"Decolorization and Kinetics of Reactive Dyes by Native Laccases from Northeast Mexico"-Edición Única
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Abstract
Laccase isoforms Lac-I and Lac-II produced by the basidiomicete Pycnoporus sanguineus were
investigated. Both enzymes presented high stability during prolonged storage under freezing
conditions (-20 o
C) with no significant activity reduction.
For RBBR, decolorization efficiencies range from 82 to 88% after 3 hours of incubation for both
isoforms at 1 and 8 U mL-1
. However, with 8 U mL-1
the decolorization ranges between 70 to 80%
during the first 5 minutes of incubation. A significant lower decolorization pattern was observed
with RB-5 reaching a maximum decolorization efficiency of 50% after 15 hr of incubation. For this
time, the enzymatic decolorization of RB-5 with 1 U mL
-1 was between 14 to 27% and at the high
laccase activity level, 8 U mL-1
, was from 33 to 53%.
The use of laccase mediators was applied to improve RB-5 decolorization rates using violuric acid
and N-hydroxypthalamide. Violuric acid reduced decolorization time from 15 hr to 25 min with 1
mM and 1 U mL
-1
of enzyme activity and reaching up to 80% decolorization. The maximum
decolorization efficiency obtained with N-HPT was 71% after 15 hr of incubation.
Kinetic parameters of the two laccases were determined using RBBR as substrate: Km was 0.243
and 0.117 mM and Vmax was 1.233 and 1.012 mM sec-1 for Lac-I and Lac-II respectively. Both
enzymes have high decolorization power for dye decolorization although Lac-I was slightly more
active against RBBR and RB-5 than Lac-II throughout the experimentation. These enzymes
demonstrated high potential against both dyes and have significant differences in comparison to
other reported enzymes.