Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Case Study Multi-step approach to add value to corncob: Production of biomass- degrading enzymes, lignin and fermentable sugars Michele Michelin a, ⁎ , Héctor A. Ruiz b,c , Maria de Lourdes T.M. Polizeli d , José A. Teixeira a a CEB – Centre of Biological Engineering, University of Minho, Campus Gualtar, 4710-057 Braga, Portugal b Biorefinery Group, Food Research Department, Faculty of Chemistry Sciences, Autonomous University of Coahuila, 25280 Saltillo, Coahuila, Mexico c Cluster of Bioalcohols, Mexican Centre for Innovation in Bioenergy (Cemie-Bio), Mexico d Department of Biology, School of Philosophy, Sciences and Literature of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP 14040-901, Brazil ARTICLE INFO Keywords: Autohydrolysis Enzymes Saccharification Aspergillus niger Trichoderma reesei ABSTRACT This work presents an integrated and multi-step approach for the recovery and/or application of the lig- nocellulosic fractions from corncob in the production of high value added compounds as xylo-oligosaccharides, enzymes, fermentable sugars, and lignin in terms of biorefinery concept. For that, liquid hot water followed by enzymatic hydrolysis were used. Liquid hot water was performed using different residence times (10–50 min) and holding temperature (180–200 °C), corresponding to severities (log(R 0 )) of 3.36–4.64. The most severe conditions showed higher xylo-oligosaccharides extraction (maximum of 93%) into the hydrolysates and higher recovery of cellulose on pretreated solids (maximum of 65%). Subsequently, hydrolysates and solids were used in the production of xylanases and cellulases, respectively, as well as, pretreated solids were also subjected to enzymatic hydrolysis for the recovery of lignin and fermentable sugars from cellulose. Maximum glucose yield (100%) was achieved for solids pretreated at log(R 0 ) of 4.42 and 5% solid loading. 1. Introduction The harvested production of cereals in the EU-28 was around 317 million tonnes in 2015. This represented about 12.5% of global cereal production (FAO, 2016). Common wheat and spelt, barley, grain maize and corn-cob-mix accounted for a high share (86% in 2015) of the cereals produced in the EU-28 (EUROSTAT, 2017). These harvests generate a large amount of lignocellulosic residues that mainly consist of cellulose (30%–50%), hemicellulose (15%–35%) and lignin (10%–20%) that are linked with each other (Michelin et al., 2015). These lignocellulosic materials (LCM) are organized in a complex matrix that needs to be broken in order to isolate the lignocellulosic components. Biomass-degrading enzymes act on hydrolysis of the polymeric cellulose or hemicellulose into oligosaccharides and after in sugars, which can be fermented by microorganisms, or used as building blocks, for synthesis of fuel or chemicals. In general, these enzymes, i.e. cellulases and hemicellulases, consist of an enzymatic complex that works synergically to hydrolyze the different regions of cellulose and hemicellulose on lignocellulose, according to their specificity (Sweeney and Xu, 2012). The enzymatic hydrolysis of cellulose has been shown to improve significantly with the removal of hemicellulose, suggesting that hemicellulose acts as a barrier to the hydrolysis of cellulose by cellu- lolytic enzymes (Yang et al., 2011). Thus, the pretreatment of LCM before hydrolysis is a prerequisite and it can be performed by different methods. Liquid hot water (LHW) pretreatment or autohydrolysis (hy- drothermal processing) allows a high recovery of hemicelluloses as soluble saccharides, while both cellulose and lignin could be recovered in the solid phase as essentially non-degraded polymers. Furthermore, it has many technological and environmental benefits, mainly related to its non-catalyzed nature, as well as limited equipment corrosion pro- blems, reduction of operational costs, and lower byproducts generation, such as furfural and hydroxymethylfurfural (Michelin et al., 2015; Michelin and Teixeira, 2016). This work uses LHW pretreatment, enzymatic saccharification and fungal fermentation to convert corncob residues into valuable products in terms of biorefinery. For that, xylanases (endoxylanase and β-xylo- sidase) and cellulases (FP activity, β-glucosidase) were produced through the fungal fermentation using the hemicellulose hydrolysates and the solid fraction (rich in cellulose), respectively, obtained from LHW pretreatment. The use of pretreated lignocellulosic residues is an important strategy to improve the enzymatic production and to com- pete with commercial substrates, because of the lower production cost of the enzymes associated with these residues. Moreover, a step of http://dx.doi.org/10.1016/j.biortech.2017.09.128 Received 11 July 2017; Received in revised form 16 September 2017; Accepted 18 September 2017 ⁎ Corresponding author. E-mail address: mimichelin.bio@gmail.com (M. Michelin). Bioresource Technology 247 (2018) 582–590 Available online 20 September 2017 0960-8524/ © 2017 Elsevier Ltd. All rights reserved. MARK