Contents lists available at ScienceDirect Biomass and Bioenergy journal homepage: www.elsevier.com/locate/biombioe Short communication Influence of white-rot fungus Polyporus brumalis BRFM 985 culture conditions on the pretreatment efficiency for anaerobic digestion of wheat straw Elsa Rouches a , Simeng Zhou b , Michelle Sergent c , Sana Raouche b , Helene Carrere a,* a LBE, Univ Montpellier, INRA, 102 Avenue des Etangs, 11100 Narbonne, France b Aix Marseille Univ, INRA, BBF, Biodiversité et Biotechnologie Fongiques, Marseille, France c Aix Marseille Univ, LISA EA4672, Campus scientifique de Saint Jérôme, 13397, Marseille, France ARTICLE INFO Keywords: Biogas Fungal pretreatment Lignocellulosic biomass Solid state fermentation Surface response methodology ABSTRACT For the first time, Polyporus brumalis BRFM985 was cultivated on wheat straw to investigate the simultaneous effects of pretreatment parameters on anaerobic digestion: these include initial substrate humidity, temperature, duration, and metal supplementation. Surface response methodology was applied to quantify the importance of each parameter, as well as the synergistic effects between them. Firstly, metal addition and secondly, pre- treatment duration, both resulted in a positive impact. According to calculations, the highest methane pro- duction (182 dm 3 of methane per kilogram of initial Total Solids) is associated to pretreatment with metal addition during 20 days. In comparison with the least optimal conditions (118 dm 3 .kg -1 without metal addition, during 15 days), this result implies a 52% increase. 1. Introduction Despite the advantages that biogas production from crop residues may display [1], its economic competitiveness still needs to be im- proved, notably by applying low-cost pretreatments. The main objec- tive of these pretreatments implies lignin degradation, which enhances methane production during anaerobic digestion. Even though diverse pretreatments have shown to be efficient at laboratory scales, their industrial applications are often restricted by excessive costs. In- vestigations on white-rot fungi pretreatments for anaerobic digestion are still scarce, but they have pointed to this procedure as efficient, low- cost and environmentally-friendly [2,3]. After an initial screening step [4], the Polyporus brumalis_BRFM 985 strain was found to be efficient in the pretreatment of wheat straw for anaerobic digestion [5]. Fungal pretreatment efficiency not only de- pends on the substrate and fungal strain, but also on the culture con- ditions [2,3]. For example the pretreatment of wheat straw by Polyporus brumalis-BRFM 985 for ethanol production was investigated by Zhou and al [6]. Depending on fungal pretreatment parameters, the authors observed net cellulose enzymatic hydrolysis yields ranging between 28% and 132% relative to the control value (without fungal pretreat- ment). Studies investigating fungal pretreatment parameters generally evaluate the efficiency by measuring cellulose hydrolysis or lignin losses [3]. This is, however, not sufficient for their impact on anaerobic digestion to be assessed. Indeed, the hydrolysis of hemicelluloses by an efficient hemicellulase cocktail must also be taken into account. Fungal biomass can also be converted into biogas. Moreover, the evaluation of pretreatment efficiency most often does not account for mass losses. Inadequate pretreatment conditions can lead to a decrease in methane production. In general, pretreatments for anaerobic digestion have been performed under fixed culture conditions, either on several fungal strains with a specific lignocellulosic substrate or with a specific strain on several lignocellulosic substrates [2]. Very few studies have in- vestigated process parameters such as moisture content [7,8] or dura- tion [9]. Consequently, the optimization of fungal pretreatment para- meters for methane production still requires further research efforts. A concomitant investigation of process parameters could lead to the identification of potential synergy effects and to the classification of their order of significance for methane production. In the present study, Surface Response Methodology was applied to investigate the influence of culture parameters on P. brumalis_BRFM 985 pretreatment efficiency for enhancing biogas production from wheat straw anaerobic digestion. https://doi.org/10.1016/j.biombioe.2018.01.018 Received 24 October 2017; Received in revised form 23 January 2018; Accepted 23 January 2018 * Corresponding author. E-mail address: helene.carrere@inra.fr (H. Carrere). Abbreviations: BRFM, Bank of Fungal Resources of Marseille; CIRM, International Center of Microbial Resources; RSM, Response Surface Methodology; TS, Total Solids; WRF, White-Rot Fungi; WW, Wet Weight Biomass and Bioenergy 110 (2018) 75–79 0961-9534/ © 2018 Elsevier Ltd. All rights reserved. T