Open Access
Izmirlioglu, Gulten
Graduate Program:
Agricultural and Biological Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Ali Demirci, Thesis Advisor
  • Saccharomyces cerevisiae
  • Waste Potato Mash
  • Ethanol Fermentation
Ethanol is one of the bio-energy sources with high efficiency and low environmental impact. Various raw materials have been used 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 processes. In order to obtain maximum fermentable sugar conversion, optimum parameters for the liquefaction and saccharification processes were determined by Box-Behnken Response Surface Methodology (RSM). The optimum combination of temperature, dose of enzyme (á-amylase), and amount of potato mash was determined as 95°C, 1 ml of á-amylase enzyme solution (944 Units/mg protein), and 4.04 g dry-weight potato mash /100 ml DI water, respectively with a 68.86% loss in dry weight during the liquefaction process. For the saccharification process, dose of enzyme, temperature, and saccharification time were also determined by using Box-Behnken RSM. The optimal of amyloglucosidase combination was 60°C-72 h-0.8 ml (300 Unit/ml) with 34.9 g/L glucose production after scaling up to increase the glucose level to about 100 g/L. The effect of pH, inoculum size, and various nitrogen sources to obtain maximum ethanol from waste potato mash was studied in batch fermentation after. 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 to be 3% for maximum ethanol yield 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 of nitrogen source than yeast extract. In conclusion, this study demonstrated the potential for utilization of potato waste for ethanol production.