Abstract
Bioethanol can be produced from any biomass that contains sugars or starch which are
lignocellulosic and do not compete with food crops. This study demonstrated the effectiveness of
sodium hydroxide (NaOH) pretreatment followed by enzymatic hydrolysis by comparing enzymes from
Penicillium and Aspergillus flavus to convert rice husk (RH) into fermentable sugars and bioethanol.
Rice husk, a lignocellulosic biomass, was subjected to NaOH pretreatment at concentrations
of 3.3%, 5%, 6.67%, 8.33%, and 10% w/v. Two different enzymes, Penicillium and Aspergillus
flavus, were compared for enzymatic hydrolysis to break down cellulose and hemicellulose into
fermentable sugars. The hydrolysates were subsequently fermented using Saccharomyces
cerevisiae to produce bioethanol. The results revealed that increasing NaOH concentration
significantly enhanced the breakdown of the lignocellulosic structure, leading to higher sugar
yields. The maximum sugar content recorded was 21.6 °Brix for Aspergillus flavus and 16.0
°Brix for Penicillium at 10% w/v NaOH. Also, the ethanol yield increased with higher NaOH
concentrations, reaching a peak of 40.95% for Penicillium and 34.35% for Aspergillus flavus
at 10% w/v NaOH. Fourier-transform infrared (FTIR) spectroscopy confirmed the presence of
ethanol in the distilled samples, and the confirmatory potassium dichromate test verified the
successful production of bioethanol.