The environmental crisis and the shortage of fossil fuels have turned public attention to the utilization of other forms of energy, which are environmentally friendly and renewable, such as bio-ethanol [1,2]. During recent years research has focused on the so-called second-generation biofuels, where wastes or by-products are utilized as raw material, compared to the first-generation biofuels where sugars and starch were utilized. This way, increasing pubic concerns about utilizing food sources for the production of biofuels can be solved, as the utilization of either sugars or corn for the production of biofuels have contributed to the increase of their price

worldwide, resulting in severe problems for the poorer countries. All these concerns led to a rapid increase in research to utilize low-cost by-products and wastes as raw material [3-6]. Lignocellulosic biomass represents great potential to be utilized as raw material due to the high amounts produced every year [7], and can be derived from woody or agricultural residues such as wheat straw, corn cobs, bagasse, rice straw, et cetera. The main challenge of utilizing lignocellulosic biomass is efficient sugar release, mainly from cellulose. In order to achieve this, an efficient pretreatment step followed by enzymatic hydrolysis have to be applied [8,9]. Generally, the pretreatment process contributes to increased costs of the whole process [10].