| dc.description.abstract | Flavonoids are a big class of plants’ secondary metabolites which possess antimicrobial, antioxidative, anti-inflammatory, etc. activities. However, their wider application is limited due to their poor solubility and stability in different environments. In order to overcome this problem and improve their biological and physicochemical characteristics, enzymatic oligomerization of flavonoids can be performed by using laccases as biocatalyst. In this study, laccase from Trametes versicolor was successfully immobilized onto two nanocarriers and used as a catalyst for the oligomerization of two flavonoids, esculin and phloridzin. For immobilization, nanocelulose prepared by ultrasonic treatment of commercial microcellulose and nanosilica from rice were used. Both carriers were modified in order to introduce amino groups on their surface: nanocelulose with poly(ethyleneimine) (NC-PEI) and nanosilica with organosylane (NS-OS). Most active preparation for NC-PEIlaccase and NS-OS-laccase showed activities of 10.05 IU/g of support and 9.08 IU/g of support, respectively. The oligomerization of flavonoids was performed using immobilized laccase and obtained results were compared with those obtained with free laccase (same amount of activity units) as biocatalyst. Immobilized preparations showed promising activities in reaction of esculin oligomerization, since after 24h of reaction the conversions of 73.3% and 61.6% with NC-PEI-laccase and NS-OS-laccase, respectively was achieved, while the soluble enzyme gave the conversion of 92.4%. On the other hand, some lower activity of NC-PEI-laccase was observed in reaction of phloridzin oligomerization, since the achieved conversion was 43.3% compared to 80.7% of phloridzin conversion obtained with soluble laccase. The lower activity could be explained by different reaction medium, since, compared to the esculin oligomerization, the phloridzin oligomerization was performed in 30% methanol, due to its low water solubility. However, obtained results indicate that novel immobilized laccase preparations can be successfully applied in the production of various flavonoid oligomers. | sr |
