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The study investigated the feasibility of co-production of nanocellulose crystal (CNC) and ethanol using the bleached pine kraft pulp (BPKP) as a substrate by enzymatic hydrolysis. An engineering strain Penicillum oxalicum cEES-XM was constructed to produce suitable cellulase used in enzymatic hydrolysis of BPKP for preparing CNC. The cellulase from Trichoderma reesei SCB18 was used for simultaneous saccharification and fermentation of residues and hydrolysates from enzymatic hydrolysis for producing ethanol. The result showed that the CNC yield reached 7.35 % (w/w) by hydrolysis at 10 % solid content, and the final ethanol concentration was 13.27 mg/mL in fermentation liquor. Using SEM, XRD, TGA, and DLS methods, the characteristics of CNC including, morphology, crystallinity, thermal stability and particle size distribution, were also examined. This work provided a reference for realizing high-efficient application of cellulose in the pulp.

Nonproductive adsorption of cellulase to lignin dramatically influenced the hydrolysis efficiency of lignocellulose. By comparing the adsorption behaviors of CBH and EG, we found that the adsorption of EG to lignin showed lower adsorption velocity and capacity versus CBH. During the adsorption of EG to lignin, carbohydrate binding domain (CBM) and catalytic domain (CD) both played an important role by a two-step adsorption process, in which CD slowly bond on lignin and developed stronger interaction with lignin. The optimal binding position of EG on lignin was consistent with that on polysaccharide located in the open catalytic tunnel. So, the adsorption of EG to lignin not only limited the movement of enzyme, but also restricted the catalytic ability of enzyme, which dramatically influenced enzymatic hydrolysis. Increasing the proportion of EG in cellulase cocktails or engineering "weak lignin adsorbed" EG was necessary to relieve the influence of lignin adsorption on hydrolysis.

Because cellulase was the main enzyme used in bioconversion of lignocellulose, it was a valid way to reduce the hydrolysis cost by increasing the adsorption and hydrolysis efficiency of cellulase. In this study, modified cellobiohydrolases (CBHs) and endoglucanases (EGs) were constructed. Two engineered cellulases CBH-TrCBMV27E,P30D,Link1 and EG-TrCBMV27E,P30D,Link1 well-performed during hydrolysis. Compared to wild-type enzymes, EG-TrCBMV27E,P30D,Link1 had relatively less adsorption ability to lignin and greater affinity to cellulose, especially Avicel. However, for CBH-TrCBMV27E,P30D,Link1, the hydrolysis manner was changed and in favor to hydrolysis process, although the adsorption properties were unexpected. It suggested that various binding conformations of polysaccharide on CBMs hypothetically resulted in different functions of CBMs, including binding ability, processive and digestive properties on fiber surface. Fusion of T. r-CBMV27E,P30D,Link1 to cellulase, both CBH and EG, gave the destruction ability of enzyme and increased the accessible surface of substrate to cellulase, enhanced the adsorption and hydrolysis efficiency of cellulase.

Commercial cellulase preparations for lignocellulose bioconversion are mainly produced by the fungus Trichoderma reesei. The maximum cellulose conversion of T. reesei cellulase mixture was 15%-20% higher than that of Penicillium oxalicum in the hydrolysis of corncob residue and Avicel. Nevertheless, both preparations hydrolyzed more than 92% of cellulose in NaOH-mercerized Avicel. When added to Avicel hydrolysis residue that was less reactive to P. oxalicum cellulases, cellobiohydrolase I (CBH I) from T. reesei resulted in a higher cellulose conversion than its homologous proteins from P. oxalicum and Aspergillus niger at the same protein loadings. Further domain exchange experiment attributed the high hydrolytic efficiency of T. reesei CBH I to its inter-domain linker and cellulose-binding domain. The results in part explained the superior performance of T. reesei cellulases on the degradation of native crystalline cellulose, and highlighted the important role of cellulose-binding region in determining the degree of hydrolysis by cellulases.

Xylo-oligosaccharides, as the important intermediates of hemicellulose degradation, widely exist in hydrolysate from pretreatment and enzymatic hydrolysis of lignocellulose. This study showed that ...

