**1.2 Pre-treatment of substrates used in SSF process**

#### *1.2.1 Enzymatic liquefaction of starch in SSF process*

It is essential to liquefy the starch as a pretreatment step before using the substrate SSF process. Liquefying enzymes are virtually all α-amylases (α-l, 4-glucane 4-glucanohydroase, E.C. 3.2.1.1) that split α-1,4 bonds in amylose and amylopectin that are basically derived from plants, bacteria and fungi. Liquefying enzymes may be classified as endo-acting enzymes and exo-acting enzymes. The α-1,6 glycosidic bonds are not hydrolyzed by alpha amylase since they are endo-acting enzymes. The enzyme activity of α-amylase is majorly dependent on the type of microorganisms

*Simultaneous Saccharification and Fermentation and Factors Influencing Ethanol Production… DOI: http://dx.doi.org/10.5772/intechopen.86480*

or plants from which it is synthesized. α-Amylases rapidly decrease the viscosity due to its endo-acting nature and is used in simultaneous saccharification and fermentation process for pretreatment.
