Ethyl lactate synthesis in organic media using a magnetic supported CALB

Abstract

The growing demand for sustainable chemical processes has spurred interest in enzymatic synthesis, particularly for valuable compounds like ethyl lactate. Traditional chemical methods often suffer from drawbacks, highlighting the potential of enzymatic catalysis using immobilized lipases. This study evaluated the performance of magnetic biocatalyst, prepared by immobilizing Candida antarctica lipase B (CALB) on magnetic nanoparticles, for the batch synthesis of ethyl lactate in hexane. Initial experiments using free CALB and commercial Novozym435 proved problematic due to enzyme denaturation and support instability, respectively. While titration-based methods for monitoring the reaction were found to be unreliable due to lactic acid's complex behavior in the reaction medium, titratable acidity reduction suggested an optimal lactic acid to ethanol molar ratio of 1/10. Subsequent HPLC analysis revealed that the magnetic biocatalyst maintained a consistent conversion (%) at higher lactic acid concentrations (up to 17 mg/mL at 45°C, with conversion above 60 % in 5 h), demonstrating its potential for processing larger amounts of substrate. The initial reaction rate was estimated to be 3.8 mM/h. The study also identified experimental challenges in accurate lactic acid quantification and potential catalyst degradation. In conclusion, the magnetic CALB biocatalyst shows promising activity and stability for ethyl lactate synthesis, especially at higher substrate loads, paving the way for further optimization and application in sustainable production.