Liberation of fermentable sugars from soybean hull biomass using ionic liquid 1‐butyl‐3‐methylimidazolium acetate and their bioconversion to ethanol

Abstract

Optimized hydrolysis of lignocellulosic waste biomass is essential to achieve the liberation of sugars to be used in fermentation process. Ionic liquids (ILs), a new class of solvents, have been tested in the pretreatment of cellulosic materials to improve the subsequent enzymatic hydrolysis of the biomass. Optimized application of ILs on biomass is important to advance the use of this technology. In this research, we investigated the effects of using 1-butyl-3-methylimidazolium acetate ([bmim][Ac]) on the decomposition of soybean hull, an abundant cellulosic industrial waste. Reaction aspects of temperature, incubation time, IL concentration, and solid load were optimized before carrying out the enzymatic hydrolysis of this residue to liberate fermentable glucose. Optimal conditions were found to be 75°C, 165 min incubation time, 57% (mass fraction) of [bmim][Ac], and 12.5% solid loading. Pretreated soybean hull lost its crystallinity, which eased enzymatic hydrolysis, confirmed by Fourier Transform Infrared analysis. The enzymatic hydrolysis of the biomass using an enzyme complex from Penicillium echinulatum liberated 92% of glucose from the cellulose matrix. The hydrolysate was free of any toxic compounds, such as hydroxymethylfurfural and furfural. The obtained hydrolysate was tested for fermentation using Candida shehatae HM 52.2, which was able to convert glucose to ethanol at yields of 0.31. These results suggest the possible use of ILs for the pretreatment of some lignocellulosic waste materials, avoiding the formation of toxic compounds, to be used in second-generation ethanol production and other fermentation processes. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 32:312-320, 2016.

Conversion of rice husk biomass into reducing sugars: influence of pretreatment with water and [C16MIM][Br-] ionic liquid

“…Hemicellulose is a complex polysaccharide, composed predominantly of xylose (pentoses sugars) and other sugars (hexoses). Lignin is a phenylpropanoic complex covalently attached to hemicellulose (Cunha-Pereira et al, 2015;Lopes et al, 2013;Vasheghani et al, 2016). Due to its ordered, rigid and complex structure, the rice husk composition hinders the access of microorganisms and enzymes.…”

“…Several ionic liquids have been described in cellulose dissolution. Some studies evaluated the pretreatment of palm with 1-butyl-3-methylimidazolium chloride ([BMIM][Cl -]) (Tan et al, 2011), of soybean hull with 1-butyl-3-methylimidazolium acetate ([BMIM][Ac]) (Cunha-Pereira et al, 2015), of rice straw and microcrystalline cellulose with 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) (Nguyen et al, 2010;Zhao et al, 2009) and of cedar and beech wood with 1-ethylpyridinium bromide ([EtPy][Br -]) (Yokoo and Miyafuji, 2014). Rice husk pretreatment has been evaluated with different ionic liquids.…”

Treatment and characterization of biomass of soybean and rice hulls using ionic liquids for the liberation of fermentable sugars

“…Some reports have shown the interesting results using ILs for the dissolution of cellulose from wood and other agro-residues (Fort et al 2007, Wei et al 2012, Yoon et al 2012, da Cunha-Pereira et al 2016, Aung et al 2018, Vasheghani Farahani et al 2016, Aid et al 2016. Among the many possible ILs to be used, interesting results have been obtained using imidazoliumbased ILs possessing short side chains, possibly because their reduced viscosity and melting point (Dadi et al 2006, Weerachanchai & Lee 2014.…”

Ionic liquid pretreatment of yellow pine followed by enzymatic hydrolysis and fermentation

“…ILs are composed of an organic cation and an inorganic anion, which are at liquid phase at room temperature or at relatively low temperature. In comparison with classical volatile solvents, ILs possess unique beneficial properties, including negligible vapour pressure, nonflammability, high chemical and thermal stability and a tendency to be present in the liquid phase over a wide temperature range . The risk of exposure is low due to their very low vapour pressure .…”