Abstract

With growing global energy demands and the environmental consequences of fossil fuel dependency, there is a critical need to develop sustainable and renewable energy alternatives. This study aims to optimize the process conditions for bioethanol production from yam (Dioscorea spp.) using acid hydrolysis and fermentation. Fresh yam tubers were processed to extract starch, which was hydrolyzed using sulfuric acid at varying concentrations (0.5M, 1.5M and 2.5M) and neutralized to different pH levels (4.5, 5.5 and 6.5). The hydrolysates were then fermented with Saccharomyces cerevisiae under controlled conditions for durations of 2, 3.5 and 5 days. Ethanol was recovered through distillation and characterized by specific gravity and purity. The results indicated that the highest ethanol yield (10.8mL, 2.7% v/v) was achieved at an acid concentration of 1.5M, pH 5.5 and a fermentation duration of 3.5 days. This optimal yield highlights the critical role of balanced acid concentration and pH in maximizing hydrolysis efficiency and fermentation activity, while prolonged fermentation led to diminishing returns due to inhibitory by-products. These findings align with previous studies, underscoring the efficiency of moderate conditions for bioethanol production. The study concludes that yam starch is a viable feedstock for bioethanol production, provided optimal process parameters are maintained. Further investigations could explore broader parameter ranges and employ modeling techniques to enhance process efficiency and scalability.

Keywords:Bioethanol; Yam (Dioscorea spp.); Fermentation; Renewable energy; Acid hydrolysis