Enzymes are nature’s catalyst of choice for the highly selective and efficient coupling of carbohydrates. Enzymatic sugar coupling is a competitive technology for industrial glycosylation reactions, since chemical synthetic routes require extensive use of laborious protection group manipulations and often lack regio- and stereoselectivity. The application of Leloir glycosyltransferases has received considerable attention in recent years and offers excellent control over the reactivity and selectivity of glycosylation reactions with unprotected carbohydrates, paving the way for previously inaccessible synthetic routes. The development of nucleotide recycling cascades has allowed for the efficient production and reuse of nucleotide sugar donors in robust one-pot multi-enzyme glycosylation cascades. In this way, large glycans and glycoconjugates with complex stereochemistry can be constructed. With recent advances, LeLoir glycosyltransferases are close to being applied industrially in multi-enzyme, programmable cascade glycosylations.

In recent years, there has been a steady increase in the interest in changing lignocellulose processing technologies from harmful and nonecological to more ecological and sustainable. Deep eutectic solvents (DESs) and ionic liquids (ILs) are green, efficient solvents/catalysts for biomass pretreatment as well as its further transformation. In many cases, they are used together with biocatalysts. Additionally, in processes where DESs and ILs are used for the pretreatment of biomass, before enzymatic transformation, traces of these solvents can influence the activity of biocatalysts. For this reason, it is important to evaluate the effect of novel, green solvents on the activity of enzymes widely applied in the biomass valorization processes. In this work, we present the impact of chosen DESs and ILs, most often applied in biomass pretreatment and transformation, on the enzymatic activity of popular cellulolytic enzymes and enzymatic preparations (namely, cellulases from Aspergillus niger, Trichoderma reesei, and Viscozyme L). The enzymatic activity was investigated in the process of transformation of cellulose or biomass to glucose. The results showed that many of the solvents tested had a negative effect on enzymatic activity, suggesting a separation of pretreatment and enzymatic processes.