8th Forum ILI

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8th Forum ILI

• A COMPARATIVE STUDY ON THE ROLES OF ABTS AND
  TWO N-OH-TYPE COMPOUNDS IN LACCASE-MEDIATOR
  SYSTEMS APPLIED TO BIOTRANSFORMATION OF A NATURAL
  AND AN INDUSTRIAL LIGNIN
• K. González Arzola a, M.C. Arévalo b, F.
  Perestelo a, A. Carnicero a,
• J.R. Hernández Fernaud c, M.A. Falcón a
• a. Department of Microbiology and Cell Biology,
  University of La Laguna, Tenerife, Spain.b.
  Department of Physical Chemistry, University of
  La Laguna, Tenerife, Spain.c. Proteomic Service,
  Mixed ULL-HUC Research Unit, La Laguna,
  Tenerife, Spain.

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Laccase-mediators
2,2-azino-bis-3- ethylbenzo thiazoline-6-sulphoni
c acid (ABTS)
Violuric acid (VA)
1-Hydroxybenzotriazole (HBT)
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Lignins

• Kraft lignin (Westvaco)KL
• Björkman lignin from pinePL

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Laccase-Mediator Systems (LMSs)
Components
1 mg Lignin (KL or PL) in 5 mM NaOH
0.2 U Laccase 0.1 M phosphate buffer pH 6
1 mM ABTS
10 mM VA
1 mM HBT
37ºC 1,400 rpm
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After 48 h of incubation
Spectroscopy UV-Vis
SE-Chromatography (HPLC)
Electrochemical study Cyclic Voltammetry
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Cyclic Voltammetry ABTS
PL ABTS
KL ABTS
ABTS2 E0 854 mV
ABTS E0 440 mV
ABTS
ABTS
PL
KL
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Cyclic Voltammetry VA
KL VA
PL VA
E0 632 mV
PL
KL
VA
VA
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Cyclic Voltammetry HBT
KL HBT
E0 840 mV
PL HBT
HBT
HBT
PL
KL
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SE Chromatography ABTS
KL
PL
87 kDa
0.8 kDa
Active Lac
Active Lac
Control
Control
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Spectroscopy UV- VIS
89.9
658.9
113.2
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SE Chromatography VA
KL
PL
Active Lac
Active Lac
Control
Control
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SE Chromatography HBT
PL
KL
Control
Control
Active Lac
Active Lac
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• When laccase was accompanied by either lignin
  or N-OH mediators, it showed increased stability
  against that detected for laccase alone.

So, the strong polymerization could be due
to both the action of radicals and the increase
in laccase stability.
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CONCLUSIONS

• The electrochemical studies revealed that ABTS
  was the best
• catalytic mediator. It was interesting that
  ABTS. oxidized KL to a
• greater extent and ABTS2 oxidized PL better.

2. LMSs made up of enzyme and ABTS depolymerized
and oxidized both lignins substantially. We
propose that ABTS radicals could inhibit
recondensation of the treated lignins.
3. The systems made up of laccase with either HBT
or VA (N-OH mediators) strongly polymerized and
oxidized both lignins. These polymerizations
were more intense than with laccase alone, which
could be partially attributable to the increased
stability of laccase.