Zehuan Liu

Synergism of cellulase, xylanase, and pectinase on hydrolyzing sugarcane bagasse resulting from different pretreatment technologies

Sugarcane bagasse (SCB) resulting from different pretreatments was hydrolyzed by enzyme cocktails based on replacement of cellulase (Celluclast 1.5 L:Novozym 188=1FPU:4pNPGU) by xylanase or pectinase at different proportions. Lignin content of NaOH pretreated SCB and hemicellulose content of H2SO4 pretreated SCB were the lowest. NaOH pretreatment showed the best for monosaccharide production among the four pretreatments. Synergism was apparently observed between cellulase and xylanase for monosaccharide production from steam exploded SCB (SESB), NaOH, and H2O2 pretreated SCB. No synergism was observed between cellulase and pectinase for producing glucose. Additionally, no synergism was present when H2SO4 pretreated SCB was used. Replacement of 20% of the cellulase by xylanase enhanced the glucose yield by 6.6%, 8.8%, and 9.5% from SESB, NaOH, and H2O2 pretreated SCB, respectively. Degree of synergism between cellulase and xylanase had positive relationship with xylan content and was affected by hydrolysis time.

Solvent extraction of antioxidants from steam exploded sugarcane bagasse and enzymatic convertibility of the solid fraction.

Solvent extraction of steam exploded lignocellulosic biomass may be a potential way to obtain antioxidative extracts and to enhance the enzymatic convertibility of the solid residue. Boiling solvent extraction (BSE) showed higher solid and phenolic yields than room temperature extraction. Solubilities of phenolics and sugars were higher in anhydrous ethanol (AE) and deionized water (DW) than in ethyl acetate under each individual extraction condition. The antioxidant activities of the AE and DW extract obtained under BSE were better than those of 10mM vitamin C. Conversion of the solid fractions into reducing sugar using Celluclast 1.5L and Novozym 188 after AE and DW extraction was 95.13% and 92.97%, respectively, higher than that obtained with SESB (88.95%).

One-pot simultaneous saccharification and fermentation: a preliminary study of a novel configuration for cellulosic ethanol production.

Combination of size reduction and mild alkali pretreatment may be a feasible way to produce bioethanol without rinsing and detoxifying the solid substrate. Based on that, a fermentation configuration named one-pot SSF in which pretreatment and fermentation steps were integrated was developed. Additionally, the effect of laccase on fermentation performance was investigated. Delignification was the major effect of the alkali pretreatment at 121°C for 60min. The highest glucose and xylose yield, which obtained from the smallest particle at a substrate loading of 2%, was 6.75 and 2.71g/L, respectively. Laccase improved the fermentation efficiency by 6.8% for one-pot SSF and 5.7% for SSF. Bioethanol from one-pot SSF with laccase supplementation reached 67.56% of the theoretical maximum, whereas that from SSF with laccase supplementation reached 57.27%. One-pot SSF might be a promising configuration to produce bioethanol because of 100% solid recovery, and rinsing water and detoxification elimination.

Ethanol production from xylan-removed sugarcane bagasse using low loading of commercial cellulase

Xylan was always extracted as the feedstock for xylooligosaccharides production. The xylan-removed residue may contain high content of cellulose and thus had a possibility to be converted into ethanol. After soaked in 12% of NaOH at room temperature overnight, solubilization of cellulose, xylan, and lignin was 4.64%, 72.06%, and 81.87% respectively. The xylan-removed sugarcane bagasse (XRSB) was enzymatically hydrolyzed by using decreased cellulase loadings. The results showed that 7.5 FPU/g cellulose could obtain a cellulose conversion yield of 82%. Increasing the cellulase loading did not result in higher yield. Based on this, bioethanol production was performed using 7.5 FPU/g cellulose by employing fed-batch fermentation mode. The final ethanol concentration reached 40.59 g/L corresponding to 74.2% of the theoretical maximum. The high titer ethanol and low cellulase loading may reduce the overall cost.

