Abstract
Glycerol-based biorefinery can be a highly profitable process by producing highly value-added products such as dihydroxyacetone via combined catalytic strategies. Here, two-enzyme system is adopted for cofactor regeneration as well as the transformation of glycerol into highly-valuable dihydroxyacetone. Glycerol dehydrogenase (GDH) and alcohol dehydrogenase (ADH) are co-immobilized within magnetically-separable and spherical mesocellular silica foam (Mag-S-MCF). GDH and ADH are adsorbed into the mesopores of Mag-S-MCF, and further crosslinked within the mesopores of Mag-S-MCF. The resulting nanoscale enzyme reactors (NER) of GDH and ADH within the mesopores can effectively prevent crosslinked enzyme aggregates from being leached out of mesopores, due to the bottle-neck mesopore structure of Mag-S-MCF, as well as stabilize the activity of GDH and ADH upon chemical crosslinking, effectively preventing the denaturation of enzyme molecules. The proximity of GDH and ADH molecules within mesopores of NER improves the efficiency of cofactor-mediated dual-enzymatic reactions by relieving mass-transfer limitations and improving cofactor recycling, expediting both glycerol oxidation and dihydroxyacetone generation. As a result, the DHA concentration obtained from NER-(GDH/ADH) and (NER-GDH)/(NER-ADH), with cofactor recycling, were 410 and 336 µM, respectively. To the best of our knowledge, this report is the first demonstration of stabilized nanoscale multi-enzyme reactor system, equipped with efficient cofactor regeneration within mesopores, for efficient glycerol transformation to high-valued dihydroxyacetone.