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Background Recently, interest in the utilization of corncob residue (CCR, with high lignin of 45.1%) as a feedstock for bioethanol has been growing. Surfactants have been one of the most popular additives intended to prevent the inhibitory effect of lignin on cellulolytic enzymes, thereby improving hydrolysis. In this study, the effects of biosurfactant tea saponin (TS) on the enzymatic hydrolysis of CCR and the bonding behavior of cellulolytic enzymes to the substrate were investigated. The surface tension in the supernatant was also detected to obtain-information about the characteristics and stability of TS. Results The glucose concentration was 17.15 mg/mL at 120 hours of hydrolysis with the low loading of cellulolytic enzymes (7.0 FPU/g cellulose and 10.5 BGU/g cellulose) and 5% CCR. The optimal dosage of TS was its critical micelle concentration (cmc, 1.80 mg/mL). The glucose yield was enhanced from 34.29 to 46.28 g/100 g dry matter by TS. The results indicate that TS can promote the adsorption of cellulolytic enzymes on the substrate and mediate the release of adsorbed enzymes. Meanwhile, TS improves the recovery of the cellulolytic enzymes after a hydrolysis cycle and prevents deactivation of the enzymes during the intense shaking process. The surface tension in supernatants of digested CCR with TS remained at 50.00 mN/m during the course of hydrolysis. It is interesting to note that biosurfactant TS can maintain the surface tension in supernatants, despite its digestibility by cellulolytic enzymes. Conclusions Serving as an accelerant of lignocellulose hydrolysis, TS can also be degraded by the cellulolytic enzymes and release glucose while retaining stability, which reduces the cost of both the cellulolytic enzymes and the additive. As the glucose from the TS could be utilized by yeast, further efforts will investigate the mechanism of function and the application of TS in the production of ethanol by simultaneous saccharification and fermentation (SSF). [ABSTRACT FROM AUTHOR]

Sugarcane bagasse was pretreated by green liquor combined with ethanol (GL-Ethanol) and green liquor combined with H2O2 (GL-H2O2). After 72 h of enzymatic hydrolysis, the glucose yields of sugarcane bagasse pretreated with GL-Ethanol and GL-H2O2 were 97.7% and 41.7%, respectively. The reason that GL-Ethanol was more effective than GLH2O2 has not been elucidated clearly. In this study, the chemical composition of the sugarcane bagasse and chemical structure of the isolated lignins after these two pretreatment methods were characterized to investigate their correlation with the enzymatic hydrolysis of sugarcane bagasse. The removal of lignins with GL-Ethanol pretreatment was much higher than that of GL-H2O2. In addition, the decomposition of cellulose was lower in the case of GL-Ethanol than in that of GL-H2O2. According to Fourier transform infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (NMR) studies, the ester bonds (belonging to lignincarbohydrate complex) could be broken during GL-Ethanol treatment. It was also found that the molecular weight of lignins obtained from GLEthanol was lower than that of lignins from GL-H2O2. [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]