Lignin prepared from different alkaline pretreated sugarcane bagasse and its effect on enzymatic hydrolysis.

Sugarcane bagasse (SCB) was pretreated by sodium hydroxide (SH), alkaline ethanol (AE) and alkaline hydrogen peroxide (AHP), and the solid residue with similar lignin content after different pretreatment was selected. Enzymatic saccharification with different substrates was performed at 2%, 10%, and 20% (w/v) solid loading. After that, the lignin from different substrate was extracted and its structure was characterized. Furthermore, the adsorption capability of isolated lignin to cellulase and its effect on enzymatic hydrolysis were studied. The results showed that, as the substrate content increased from 2% (w/v) to 20% (w/v), the glucose yield after digestion of SH, AE, and AHP pretreated SCB reduced by 41.8%, 35.4%, and 28.7%, respectively. The inhibitory effect of different prepared lignin on the digestibility of Avicel was as follows, SH pretreated lignin (SHL) > cellulase enzymatic hydrolysis lignin (CEL) > AE pretreated lignin (AEL) > AHP pretreated lignin (AHPL), which exhibited positive correlation with its non-productive adsorption capability to cellulase. Lignin samples with low negative zeta potential, high hydrophobicity and high ration of syringyl (S) to guaiacyl (G) were unfavorable for the enzymatic saccharification of cellulose.

Xu C ，Zhang J ，Zhang Y ，Guo Y ，Xu H ，Liang C ，Wang Z ，Xu J ... -  《-》

Comparative study on the properties of lignin isolated from different pretreated sugarcane bagasse and its inhibitory effects on enzymatic hydrolysis.

Five sugarcane bagasse lignin samples, namely, dilute sulfuric acid (DSAL), sodium hydroxide (SHL), ethanol (EL), hot liquid water (HLWL)-pretreated residual solids, and raw material (cellulolytic enzyme lignin, CEL), were extracted. Comparative studies on the physicochemical properties of isolated lignin, nonproductive adsorption of cellulase by lignin, and its effect on enzymatic hydrolysis was performed. Results showed that the molecular weight and homogeneity of lignin remarkably decreased after pretreatment compared with CEL. Lignin with low negative zeta potential, high phenolic hydroxyl group content and hydrophobicity exhibited strong nonproductive adsorption performance to cellulase. This phenomenon was positively correlated with it's inhibitory effect on enzymatic hydrolysis. Compared with the control (without lignin), the Avicel conversion rate (40 mg lignin/200 mg Avicel) decreased by 10.74%, 9.28%, 8.73%, 4.22%, and 2.80% after digestion of Avicel for 72 h with the presence of EL, SHL, CEL, HLWL, and DSAL, respectively.

Xu C ，Liu F ，Alam MA ，Chen H ，Zhang Y ，Liang C ，Xu H ，Huang S ，Xu J ，Wang Z ... -  《-》

Adsorption characteristics of cellulase and β-glucosidase on Avicel, pretreated sugarcane bagasse, and lignin.

Although adsorption is an essential step in the enzymatic hydrolysis of lignocellulosic materials, literature reports controversial results in relation to the adsorption of the cellulolitic enzymes on different biomasses/pretreatments, which makes difficult the description of this phenomenon in hydrolysis mathematical models. In this work, the adsorption of these enzymes on Avicel and sugarcane bagasse pretreated by the hydrothermal bagasse (HB) and organosolv bagasse (OB) methods was evaluated. The results have shown no significant adsorption of β-glucosidase on Avicel or HB. Increasing solids concentration from 5% (w/v) to 10% (w/v) had no impact on the adsorption of cellulase on the different biomasses if stirring rates were high enough (>100 rpm for Avicel and >150 rpm for HB and OB). Adsorption equilibrium time was low for Avicel (10 Min) when compared with the lignocellulosic materials (120 Min). Adsorption isotherms determined at 4 and 50 °C have shown that for Avicel there was a decrease in the maximum adsorption capacity (Emax) with the temperature increase, whereas for HB increasing temperature increased Emax . Also, Emax increased with the content of lignin in the material. Adsorption studies of cellulase on lignin left after enzymatic digestion of HB show lower but significant adsorption capacity (Emax = 11.92 ± 0.76 mg/g).

Machado DL ，Moreira Neto J ，da Cruz Pradella JG ，Bonomi A ，Rabelo SC ，da Costa AC ... -  《-》

Effect of bisulfite treatment on composition, structure, enzymatic hydrolysis and cellulase adsorption profiles of sugarcane bagasse.

The effect of sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL) on composition, structure, enzymatic hydrolysis and cellulase adsorption profiles of sugarcane bagasse (SCB) was investigated. SPORL gave a higher SCB hydrolysis yield (85.33%) compared to dilute acid pretreatment (DA) (64.39%). The SEM pictures showed that SPORL SCB structure became more disordered and looser, suggesting SPORL SCB was more accessible to cellulase. The zeta potential of SPORL SCB suspension (-21.89mV) was significantly different from that of DA SCB (-12.87mV), which demonstrated the lignin in SPORL SCB was more hydrophilic. With regard to cellulase adsorption profiles, SPORL SCB had a lower non-productive adsorption (14.87mg/glignin) and a higher productive adsorption (37.67 mg/gcarbohydrate) compared with DA SCB (17.05mg/glignin; 25.79mg/gcarbohydrate). These results indicated that SPORL SCB had better accessibility to cellulase and the higher productive cellulase adsorption of SPORL SCB had improved hydrolysis.

Liu ZJ ，Lan TQ ，Li H ，Gao X ，Zhang H ... -  《-》

Comprehensive understanding of enzymatic saccharification of Betaine:Lactic acid-pretreated sugarcane bagasse.

Green solvents, especially deep eutectic solvents (DESs), are widely applied to pretreat biomass for enhancing its enzymatic hydrolysis. In this work, lactic acid was selected as the hydrogen-bond-donor to prepare Betaine-base DES (Betaine:LA), The DES was utilized to pretreat sugarcane bagasse (SCB) at 160 ℃ for 80 min (severity factor LogR0 = 3.67). The influences of Betaine:LA treatment on the chemical composition, crystal and microstructure structure of cellulose, and cellulase digestion were investigated. The results showed that the lignin (47.1%) and xylan (44.6%) were removed, the cellulase digestibility of Betaine:LA-treated SCB was 4.2 times that of the raw material. This improved efficiency was attributed to the enhanced accessibility of cellulose, the weakened surface area of lignin, the declined hydrophobicity, and the decreased crystallinity of cellulose. Several compelling linear correlations were fitted between enzymatic hydrolysis and these alterations of physicochemical features, comprehensively understanding enzymatic saccharification of Betaine:LA-pretreated SCB.

Chen Y ，Ma C ，Tang W ，He YC ... -  《-》