Assessment of Enzymatic Bioremediation for Catechol in Water by the Role of Immobilized Catechol 1,2-dioxygenase on Biosilica of Diatoms Frustule and other Polymers

Abstract

The highest specific activity for (C12O) enzyme purification was within the second stage of the purification
steps represented by precipitation with ammonium sulfate AS 2% (weight / volume), reaching about 14.56
U. mg-1 after achieving the purification by 6.6 folds with a recovery rate of 78.3%. The optimum catalytic
activity of the enzyme (C12O) was within the pH of 6.5-8.5 and the temperature of 25 ° C. Immobilization of
(C12O) enzyme by biosilica of diatom frustules DFS/G GA gave a double shifting of 20 ° C from the optimum
temperature for enzyme activity, within all the purification stages, as the percentage of catechol degradation
through it at the temperature of 45 ° C reached about 93% and 87.2% and 85% were in the precipitation
stage with ammonium sulfate AS and the precipitation with streptomycin sulfate SS and the enzymatic crude
extract CEE respectively. While the shifting was only 10 ° C in the case of immobilization on polymeric
supports types: PAN / G and PAA / G. In contrast, the soluble (C12O) enzyme which did not show any
shifting by its optimum temperature , and its highest activity values were within the optimum temperature
of 25 ° C. While the method of immobilization for (C12O) enzyme by biosilica of diatom frustules DFS/G
gave a 1.5-degree shifting for the optimum pH of the enzyme activity, within all the purification stages, the
highest rates of catechol degradation were reached through it at the base pH 9-10 about 91.8% and 86.5. %
And 85.0% in the AS, CEE and SS stages, respectively. Whereas, the enzyme immobilization methods of
(C12O) by PAN / G and PAA / G did not show such displacement during the enzymatic purification stage
with streptomycin sulfate SS but were limited to the primarily stages of enzymatic purification. , As it was
able to shift the optimal pH of the (C12O) enzyme by 1.5 degrees also within the purification stages of AS
and CEE. The rates of catechol biodegradation through it at the base pH 9-10 were about 79.0% and 71.8%,
respectively, in the case of immobilization by PAN /G and PAA / G with percentages of 71.8% and 62.0%,
respectively. In contrast, soluble (C12O) enzyme did not show any shifting by its optimum pH, and its
highest activity values were within the optimum pH of 6.5-8.5. The reason for these results may be attributed
to the role of the large surface area ready for covalent immobilization of (C12O) enzyme by biosilica of
diatom frustules compared with the surface area of pores of the two types of polymeric membranes used in
current study.