Sustainable Utilization of Agricultural Sugar Substrates for Bioethanol Production

Abstract

Optimization of fermentation conditions is essential for the sustainable conversion of agricultural sugar resources into bioethanol. In this study, the effects of pH and urea concentration on ethanol production from two agro-derived substrates, molasses and date juice, were evaluated using Saccharomyces cerevisiae over a 9-day fermentation period. Fermentation was conducted at pH levels ranging from 3.5 to 5.5 and urea concentrations of 0.25–1.0% (w/v), with ethanol concentration monitored daily. The highest ethanol yields were obtained at pH 4.5, reaching 9.4% (v/v) for molasses and 9.3% (v/v) for date juice, followed by pH 4.0. Two-way ANOVA revealed significant effects of substrate type and fermentation duration (p < 0.001), while their interaction was not significant. Urea supplementation at 0.5% (w/v) resulted in maximum ethanol production (10.0% (v/v) for molasses and 9.6% (v/v) for date juice), whereas higher concentrations did not enhance yields and, in some cases, reduced final ethanol levels. Ethanol production increased rapidly during the first 5–6 days and subsequently plateaued. These findings demonstrate that optimizing pH and nitrogen input can enhance bioethanol production from agricultural sugar substrates, supporting sustainable waste valorization and efficient bioenergy generation within agricultural systems.