This study aimed to determine the effect of applying stimulatory agents to liquid cultured Inonotus obliquus on the simultaneous accumulation of exo-polysaccharides (EPS) and their monosaccharide composition. Different stimulatory agents (VB6, VB1, betulin and birch extract) were investigated for their effects on active exo-polysaccharides by submerged fermentation of I. obliquus. The mycelial biomass, reducing sugar content, EPS yield and α-glucosidase inhibition rate were determined, and the EPS obtained was analyzed for monosaccharide composition. The results showed that the addition of all the four stimulatory agents could significantly increase the inhibitory activity against α-glucosidase of EPS than the control, whereas EPS from 4 μg/mL VB1-containing medium had the best effect with an estimated IC50 value 24.34 μg/mL. Among the four stimulatory agents, VB6 gave maximum production of mycelial biomass and EPS at the concentration of 4 μg/mL with a increase of 50.79% and 114.46%, respectively. In addition, betulin had a significant effect on increasing the EPS yield and activity, and birch extract had a significantly stimulatory effect on the mycelial growth and the polysaccharides activity, only slightly worse than VB6 and VB1. Moreover, the addition of different stimulatory agents changed the monosaccharide composition of polysaccharides, which had a correlation with polysaccharide activity.

Previous studies showed that aromatic compounds such as lignin, phenols, and furans were main inhibitors of cellulase hydrolysis in recycled alkali black liquor (RBL), which should be removed to improve alkali utilization. In this study, three polymeric resins, XAD-4, XAD-16N, and XAD-7HP, were evaluated for their abilities to remove lignin from alkali black liquor recycled at the third time. Adsorption conditions of adsorbent dose and equilibrium time, isotherms, and kinetics were investigated. Of three tested adsorbents, XAD-16N was the most efficient, which can remove 89.84% of lignin after adsorption at an adsorbent-to-solution ratio of 1:4 for 2.5 h. Pseudo-second-order model was efficient to represent XAD-16N and XAD-7HP adsorption kinetics. Adsorption behavior of XAD-4 on RBL was fitted better to Langmuir model, while XAD-16N and XAD-7HP adsorption were more consistent with Freundlich model. The cellulase hydrolysis rate of corn straw treated with RBL after XAD-16N adsorption combined with ozone was 86.89%, which was only 0.89% lower than that of sodium hydroxide combined with ozone treatment. Structure characterization proved that the damage of XAD-16N adsorbed RBL to corn straw was similar to that of sodium hydroxide. It indicated that adsorption was effective in inhibitor removal from RBL to improve alkali utilization.

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In this study, the effects and mechanism of pretreatments of three types of chemical reagents combined with Fenton on poplar sawdust were studied and the optimization of enzymatic hydrolysis conditions was conducted using response surface methodology. The results showed that cellulase and hemicellulase had the best hydrolysis effect after NaOH-Fenton pretreatment, which were 63.73% and 29.29%, respectively. The optimal process of poplar substrate was to react in 1% NaOH at 100 ℃ for 1 h, then placed in the Fenton reaction system of 0.2 mmol Fe 2+ and 25 mmol H2O2 for 7 h, and finally subjected to enzymatic hydrolysis for 72 h at 52 ℃, with a liquid-solid ratio of 33 and 15 μL/g of β-glycosidase. Under this condition, the enzymatic hydrolysis rates of cellulase and hemicellulase reached 86.65% and 43.9%, respectively. In conclusion, the combination of NaOH and Fenton pretreatment can effectively promote the enzymatic hydrolysis of poplar sawdust, which has great potential in the production of cellulosic ethanol.