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Abundant seawater resources can replace the shortage of freshwater resources. The co-production of xylo-oligosaccharides and glucose from sugarcane bagasse by subcritical CO2-assisted seawater pretreatment was studied in this paper. We investigated the effects of pretreatment conditions of temperature, CO2 pressure and reaction time on the yield of xylo-oligosaccharides in subcritical CO2-assisted seawater systems. The maximum xylo-oligosaccharide yield of 68.23% was obtained at 165 °C/2 MPa/5 min. After further enzymatic hydrolysis of the solid residue, the highest glucose yield of 94.45% was obtained. In this system, there is a synergistic effect of mixed ions in seawater and CO2 to depolymerize xylan into xylo-oligosaccharides with a lower degree of polymerization. At the same time, the addition of CO2 increased the pore size and porosity of sugarcane bagasse, improved the efficiency of enzymatic hydrolysis and increased the yield of glucose. Therefore, this study provides a more environmentally friendly and sustainable process for the co-production of xylo-oligosaccharides and glucose from sugarcane bagasse, and improves the utilization of seawater resources. [ABSTRACT FROM AUTHOR]

Abstract Background Corn cob residue (CCR) is a kind of waste lignocellulosic material with enormous potential for bioethanol production. The moderated sulphite processes were used to enhance the hydrophily of the material by sulfonation and hydrolysis. The composition, FT-IR spectra, and conductometric titrations of the pretreated materials were measured to characterize variations of the CCR in different sulfite pretreated environments. And the objective of this study is to compare the saccharification rate and yield of the samples caused by these variations. Results It was found that the lignin in the CCR (43.2%) had reduced to 37.8%, 38.0%, 35.9%, and 35.5% after the sulfite pretreatment in neutral, acidic, alkaline, and ethanol environments, respectively. The sulfite pretreatments enhanced the glucose yield of the CCR. Moreover, the ethanol sulfite sample had the highest glucose yield (81.2%, based on the cellulose in the treated sample) among the saccharification samples, which was over 10% higher than that of the raw material (70.6%). More sulfonic groups and weak acid groups were produced during the sulfite pretreatments. Meanwhile, the ethanol sulfite treated sample had the highest sulfonic group (0.103 mmol/g) and weak acid groups (1.85 mmol/g) in all sulfite treated samples. In FT-IR spectra, the variation of bands at 1168 and 1190 cm-1 confirmed lignin sulfonation during sulfite pretreatment. The disappearance of the band at 1458 cm-1 implied the methoxyl on lignin had been removed during the sulfite pretreatments. Conclusions It can be concluded that the lignin in the CCR can be degraded and sulfonated during the sulfite pretreatments. The pretreatments improve the hydrophility of the samples because of the increase in sulfonic group and weak acid groups, which enhances the glucose yield of the material. The ethanol sulfite pretreatment is the best method for lignin removal and with the highest glucose yield.

Although great progress has been made in the research on conversion of cellulosic ethanol, the high conversion cost still exists as an obstacle. Thus, various measures such as reducing the chemical usage, minimizing the enzyme loading, and decreasing the energy consumption are required to lower the cost. Adding surfactants in bioethanol production process is recognized as a simple, effective, and economical strategy to enhance the fermentable sugars production. Therefore, making full use of surfactants (e.g., natural saponin from agricultural and forestry wastes and lignosulfonate) and other industrial wastes in the production of cellulosic ethanol would bring significant economic and environmental benefits. In this review, the recent progress on the application of different types of surfactants (synthetic, natural, and biosurfactant) in cellulosic ethanol production was summarized. The possible mechanism by surfactants was explored. The challenges of current research and outlook of surfactants used in the bioconversion of lignocellulosic biomass were also discussed. • Adding surfactants is an efficient method to boost fermentable sugars yield. • Application of different types of surfactants in bioethanol production is summarized. • Role of surfactants in enhancing enzymatic hydrolysis of lignocellulose is discussed. • Surfactant addition efficiently reduces cellulase-lignin binding. • Challenge and future research are given to develop a promising bioconversion process. [ABSTRACT FROM AUTHOR]

A one-pot fractionation method of Moso bamboo into hemicellulose, lignin, and cellulose streams was used to produce furfural, phenolated lignin, and fermentable sugars in the acidic 1,4-dioxane system. Xylan was depolymerized to furfural at a yield of 93.81% of the theoretical value; however, the prolonged processing time (5 h) led to a high removal ratio of glucan (37.21%) in the absence of phenol. The optimum moderate condition (80 °C for 2 h with 2.5% phenol) was determined through the high fractionation efficiency. Consequently, 77.28% of xylan and 84.83% of lignin were removed and presented in the hydrolysate, while 91.08% of glucan was reserved in the solid portion. The formation of furfural from xylan remained high, with a yield of 92.92%. The extracted lignin was phenolated with an increasing content of phenolic hydroxyl. The fractionated lignin yield was 51.88%, which suggested this could be a low-cost raw material to product the activated carbon fiber precursor. The delignified pulp was subjected to enzymatic hydrolysis and the glucose yield reached up to 99.03% of the theoretical. [ABSTRACT FROM AUTHOR]

[Display omitted] • Glutamic acid (GA) can selectively hydrolyze hemicellulose in sugarcane bagasse. • GA promoted the enzymatic reaction of cellulase. • Separation of GA and xylo -oligosaccharide (XOS) solution was not required. • The yield of XOS obtained from sugarcane bagasse by GA hydrolysis was 56.42%. • Efficient co-production of XOS and fermentable sugars from sugarcane bagasse. In the production of xylo -oligosaccharides (XOS) by organic acid pretreatment, it is often difficult to isolate organic acids from XOS. Here, an acidic amino acid, glutamic acid (GA), was used to pretreat sugarcane bagasse (SCB) to prepare XOS and fermentable sugars. The effects of GA concentration, hydrolysis temperature, and pretreatment time on the yield and polymerization distribution of XOS were investigated. After hydrolysis by 0.2 M GA at 140 °C for 30 min, the maximum yield of X 2-5 was 53.3%, and the concentrations of xylose and furfural were 1.8 g/L and 0.1 g/L, respectively. Meanwhile, GA increased the pore size and porosity of SCB as well as the number of functional groups of amino acid residues, which improved the enzymatic efficiency and the maximum yield of glucose was 95.3%. Thus, GA pretreatment provides a more economical, environmentally friendly and sustainable method for the co-production of XOS and glucose from SCB. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel process for integration of bioethanol and biodiesel production is proposed. • The retained fatty acid soap reduced lignin redeposition and cellulase absorption. • Pressure filtration is a superior method for minimized water use. • A high glucose yield of 94.95% and the ethanol yield of 73.10% were achieved. Abstract Utilization of sustainable energy is limited by energy requirement for the manufacturing of renewable fuels. Moso bamboo was pretreated with industrially derived crude glycerol obtained from different sources at 150/160 °C for 3 h. This bamboo, pretreated with base biodiesel glycerol with pressure filtration removal method, showed a high glucose yield of 94.95% and an ethanol yield of 73.10% of the theoretical. Major glycerol content was removed by pressure filtration, leaving a small amount of fatty acid soap in the pretreated sample, which formed an emulsion that reduced lignin redisposition onto the biomass surface and effectively blocked lignin absorption of cellulase, allowing greater enzymatic hydrolysis and fermentation system function. The surface was more hydrophilic and a higher lignin removal was achieved: 39.24% with base biodiesel glycerol pretreatment compared to 26.08% with sodium hydroxide glycerol pretreatment. This study provides a useful and cost-effective process, BBGP, for high-yield ethanol production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Syringic acid (SA) pretreatment was used to achieve the full utilization of SCB. • 58.7% XOS DP 2–6 was obtained at 180 °C/20 min with 9% SA additive. • Lignin degree of condensation decreased from 0.55 to 0.42 after SA additive. • Glucose yield reached 92.4% at lower enzyme due to the less lignin inhibition. • SA is a catalyst, lignin condensation inhibitor, and antimicrobial. Current strategies for the production of xylooligosaccharides (XOS) from biomass through non–enzymatic catalysis often led to a certain degree of lignin condensation, which severely restrains subsequent enzyme hydrolysis of cellulose. Herein, syringic acid (SA) pretreatment was investigated to coproduce XOS, glucose, and less-condensed lignin from sugarcane bagasse. SA acted as a catalyst and lignin condensation inhibitor during the pretreatment. The highest XOS yield of 58.7% (27.7% xylobiose and 24.7% xylotriose) was obtained at 180 °C − 20 min − 9% SA, and the corresponding xylose/XOS ratio was only 0.42. Compared with the pretreatment at 180 °C − 20 min − 0% SA, the addition of 9% SA increased the glucose yield from 85.7% to 92.4% and decreased the degree of lignin condensation from 0.55 to 0.42. Moreover, 26.7% of SA could be easily recovered. This work presents a pretreatment strategy in which the efficient production of XOS and the suppression of lignin condensation are achieved simultaneously. [ABSTRACT FROM AUTHOR]

Green liquor (GL) is readily available in any pulp mills which could be recycled. Alkaline sulfite pretreatment process was developed for non-woody biomass biorefinery. In this study, GL combined with sulfite was effectively utilized to improve the enzymatic hydrolysis of sugarcane bagasse by selectively removing lignin. Compare to conventional alkaline sulfite pretreatment, the solid yield could be higher with low degradation of polysaccharide. With the increment of the pretreatment temperature from 100 to 140 °C, the enzymatic hydrolysis efficiency was improved. And a higher glucose yield was achieved under pretreatment condition of 0.4 g/g-DS Na 2 SO 3 and 1.5 mL/g-DS GL due to the higher degradation of xylan. The highest glucose yield of 96.8% could be reached with 3.36 g/(L·h) of initial rate after Kraft GL-sulfite pretreatment at 140 °C. The superior performance of Kraft GL allows conversion of cellulose to glucose more significantly than Soda GL. In addition, surface tension test indicated that a part of lignin was dissolved in the pretreatment liquor as lignosulfonate. The results showed that GL combined with sulfite is a promising way for sugarcane bagasse pretreatment. [ABSTRACT FROM AUTHOR]

Co-production of glucose, furfural and other green materials based on a lignocellulosic biorefinery is a promising way to realize the commercial application of corncob residues. An effective process was developed for glucose production using low temperature bisulfite pretreatment and high-solids enzymatic hydrolysis. Corncob residues from furfural production (FRs) were pretreated with 0.1 g NaHSO 3 /g dry substrate at 100 °C for 3 h. Lignin was sulfonated and sulfonic groups were produced during pretreatment, which resulted in decreasing the zeta potential of the samples. Compared with raw material, bisulfite pretreatment of FRs increased the glucose yield from 18.6 to 99.45% after 72 h hydrolysis at a solids loading of 12.5%. The hydrolysis residues showed a relatively high thermal stability and concentrated high derivatives. Direct pretreatment followed by enzymatic hydrolysis is an environmentally-friendly and economically-feasible method for the production of glucose and high-purity lignin, which could be further converted into high-value products. [ABSTRACT FROM AUTHOR]

Kraft green liquor (GL) mainly consisting of sodium carbonate and sodium sulfide are available from Kraft mills. Kraft GL combined with ethanol (Kraft GL-ethanol) was chosen to pretreat sugarcane bagasse for effective enzymatic hydrolysis. And the obtained lignins and cellulose rich fractions were characterized in detail. The highest lignin removal of 95.3% was observed at a pretreatment temperature of 160 °C, and approximately 70.8% of lignin was removed at the pretreatment temperature of 100 °C. The lignin removal with Kraft GL-ethanol pretreatment was higher than that with Soda GL-ethanol pretreatment at 140 °C. An FT-IR study of the isolated lignins showed that an increase in pretreatment temperature resulted in the cleavage of ester bonds. GPC results revealed that the molecular weight decreased with increasing pretreatment temperature. The 2D HSQC NMR data showed that the cleavage of β- O -4 became more severe with increasing pretreatment temperature from 80 to 160 °C. Fewer condensation reactions between lignin units occurred when the pretreatment temperature was above 100 °C. Moreover, the enzymatic hydrolysis efficiency of sugarcane bagasse increasing with increasing pretreatment temperature. The glucose yield reached 65.13% at a pretreatment temperature of 80 °C. The maximum glucose yield (98.26%) of sugarcane bagasse after 72 h of enzymatic hydrolysis was achieved at a pretreatment temperature of 160 °C. When lignin content was low in samples after pretreatment at 140–160 °C, the enzymatic hydrolysis efficiency of the substrate increased because the number of crystalline cellulose regions decreased. Scanning electron microscopy showed that the surfaces of Kraft GL-ethanol pretreated sugarcane bagasse were separated into individual fibers. In addition, contact angle analysis showed that the Kraft GL-ethanol pretreated sugarcane bagasse was more hydrophilic than untreated sugarcane bagasse. [ABSTRACT FROM AUTHOR]

