Exploring the biotechnological applications of a halotolerant pH-versatile laccase produced by Streptomyces ipomoea CECT 3341

The ability of a laccase (EC 1.10.3.2) produced by Streptomyces ipomoea CECT 3341 (SilA) to delignify eucalyptus kraft pulp at acidic pH and to decolourise and detoxify an azo dye at alkaline pH was assessed. The biobleaching process of a eucalyptus kraft pulp carried out with SilA using ABTS as mediator result in a 12 % decrease in kappa number and in a significant increase in % ISO brightness. Moreover, it is also remarkable the save in H202 consumption obtained after the peroxide bleaching in the pulp treated with this laccase-mediator system. The decolourisation of Reactive Green 19 using a non-chromogenic mediator such as acetosyringone was assayed. Results showed that SilA-acetosyringone system at alkaline pH produced a 90% colour decrease and more than 50% detoxification after 4 h incubation. In addition, the efficiency of this enzyme was also supported by the maintenance of its activity in the presence of high concentration of salts which are commonly present in different steps industrial processes and/or their effluents.