Sawdust waste as a low-cost support-substrate for laccases production and adsorbent for azo dyes decolorization.

Dalel Daâssi,Hela Zouari-Mechichi,Fakher Frikha,Moncef Nasri,Tahar Mechichi,Susana Rodríguez-Couto

doi:10.1186/s40201-016-0244-0

Abstract

BackgroundLaccases are multicopper oxidases with high potential for environmental and industrial applications. Low-cost laccase production could be achieved by solid state fermentation on agro-industrial by-products.MethodsA number of agro-industrial solid wastes were tested as support-substrate for laccase production by Coriolopsis gallica under solid-state fermentation (SSF) conditions. Response surface methodology (RSM) was used to optimize the medium composition for laccase production. Initial screening by Plackett-Burman design was performed to select the major variables out of 20 tow medium components fellowing this Central composite design (CCD) was employed to optimize the level of the selected variables.ResultsSawdust waste was shown to be the best support-substrate for laccase production by the C. gallica. Peptone as source of organic nitrogen, Cd2+ as laccase inducer and liquid/solid (L/S) ratio were found to have significant effects on laccase production. Operating at optimum concentrations of the most significant variables (peptone, 4.5 g L−1, L/S ratio, 5.0 and Cd+2 1.0 mM) extracellular laccase activity was enhanced from 1480 U L−1 (60.5 U g−1), to 4880 U L−1 (200 U g−1) which meant a 3.2-fold increase in laccase activity. On the other hand, sawdust waste was studied as a low cost adsorbent to remove the azo dyes Reactive Black 5 (RB5) and Acid Orange 51 (AO51). Decolorization percentages around 67 and 75 % were obtained in 24 h for RB5 and AO51, respectively.ConclusionWhen used as a support substrate, sawdust yielded the highest laccase production which was increased 3.2 times using RMS optimization.

Highlights

Laccases are multicopper oxidases with high potential for environmental and industrial applications
The aims of this study were: (a) to assess the potential of selected agro-wastes for laccase production by the whiterot fungus C. gallica under solid-state fermentation (SSF) conditions, (b) to optimize the laccase production by C. gallica under SSF conditions operating with sawdust waste as support-substrate using Central composite design (CCD) and (c) to test the ability of the ligninolytic complex secreted in SSF conditions for azo dyes biodecolorization
Selection of the support-substrate Firstly, a series of experiments were carried out to select the best support-substrate for laccase production by C. gallica under SSF conditions

Summary

Introduction

Laccases are multicopper oxidases with high potential for environmental and industrial applications. Low-cost laccase production could be achieved by solid state fermentation on agro-industrial by-products. Laccases (p-diphenol: dioxygen oxidoreductases; EC 1.10.3.2) are abundant in white-rot fungi, which are the only organisms able to degrade the whole wood components [1]. Most studies on laccase production by white-rot fungi have been performed in liquid cultures, which do not reflect the natural living conditions of such fungi (wood). In solid-state cultures, white Coriolopsis is assumed to be one of the most efficient lignin degraders -rot fungi grow under conditions close. Daâssi et al Journal of Environmental Health Science & Engineering (2016) 14:1 consumption and reproduces the natural living conditions of the white-rot fungi [4]. Two types of SSF systems can be differentiated depending on the nature of the solid support used. Many studies reported the exploitation of SSF to give an extra value to agro-industrial residues [9, 10] and different reactors for SSF were described [11]

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