Gleditsia saponin (GS) assisted high-solids enzymatic hydrolysis and fermentation for alkaline peroxide (AP)-pretreated furfural residues (FRs) was investigated. The addition of GS increased the glucose yield of untreated FRs to 74.8% in high-solids-loading enzymatic hydrolysis. AP pretreatment before enzymatic hydrolysis resulted in a high sugar concentration (115.4 g/L) and a glucose yield of 57.5% by the end of hydrolysis at 20% solids loading. It was suggested that GS could improve significantly the glucose yields of FRs with high lignin content. After simultaneous saccharification and fermentation (SSF), the total cellulose conversion of FRs with 14.3% lignin content reached 82.2% and the highest ethanol concentration (69.1 g/L) was achieved, which was 121% higher than that of untreated FRs (30.1 g/L). The results indicated that the main reason behind the decreased glucose yield at high-solids loadings was product inhibition. Moreover, the lignin content plays an important role in the enhancement of GS-assisted high-solids enzymatic hydrolysis of AP-treated FRs. [ABSTRACT FROM AUTHOR]

This study reports four schemes to pretreat wet furfural residues (FRs) with sodium bisulfite for production of fermentable sugar. The results showed that non-detoxified FRs (pH 2–3) had great potential to lower the cost of bioconversion. The optimal process was that unwashed FRs were first pretreated with bisulfite, and the whole slurry was then directly used for enzymatic hydrolysis. A maximum glucose yield of 99.4% was achieved from substrates pretreated with 0.1 g NaHSO 3 /g dry substrate (DS), at a relatively low temperature of 100 °C for 3 h. Compared with raw material, enzymatic hydrolysis at a high-solid of 16.5% (w/w) specifically showed more excellent performance with bisulfite treated FRs. Direct bisulfite pretreatment improved the accessibility of substrates and the total glucose recovery. Lignosulfonate in the non-detoxified slurry decreased the non-productive adsorption of cellulase on the substrate, thus improving enzymatic hydrolysis. [ABSTRACT FROM AUTHOR]

Green liquor (GL) combined with H 2 O 2 (GL-H 2 O 2 ) and green liquor (GL) combined with ethanol (GL-ethanol) were chosen for treating sugarcane bagasse. Results showed that the glucose yield (calculated from the glucose content as a percentage of the theoretical glucose available in the substrates)of sugarcane bagasse from GL-ethanol pretreatment (97.7%) was higher than that from GL-H 2 O 2 pretreatment (41.7%) after 72 h hydrolysis with 18 filter paper unit (FPU)/g-cellulose for cellulase, 27,175 cellobiase units (CBU)/g-cellulose for β-glucosidase. Furthermore, about 94.1% of xylan was converted to xylose after GL-ethanol pretreatment without additional xylanase, while the xylose yield was only 29.2% after GL-H 2 O 2 pretreatment. Scanning electron microscopy showed that GL-ethanol pretreatment could break up the fiber severely. Moreover, GL-ethanol pretreated substrate was more accessible to cellulase and more hydrophilic than that of GL-H 2 O 2 pretreated. Therefore, GL-ethanol pretreatment is a promising method for improving the overall sugar (glucose and xylan) yield of sugarcane bagasse. [ABSTRACT FROM AUTHOR]

