A novel staggered hybrid SSF approach for efficient conversion of cellulose/hemicellulosic fractions of corncob into ethanol K.K. Brar a, b , Satindar Kaur b , B.S. Chadha a, * a Department of Microbiology, Guru Nanak Dev University, Amritsar, Punjab 143005, India b Department of Food Science & Technology, Guru Nanak Dev University, Amritsar, Punjab 143005, India article info Article history: Received 29 December 2015 Received in revised form 22 March 2016 Accepted 24 March 2016 Available online xxx Keywords: H 2 SO 4 pretreatment Corncob residue Enzymatic hydrolysis Saccharification Cellic CTec2 Malbranchea cinnamomea abstract The following study reports bioconversion of corncob into ethanol using hybrid approach for co- utilization of dilute acid hydrolysate (pentose rich stream) and hexose rich stream obtained by enzy- matic saccharification employing commercial cellulase Cellic CTec2 as well as in-house cellulase prep- arations derived from Malbranchea cinnamomea, Scytalidium thermophilium and a recombinant Aspergillus strain. Acid hydrolysis (1% H 2 SO 4 ) of corncob at 1:15 solid liquid ratio led to removal of 80.5% of hemicellulosic fraction. The solid glucan rich fraction (63.5% glucan, 8.3% pentosans and 27.9% lignin) was hydrolysed at 10% substrate loading rate with different enzymes for 72 h at 50  C resulting in release of 732 and 535 (mg/g substrate) total sugars by Cellic CTec2 and M. cinnamomea derived enzymes, respectively. The fermentation of enzyme hydrolysate with co-culture of Saccharomyces cerevisiae and Pichia stipitis added in sequential manner resulted in 3.42 and 2.50% (v/v) ethanol in hydrolysate ob- tained from commercial Cellic CTec2 and M. cinnamomea, respectively. Employing a hybrid approach, where dilute acid hydrolysate stream was added to solid residue along with enzyme Cellic CTec2 during staggered simultaneous saccharification and fermentation at substrate loading rate of 15% resulted in 252 g ethanol/kg corncob. © 2016 Published by Elsevier Ltd. 1. Introduction Corncob, by product in corn (maize) production, is energy dense agro-waste with high xylose content, when compared to corn stover [1] is suitable lignocellulosic substrate for developing bioconversion technology. However, only limited reports on its bioconversion are available [2]. Selection of efficient pretreatment technology followed by enzymatic saccharification for achieving high sugars yield is the key to successful conversion of lignocellu- losic biomass into ethanol [3,4]. However, the energy intensive pretreatment and cost of enzyme are considered to be the major constraints in commercial viability of this process. The literature and patent search suggest that few robust pretreatment technolo- gies based on thermochemical/steam explosion for disintegration and separation of cellulose fibres from the intricate lignocellulosics complex are available and subsequent conversion of cellulosic fraction into monomeric sugars [3,5]. A few studies have also reported the use of dilute inorganic acids for pretreatment in conjunction with steam explosion but at relative lower tempera- tures thus making process energy efficient. During acid mediated pretreatment most of the hemicelulosic fraction is recovered as xylose rich stream leaving most of the cellulose intact for cellulase based hydrolysis [6]. The method of pretreatment affects attributes like adsorption behavior of enzymes [7] as well as results in increased crystalinity and recalcitrance of cellulose to cellulase mediated hydrolysis requiring higher enzyme loading rates to achieve efficient hydrolysis. Generally commercial cellulase prep- arations derived from Trichoderma reesei are used for hydrolysis, however, these are costly. In light of this it is very important that catalytically efficient indigenous enzyme producing strains are identified and evaluated. Therefore, the enzymatic hydrolysis po- tential of cellulase/hemicellulases derived from indigenous strains Malbranchea cinnamomea (CM-10T), Scytalidium thermophilium (CM-8T) and Aspergillus strain (AN-64) were evaluated and compared to the commercial cellulase preparation Cellic CTec2 (Novozyme). Furthermore methods for co-utilization of pentose rich stream recovered during dilute acid hydrolysis for effective bioconversion of both C6 and C5 sugars into ethanol using glucose * Corresponding author. E-mail addresses: kamalbrarmft@gmail.com (K.K. Brar), satindar_gndu@yahoo. com (S. Kaur), chadhabs@yahoo.com (B.S. Chadha). Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene http://dx.doi.org/10.1016/j.renene.2016.03.082 0960-1481/© 2016 Published by Elsevier Ltd. Renewable Energy xxx (2016) 1e7 Please cite this article in press as: K.K. Brar, et al., A novel staggered hybrid SSF approach for efficient conversion of cellulose/hemicellulosic fractions of corncob into ethanol, Renewable Energy (2016), http://dx.doi.org/10.1016/j.renene.2016.03.082