P60: Use of industrial sweet potatoes as a feedstock for biofuel production

With rising fuel costs, there is a critical need for alternative energy sources.  Industrial sweet potatoes (ISP) are a non-food based high starch alternative to corn based ethanol currently used.  ISPs produce approximately 5 times the amount of ethanol per acre compared to corn.  ISPs do not compete for land used for food crops as they can grow in sandy loam soils and are drought resistant.  In addition, unlike potatoes used for food, ISPs can be harvested mechanically, significantly reducing labor costs.  Based on these properties, we undertook a preliminary study to evaluate the utility of ISPs for production of ethanol.  The process included liquefaction and saccharification of the ISPs by alpha-amylase and glucoamylase followed by fermentation using yeast.  Two varieties of ISPs were used for the fermentation, ISP1 and ISP2.  The ISP1 and ISP2 varieties resulted in 26.0 and 54.8 g/L Ethanol at 25h elapsed fermentation time.  The maximum yield coincided with total loss of soluble sugars.  The results indicate that ISPs are a viable feedstock for production of fuels and chemicals from fermentation however, additional work is required to optimize enzyme doses and ethanol yield from fermentation.