Laccase production by Trametes versicolor under limited-growth conditions using dyes as inducers

Abstract

Laccase production by pre-growth pellets of Trametes versicolor using two types of textile dyes as inducers was studied. By decoupling the enzyme production phase from the growth phase, it is possible to reduce the time and nutrients required for laccase production. At the glucose maintenance level, the effect of the nitrogen source and textile dye was analysed using response surface methodology. Ammonium chloride was used as the inorganic nitrogen source. Two types of dyes were tested: Grey Lanaset G (GLG), a metal complex dye mixture containing nitrogen; and Alizarin Red (AR), an anthraquinonic dye with no nitrogen in its chemical structure. GLG induces laccase production at a higher extent than AR. Despite the limiting conditions required for the production of laccase, enzyme production increases with increasing ammonium chloride. When AR, the N-free dye, was used as an inducer, the optimal supply of N for laccase production was 1.2 mg/(g dry cell weight·d) as ammonium chloride. The reuse of fungal pellets in the repeated-batch mode under maintenance conditions was found to be a good strategy for improving laccase production, as enzyme production increased to up to seven times the production of the first cycle. It was demonstrated that GLG can be used as an inducer and as an N source and, thus, it is possible to decolorize the dye and to induce laccase production at the same time without adding an extra N source.

Keywords:

• pre-growth pellets
• sequential batch reactor
• inducers
• bioreactor
• response surface methodology

Acknowledgements

This work was financially supported by the Spanish Plan Nacional de I+D+I, project number CTM2007-60971. The authors are members of the consolidated research group in Catalonia (2009-SGR-656). The Department of Chemical Engineering of the Universitat Autònoma de Barcelona is the Biochemical Engineering Unit of the Xarxa de Referència en Biotecnologia (XRB) de la Generalitat de Catalunya. N.C. acknowledges the Department of Universities, Research and Information Society (DURSI) for a predoctoral grant.