Abstract: In this era fossil fuel like coal, oil and natural gas are playing a major role and being the primary source of energy. It is expected to deplete within next 50 years. So scientists are in the urge of finding an alternative source of energy like electrically driven car, petrol from plastic, changing sea water to usable source of energy and bioethanol or biofuel production from renewable products. This article is based on the comparative study on the production of bioethanol from various raw materials like sugar, starch, cellulose and algal biomass. Basic four steps being followed in the process of bioethanol production. They are pretreatment, hydrolysis, fermentation and recovery. All these biomass used for bioethanol production are sugary material made of simple or complex saccharide compound. They are pretreated to get rid of any foreign particles and are hydrolyzed to breakdown the complex polysaccharide. In all these bioethanol production process, yeast plays a vital role and is preferred widely as they are commercially and easily available product. And bacterial species like Zymomonas mobilis is also potentially used now days. Various factors influence the process of formation of ethanol and these factors are needed to be optimized for efficient ethanol production.

Keywords: Bioethanol, hydrolysis, pretreatment, fermentation, biomass, sugar, enzyme, yeast, temperature, pH.

| DOI: 10.17148/IARJSET.2021.8420