Lignin waste as co-substrate on decolorization of azo dyes by Ganoderma lucidum

Improvement of dye removal efficiency is beneficial to development of bioremediation for textile effluent. In this study, the effect of lignin model compounds (LMCs) and enzymatic/mild acidolysis lignin (EMAL) from rice straw as co-substrate on dye decolorization by Ganoderma lucidum EN2 were evaluated. Two azo dyes, Remazol Brilliant Violet 5R (RBV5) and Sunset Yellow (SY) were tested. Eight of the thirty tested LMCs could significantly improve both RBV5 and SY decolorization, including 3,4,5-trimethoxycinnamic acid, 4-hydroxycinnamic acid, 3,5-dimethoxy-4 -hydroxybenzaldehyde, 3-hydroxybenzoic acid, 3‑hydroxy-4-methoxycinnamic acid, guaiacol, acetosyringone, and 2,6-dimethoxyphenol. The decolorization of RBV5 (from 87.04% to 97.90%) and SY (from 62.41% to 97.40%) by G. lucidum EN2 could be efficiently enhanced in the presence of EMAL. The addition of EMAL could increase the decolorization of higher concentration of azo dyes which is more difficult to be decolorized alone. Noteworthy, laccase activity increased with the increasing amount of EMAL. EMAL showed a positive effect on fungal growth but a negligible effect on pH. These results indicated that EMAL may act as inducer to stimulate the laccase production, and the increase of laccase activity accelerated dye decolorization.