1. Introduction
Ethanol production from lignocellulosic biomass has become increasingly vital in this century due to the increasing fuel demand, decreasing fossil fuel reserves, environmental concerns and national energy security (Roman-Leshkov et al., 2007). Currently, ethanol produced from lignocellulosic biomass is considered as the most feasible replacement of fossil fuels for transportation (Kuhad et al., 2011). Because maize and sugar cane have been primary feedstock for ethanol production in the United States and Brazil, respectively, there is some concern of a negative impact on food supply, especially when there is limited fertile land and water available to meet the demands for food, feed and energy production (Valentine et al., 2012).