Using fermentable sugars from lignocelluloses to produce chemicals and fuels was a way to resolve the energy crisis and environmental problems, but nonproductive adsorption of cellulase onto lignin is big challenge for bioconversion of cellulose to fermentable sugars. As cellobiohydrolase (CBH) is the main enzyme in cellulase mixture, understanding the adsorption mechanism of CBH onto lignin is important to enhance CBH catalytic efficiency by avoiding the nonproductive adsorption. This study suggested that CBH displayed high adsorption affinity to lignin, especially for the lignin isolated from liquid-hot-water pretreated substrate, and a stable combination of lignin-CBH was formed. The CBH adsorbed to lignin still had the catalytic ability on Avicel, although the ability was decreased. The possible reason, by molecular docking, was that the catalytic domain of CBH was irreversibly adsorbed onto lignin mainly through a hydrophobic cleft located oppositely to catalytic tunnel, not influencing the catalytic...

Non-productive adsorption of cellulase onto lignin restricted the movement of cellulase and also hindered the cellulase recycling in bioconversion of lignocellulose. In this study, effect of temperature and pH on adsorption and desorption of cellobiohydrolase (CBH) on lignin and its possible mechanism were discussed. It found that pH value and temperature influenced the adsorption and desorption behaviors of CBH on lignin. Different thermodynamic models suggested that the action between lignin and CBH was physical action. More CBH was adsorbed onto lignin, but lower initial adsorption velocity was detected at 50 °C comparing with 4 °C. Elevating pH value could improve desorption of cellulase from lignin. The changes of hydrophobicity and electric potential on protein surface may partially explain the impact of environmental conditions on the adsorption and desorption behaviors of CBH on lignin, and comparing to electrical interaction, the hydrophobicity may be the dominating factor influencing the behaviors.

Cellulase (mainly endoglucanase, EG) has been used in pulp modification for improving paper quality through environmentally friendly process. But low activity in alkaline pH and high filter paper activity (FPA) were still obstacles for extending the cellulase application in papermaking industry. In the study, an alkali-tolerant EG gene of Bacillus subtilis Y106 was homologous over-expressed for obtaining suitable enzyme used in pulp modification. The engineering strain could produce the crude enzyme with more alkali-tolerant EG and little PFA. Potential of the crude enzyme in modification of different pulps were investigated. It was found that the enzyme could be used for improving drainage and strength properties of pulps from softwood, hardwood and non-wood materials, especially non-wood pulp such as wheat straw pulp. The underlying mechanisms of pulp modification and different effects on various types of pulps by the EG treatment were also discussed by studying the change in fibers characteristics and fiber bonding.

Because of the inferior properties of wheat straw pulp compared with wood pulp, wheat straw pulp needs to be ameliorated to meet the requirements of high-grade paper production. Enzymatic treatment with cellulase and/or xylanase is recognized as an environmentally friendly and effective method for pulp modification; however, an improper enzyme system and low enzyme activity in alkaline pH are still the main obstacles to the industrial application of the enzymes. In this study, we co-expressed alkali-tolerant endoglucanase (EG) and xylanase in Bacillus subtilis Y106-WT and successfully produced alkali-tolerant enzymes that simultaneously contained high EG and xylanase activity, but little FPA and cellobiohydrolase (CBH) activity, i.e., the activities of EG, xylanase, FPA and CBH of the crude enzyme from the fermentation liquor were 8.20, 60.40, 0.12 and 0.02 IU/ml, respectively, after 64 h of fermentation. Compared to the control, the pulp brightness, breaking length, burst index and tear index of wheat straw chemical pulp increased by 2.0% ISO, 8.7%, 16.6% and 9.3%, respectively, and the beating degree decreased by 15% after treatment using the recombinant enzyme with 0.20 IU/ml EG and 1.5 IU/ml xylanase. The synergistic effect between endoglucanase and xylanase occurred during the enzymatic treatment. The possible mechanism of pulp modification was also discussed.

