Valorization of biomass to furfuryl alcohol via chemoenzymatic cascade catalysis by deep eutectic solvent-silica heterogeneous catalyst and reductase biocatalyst in the aqueous system

A new type of metal-free solid acid catalyst ChCl:OA-SG(SiO 2 ) was firstly synthesized by loading deep eutectic solvent ChCl:oxalic acid on silica with sol–gel process using tetraethyl orthosilicate as silicon source. The properties of the catalyst were characterized by Fourier transform infrared spectrum, X-ray diffraction, scanning electron microscope, and Brunauer-Emmet-Teller. Highest furfural (FF) yield reached 41.2% from corncob with ChCl:OA-SG(SiO 2 ) catalyst (2.0 wt%) in water at 170 °C for 0.5 h. The catalytic mechanism of ChCl:OA-SG(SiO 2 )-catalyzed biomass into furfural was interpreted in the aqueous system. Corncob-valorized FF was wholly transformed to furfuryl alcohol with recombinant Escherichia coli CG-19 cells after bioreduction for 3 h of at 30 °C and pH 7.0. Yield of 0.416 g furfuryl alcohol/g xylan in corncob was obtained. This established hybrid catalysis could efficiently valorize biomass into value-added furfuryl alcohol.