Ionic Liquids in Sustainable Biocatalytic Lactone Synthesis: Green Chemistry Metrics and Process Evaluation

Ionic liquids remain attractive alternatives as multifunctional media for the sustainable biosynthesis of lactones. Their unique physicochemical properties, including negligible vapor pressure, high thermal stability, and tunable polarity, offer significant advantages in terms of biocatalyst stabilization and reaction selectivity. For lactone synthesis, ionic liquids facilitate improved control over enzymatic transformations, enable efficient catalyst recycling, and reduce solvent consumption. This review summarizes recent advances in the application of ionic liquids as solvents or support modifiers in enzymatic lactone synthesis, focusing also on ε-caprolactone biosynthesis. A green chemistry metrics evaluation was also performed for selected examples from the literature. The role of ionic liquids in enhancing process efficiency and supporting green, sustainable process design is critically discussed, highlighting their potential for the development of more sustainable and environmentally friendly lactone production technologies.