Delignification of Pinus radiata kraft pulp by treatment with a yeast genetically modified to produce laccases

Abstract

Cellulose pulp bleaching is one of the main biotechnological applications of fungal laccases due to their capacity to degrade lignin from the unbleached pulp. For this application, not only a low cost enzyme production, but also higher enzyme concentrations than those obtained by its natural producers are needed. Heterologous expression of laccase in yeasts is an option for producing these enzymes at industrial scale. In this work the heterologous expression of the cglcc1 gene, responsible for laccase production in the basidiomicetous fungus Coriolopsis gallica, in the yeast Kluyveromyces lactis has been tested. In order to know if the transformed yeast obtains delignificant capability, a Pinus radiata kraft pulp has been incubated with it. After the treatment, an important decrease in kappa number (13%) and in lignin content (22%) has been observed. These results showed the delignificant capacity of this transformed yeast. It can be concluded that the employment of genetically modified microorganisms, without cellulolitic activity, to produce high laccase levels could be a feasible option to delignify cellulose pulps with a potential application in cellulose pulp bleaching.