Pretreatment of Guinea grass (Panicum maximum) with the ionic liquid 1-ethyl-3-methyl imidazolium acetate for efficient hydrolysis and bioethanol production

Abstract

In the present study, we pretreated the plant Guinea grass (Panicum maximum) with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] to expose its cellulose fibers. For this, we first determined the composition of Guinea grass, with 6.87 ± 1.21% of ash, 14.33 ± 1.18% of lignin, 70.55 ± 1.15% of holocellulose, 29.9 ± 1.20% of cellulose, and 40.65 ± 1.20% of hemicellulose. After characterizing the material, we determined the IL pretreatment conditions that maximized the enzymatic and acid hydrolysis stages [namely: temperature = 157 °C, reaction time = 30 min, and biomass concentration (relative to total mass) = 14%]. Under these conditions, the enzymatic hydrolysis conversions of glucose and total reducing sugars were respectively 69.8 and 54.2%, determined by enzymatic and DNS methods. The acid hydrolysis was also carried out, and conversions of 57.4 and 27.2% were verified by the enzymatic and DNS methods, respectively. Finally, the hydrolysate obtained after the enzymatic hydrolysis was fermented by the yeast Saccharomyces cerevisiae, and the ethanol yield (81.9%) was determined through gas chromatography.