A Forward-Looking Reflection on Deep Eutectic Solvents and Biocatalysis: From Environmental to Process-Related Angles

Abstract

Deep eutectic solvents (DESs) and biocatalysis are assumed to be a “green synergy” by default, with applications that will be straightforwardly implemented at industrial scale. This review critically examines the state-of-the-art of DESs in enzymatic reactions, with a focus on several aspects. First, the environmental benignity of DESs is built from a holistic approach, covering their origin and fate, toxicity and biodegradability, and degree of intensification in enzymatic reactions, which ultimately drives the actual greenness (optimized product-to-solvent ratio and recycling). Second, the selected reported examples are used to illustrate how research in DESs and biocatalysis should move from mere proof-of-concept considerations to forward-looking in-depth contributions in different areas like (i) rational solvent design combining in silico and wet-lab results, together with data-driven AI-readable options; (ii) exhaustive parameter determination for the process design; (iii) assessment of reactor types and scale-up, addressing expected challenges when large volumes are used; and (iv) tackling the downstream of DES-based reactions to propose alternatives that may align efficiency with sustainability. Overall, DESs and biocatalysis may have, in fact, the potential to become a green synergy with high usefulness in future (bio)processes. Yet, process-oriented fundamental work and understanding of the above-mentioned aspects are necessary to discern the right choice of solvent, process, and reactor, combined with enzymes—free, immobilized, or as whole-cells—to establish solid and green-by-design synthetic systems.