Combination of ammonia and xylanase pretreatments: Impact on enzymatic xylan and cellulose recovery from wheat straw C. Rémond a,b, * , N. Aubry a,b , D. Crônier a,b , S. Noël c , F. Martel c , B. Roge a,b , H. Rakotoarivonina a,b , P. Debeire a,b , B. Chabbert a,b a INRA, UMR 614, Fractionnement des AgroRessources et Environnement, F-51686 Reims, France b University of Reims Champagne Ardenne, UMR 614, Fractionnement des AgroRessources et Environnement, F-51686 Reims, France c ARD, Agroindustrie Recherches et Développements, route de Bazancourt, F-51110 Pomacle, France article info Article history: Received 28 November 2009 Received in revised form 19 March 2010 Accepted 23 March 2010 Keywords: Wheat straw Pretreatment Ammonia Xylanase Cellulases abstract Soaking in aqueous ammonia (SSA) and/or xylanase pretreatments were developed on wheat straw. Both pretreatments were conducted at high-solids conditions: 15% and 20%, respectively, for SSA and xylanase pretreatments. SSA pretreament led to the solubilisation of 38%, 12% and 11% of acid insoluble lignin, xylan and glucan, respectively. In case of xylanase pretreatment, 20% of xylan were removed from native wheat straw. When pretreatments were applied consecutively (SSA and xylanase) on straw, 56% of xylans were hydrolysed and a rapid reduction of media viscosity occurred. The enzymatic hydrolysis of cellulose with cellulases was evaluated from the different combinations of pretreated wheat straw. Cellulose hydrolysis was improved by 2.1, 2.2 and 2.9, respectively, for xylanase, SSA and SSA/xylanase pretreated straw. Xylans from untreated and pretreated wheat straws were also solubilised with cellulases. Chem- ical analysis of pretreated straw residues in connection with yields of cellulose hydrolysis highlighted the role of phenolic acids, acetyl content and cellulose crystallinity for cellulase efficiency. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Being abundant and renewable, lignocellulose is an attractive energy feedstock for the production of bioethanol. Many lignocel- lulosic species, as crop residues, hardwood and softwood, herba- ceous plants, cellulosic and municipal wastes, have been tested for the production of ethanol. Among various sources of lignocellu- lose, wheat straw is a widespread available and cheap raw mate- rial, notably in Europe. Wheat straw is produced in large quantities as by-product of the milling industry. Although various process configurations are possible, techno- logical outline developed for the production of ethanol from ligno- cellulose require three steps involving pretreatment of biomass, enzymatic hydrolysis of polysaccharides into monomeric sugars and their further fermentation. Chemical and structural complexities of lignocellulosic biomass represent a challenge for biocatalysts. A pretreatment step is usu- ally conducted to reduce recalcitrance of biomass by breaking down the macroscopic rigidity of biomass, removing part of hemi- celluloses and lignin, improving accessibility for cellulases and diminishing crystallinity of cellulose. Pretreatment strategies cate- gorized into physical and chemical or combining both improve enzymatic hydrolysis yields of cellulose. An effective pretreatment technology should respond to various criteria as preserving poly- saccharides, limiting production of degradation products from sug- ars and lignin, resulting in high enzymatic recovery of cellulose, and being low costly and low energetically consuming. Drastic pre- treatments combining high temperature and extreme pH (acid or alkali) require adapted costly equipments and are energetically consuming (Eggeman and Elander, 2005). Furthermore, acid pre- treatments in conjunction with high temperatures commonly con- duct to a loss of polysaccharides and generate weak acids, furfural and 5-hydroxyfurfural which negatively impact microorganisms involved in the fermentation step (Palmqvist and Hahn-Hagerdal, 2000). Alkali based pretreatments represent alternative methodol- ogies to restrain the formation of these inhibitory molecules. Among well-established technologies, ammonia-based pretreat- ments allow to retain most part of cellulose and hemicellulose con- tents into biomass while removing an important part of lignin and altering its structure, decrystalizing cellulose and increasing sur- face accessibility (Mosier et al., 2005; Wyman et al., 2005). Economical feasibility for production of bioethanol from ligno- cellulose represents a technological challenge. Currently, cellulosic ethanol production at industrial level remains still too costly (Egg- eman and Elander, 2005; Zhang, 2008). Hence, the development of 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.03.115 * Corresponding author at: University of Reims Champagne Ardenne, UMR 614, Fractionnement des AgroRessources et Environnement, F-51686 Reims, France. Tel.: +33 3 26 35 53 63; fax: +33 3 26 35 53 69. E-mail address: caroline.remond@univ-reims.fr (C. Rémond). Bioresource Technology 101 (2010) 6712–6717 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech