Pretreatment of wheat straw leads to structural changes and improved enzymatic hydrolysis

Abstract

Wheat straw (WS) is a potential biomass for production of monomeric sugars. However, the enzymatic hydrolysis ratio of cellulose in WS is relatively low due to the presence of lignin and hemicellulose. To enhance the enzymatic conversion of WS, we tested the impact of three different pretreatments, e.g. sulfuric acid (H2SO4), sodium hydroxide (NaOH), and hot water pretreatments to the enzymatic digestions. Among the three pretreatments, the highest cellulose conversion rate was obtained with the 4% NaOH pretreatment at 121 °C (87.2%). In addition, NaOH pretreatment was mainly effective in removing lignin, whereas the H2SO4 pretreatment efficiently removed hemicellulose. To investigate results of pretreated process for enhancement of enzyme-hydolysis to the WS, we used scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to analyze structural changes of raw and treated materials. The structural analysis indicated that after H2SO4 and NaOH pretreatments, most of the amorphous cellulose and partial crystalline cellulose were hydrolyzed during enzymatic hydrolysis. The findings of the present study indicate that WS could be ideal materials for production of monomeric sugars with proper pretreatments and effective enzymatic base hydrolysis.

Production of Cellulosic Ethanol from Enzymatically Hydrolysed Wheat Straws

“…Figure 1D shows that initial uniform and rigid structure of the WS was changed after pretreatment, obtaining a porous structure which can positively influence the enzymatic action. This modification has also been reported by Zheng et al (2018) and Momayez et al (2019) [24,54].…”

“…Chen et al (2018) studied the chemical compounds of rice straws after pretreatment with 2% H2SO4 By comparison to the spectra of the untreated sample, the solid fraction of pretreated and enzymatically hydrolysed straw presented notable changes in the wide absorption band at 3400 cm -1 in function of the volume of sulfuric acid, the enzyme dose and the S/L ratio. A decrease of the intensity of the absorption band in this region indicated a reduction of the cellulose content, as previously reported by Zheng et al (2018) [24]. When considering the conditions of the pretreatment and enzymatic hydrolysis applied, the reduction of cellulose content seems to be more pronounced when an enzyme dose of 90 µL was used.…”

“…Zheng et al (2017) studied the impact of acid pretreatment on WS, using 2% and 4% of H 2 SO 4 . This pretreatment led to the elimination of high amount of hemicellulose [24]. The acid pretreatment is most suitable for WS, but also has some disadvantages, such as acid pollution of the environment and feed, and production of secondary compounds [25][26][27].…”

Co-Ensiling of Wheat Straw as an Alternative Pre-Treatment to Chemical, Hydrothermal and Mechanical Methods for Methane Production

“…As such, the opened structure during the co-ensiling and CCT pre-treatment provided a higher accessible surface area that could undergo hydrolysis and be digested, which may partly be the cause for the increment in the CH4 yield and biodegradability after pre-treatment. Similar disruptions in the surface structure were reported by Zheng et al after both alkali, acid and hot water pre-treatment of wheat straw [54] and by Barman et al after alkali pre-treatment on wheat straw [55].…”

Enhanced Saccharification and Fermentation of Rice Straw by Reducing the Concentration of Phenolic Compounds Using an Immobilized Enzyme Cocktail

“…The contents of the biomass significantly varied after different types of pretreatments using acid, alkali, or hydrothermal processes, and showed a profound influence on the saccharification using cellulase . Therefore, the composition of rice straw before and after pretreatment was analyzed (Table S1, Supporting Information).…”