Immobilization in quartz fiber felt reinforced silica aerogel improves the activity of Candida rugosa lipase in organic solvents

Candida rugosa lipase is a very useful catalyst, but its rapid inactivation by simple alcohols is a drawback. The present study was focussed on the encapsulation of this enzyme in silica aerogels reinforced with quartz fiber felt. The activity of the immobilized lipase in an organic solvent could be significantly improved over that of the free enzyme and of previous immobilization techniques, by evaporating the alcohol formed during a pre-hydrolysis of the silica precursor, before adding the aqueous enzyme solution. The alcohol evaporation technique was previously used by other authors to immobilized enzymes, but applied to xerogels dried by evaporation, while in the present case the wet gels obtained were dried by the CO2 supercritical method to obtain aerogels. Besides, such silica aerogels were also reinforced by impregnating a commercial ceramic quartz fiber felt of St. Gobain with the silica sol containing the enzyme, before gelation. The ceramic composites heterogeneous biocatalysts obtained could be used for a large number of times without any apparent deterioration.