Efficient deconstruction of lignocellulose is achieved by the synergistic action of various hydrolytic and oxidative enzymes. However, the aldonolactones generated by oxidative enzymes have inhibitory effects on some cellulolytic enzymes. In this work, D-glucono-1,5-lactone was shown to have a much stronger inhibitory effect than D-glucose and D-gluconate on β-glucosidase, a vital enzyme during cellulose degradation. AltA, a secreted enzyme from Penicillium oxalicum, was identified as an aldonolactonase which can catalyze the hydrolysis of D-glucono-1,5-lactone to D-gluconic acid. In the course of lignocellulose saccharification conducted by cellulases from P. oxalicum or Trichoderma reesei, supplementation of AltA was able to relieve the decrease of β-glucosidase activity obviously with a stimulation of glucose yield. This boosting effect disappeared when sodium azide and ethylenediaminetetraacetic acid (EDTA) were added to the saccharification system to inhibit the activities of oxidative enzymes. In summary, we describe the first heterologous expression of a fungal secreted aldonolactonase and its application as an efficient supplement of cellulolytic enzyme system for lignocellulose biodegradation.

In this study, three endoglucanases (EGs; Cel7B, Cel5B, and Cel12A), one cellobiohydrolase (CBH), and two auxiliary proteins (swollenin: SWO1 and SWO4) were used to hydrolyze microcrystalline cellulose (MCC) for cellulose nanocrystal (CNC) preparation. The mixture experiment of the three EGs showed that high CNC yield was obtained when the ratio of Cel7B and Cel5B is 1:1.11 (protein weight). Moreover, the addition of CBH (1 mg/g) and SWO1 from Trichoderma reesei effectively increased the yield of CNC. On the basis of the results, the cellulase-producing strain of Penicillium oxalicum M12 was engineered to improve its cellulase system. An engineered strain of cEES performed well in CNC preparation. CNC with a yield of 11.79 % and a crystallinity of 83.85 % were produced using the crude enzyme from cEES as a means to hydrolyze MCC, and the size and shape of CNC were uniform and fusiform.

Bisulfite pretreatment is a proven effective method for improving the enzymatic hydrolysis of empty fruit bunch (EFB) from oil palm for bioethanol production. In this study, we set out to determine the changes that occur in the structure and properties of EFB materials and fractions of hemicellulose and lignin during the bisulfite pretreatment process. The results showed that the crystallinity of cellulose in EFB increased after bisulfite pretreatment, whereas the EFB surface was damaged to various degrees. The orderly structure of EFB, which was maintained by hydrogen bonds, was destroyed by bisulfite pretreatment. Bisulfite pretreatment also hydrolyzed the glycosidic bonds of the xylan backbone of hemicellulose, thereby decreasing the molecular weight and shortening the xylan chains. The lignin fractions obtained from EFB and pretreated EFB were typically G-S lignin, and with low content of H units. Meanwhile, de-etherification occurred at the β-O-4 linkage, which was accompanied by polymerization and demethoxylation as a result of bisulfite pretreatment. The adsorption ability of cellulase differed for the various lignin fractions, and the water-soluble lignin fractions had higher adsorption capacity on cellulase than the milled wood lignin. In general, the changes in the structure and properties of EFB provided insight into the benefits of bisulfite pretreatment.

β-Xylosidase activity is deficient in most cellulase enzymes secreted by filamentous fungi, which limits effective enzymatic hydrolysis of hemicellulose in lignocellulose materials and resulted in accumulation of xylo-oligosaccharides that inhibit the cellulase and xylanase activitives. An endogenous β-xylosidase gene, xyl3A , was overexpressed using two types of promoters in cellulolytic P. oxalicum RE-10. The mutants RXyl, RGXyl-1 and RGXyl-2 displayed higher β-xylosidase production than native strain RE-10 besides higher cellulase and xylanase activities, especially RGXyl-1, showing the highest β-xylosidase activity of 15.05 ± 1.79 IU/mL, about 29 folds higher than native strain, more than the highest level reported by literature. Enzymatic hydrolysis results indicated the cellulase RGXyl-1 not only increased glucose and xylose yields and thus resulted in high ethanol yield during the simultaneous saccharification and fermentation, but decreased the total enzyme loading compared to starting RE-10, which indicated a good prospect of industrial application in bioconversion of lignocellulose.

