Enzyme-Catalyzed Synthesis of Glycerol Carbonate in Solventless Liquid One Phase Conditions: Role of Reaction Medium Engineering on Catalytic Performance

This study pursues the efficient synthesis of glycerol carbonate (GC) using immobilized lipases on octyl agarose by means of interfacial activation under solventless conditions. The monophasic system formed between glycerol and ethylene carbonate at elevated temperatures displays low viscosity and minimizes mass transfer hindrances, which represent promising novel conditions in this biocatalytic process. Immobilized lipases from Candida rugosa and Thermomyces lanuginosus on octyl agarose were identified as suitable catalysts. While thermally denatured biocatalysts lost their catalytic capacity completely, biocatalysts with the catalytic Ser irreversibly inhibited showed significant enzymatic activity, suggesting that the catalytic Ser may not play a key role in the reaction. The influence of various operational variables and conditions: temperature, catalyst concentration, and reaction setup (2 mL vials and 100 mL round-bottom flasks with magnetic stirring were used) were studied with the aim of achieving high conversions (>99%) and yields (>99%) in short reaction times. Among the tested lipases, immobilized C. rugosa lipase exhibited the highest turnover numbers. The use of immobilized lipases allowed for multiple reaction cycles without a significant decrease in the initial reaction rate or the final conversion, highlighting the potential for catalyst reuse. This research achieved remarkable results in terms of reaction productivity, product concentration, atom efficiency, and turnover number compared to any previous study, emphasizing the significance of reaction engineering approaches in developing efficient sustainable processes for synthesizing valuable chemicals. The study emphasizes the potential of lipases as catalysts for GC synthesis and underscores the importance of considering monophasic solventless conditions at high temperatures for improved reaction efficiency and high reaction atomic efficiency.