Bioethanol production from Quercus aegilops using Pichia stipitis and Kluyveromyces marxianus

Abstract

Biofuel derived from lignocellulosic biomasses recently emerged as one of the most suitable environmental friendly substrates that cannot only lead the renewable energy, but also minimizing the emission of greenhouse gases. Lignocellulosic materials are considered to be the major components as of yet unexploited source of for bioethanol production. The main aim of the current works was to discover the optimal bioethanol production from a local wild plants biomass Quercus aegilops, which are very common in Kurdistan region, Iraq. Pretreatment with different sulfuric acid concentrations at varied reaction times and temperatures was used. Three-step conversion process, separate hydrolysis, and fermentation (SHF) were used to evaluate the conversion of both cellulose and hemicellulose to monomeric sugars, and ethanol production. The results showed that the maximum yields of glucose and xylose were 5.7 g L⁻¹ and 21.1 g L⁻¹, respectively, when the biomass pretreated with 15% total solid, 2% acid concentrations at 120 °C for 120 min. During 48 h of enzymatic hydrolysis, the maximum glucose and xylose concentrations were 5.97 g L⁻¹ and 17.53 g L⁻¹, respectively, showing a conversion rate of 21.8% and 80.1% for the corresponding sugars. The highest ethanol yield of 6.01 g L⁻¹ at 96 h fermentation with the productivity of 0.049 g L⁻¹ h⁻¹ was obtained when fermentation carried out with Pichia Stipitis yeast strain, while the maximum ethanol concentration and ethanol yield the productivity of 6.93 g L⁻¹ and of 0.242 g L⁻¹ h⁻¹, respectively, were obtained during 24 h of fermentation by Kluyveromyces marxianus yeast strain. From the outcomes, it was obvious that K. marxianus was the favored yeast strain to be used for the generation of bioethanol from leaves of Q. aegilops, and Q. aegilops has potential to be exploited as a native, abundant raw material for the production of ethanol.