An overview of simultaneous saccharification and fermentation of starchy and lignocellulosic biomass for bio-ethanol production

For the last few decades, fossil fuels have played a dominant role as an important energy resource in the enormous worldwide energy demand. However, as conventional fossil fuel resources are limited, excessive exploitation of such fossil fuel comes with the major global problem of energy resource scarcity. Thus, renewable sources of energy, such as solar, wind, and biofuel, have gained huge attention from governments of many countries across the world. These renewable resources are indigenous, non-polluting and virtually inexhaustible. Among these alternate energy sources, bio-ethanol was proved to be a most promising energy source with various added advantages. Conventional indigenous raw materials for bio-ethanol production include sugarcane, molasses and corn-based materials, although the amount of bio-ethanol produced can hardly meet the current global demand. An extensive search for the most promising feedstock for ethanol production pioneered the use of ligno- and starch-based biomass. For successful conversion of starch and lignocellulosic material to bio-ethanol, a microbial single stage simultaneous saccharification and fermentation (SSF) approach has successfully evolved in recent years, overcoming the problems associated with using harmful chemicals and an expensive enzymes stage, the substrate inhibition effects and the reaction time. In this review, multiple aspects of the SSF process will be highlighted.