Authors:

Abstract

The ever-increasing population of the world, extended urbanization/industrialization in developing countries, improvements in quality of life, and increasing oil prices have accelerated the need for sustainable energy sources. Among different alternatives, biofuels in general and bioethanol in particular are promising sustainable and eco-friendly energy sources. However, cheap feedstocks and new production technologies are required to make bioethanol economically comparable with traditional fossil fuels. An efficient, cost-effective, and promising technology is solid-state fermentation (SSF) in which microorganisms grow on the surface of solid materials in the absence of free water resulting in elimination of sugar extraction process and less wastewater production, which in turn yields lower distillation and purification costs. Furthermore, SSF is a well-established technology for production of different enzymes. This potential of SSF makes it an appropriate process for enzymatic pretreatment and hydrolysis of substrates and subsequent bioethanol production. This review gives an overview of the applications of SSF in every step of bioethanol production; compares its efficiency and feasibility with the submerged fermentation process; and for brevity of exposition, highlights the great promise of this technology for sustainable and cost-effective bioethanol production.