Improved catalytic properties of Candida antarctica lipase B multi-attached on tailor-made hydrophobic silica containing octyl and multifunctional amino- glutaraldehyde spacer arms

Abstract

Abstract This work evaluated the immobilization of Candida antarctica lipase B (CALB) on a new heterofunctional support, prepared by silanization of silica particles with triethoxy(octyl)silane and trietoxy(3-aminopropyl)silane, followed by activation with glutaraldehyde. The new support (octyl-silica-amino-glutaraldehyde, OSGlu) exhibits features of an anionic exchanger and hydrophobic adsorbent capable of adsorbing and covalently linking the lipase under mild conditions in a single step. As comparison, CALB was also immobilized on silica coated with octyl, amino-glutaraldehyde, octyl and glyoxyl, and octyl and epoxy groups. Among these supports, CALB immobilized on OSGlu (namely CALB-OSGlu), showed the highest recovered activity (71 ± 2%) and thermal stability in tert -butyl alcohol (full activity was recovered after 100 h at 65 °C). CALB immobilized on silica coated with octyl or amino-glutaraldehyde yielded biocatalysts with lower recovered activities, compared to CALB-OSGlu, with values of 43% and 32%, respectively. CALB-OSGlu was chosen to be evaluated in the synthesis of fructose oleate in tert -butyl alcohol medium and at high temperature, achieving conversions above 70% in nine 6 h-cycles at 55 °C. CALB-OSGlu showed better operational stability than benchmark immobilized CALB (Novozym 435) in the same reaction conditions, with the conversion of the later decreasing from 84% (first cycle) to 53% (ninth cycle).