Towards the one-pot upgrading of glucose to HMF through hybrid chemo-enzymatic catalysis

In a world where the demand for specialty chemicals is ever increasing, the need for a renewable alternative to their typical fossil source is inevitable. One of green chemistry’s most promising tools is given to us by nature: enzymes. Their ability to catalyze chemical reactions with very high selectivity and specificity makes them extremely powerful when it comes to create high value-added chemicals. Unfortunately, the intrinsic nature of enzymes also makes them hard to stabilize, recover and ultimately reuse. In this regard, efforts are made to immobilize enzymes on a solid carrier and turn them into a heterogeneous (bio)catalyst. Thus, new class of catalysts is emerging: Hybrid Chemo-Enzymatic Heterogeneous Catalysts (HCEHC). HCEHC are multifunctional catalysts combining the action of the enzyme and of the solid; in this class of catalysts, the support is more than an inert solid; it is catalytically active, working in concert with the enzyme. This allows for one-pot cascade reactions (even with unstable chemical intermediates) while benefiting from both the advantages of the enzymes and the robustness of heterogeneous catalysts. Here, we will develop new hybrid chemoenzymatic heterogeneous catalysts dedicated to the direct production 5-HMF from glucose. In continuity with the concept previously developed in our group, this catalyst would be made of aggregated Glucose Isomerase encapsulated in hollow spheres of H-ZSM-5, a material displaying high Bronsted acidity and reportedly catalyzing the dehydration of fructose in aqueous or biphasic media. In this cascade of reactions, the first step is thermodynamically limited to a maximum conversion of <60%. The one-pot cascade reaction would then have the added benefit of negating this equilibrium via the dehydration of fructose produced in the medium. Before performing the cascade reaction, both steps must be optimized. So far, optimal conditions have been found for the isomerization of glucose to fructose by Glucose Isomerase from S. rubiginosus. The enzyme has also shown to be stable and active at up to 80°C in water. More work is being carried out to synthesize a dehydration catalyst able to operate under these mild conditions. To better discriminate the capabilities of different materials, catalytic tests are currently performed in a water/organic biphasic medium at 120°C, which are more favorable conditions for the dehydration step

Towards the one-pot upgrading of glucose to HMF through hybrid chemo-enzymatic catalysis

In a world where the demand for specialty chemicals is ever increasing, the need for a renewable alternative to their typical fossil source is inevitable. One of green chemistry’s most promising tools is given to us by nature: enzymes. Their ability to catalyze chemical reactions with very high selectivity and specificity makes them extremely powerful when it comes to create high value-added chemicals.[1] Unfortunately, the intrinsic nature of enzymes also makes them hard to stabilize, recover and ultimately reuse. In this regard, efforts are made to immobilize enzymes on a solid carrier and turn them into a heterogeneous (bio)catalyst. Thus, new class of catalysts is emerging: Hybrid Chemo-Enzymatic Heterogeneous Catalysts (HCEHC).[2] HCEHC are multifunctional catalysts combining the action of the enzyme and of the solid; in this class of catalysts, the support is more than an inert solid; it is catalytically active, working in concert with the enzyme. This allows for one-pot cascade reactions (even with unstable chemical intermediates) while benefiting from both the advantages of the enzymes and the robustness of heterogeneous catalysts.[3] Here, we will develop new hybrid chemoenzymatic heterogeneous catalysts dedicated to the direct production 5-HMF from glucose. In continuity with the concept previously developed in our group,[4] this catalyst would be made of aggregated Glucose Isomerase encapsulated in hollow spheres of H-ZSM-5, a material displaying high Bronsted acidity and reportedly catalyzing the dehydration of fructose in aqueous or biphasic media. [5] In this cascade of reactions, the first step is thermodynamically limited to a maximum conversion of <60%. The one-pot cascade reaction would then have the added benefit of negating this equilibrium via the dehydration of fructose produced in the medium. Before performing the cascade reaction, both steps must be optimized. So far, optimal conditions have been found for the isomerization of glucose to fructose by Glucose Isomerase from S. rubiginosus. The enzyme has also shown to be stable and active at up to 80°C in water. More work is being carried out to synthesize a dehydration catalyst able to operate under these mild conditions. To better discriminate the capabilities of different materials, catalytic tests are currently performed in a water/organic biphasic medium at 120°C, which are more favorable conditions for the dehydration step

Hybrid chemoenzymatic heterogeneous catalysts

Through selected recent examples, we show that a new class of catalysts — hybrid chemoenzymatic heterogeneous catalysts — is currently emerging. These multifunctional solid materials have a bright forecast for the development of green and sustainable chemistry. By combining the actions of a solid chemical catalyst and that of an enzyme, these formulations can catalyze multiple reactions in one pot thereby merging the best of two worlds: robustness and recyclability of heterogeneous catalysts on the one hand and outstanding selectivity and specificity of biocatalysts on the other hand. The preparation of such hybrid materials, however, represents a multidisciplinary challenge for catalysis scientists and materials chemists

Conference Report: YEuCat Better Together - Collaborative Catalysis in a Changing World

"YEuCat Better Together was the first collaborative event organized by the Young European Catalysis Network with the goal of joining young minds to propose an innovative catalytic solution to a global problem." This and more about YEuCat Better Together can be found in this Guest Editorial.