A polygalacturonate lyase (PGL), PelA, was purified from the culture broth of Bacillus subtilis 7-3-3, with a molecular weight, optimal temperature, and pH of approximately 45 kDa, 55 °C, and 9.4, respectively. The PGL gene ( pelA ) was homologously overexpressed in B. subtilis 7-3-3 to increase the gene copies and enhance the PGL production. The resulting PGL activity was 2138 U mL −1 at 44 h, and the productivity reached 48.58 U (mL h) −1 through the homologous overexpression of strain B-pN-pelA in a 7.5 L fermentor, the highest PGL production compared to those reported in literature to the best of our knowledge. Crude enzyme has high PGL and PGase activity, which can remove 50.58% of pectin in unpretreatment ramie fibers at 50 °C for 4 h. Meanwhile, the enzyme system with a low level hemicellulase and almost no cellulase will further help in enhancing the efficiency of degumming besides maintaining tenacity of plant fiber. The B. subtilis B-pN-pelA shows high genetic stability and has great potential in the textile industry.

Background In the bioconversion of lignocellulosic substrates, the adsorption behavior of cellulase onto lignin has a negative effect on enzymatic hydrolysis of cellulose, decreasing glucose production during enzymatic hydrolysis, thus decreasing the yield of fermentation and the production of useful products. Understanding the interaction between lignin and cellulase is necessary to optimize the components of cellulase mixture, genetically engineer high-efficiency cellulase, and reduce cost of bioconversion. Most lignin is not removed during liquid hot water (LHW) pretreatment, and the characteristics of lignin in solid substrate are also changed. To understand the interactions between cellulase and lignin, this study investigated the change in the characteristics of lignin obtained from corn stover, as well as the behavior of cellulase adsorption onto lignin, under various severities of LHW pretreatment. Results LHW pretreatment removed most hemicellulose and some lignin in corn stover, as well as improved enzymatic digestibility of corn stover. After LHW pretreatment, the molecular weight of lignin obviously increased, whereas its polydispersity decreased and became more negative. The hydrophobicity and functional groups in lignin also changed. Adsorption of cellulase from Penicillium oxalicum onto lignin isolated from corn stover was enhanced after LHW pretreatment, and increased under increasing pretreatment severity. Different adsorption behaviors were observed in different lignin samples and components of cellulase mixtures, even in different cellobiohydrolases (CBHs), endo-beta-1, 4-glucanases (EGs). The greatest reduction in enzyme activity caused by lignin was observed in CBH, followed by that in xylanase and then in EG and β-Glucosidase (BGL). The adsorption behavior exerted different effects on subsequent enzymatic hydrolysis of various biomass substrates. Hydrophobic and electrostatic interactions may be important factors affecting different adsorption behaviors between lignin and cellulase. Conclusions LHW pretreatment changed the characteristics of the remaining lignin in corn stover, thus affected the adsorption behavior of lignin toward cellulase. For different protein components in cellulase solution from P. oxalicum, electrostatic action was a main factor influencing the adsorption of EG and xylanase onto lignin in corn stover, while hydrophobicity affected the adsorption of CBH and BGL onto lignin.

Background Non-productive cellulase adsorption onto lignin has always been deemed to negatively affect the enzymatic hydrolysis of lignocellulosic feedstocks. Therefore, understanding enzyme-lignin interactions is essential for the development of enzyme mixtures, the processes of lignocellulose hydrolysis, and the genetic modification of lignocellulosic biomass and enzymes. In this work, we examined the properties of six lignins from diverse types of lignocellulosic biomass (aspen, pine, corn stover, kenaf, and two Arabidopsis lines, wild-type and SALK mutant of fah1) to determine the mechanism of differences in their adsorption of enzymes. Results We found that lignin sources affected enzyme adsorption using structural features, such as functional groups and lignin composition. Guaiacyl (G) lignin had a higher adsorption capacity on enzymes than syringyl (S) lignin. The low S/G ratio and high uniform lignin fragment size had good correlations with high adsorption capacity. A higher content of phenolic hydroxyl groups and a lower content of carboxylic acid groups resulted in stronger adsorption affinity for corn stover lignin (CL) than for kenaf lignin (KL) and aspen lignin (AL). The lower amount of aliphatic hydroxyls that reduced hydrophobic interactions could explain the higher adsorption capacity of pine lignin (PL) than CL. Enzyme activity assays, as well as the hydrolysis of Avicel, phosphoric acid-swollen cellulose (PASC), and holocellulose, were performed to study the behaviors of mono-component enzymes that resulted in adsorption. We found that cellobiohydrolase (CBH) and xylanase were adsorbed the most by all lignins, endoglucanase (EG) showed less inhibition, and β-glucosidase (BG) was the least affected by lignins, indicating the important role of carbohydrate-binding module (CBM) in protein adsorption. Conclusion Lignin sources affect enzyme adsorption using structural features and lignin composition, such as S/G ratio, carboxylic acid, aliphatic hydroxyl, and phenolic hydroxyl. For mono-component enzymes, the adsorption capacity decreased in the order CBH, xylanase > EG > BG. These investigations revealed the difference in lignin properties between diverse biomass and adsorption capacity of enzymes to lignins, and the possible underlying mechanism. The results can also serve as a reference for the genetic modification of lignocellulosic biomass and enzymes.

