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 ... -  《-》

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 ... -  《-》

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 ... -  《-》

Impact of bagasse lignin-carbohydrate complexes structural changes on cellulase adsorption behavior.

Pretreatment technology has attracted much attention as an effective method for the conversion of sugarcane bagasse into biochemicals. However, residual lignin-carbohydrate complexes (LCC) can negatively impact the subsequent enzymatic hydrolysis of bagasse. In this work, the changes in bagasse LCC after pretreatment with hot water and dilute acid were characterized by component analysis, 13C NMR and 1H-13C HSQC NMR to reveal the correlation between LCC structure and cellulase adsorption. A real-time dynamic model of LCC affecting adsorption of cellulase was constructed using a quartz crystal microbalance (QCM-D). The QCM-D results demonstrated that cellulase exhibited different adsorption characteristics on different LCCs. For example, the maximum adsorption capacities for cellulase onto the raw material LCC (RW-LCC), hot water pretreated LCC (LHW-LCC), and dilute acid pretreated LCC (AP-LCC) at 4 °C were 29.0 ng/cm2, 94.9 ng/cm2 and 129.8 ng/cm2, respectively. In addition, the adsorption rate constants for cellulase on RM-LCC, LHW-LCC and AP-LCC at 4 °C were 0.09, 0.14 and 0.19, respectively.

Zhang Q ，Wan G ，Li M ，Jiang H ，Wang S ，Min D ... -  《-》

Investigation of the pellets produced from sugarcane bagasse during liquid hot water pretreatment and their impact on the enzymatic hydrolysis.

In the process of liquid hot water (LHW) pretreatment, there are numbers of pellets formed on the lignocellulosic surface. The characteristics and effect of pellets on the enzymatic hydrolysis of LHW-treated sugarcane bagasse (SCB) were investigated. After SCB was treated with LHW at 180°C, the pellets deposited on the surface of solid residues were extracted gently with 1% sodium hydroxide (NaOH) solution. They were composed of 81.0% lignin, 7.0% glucan, and 3.2% xylan. The LHW pretreatment solution (PS) was sprayed to the filter paper, and the pellets were observed on its surface. Fourier transform infrared spectroscopy (FTIR) data showed that lignin was also the main component of the PS pellets. The effect of the pellets on enzymatic hydrolysis was chiefly attributed to the steric hindrance, not the cellulase adsorption. The structural characteristics of LHW-treated SCB might play a more important role in influencing the enzymatic hydrolysis than the pellets.

Wang W ，Zhuang X ，Yuan Z ，Yu Q ，Qi W ... -  《-》