OPERATIONAL STABILITY STUDY OF NOVOZYM 435 LIPASE IN GERANYL CINNAMATE SYNTHESIS WITHIN A BATCH STIRRED TANK REACTOR

Monoterpenic esters, such as geranyl cinnamate (GC), are widely used in food and other industries as natural flavoring agents. Their synthesis can be conducted in a sustainable way through solvent-free enzymatic reactions, employing lipases as catalysts, thus obtaining a natural product. However, there is still insufficient information available regarding the applicability of this enzymatic esterification in the industry. Considering the costs associated with the synthesis, especially in relation to the biocatalyst's value, further research into the reusability of immobilized lipases involved in geranyl cinnamate synthesis remains essential. Consequently, the current study aimed to investigate the operational stability of immobilized Novozym 435 (N435) lipase in a batch stirred tank reactor (BSTR) for GC synthesis. To define optimum conditions and the reaction time for assessing BSTR operational stability, 2³ factorial designed experiments were previously conducted. Then, operational stability was evaluated in the reactional conditions: 15% (w/w) N435 and 1:4 cinnamic acid/geraniol molar ratio at 80 °C and 200 rpm for 8 h. At the end of the reaction, the immobilized derivative was washed with hexane. The procedure was repeated for successive cycles until ester production decreased considerably. GC conversion was determined by gas chromatography using a standard curve. The thermal deactivation of N435, assumed to follow first-order kinetics, was investigated, and the half-life (t1/2) of the biocatalyst was estimated from the deactivation coefficient (Kd). The following kinetic parameters were obtained: Kd = 0.033 h and t1/2 = 20.50 h. Lipase’s activity before (1931.86 U/g) and after (1100.88 U/g) the reuse were also determined. These results affirm the fine stability of N435 during the synthesis of GC within the tested conditions. Notably, the observed decline in activity and thermal deactivation of the enzyme at 80°C were found to be influenced by the interplay between cinnamic acid concentration and reaction temperature.