As the world population and industrialization are increasing, the demand for energy is also increasing. Therefore, the cost of coal, natural gas, and crude oil is increasing. Thus the uncertainty of the fossil fuel and global climate changes have led to renewable energy development. Among biofuels biodiesel, biogas and bioethanol are dominant renewable energy. In the transportation sector, bioethanol is the most commonly used biofuel. Several substrates have been used for ethanol production such as lignocelluloses, starch, and different wastes. Lignocellulosic biomass (LCB) is more preferred for ethanol production because of the two major reasons:it does not compete with food,it takes care of plant and agricultural residues in environmentally sustainable process .
Due to high processing cost, cellulosic ethanol production at industrial level is still a challenge. The major reason for the high cost is the consumption of high steam energy for distillation of fermentation broth with the low ethanol titer when LCB is used as feedstock. Higher feedstock price is the second reason for the high cost of ethanol production. Ethanol titer can be upgraded by different pretreatment methods that increase cellulosic content in fermentation system and hence reduces the cost.