Solid-State Fermentation from Dried Sweet Sorghum Stalk for Bioethanol Production

Abstract

Due to depletion of global crude oil, countries are interested to alternate fuel energy resources. Presently bioethanol as a source of energy has been a subject of great interest for the industrialized countries. Therefore, there is a need for efficient bioethanol production with low cost raw material and production process. Among energy crops, sweet sorghum is the best candidate for bioethanol production. It has been identified as having higher drought tolerance, lower input cost and higher biomass yield than other energy crops. In addition it has a wide adaptability and tolerance to abiotic stresses. Water requirement of sweet sorghum is one third of sugarcane and one half of corn that are currently used for bioethanol production. Moreover due to the shortage of water in dry and hot countries, there is a need to reduce water requirements for bioethanol production and solid state fermentation could be the best process for making bioethanol in these countries. The purpose of this study was to achieve the highest ethanol yield with lowest amount of water in solid state fermentation using dry sweet sorghum stalks. Fermentation medium were: dry sweet sorghum powder with nutrient media, active yeast powder and different moisture contents. The fermentation medium was incubated for 48 to 96 hr.at 35 ºC temperature. The results showed sweet sorghum powder (15% w/w) fermented in medium containing 0.5% yeast inoculums, 60% moisture content and 72 hr. incubation period produced the highest ethanol yield of 12.16% w/w dry sweet sorghum powder.