Abstract
Rice straw (RS) is a promising feedstock for transformation into biofuels and bioproducts due to its high sugar content and worldwide availability. However, a pretreatment step is necessary in order to disrupt the RS complex lignocellulosic matrix. The aim of this work was to study RS pretreatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) to maximize the enzymatic hydrolysis yield. For this purpose, a response surface method (RSM) based on a central composite design (CCD) was used, with temperature (53–137 °C), time (0.3–6.2 h), and solid loading (3.3–11.7% dry weight) as process variables. The analysis of variance (ANOVA) results suggested that temperature was the most significant factor affecting the fermentable sugar yield of [Emim][OAc]-pretreated RS samples. The selected conditions for this pretreatment were 120 °C, 5 h, and 5% (w/w), obtaining 29.8 g/L of potentially fermentable sugars. In these conditions, maximum delignification was achieved (64.9%) as well as maximum reduction of the crystallinity index (62.2%), as determined by X-ray diffraction analysis. Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis were used to confirm the RS amorphous structure after the pretreatment with [Emim][OAc] and showed that it had a more disordered and accessible structure.
Highlights
The depletion of fossil fuel resources and the associated environmental pollutions such as climate change and greenhouse gas emissions have increased interest in the search for sustainable and renewable sources of energy [1]
Compared to other Rice straw (RS) batches reported elsewhere [4, 35], the RS of this study showed a greater susceptibility for its sugar exploitation due its lower lignin content, which is known to increase the recalcitrance of lignocellulosic material hindering accessibility to enzymes
Glucan recovery after pretreatment varied in the range from 57.6 to 79.5%, while xylan and arabinan recovery varied between 54.8% to 100% and 57.9% to 89.6%, respectively
Summary
The depletion of fossil fuel resources and the associated environmental pollutions such as climate change and greenhouse gas emissions have increased interest in the search for sustainable and renewable sources of energy [1]. ILs are salts consisting entirely of ions with low melting points and special properties including low or negligible vapor pressure, high chemical and thermal stability, non-flammability, and recyclability [11]. Their strong hydrogen bonding coordination promotes the alteration of the involved network among carbohydrates and lignin allowing their separation, alongside the minimum formation of degradation products during the process [12]. These solvents are effective for dissolving cellulose by breaking the hydrogen bonds between its molecular chains through the interaction with cellulose’s hydroxyl groups [13]. Haykir and Bakir [21] demonstrated [Emim] [OAc] was better than alkali pretreatment in enhancing enzymatic hydrolysis of pretreated cotton stalks regardless of the substrate loading used, mainly due to its ability to disrupt the crystalline structure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
