Laccase Production From Trametes hirsuta and Decolourisation of Phenolic Textile Dye In a Laccase Mediator System (LMS)

In
this study, fungal laccase was produced from Trametes
hirsuta DSMZ 5072 at 28 °C in a submerged
cultivation medium comprising: potato infusions from 200gm/L, glucose (1%) and malt
extract (1%). The maximum laccase activity
(129 U/L) was observed at day eight post-cultivation in the presence of 2mM of 2,5-xylidine, as an inducer. Fungal laccase from Tramates
versicolor as a commercial enzyme, and home prepared laccase from T. hirsuta, were used to decolourise phenol
red. The effects of initial medium pH, different
systems, type of mediator and incubation temperature were investigated. It was
observed that, for both commercial and homemade laccases, pH 4.5 allowed more
efficient decolourisation of the dye at 30 °C.
In an aqueous system, high decolourisation
percentages, of 42.8% and 36.4%, were revealed within 72 hours in the
presence of T. versicolor and T. hirsuta laccases respectively. The
degree of decolourisation increased in the aqueous system when a different
mediator was added. Results showed that the 1-hydroxybenzotriazole (HBT) has a much
better decolourisation ability than the other mediators tested, such that decolourisation
percentages as high as 73.6% and 79.4 were observed in the presence of 8mM HBT
and laccase from T. hirsuta (40 °C/120 minutes) or T. versicolor
(30 °C/120 minutes), respectively.