Lignocellulose resources for the Myrothecium roridum laccase production and their integrated application for dyes removal

In this study, the extracts of lignocellulosic materials such as sawdust, hay, and rapeseed press cake were used as medium for the production of laccase of the non-ligninolytic fungus Myrothecium roridum. Media prepared from hay extract and rapeseed press cake extract contributed to the highest quantity of the enzyme produced (ranging from 465 to 728U/L after 24h of cultivation). It could have resulted from the high content of reducing sugars and phenolic compounds such as gallic or ferulic acid identified in media by liquid chromatography coupled with tandem mass spectrometry. The enzyme was found to be stable in the pH ranging from 2 to 8 and decolorized up to 90% of Amaranth (400mg/L) after 24-h incubation in the presence of a selected redox mediator. After 24h of incubation, laccase almost completely (97%) decolorized the simulated dye effluent containing several dyes, metal ions, reducing agents, and detergents. An environment-friendly approach for dyes removal by laccase immobilized together with rapeseed press cake was proposed. After 24-h incubation of a dye (acid orange 7, trypan blue, and Amaranth) with laccase-rapeseed press cake alginate beads, more than 70% decolorization was obtained. The rate of Amaranth removal was found to be about 50% after five successive batches. Low-cost production and high decolorization efficiency in the presence of additional compounds make M. roridum laccase and its newly developed immobilization technique a promising option as a green catalyst for azo dyes containing wastewater treatment.