**3. Pretreatment**

Lignin is a recalcitrant component of the lignocellulosic biomass. Resistance to chemical and enzymatic attack increases with increase in lignin content [32]. Lignin the natural cement, acts as a ceiling for microbial/enzymatic attack. Hence, it is one of the major hurdles in using lingo-cellulosic materials in fermentation. Pretreatment is one of the most important steps in the process of converting renewable lignocellulosic biomass into useful products. The main target of any pretreatment is to alter or remove structural and compositional resistant to hydrolysis which further enhance digestibility of biomass [33]. It exposes cellulose and hemicellulose chains by breaking the crystalline matrix (**Figure 5**). To remove the obstacles for enzymatic scarification of lignocellulosic material following pretreatment used.
