Bacterial Enzymes and Multi-enzymatic Systems for Cleaning-up Dyes from the Environment - Microbial Degradation of Synthetic Dyes in Wastewaters - page 41

Fig. 13 a PpAzoR activity measured at 30 ° C after incubation at different temperature (55 - 70 ° C)
for 1 h: wild type PpAzoR (circles) and 1B6 variant (squares). b Thermal inactivation of wild type
PpAzoR (circles) and 1B6 variant (squares). Enzyme samples were incubated at 50 ° C and

catalytic activity was measured at known time intervals at 30 ° C (adapted from Brissos et al. 2014 )

have a considerable potential for application in many different areas. In particular,
the interest in ligninolytic peroxidases, harbouring the highest redox potential
among peroxidases, for biotechnological applications has increased rapidly in
industrial areas related with the biore neries, in particular for the selective delig-

ni cation of lignocellulosic materials for production of biofuels (Martinez et al.

2009 ; Ruiz-Duenas and Martinez 2009 ). These enzymes are also suitable for
environmental applications, including the treatment of toxic ef uents, containing

synthetic dyes, generated in various industrial processes (Wesenberg et al. 2003 ;
Kandelbauer and Guebitz 2005 ; Husain 2006 ; Rodriguez Couto 2009b ; Chacko and
Subramaniam 2011 ; Khan et al. 2013 ). However, these enzymes are still not
commercially available, in part due to constraints related to the genetic manipula-
tion and relatively low levels of protein expression in both native and fungal host
strains.
A new family of microbial peroxidases, known as dye decolorizing peroxidases
(DyPs), was demonstrated to successfully degrade not only high redox anthraqui-
none-based, but also azo dyes, des

(van Bloois et al. 2010 ), phenolic or non-phenolic lignin compound units (Liers
et al. 2010 ; van Bloois et al. 2010 ; Brown et al. 2012 ) and manganese (Roberts
et al. 2011 ; Brown et al. 2012 ). The physiological function of these enzymes is at
present unclear, but there are increasing evidences of their involvement in the
degradation of lignin (Ahmad et al. 2011 ; Salvachua et al. 2013 ; Singh et al. 2013 ),
and therefore, DyPs seem to have the potential to replace the high-redox fungal
ligninolytic peroxidases in biotechnological applications. DyPs have primary
sequence, structural and apparently, mechanistic features, unrelated to those of
other known

ʲ -carotene (Scheibner et al. 2008 ), aromatic sul

plant and animal peroxidases (Sugano et al. 2007 ; Liu et al.
2011 ; Yoshida et al. 2011 ; Singh et al. 2012 ; Strittmatter et al. 2012 ). The
uniqueness of these enzymes is, therefore, interesting both at the fundamental and

“ classic ”