatalysts were also assessed by vibrational magnetometer, thermal analysis, X-ray diffraction, scanning electron microscopy and nitrogen sorption (BET). The transesterification reactions were carried out by operating the bioreactor at differential mode, considering a maximum conversion around 12%, with reaction temperature at 30, 45 and 60 °C, molar ratios of oil: alcohol of 1:6, 1:9 and 1:12, and magnetic induction values of 6.5, 9.7 and 13.0 mT. The optimal reaction parameters were maximized at differential mode reactor at 12 h, with molar ratio of 1:11.25; reaction temperature at 47.5 °C and magnetic induction of the 9.7 mT. The attained results suggest that synthesis of ethyl esters in this unconventional bioreactor assisted by magnetic field was positively influenced by molar ratio and temperature, while magnetic induction was important for establishment of the magnetically stabilized bed, and in addition retain/separate the magnetic biocatalysts for further reuse. [ABSTRACT FROM AUTHOR]