Functionalization of Porous Cellulose with Glyoxyl Groups as a Carrier for Enzyme Immobilization and Stabilization

The functionalization of the internal surface of macroporous carriers with glyoxyl groups has proven to highly stabilize a large variety of enzymes through multipoint covalent immobilization. In this work, we have translated the surface chemistry developed for the fabrication of glyoxyl-agarose carriers to macroporous cellulose (CEL). To that aim, CEL-based microbeads were functionalized with glyoxyl groups through a stepwise alkoxylation (or alkylation)/oxidation synthetic scheme. This functionalization sequence was analyzed by solid-state NMR, while the scanning electron miscroscopy of CEL microbeads reveals that the mild oxidation conditions negligibly affect the morphological properties of the material. Through the optimal functionalization protocol using rac-glycidol, we introduce up to 200 μmols of aldehyde groups per gram of wet CEL, a similar density to the one obtained for the benchmarked agarose-glyoxyl carrier. This novel CEL-based carrier succeeds to immobilize and stabilize industrially relevant enzymes such as d-amino acid oxidase from Trigonopsis variabilis and xylanases from Trichoderma reseei. Remarkably, the xylanases immobilized on the optimal CEL-based materials present a half-life time of 51 h at 60 °C and convert up to 90% of the xylan after four operation cycles for the synthesis of xylooligosaccharides.
The authors acknowledge funding from the National Council for Scientific and Technological Development (CNPq) for financial support for the PhD scholarships of S.M.O (Process CsF 201683/2014–2008). J.M.G thanks the funding from the EU FP7 project Lignofood (Ingredients for Food and Beverage Industry from a Lignocellulosic Source, grant agreement no 606073). F.L-G acknowledges the funding of IKERBASQUE. This work was performed under the Maria de Maeztu Units of Excellence Program from the Spanish State Research Agency—grant no. MDM-2017-0720. J.M.F., thanks to the funding from the Spanish Ministerio de Ciencia e Innovación (grant RTI2018-093431-BI00).