(47e) Ethanol Production from Waste Sweet Potato Using Recombinant Zymomonas Mobilis

Abstract: This research focuses on converting waste sweet potatoes that are left in the fields and cannot be marketed for various reasons. Sweet potato collected from a field in one of the family-owned farms in Texas is analyzed for its sugar content using HPLC. The sugars in these sweet potato samples include three major components, sucrose, fructose, and glucose. Based on the fresh biomass, the sucrose, glucose and fructose content is 4.35 ± 0.33%, 2.68 ± 0.64% and 2.21 ± 0.43%, respectively. However, since the dry mass content is only 19.4%, the average sugar content based on the dry biomass is close to 50% Prior to the fermentation, the sweet potato was pretreated and the free sugar was extracted using DI water at different temperatures. The results show that the higher the extracting temperature, the higher the extraction efficiency. recombinant Zymomonas mobilis, 8b and AX101 which are obtained from National Renewable Energy Laboratories, Golden, Colorado. Anaerobic fermentation and aerobic incubation have been evaluated and compared in terms of the ethanol production, at various bacteria loads. The effects of the enzyme ratio, the enzymatic reaction time, and the incubation time have been investigated. The results show that recombinant Z mobilis is capable of converting all sugars effectively. Additional studies are designed to optimize the fermentation conditions, and perform a feasibility study for a small industrial scale plant.