Properties of catechol 2,3-dioxygenase from crude extract of Stenotrophomonas maltophilia strain KB2 immobilized in calcium alginate hydrogels

In this paper we report the immobilization of catechol 2,3-dioxygenase from Stenotrophomonas maltophilia KB2 in alginate hydrogel with the aim of improving its functional stability by increasing structural rigidity of the enzyme. Immobilization yield and expressed activity were 49.4% and 49.4%, respectively. The storage stability of entrapped catechol 2,3-dioxygenase at 4 degrees C was found up to 35 days (266.3 mU/mg protein), while at 4 degrees C the free enzyme lost its activity within 24 h. Immobilization of dioxygenase increased the optimum temperature for activity by 10 degrees C, while both soluble and immobilized enzyme showed maximum activity at the same pH. The K-m, V-max, and Hill constant values for immobilized enzyme were 0.2 mu M, 604.6 mU/mg protein, and 1.00. respectively, whereas those for the free enzyme were 46.3 mu M, 1602.0 mU/mg protein, and 4.1, respectively.The immobilized catechol 2,3-dioxygenase from KB2 strain showed relatively higher activity against 3-methylcatechol, 4-methylcatechol, 4,5-dichlorocatechol, 3,5-dichlorocatechol, hydroquinone and tetrachlorohydroquinone than soluble enzyme. Immobilization of catechol 2,3-dioxygenase from KB2 strain protected the enzyme from the inhibition and enhanced its resistance to inactivation during catalysis. That makes the enzyme suitable for the bioremediation and detoxification of xenobiotic-contaminated environments. (c) 2012 Elsevier B.V. All rights reserved.