Corn stover is a promising feedstock for bioethanol production because of its abundant availability in China. To obtain higher ethanol concentration and higher ethanol yield, liquid hot water (LHW) pretreatment and fed-batch semi-simultaneous saccharification and fermentation (S-SSF) were used to enhance the enzymatic digestibility of corn stover and improve bioconversion of cellulose to ethanol. The results show that solid residues from LHW pretreatment of corn stover can be effectively converted into ethanol at severity factors ranging from 3.95 to 4.54, and the highest amount of xylan removed was approximately 89%. The ethanol concentrations of 38.4 g/L and 39.4 g/L as well as ethanol yields of 78.6% and 79.7% at severity factors of 3.95 and 4.54, respectively, were obtained by fed-batch S-SSF in an optimum conditions (initial substrate consistency of 10%, and 6.1% solid residues added into system at the prehydrolysis time of 6 h). The changes in surface morphological structure, specific surface area, pore volume and diameter of corn stover subjected to LHW process were also analyzed for interpreting the possible improvement mechanism.

Reed was pretreated with liquid hot water (LHW) and then subjected to fed-batch semi-simultaneous saccharification and fermentation (S-SSF) to obtain high ethanol concentration and yield. Results show that water-insoluble solid (WIS) produced from reed pretreated at 180 and 210°C could be effectively converted to ethanol by using Saccharomyces cerevisiae. The optimum conditions for bio-ethanol production are as follows: fermentation temperature of 36°C, pH of 4.8 with cellulase loading of 40 filter paper activity units/g oven-dried WIS, and 18 h pre-hydrolysis at 50°C. Approximately 6.4% (w/v) fed-batch substrate was added after 6 h of the 18 h enzymatic pre-hydrolysis. The highest ethanol concentration of 39.4 g/L was achieved. The conversion of glucan in the WIS to ethanol reached 79.1% (180°C) and 75.1% (210°C) respectively. The ethanol yields per kg of oven-dried reed were 283 g/L at 180°C and 244 g/L at 210°C.

Reed is a widespread-growing, inexpensive, and readily available lignocellulosic material source in northeast China. The objective of this study is to evaluate the liquid hot water (LHW) pretreatment efficiency of reed based on the enzymatic digestibility and ethanol fermentability of water-insoluble solids (WISs) from reed after the LHW pretreatment. Several variables in the LHW pretreatment and enzymatic hydrolysis process were optimized. The conversion of glucan to glucose and glucose concentrations are considered as response variables in different conditions. The optimum conditions for the LHW pretreatment of reed area temperature of 180°C for 20min and a solid-to-liquid ratio of 1 : 10. These optimum conditions for the LHW pretreatment of reed resulted in a cellulose conversion rate of 82.59% in the subsequent enzymatic hydrolysis at 50°C for 72 h with a cellulase loading of 30 filter paper unit per gram of oven-dried WIS. Increasing the pretreatment temperature resulted in a higher enzymatic digestibility of the WIS from reed. Separate hydrolysis and fermentation of WIS showed that the conversion of glucan to ethanol reached 99.5% of the theoretical yield. The LHW pretreatment of reed is a suitable method to acquire a high recovery of fermentable sugars and high ethanol conversion yield.

