Ethanol production from waste potato mash by using Saccharomyces cerevisiae

Ethanol is one of the bio-energy sources with high efficiency and low environmental impact. Various raw materials have been using as carbon sources for ethanol production. In this study, waste potato mash was chosen as a carbon source; however, a pretreatment process is needed to convert starch of potato to fermentable carbon sources through liquefaction and saccharification process. Then, the effect of pH, inoculum size and various nitrogen sources to obtain maximum ethanol from waste potato mash was studied. The maximum ethanol concentration and production rates were 27.7 g/L and 5.47 g/L/h, respectively, at controlled pH 5.5, whereas 22.75 g/L and 2.22 g/L/h were obtained at uncontrolled pH. Optimum inoculum size was determined as 3% for maximum ethanol concentration and production rate. Furthermore, five different nitrogen sources (yeast extract, poultry meal, hull and fines mix, feather meal, and meat and bone meal) were evaluated to determine an economical alternative nitrogen source to yeast extract. In conclusion, this study demonstrated the potential for utilization of potato waste for ethanol production.