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The presence of hemicellulose inhibits the enzymatic hydrolysis of lignocellulosic biomass. The purpose of this study is to investigate the effect of different hemicellulose fractions on the enzymatic hydrolysis and the way to eliminate the inhibiting effect caused by hemicellulose. Four kinds of hemicelluloses, namely, HXF, H15, H30, and H60, were first extracted from corn stover by ethanol fractional precipitation. The structures of hemicellulose samples were analyzed using Fourier transform infrared spectroscopy, 1H and 13C nuclear magnetic resonance, and high-performance ion chromatography. The results show that H30 has the strongest inhibition on the enzymatic hydrolysis of Avicel and corn stover, presenting inhibition ratio of 13.35% and 9.98%, respectively. The inhibition ratios of other hemicelluloses in Avicel and corn stover are 8–12% and 5–9%, respectively. However, the inhibiting effect caused by H30 is removed by adding hemicellulase, which even presents a 4.99% increase in the efficiency of enzymatic hydrolysis of corn stover. The corresponding glucose concentration reached 68.11 g/L. This research could help design effective processes to promote the enzymatic hydrolysis of lignocellulosic biomass. [ABSTRACT FROM AUTHOR]

The enzymatic hydrolysis of sugarcane bagasse cellulose (SBC) was performed after acid/peroxide-alkali (APA) pretreatment, soda/AQ pulping, and bleaching steps for producing glucose. Cellic® CTec3 (CT) and Celluclast®1.5L (CL) complexes were evaluated in both individual and mixed systems for observing their influence in cellulose conversion. Deconvolution of XRD patterns and SEM images proved the low crystallinity and high accessibility of SBC, thus being able to provide significantly higher glucose yield than the commercial cellulose with predominant Iβ polymorphism. The analysis of variance (ANOVA) and the response surface methodology (RSM), applied to a full factorial 24 design of experiments built for assessing the activity of CT and CL enzymes together in the hydrolytic system, were accurate in describing that the feedstock (SBC or commercial cellulose) and the treatment of cellulose are the factors with major effect on the saccharification efficiency (F = 744.12, p < 0.0001), thus predicting 53.71 g/L maximum glucose yield for the experimental conditions studied (near to the maximum yield reached, 55.77%) when using SBC, more than double the conversion reached for commercial cellulose, and showing the cooperative work of both complexes together for converting cellulose. [ABSTRACT FROM AUTHOR]

Rice straw is an abundant lignocellulosic biomass used to produce biogas. However, its resistant structure hinders biogas production. In this study, three pretreatments, microwave, ammoniation, and microwave-assisted ammoniation (MAA), were evaluated for their use in improving biogas production from rice straw. After an 18-day digestion, methane production by rice straw pretreated with MAA was 281.56 mL/g (volatile solids of substrate), which was 25.43%, 7.96%, and 18.18% more than that produced following the control, microwave, and ammoniation pretreatments, respectively. These increases were mainly attributed to the change in the resistant structure of rice straw following the MAA pretreatment and a more stable anaerobic digestion system. The degradation rate for the volatile solids of the rice straw pretreated with MAA during anaerobic digestion was 71.20%, which was 4.71%, and 4.86% higher than the rates observed using microwave and ammoniation pretreatments, respectively. In addition, the MAA method had a T90 fermentation cycle of 6 days, which was 33.3%, 25.0%, and 33.3% shorter than those for the control, microwave, and ammoniation methods, respectively. This technology shows the potential to enhance biogas production from the anaerobic digestion of rice straw. [ABSTRACT FROM AUTHOR]

Cellulose was isolated from wheat straw by the combined pretreatment including dilute acid hydrolysis, ethanol extraction, and alkaline H2O2 delignification. The effects of varying the parameters on carboxymethylation on isolated cellulose were investigated. Furthermore, the chemical structure of carboxymethyl cellulose (CMC) prepared from wheat straw was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscope analysis. The isolated cellulose is mainly composed of cellulose without hemicellulose and with minors of lignin and ash. The optimal conditions for carboxymethylation were base concentration, 20%; reaction temperature, 70°C; reaction time, 2 h; mass ratio of etherifying agent to cellulose, 1.75. Under the optimized conditions, CMC with high degree of substitution (0.88) and low viscosity (18 mPa·s) was synthesized. Chemical structural characterization showed the feasibility of the preparation of CMC from wheat straw. The constituents of wheat straw would be maximally utilized by the proposed method. [ABSTRACT FROM AUTHOR]

The aim of this study was to increase the sludge disintegration and reduce the cost of microwave (MW) pretreatment. Thermodynamic analysis of MW hydrolysis revealed the best fit with a first-order kinetic model at a specific energy of 18,600 kJ/kg total solids (TS). Combining HO with MW resulted in a significant increment in solubilization from 30 to 50 % at 18,600 kJ/kg TS. The pH of HO-assisted MW-pretreated sludge (MW + HO) was in the alkaline range (pH 9-10), and it made the sludge unfavorable for subsequent anaerobic digestion and inhibits methane production. In order to nullify the alkaline effect caused by the MW + HO combination, the addition of acid was considered for pH adjustment. HO-assisted MW-pretreated sludge in acidic conditions (MW + HO + acid) showed a maximum methane production of 323 mL/g volatile solids (VS) than others during anaerobic biodegradability. A cost analysis of this study reveals that MW + HO + acid was the most economical method with a net profit of 59.90 €/t of sludge. [ABSTRACT FROM AUTHOR]

Combined pretreatment methods for improving sugar yield as well as the economic aspects of lignoethanol production processes have gained a great deal of interest. However, most investigations involving such methods have been conducted under optimum conditions. Such fully-optimized combinations although improve enzymatic digestion, they could also degrade cellulose structure resulting in reduced sugar yield in some cases. The present study was set to prepare rice straw for the 1-ethyl-3-methylimidazolium acetate pretreatment step (2 h, 120 °C), by mild alkaline extraction (30 min, 80 °C, 0.3 % NaOH) with a focus on only 30 % lignin removal to minimize the hemicelluloses degradation. Moreover, the effect of size reduction (<0.42 mm and <2 cm) was also investigated. The results showed that the novel combination method based on only 30 % lignin removal led to an increased sugar yield by 17 %. Unexpectedly, although IL pretreatment needs material to be ground (<0.42 mm), the difference in sugar yields for the two sized tested was negligible. Graphical Abstract: The overall lignocellolusic bioethanol production pathway including the combined AE-IL process proposed in the present study based on 30 % lignin removal through the first AE step.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]