A comparative study on normal and high sugary corn genotypes for evaluating enzyme consumption during dry-grind ethanol production H. Zabed a , G. Faruq a , J.N. Sahu b,c , A.N. Boyce a,⇑ , P. Ganesan d a Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia b Petroleum and Chemical Engineering Program Area, Faculty of Engineering, Institut Teknologi Brunei, Tungku Gadong, P.O. Box 2909, Brunei Darussalam c Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia d Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia highlights  Free sugars in corn should be evaluated for cost effective ethanol production.  We compared normal and high sugary corn genotypes (HSGs) for enzyme requirements.  HSGs produced higher amounts of reducing sugars with lower enzyme dose.  HSGs produced higher amounts of ethanol with lower enzyme dose.  HSGs could be viable feedstocks for the dry-grind ethanol production. graphical abstract article info Article history: Received 17 July 2015 Received in revised form 21 November 2015 Accepted 25 November 2015 Available online 28 November 2015 Keywords: Sugary corn Bioethanol Starch hydrolyzing enzyme Fermentable sugar Granular starch hydrolysis Ethanol fermentation abstract The necessity of amylolytic enzymes to convert starch into glucose during ethanol production is consid- ered one of the cost increasing factors for corn ethanol. Enzyme consumption could be decreased partially by increasing free sugar contents in corn kernels that will be released and fermented simultaneously with the product of starch hydrolysis, producing an additional amount of ethanol without consuming any enzyme. The present work was conducted to evaluate the effects of grain sugar on the fermentable sugar and ethanol yields as well as enzyme requirement using four high sugary corn genotypes (HSGs) and their parent field corn lines (PFCs). The reducing sugar yield in HSGs did not vary significantly above the enzyme load of 1.5 kg/MT of dry corn, while PFCs showed a range between 2.0 and 2.5 kg/MT. The average final ethanol concentrations in HSGs and PFCs ranged from 15.25% to 17.5% (v/v) and 11.66% to 13.65%, respectively with the enzyme load at 1.5 kg/MT, which reached to 16.49–17.94% in HSGs and 14.32–16.85% in PFCs as the enzyme load increased to 2.0 kg/MT. These results suggest that high sugar content in corn kernels has the potential for decreasing enzyme consumption during dry-grind ethanol production with higher yields. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction The growing concerns on energy security, declining in oil reserves, unstable prices of fossil fuels and global warming have boosted the demand for producing bioethanol as an alternative fuel. Three types of raw materials are being used in current bioethanol research, such as sugar crops, starchy crops and lignocellulosic biomass, which differ considerably from each other http://dx.doi.org/10.1016/j.cej.2015.11.082 1385-8947/Ó 2015 Elsevier B.V. All rights reserved. Abbreviations: CFU, colony forming unit; GSH, granular starch hydrolysis; GSHE, granular starch hydrolyzing enzyme; GSHSF, granular starch hydrolysis and simultaneous fermentation; HSGs, high sugary corn genotypes; PFCs, parent field corn lines; RS, reducing sugars; TSS, total soluble sugars. ⇑ Corresponding author. Tel.: +60 379674381. E-mail addresses: zabedctgbd@yahoo.com (H. Zabed), faruqwrc@gmail.com (G. Faruq), jay_sahu@yahoo.co.in (J.N. Sahu), amru@um.edu.my (A.N. Boyce), poo_ganesan@um.edu.my (P. Ganesan). Chemical Engineering Journal 287 (2016) 691–703 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej