Enhancement of biodegradation potential of catechol 1,2-dioxygenase through its immobilization in calcium alginate gel

Abstract

Background: In biodegradation processes free enzymes often undergo deactivation. Thus, it is very important to obtain highly stable enzymes by different methods. Immobilization allows for successful stabilization of many multimeric enzymes by increasing the rigidity of the enzyme structure. This study aimed to evaluate some environmental factors that affect catechol 1,2-dioxygenase from Stenotrophomonas maltophilia KB2 immobilized in alginate hydrogel. The goal of the present work was to improve the functional stability of the enzyme by increasing its structural rigidity.

Results: Immobilization yield and expressed activity were 100% and 56%, respectively. Under the same storage conditions, the activity of the immobilized enzyme was still observed on the 28th day of incubation at 4°C, whereas the free enzyme lost its activity after 14 days of incubation. The immobilized enzyme required approximately 10°C lower temperature for its optimal activity than the free enzyme. Immobilization shifted the optimal pH from 8 for the soluble enzyme to 7 for the immobilized enzyme. The K_m, V_max, and Hill constant values for immobilized enzyme were 19.00 μM, 140.79 U mg^-1 protein, and 1.68, respectively whereas K_m, V_max, and the Hill constant of the free enzyme were 12.18 μM, 1,218.8 U mg^-1 protein and 1.0, respectively. The immobilized catechol 1,2-dioxygenase from KB2 strain showed activity against 3-methylcatechol, 4-methylcatechol, 3-chlorocatechol, 4-chlorocatechol, and 3,5-dichlorocatechol. Immobilization of the enzyme promoted its stabilization against any distorting agents: aliphatic alcohols, phenols, chelators.

Conclusions: Entrapment of the catechol 1,2-dioxygenase from Stenotrophomonas maltophilia KB2 has been shown to be an effective method for improving the functional properties of the enzyme. Increased resistance to inactivation by higher substrate concentration and other factors affecting enzyme activity as well as broadened substrate specificity compared to the soluble enzyme, make the immobilized catechol 1,2-dioxygenase suitable for the bioremediation and detoxification of xenobiotic-contaminated environments.