Abstract: The steam pre-treatment with low severity preserves valuable biomass components, and further delignification with alkaline peroxide could improve hydrolysis. A combination of low severity steam pretreatment and alkaline peroxide post-treatment of Lespedeza stalks was investigated. The post-treatment of steam-pretreated Lespedeza stalks with alkaline peroxide significantly increased the cellulose content and changed the structure of the cellulose-rich fractions. A glucose yield of 503.5mgg−1 raw material from enzyme hydrolysis was obtained when the steam-pretreated material (184°C for 4min) was post-treated with 2% hydrogen peroxide at 60°C for 24h with a substrate concentration of 3.3%. Its hydrolysis yield is 88.8%, which is higher than that of samples processed by steam pretreatment alone (63.7%). The samples obtained by post-treatment with alkaline peroxide were found to have a smoother surface and looser structure in scanning electron microscopy images. The isolated lignin preparations had a yield range from 10.9 to 14.7 (% dry matter). The lignin was characterized by thermogravimetric analysis/differential thermal analysis, Fourier transform infrared spectroscopy, and gel permeation chromatography. Alkaline peroxide treatment increased the thermal stability of lignin, and decreased the amounts of all functional groups. Depolymerization and repolymerization occurred during the alkaline peroxide treatment. [Copyright &y& Elsevier]

• SCB was first treated with seawater for coproduction of XOS and glucose. • High yields of XOS were obtained with milder hydrothermal pretreatment conditions. • Seawater was used for pretreatment to conserve freshwater. • More X 4 was generated by seawater hydrothermal pretreatment. • 94.7% glucose yield was achieved from the solids after treatment. In this study, natural seawater without additional chemicals was selected to treat sugarcane bagasse for the production of xylooligosaccharides and glucose. This pretreatment not only more effectively conserves freshwater resources than hydrothermal pretreatment and enzymatic hydrolysis, but also decreases corrosion of the equipment relative to techniques utilizing acid and alkaline pretreatment. The maximum yield of 67.12% xylooligosaccharides (of initial xylan), including 11.49% xylobiose, 16.23% xylotriose, 23.82% xylotetraose, and 15.58% xylopentaose was obtained under mild condition (175 °C for 30 min). Moreover, greater amounts of xylotetraose were generated during seawater hydrothermal pretreatment under all conditions, likely because NaCl in seawater cut the hydrogen bonds between xylo-oligomers. In addition, 94.69% cellulose digestibility and 78.58% xylan digestibility were achieved from the solid residue with an enzyme dosage of 30 FPU/g cellulose. Results indicated that seawater hydrothermal pretreatment is a more environmentally-friendly and sustainable technique for producing xylooligosaccharides and fermentable sugars than other methods. [ABSTRACT FROM AUTHOR]

• XOS is produced by the co-catalysis of MgCl 2 /FeCl 2 and autohydrolysis. • Fe2+ and Mg2+ of co-catalyst are essential for good human health without separation. • 54.68% XOS was obtained from co-catalysis of 0.05 M MgCl 2 + 0.05 M FeCl 2 only at 140 °C. • Co-catalysis of MgCl 2 + FeCl 2 effectively increases the contents of X 2 and X 3. • The Mg2+ ion of the solid residue could accelerate the enzymatic hydrolysis. Inorganic salt treatment is a novel, high-yield, and environmentally friendly approach for the production of xylo-oligosaccharides from Sugarcane bagasse with degree of polymerization of 2–5. A xylo-oligosaccharides yield of 53.79% was obtained with 0.1 M MgCl 2 treatment at 180 °C/10 min, and 41.89% with 0.1 M FeCl 2 treatment at 140 °C/30 min. The xylo-oligosaccharides yield from the co-catalysis of 0.05 M FeCl 2 + 0.05 M MgCl 2 reached 54.68% (29.34% xylobiose and 20.94% xylotriose) at 140 °C/30 min. The co-catalysis not only effectively improved the xylobiose and xylotriose contents but also increased the total yield of xylo-oligosaccharides under mild reaction conditions. Additionally, the glucose yield observed from the solid residue after inorganic salt treatment was 71.62% by enzymatic hydrolysis. Mg2+ and Fe2+ are essential for good human health without separation from the system, therefore, the inorganic salt treatment can be potentially applied in the co-production of xylo-oligosaccharides and glucose. [ABSTRACT FROM AUTHOR]