phd philipe

Production of aroma esters by enzymatic-catalyzed reactions in supercritical carbon dioxide (CO₂)

Author: Philipe dos Santos (2017)

The use of supercritical carbon dioxide (CO₂) as reaction medium has gained attention in recent years due to their non-toxic, non-flammable, inert, non-polluting and recoverable characteristics of this solvent. Besides, the discovery that some enzymes are stable in non-aqueous reaction media has expanded the applicability of enzymes in organic synthesis reactions, such as the production of terpenic esters catalyzed by lipases in supercritical CO₂. However, few studies evaluate the production of aromatic esters using supercritical CO₂ in continuous mode. Therefore, the objective of this work is the scientific evaluation of chemical reactions catalyzed by lipases using supercritical CO₂ as reaction medium in a homemade unit that operates in batch and continuous flow modes. First, the high-pressure unit was designed and assembled. Next, the study of stability and activity of an immobilized lipase in supercritical media was performed. After this step, the production of eugenyl acetate and isoamyl acetate in supercritical CO₂ was evaluated, aiming to verify the influence of process variables on the esterification rate (X; %), productivity (P; kg/h) and specific productivity (SP; kg/kg.h). Finally, the mass transfer analyses in the batch reactor and the production of isoamyl acetate in continuous mode were performed. The results showed that the exposure of the commercial immobilized enzyme Lipozyme 435 to supercritical CO₂ reduced its catalytic activity in all experimental conditions. In spite of the decreased residual activity, about 10% in optimal condition, it was possible to obtain high esterification rate, productivity and specific productivity of eugenyl acetate (50% of X) and isoamyl acetate (100% of X) in specific operating conditions. Continuous mode experiments showed lower conversion, but higher productivity than those obtained in the batch reactor. It is possible to conclude that the application of supercritical fluid technology in chemical reactions, in particular with supercritical CO₂, is technically viable.