Optimizing Dilute-Acid Pretreatment of Rapeseed Straw for Extraction of Hemicellulose

Abstract

Biological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars prior to fermentation. Hydrolysis can be performed enzymatically or with mineral acids. In this study, dilute sulfuric acid was used as a catalyst for the pretreatment of rapeseed straw. The purpose of this study is to optimize the pretreatment process in a 15-mL bomb tube reactor and investigate the effects of the acid concentration, temperature, and reaction time. These parameters influence hemicellulose removal and production of sugars (xylose, glucose, and arabinose) in the hydrolyzate as well as the formation of by-products (furfural, 5-hydroxymethylfurfural, and acetic acid). Statistical analysis was based on a model composition corresponding to a 3(3) orthogonal factorial design and employed the response surface methodology to optimize the pretreatment conditions, aiming to attain maximum xylan, mannan, and galactan (XMG) extraction from hemicellulose of rapeseed straw. The obtained optimum conditions were: H2SO4 concentration of 1.76% and temperature of 152.6 degrees C with a reaction time of 21 min. Under these optimal conditions, 85.5% of the total sugar was recovered after acid hydrolysis (78.9% XMG and 6.6% glucan). The hydrolyzate contained 1.60 g/L glucose, 0.61 g/L arabinose, 10.49 g/L xylose, mannose, and galactose, 0.39 g/L cellobiose, 0.94 g/L fructose, 0.02 g/L 1,6-anhydro-glucose, 1.17 g/L formic acid, 2.94 g/L acetic acid, 0.04 g/L levulinic acid, 0.04 g/L 5-hydroxymethylfurfural, and 0.98 g/L furfural.

Pretreatment of rapeseed straw by sodium hydroxide

“…Biological conversion of biomass into biofuels and chemicals requires hydrolysis of polysaccharides into monosaccharide prior to fermentation. Hydrolysis can be carried out by enzyme or chemical catalyst [2]. Hydrolysis of biomass is dependent on the characteristics of biomass.…”

“…However, their effectiveness varies depending on the characteristics of biomass. Therefore, optimal pretreatment conditions must be established for each type of lignocellulosic biomass [1][2][3][4].…”

“…After seed harvesting, rapeseed straw is useful as a resource for biofuel production [9][10][11][12]. Due to its high content of fermentable sugars (more than 60%), rapeseed straw has been suggested as a raw material for use as a biofuel feedstock [2]. In general, rapeseed straw is composed of three main fractions, including 34% cellulose, 19% hemicelluloses, and 6.9% lignin [12].…”

Effect of Boric Acid Addition on the Prehydrolysis of Whangee

“…Furthermore, ideal bamboo-dissolving pulp with high brightness (92.4% ISO) and α-cellulose content (94.9%) has been obtained (Batalha et al 2012). Presently, a number of methods have been proposed for extracting hemicellulose in the prehydrolysis stage, including auto-hydrolysis (Leppänen et al 2011), dilute acid (Jeong et al 2010), mild alkali extraction (Huang and Ragauskas 2013), organic acid (Li et al 2010;Scordia et al 2011), and solid acid pretreatment (Dhepe and Sahu 2010). Among those methods, dilute acid extraction usually resulted in a lower pulp yield and physical properties, which were attributed to the acidity in the pretreatment medium (Aldajani et al 2009).…”

Bioethanol production from oilseed rape straw hydrolysate by free and immobilised cells ofSaccharomyces cerevisiae

“…Dilute acid pre-treatment has been widely studied for a range of feedstocks. Jeong et al [8] optimised the dilute acid pre-treatment of OSR straw based on the extent to which hemicellulosic sugars (mainly xylose, mannose and galactose) were extracted. Under optimum pre-treatment conditions (1.76% H 2 SO 4 , 152.6 o C for 21 min) 85.5% of total sugars were recovered from OSR straw.…”