This study reports the synthesis of polymeric matrices based onN-isopropylacrylamide and itaconic acid and its application for immobilization of lipase fromCandida rugosa. The lipase was immobilized by entrapment method. Free and immobilized lipase activities, pH and temperature optima, and storage stability were investigated. The optimum temperature for free and entrapped lipase was found to be 40 and 45°C, while the optimum pH was observed at pH 7 and 8, respectively. Both hydrolytic activity in an aqueous medium and esterolytic activity in an organic medium have been evaluated. Maximum reaction rate (Vmax) and Michaelis-Menten constants (Km) were also determined for immobilized lipase. Storage stability of lipase was increased as a result of immobilization process. Furthermore, the operational stability and reusability of the immobilized lipase in esterification reaction have been studied, and it was observed that after 10 cycles, the residual activity for entrapped lipase was as high as 50%, implying that the developed hydrogel and immobilized system could provide a promising solution for the flavor ester synthesis at the industrial scale.

The present work was aimed to study swelling kinetics of polylactic acid (PLA) and its impregnation with thymol in supercritical carbon dioxide (scCO2) medium. The influences of temperature and soaking time on the swelling kinetics and impregnation yield of PLA cylindrical disc and film were investigated. Swelling experiments were performed in a high pressure view cell at 10 MPa and temperatures of 40°C, 60°C and 75°C for 2 to 24 h. On the basis of swelling kinetics, pressure of 10 MPa and temperature of 40°C were chosen for supercritical solvent impregnation (SSI) of the PLA samples during 2 to24 h. The highest swelling extent was observed for the PLA monolith after 24 h treatment with pure scCO2 (7.5%) and scCO2 with thymol (118.3%). It was shown that sufficiently high amount of thymol can be loaded into both PLA monolith and film using SSI after only 2 h (10.0% and 6.6%, respectively). Monolith and film of PLA impregnated with thymol could be suitable for active food packaging and sterile medical disposables.

The aim of the present study was to investigate starch-based materials, prepared in an environmentally friendly way and from renewable resources, suitable for the development of biodegradable active food packaging. For this purpose, a bioactive compound (thymol) was incorporated into thermoplastic starch (TPS) and a TPS blend with poly (ε-caprolactone) (TPS–PCL) by the supercritical CO₂ (scCO₂) impregnation process. Impregnation experiments with scCO₂ were carried out at a pressure of 30 MPa and temperatures in the range of 40–100 °C during 1 to 20 h. The structural, morphological, and thermal properties of the obtained materials were comprehensively evaluated. Bioactive component release kinetic studies were performed in water at 6 °C and 25 °C. It was shown that the scCO₂ impregnation process could be successfully employed for thymol loading into TPS and TPS–PCL. The process was significantly influenced by the operating temperature and time as well as content of PCL. The samples showed a controlled release of thymol within seven days with a higher amount of released thymol from the TPS–PCL blend. The obtained materials are solvent-free and release the bioactive component in a controlled manner.