Effect of Extractives on Digestibility of Cellulose in Corn Stover with Liquid Hot Water Pretreatment

Abstract

Many herbaceous lignocelluloses suitable for ethanol production have high extractives contents, such as some straws and corn stover. The high extractives content might affect pretreatment or enzymatic hydrolysis. In this study, extractives were removed from corn stover, and then extractives-free corn stover and ordinary corn stover were respectively pretreated using a liquid hot water (LHW) method and hydrolyzed to evaluate the effect of extractives on cellulose digestibility. Extractives-free corn stover presented higher cellulose digestibility than ordinary corn stover after the same pretreatment conditions. A total of 87.3% of cellulose was digested in extractives-free corn stover, compared to 71.0% in ordinary corn stover, after pretreatment at 200 °C for 20 min. It is speculated that some water-soluble extractives could buffer H + ions from water and acetic acid during LHW pretreatment process, reducing xylan removal. Another reason for these results might be that some extractives could condense on corn stover after LHW pretreatment, which hinders cellulose hydrolysis.

Design and Optimization of Sulfuric Acid Pretreatment of Extracted Olive Tree Biomass Using Response Surface Methodology

“…Before the acid pretreatment, raw OTB was subjected to an aqueous extraction in order to remove soluble components like extractives, avoiding the formation of complex lignin-carbohydrates (Ballesteros et al 2011). Li et al (2016) also tested the effect of removing water extractives from corn stover, and determined a significant increase in the enzymatic digestibility after liquid hot water pretreatment.…”

Enhance photocatalytic hydrogen evolution by using alkaline pretreated corn stover as a sacrificial agent

“…In the first stage (≤100°C), free water and bound water in the sample begin to evaporate. In the second stage (160°C‐240°C), the extracts with low thermal stability begin to decompose, and the temperature rises further to the superposition region of cellulose and hemicellulose, resulting in severe weight loss . And this process is mainly endothermic .…”

“…In the third stage (≤290°C‐400°C), the residue began to carbonize, and the weight loss rate decreased compared with the previous stage . Moreover, the DTG curves showed that there was a platform at 240°C‐290°C for raw corn stover, which was caused by the separation of the DTG peaks of extractives, cellulose, and hemicellulose . On the other hand, as shown in the TGA curve of corn stover after alkali treatment, it can be seen that the pyrolysis temperature and weight loss rate of corn stover after alkali treatment increased significantly, and the corresponding absorption peak caused by extractives and hemicellulose almost disappeared in the DTG curve, while the corresponding absorption peaks of cellulose increased.…”

“…Especially when NaOH concentration was 6% and 8%, the corresponding curve tends to be the same, which indicated that the use of excessive sodium hydroxide concentration in the pretreatment process was useless for photocatalytic hydrogen production and would play an inhibitory role. This phenomenon could be explained by the destruction of the structure of cellulose at high alkali concentration, and the agglomeration of some organic sugars and organic matter on the stover surface during cooling and washing to neutrality hindered the hydrogen production process . This could be well observed in the SEM images, Figure S5.…”

“…In the second stage (160 C-240 C), the extracts with low thermal stability begin to decompose, and the temperature rises further to the superposition region of cellulose and hemicellulose, resulting in severe weight loss. 51 And this process is mainly endothermic. 52 In the third stage (≤290 C-400 C), the residue began to carbonize, and the weight loss rate decreased compared with the previous stage.…”