Enzymatic and Dilute Acid Hydrolyses of Maize Stalk Substrate in Bio-ethanol Production

Abstract

Biofuels have been identified as suitable in combating climate change as a result of green gas emissions from fossil fuels. Bioethanol is a biofuel from lignocellulosic biomass is considered a viable renewable energy alternative to fossil fuels. However, the recalcitrance of biomass feedstocks due to the presence of lignin, creates a barrier to glucose fermentation. This study compares enzymatic and dilute acid hydrolyses of cellulose substrates obtained from pretreated maize stalk. The cellulose substrates were hydrolysed into glucose using dilute H2SO4, dilute HCl and Cellulase enzyme. The glucose obtained was fermented using an active yeast strain (Saccaromyces cerevisae) and then distilled in accordance with ASTM D1078 to obtain bio-ethanol. High Performance Liquid Chromatography (HPLC) was used in quantitative analyses of the bio-ethanol produced while qualitative tests were done based on ASTM D7795-12 for physical tests (density, boiling point, miscibility, non-volatile residues, colour, flammability and distillation range) and chemical tests (Acidity, Alkalinity, Fusel oil, Readily carbonizable substances and readily oxidizable substances). Enzymatic hydrolysis gave a higher glucose yield, while there was no significant difference between hydrolysis using dilute acids. There was significant difference in extraction efficiencies between acid and enzymatic hydrolysis methods. The bio-ethanol produced has similar purity levels with qualitative properties to that of an industrial grade ethanol.