Comparative study of different alcoholate pretreatments for enhanced enzymatic hydrolysis of sugarcane bagasse

Pretreatment of sugarcane bagasse (SCB) with alcoholates, sodium methoxide (CH3ONa), potassium methoxide (CH3OK) and sodium ethoxide (C2H5ONa), was investigated. Analyses of lignocellulose composition and enzymatic saccharification indicated that C2H5ONa showed the highest enzymatic efficiency of 102.1%. The response surface optimization of C2H5ONa pretreatment showed that under optimal conditions (4% of C2H5ONa, 121°C, 1h), 65.4% of lignin was removed and the enzymatic efficiency reached 105.2%. Hydrolysis of SCB with cellulases and xylanase at a ratio of 4:1 showed the strongest synergism with reducing sugar production of 21g/L and conversion rates of cellulose and xylan reaching 110.4% and 94.5%, respectively. These results indicated that C2H5ONa is a promising alkali to pretreat SCB and the synergism between cellulases and xylanase has a significant effect on enzymatic saccharification of the pretreated SCB.

Polymorphisms in TLR1, TLR6 and TLR10 genes and the risk of Graves' disease.

Abstract Graves’ disease (GD) is postulated to be caused by the combined effects of susceptibility genes and environmental triggers. Toll-like receptors (TLRs) play a role in the activation of innate and adaptive immune responses in mammalians. The aim of this study was to evaluate the potential association of polymorphisms in TLR1, TLR6 and TLR10 genes with GD in Chinese Cantonese population. Seven single nucleotide polymorphisms (i.e. rs4833095 and rs5743565 in TLR1; rs5743808 in TLR6; and rs4504265, rs11466655, rs11096957 and rs10856839 in TLR10) were evaluated in 332 GD patients and 351 unrelated controls from Chinese Cantonese population. SNP rs5743565 in TLR1 conferred a protective effect against GD. The minor allele G of rs5743565 decreased the risk of GD in all cases (odds ratio; ORG vs. A = 0.72 (0.58–0.91); p = 0.005; ptrend = 0.004) and early onset patients (ORG vs. A = 0.72 (0.56–0.91); p = 0.007; ptrend = 0.006). This study provided evidence that genetic variation rs5743565 in TLR1 might be associated with the decreased susceptibility of GD.

Vacuum-assisted alkaline pretreatment as an innovative approach for enhancing fermentable sugar yield and decreasing inhibitor production of sugarcane bagasse

Sodium hydroxide pretreatment of sugarcane bagasse under vacuum conditions was established and evaluated in this study. Compared to pretreatment under conventional moderate pressure conditions, only half of the total phenolic compounds and less than half of the formic acid were produced under vacuum conditions, while the yield of total fermentable sugar was significantly increased by 31.38%. The pretreatment parameters: NaOH concentration, pretreatment time, and pretreatment temperature, were optimized using response surface methodology based on the response values of the total fermentable sugar yield (TFSY) and the total fermentable sugar concentration (TFSC), respectively. Under the optimal conditions, the TFSY of 0.5146g/g and the TFSC of 17.37g/L were achieved, respectively. By adjusting the ratio of cellulases to xylanase, the TFSY reached a maximum of 0.5213g/g when the ratio was 1:1, while the maximum TFSC of 17.71g/L was achieved when the ratio was 1:4.

Enhanced enzymatic saccharification of sugarcane bagasse pretreated by sodium methoxide with glycerol

Sodium methoxide (CH3ONa) with glycerol pretreatment (CWGP) was performed to improve the enzymatic digestibility of sugarcane bagasse (SCB). Response surface methodology was utilized to optimize the CWGP parameters for pretreating SCB from the perspective of total fermentable sugar yield (TFSY) and total fermentable sugar concentration (TFSC). Under the optimal CWGP conditions, 0.5666g/g of TFSY (0.82% CH3ONa, 1.11h, 150°C) and 17.75g/L of TFSC (0.87% CH3ONa, 1.38h, 149.27°C) were achieved, corresponding to delignification of 79.05% and 79.34%, respectively. Compared the pretreatment using glycerol or CH3ONa alone, the CWGP has significant synergies to enhance the enzymatic efficiency of SCB. The physical and chemical characteristics of untreated and pretreated SCBs were analyzed using FT-IR, XRD, and SEM, and the results suggest that CWGP significantly increased the susceptibility of the substrates to enzymatic digestibility. Ultimately, CWGP might be a prospective candidate for the pretreatment process of enzyme-based lignocellulosic biorefineries.