**2. Conclusion**

SSF process is found to be a promising technology for industrial ethanol production from cheaper substrates like cellulose and starchy substrates. The success of the SSF process depends mainly on pre-treatment step using suitable enzymes for cellulose hydrolysis and starch hydrolysis. Starchy substrates can be easily liquefied using low cost commercially available alpha amylase enzymes at optimum conditions and can be utilized in SSF process. But the pre-treatment steps in cellulosic materials are more challenging because of the presence of lignin and hemicelluloses. A suitable pre-treatment steps to separate cellulose from naturally occurring lignin and hemicelluloses substrates involves energy intensive process. Furthermore, presence of inhibitory end products from hemicelluloses may hinder the SSF process. SSF process using starch substrates are more promising and also commercial industrial production is feasible in many countries. The advantages of the process are reduction in investment by having single fermenter for both saccharification and fermentation. The feedback inhibition of sugars is greatly reduced. The fermentation time is very less in SSF process.
