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Background: Efficient cofermentation of glucose and xylose is necessary for economically feasible bioethanol production from lignocellulosic biomass. Here, we demonstrate pretreatment of sugarcane bagasse (SCB) with green liquor (GL) combined with ethanol (GL-Ethanol) by adding different GL amounts. The common Saccharomyces cerevisiae (CSC) and thermophilic S. cerevisiae (TSC) strains were used and different yeast cell mass ratios (CSC to TSC) were compared. The simultaneous saccharification and cofermentation (SSF/SSCF) process was performed by 5-20% (w/v) dry substrate (DS) solid loadings to determine optimal conditions for the co-consumption of glucose and xylose. Results: Compared to previous studies that tested fermentation of glucose using only the CSC, we obtained higher ethanol yield and concentration (92.80% and 23.22 g/L) with 1.5 mL GL/g-DS GL-Ethanol-pretreated SCB at 5% (w/v) solid loading and a CSC-to-TSC yeast cell mass ratio of 1:2 (w/w). Using 10% (w/v) solid loading under the same conditions, the ethanol concentration increased to 42.53 g/L but the ethanol yield decreased to 84.99%. In addition, an increase in the solid loading up to a certain point led to an increase in the ethanol concentration from 1.5 mL GL/g- DS-pretreated SCB. The highest ethanol concentration (68.24 g/L) was obtained with 15% (w/v) solid loading, using a CSC-to-TSC yeast cell mass ratio of 1:3 (w/w). Conclusions: GL-Ethanol pretreatment is a promising pretreatment method for improving both glucan and xylan conversion efficiencies of SCB. There was a competitive relationship between the two yeast strains, and the glucose and xylose utilization ability of the TSC was better than that of the CSC. Ethanol concentration was obviously increased at high solid loading, but the yield decreased as a result of an increase in the viscosity and inhibitor levels in the fermentation system. Finally, the SSCF of GL-Ethanol-pretreated SCB with mixed S. cerevisiae strains increased ethanol concentration and was an effective conversion process for ethanol production at high solid loading. [ABSTRACT FROM AUTHOR]

The price of raw material, energy demand in the pretreatment step, and enzyme usage rate are the major cost factors in the process of converting biomass to bioethanol. Unwashed furfural residues (FRs) possess great potential for application in bioethanol production. Surfactant addition is an effective method to enhance the fermentation rate. In this study, unwashed FRs were used directly as raw materials to produce bioethanol. Tea-seed cake (TSC), tea seed residues that contained protein and saponin, was added in the simultaneous saccharification and fermentation (SSF) process. The effect of TSC dosage on SSF was compared. TSC was added at the dosage of 10 g/L, which resulted in a final ethanol yield of 87.2%. However, a high concentration of TSC could induce cytotoxicity in yeast. The surface tension (approximately 33.92 mM/m) at SSF using TSC-medium was much lower than that of other fermentation systems (about 64.67 mN/m). Further contact angle testing showed that TSC-medium (21.7°) had better wetting capacity than FRs (45.6°). This study provided a proposed process strategy that SSF with the addition of TSC could be a minimum consumption of chemicals and enzymes for future cellulosic ethanol production process. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse (SCB) was modified by steam explosion pretreatment at 190℃ for 10 min and 210℃ for 5 min using green liquor (GL) combined with hydrogen peroxide (GL-H2O2) and ethanol (GL-Ethanol) for simultaneous saccharification and fermentation (SSF)- based ethanol production. The results showed that 85.02% and 100% of hemicelluloses were solubilized by steam explosion pretreatment at 190℃ for 10 min and 210℃ for 5 min, respectively. Moreover, 20.08% and 73.77% of the lignin was removed through GL-H2O2 and GL-Ethanol pretreatments, respectively. The steam explosion pretreatments greatly improved the specific surface area of the SCB and led to the highest ethanol yield of 92.20% at 190℃ for 10 min and 93.19% of 210℃ for 5 min, respectively. In addition, the ethanol yield reached 72.58% for the GL-Ethanol pretreatment, and about 70% of active lignin could be recovered from the pretreatment liquid. When the GL-H2O2 pretreatment was used, the maximum ethanol yield of 20.92% was achieved. [ABSTRACT FROM AUTHOR]

The article presents a study which compared the bioethanol production from the furfural residue (FR) samples after delignification pretreatment. The relationship between hydrophilicity of the samples and bioethanol production was determined by measuring hydrophilic variation through conductometric titration. Results suggest that some new hydrophilic groups were formed during pretreated delignification which could benefit enzymatic hydrolysis.

Furfural residues (FRs) were pretreated with laccase or a laccasemediator (1-hydroxybenzotriazole, HBT) system to produce fermentable sugar for bioethanol production. Compared to laccase-only pretreatment, laccase-mediator pretreatment dissolved more lignin. Approximately 10.5% of the initially present lignin was removed when FRs were treated with a laccase loading of 100 U/g of dry substrate in 1% (w/w) HBT at 48 °C for 24 h in an acetate buffer (pH 4.8). The enzymatic saccharification process was carried out by a combined laccase or laccase-mediator pretreatment without washing of the treated solids. The results showed that active laccase had a negative effect on the rate and yield of enzymatic hydrolysis. Laccase-oxidized HBT seriously reduced glucose yield. However, non-oxidized HBT increased glucose yield when laccase was deactivated at 121 °C for 20 min prior to enzymatic hydrolysis. The highest glucose yield, 80.9%, was obtained from the substrate pretreated with 100 U/g of dry substrate laccase and 1% (w/w) HBT at 48 °C for 24 h in an acetate buffer (pH 4.8). Furthermore, the structures of FRs before and after laccase-mediator pretreatment were characterized by scanning electron microscopy (SEM) and Fourier Transform Infrared spectroscopy (FT-IR). [ABSTRACT FROM AUTHOR]