Biofuels and bio-based chemicals from lignocellulosic biomass are sustainable, making them alternatives to petroleum-derived fuels and chemicals to address the challenges of the shortage of crude oil supply and climate change resulted from the overconsumption of petroleum-based products, particularly in China. However, high cost in liberating sugars from lignocellulosic biomass is still the bottleneck of the commercialization of biofuels and bio-based chemicals. In this article, the major components of cellulases and their synergistic role in the hydrolysis of pre-treated biomass is reviewed, followed by how to evaluate the enzymatic hydrolysis. With the elucidation of the underlying mechanism of the conformations of the enzyme molecules and their effectiveness in attacking cellulose substrate, more efficient enzymes are expected to be developed. Using the high production strain Penicillium decumbens, the on-site production of cellulases for cellulose ethanol production is discussed.

Reducing process cost of the bioconversion of lignocellulosic is a challenge. In China, abundant acidic wastewater from monosodium glutamate production is difficult to treat, leading to serious water pollution. In this study, acidic liquid (ALC) and solid residue components (SC) obtained from the wastewater were used in pretreatment and cellulase production, respectively, to evaluate their potential in bioconversion of corn stover. Optimum pretreatment conditions (170 degrees C, 60min, 0.75% ALC) were identified by a central composite design method. There were little difference in the chemical components and digestibility (above 84%) of between ALC and H(2)SO(4)-treated corn stover, and amounts of HMF and furfural in liquor after pretreatment with ALC and H(2)SO(4) under optimum conditions. SC can be substituted for (NH(4))(2)SO(4) in liquor fermentation to produce cellulase with comparable filter paper (about 10.7U/ml) and beta-glucosidase (about 2.7U/ml) activities.

Ethanol production from corncob residues (CCR) pretreated by different methods was studied. The structure features of these CCR were analyzed by Fourier transform-infrared spectrum (FT-IR), X-ray diffraction (XRD), and field emission scanning electron microscope (SEM). Simultaneous saccharification and fermentation (SSF) was performed by adding crude cellulase preparations from Penicillium decumbens JUA10-1 at 30 degrees C. The results suggested that different pretreatments resulted in different composition and structure of residues; these changes had a significant influence on ethanol productivity and concentration. The fed-batch method was combined with SSF to enhance ethanol concentration further and reduce enzyme dosage. Moreover, the absorption and desorption phenomena of cellobiohydrolase I (CBH I) (70 kDa) were observed to be related to lignin contents in residues. These results demonstrated that despite the application of low enzyme dosage, high concentration ethanol could be produced from pretreated corncobs by combining fed-batch method with SSF.

Aims: To screen and characterize a novel fungus with powerful and selective delignification capability on wheat straw. Methods and Results: A fungus capable of efficient delignification under solid-state fermentation (SSF) conditions on wheat straw was screened. After 5 days of incubation, 13·07% of the lignin was removed by fungal degradation, and 7·62% of the holocellulose was lost. Furthermore, 46·53% of the alkali lignin was removed after 2 days of liquid fermentation. The fungus was identified as Fusarium concolor based on its morphology and an analysis of its 18S rDNA gene sequence. The molecular weight distribution of lignin was evaluated by gel permeation chromatography. Enzyme assay indicated that the fungus produced laccase, cellobiose dehydrogenase, xylanase and cellulase during the incubation period. Intracellular lignin peroxidase, manganese peroxidase and laccase were produced during liquid fermentation. Conclusions: We have successfully screened a fungus, F. concolor, which can efficiently degrade the lignin of wheat straw, with slight damage to the cellulose, after 5 days of SSF. Significance and Impact of the Study: The newly isolated strain could be used in pretreatment of lignocellulose materials prior to biopulping, bioconversion into fuel and substrates for the chemical industry.

The effects of the starch, protein, and soluble oligosaccharides contents in wheat bran on the extracellular biomass-hydrolyzing enzymes activities released by Penicillium decumbens mycelia grown in batch fermentations have been examined. The results showed increased starch content correlated directly with an increase in released amylase activity but inversely with the levels of secreted cellulase and xylanase. High amounts of protein in wheat bran also reduced the activities of cellulase, xylanase and protease in the culture medium. The effects of the soluble and insoluble components of wheat bran and cello-oligosaccharides supplements on production of extracellular cellulase and xylanase were compared. The soluble cello-oligosaccharides compositions in wheat bran were proved to be one of the most significant factors for cellulase production. According to the results of this research, determining and regulating the composition of wheat bran used as a fermentation supplement may allow for improved induction of cellulase and xylanase production.

Crude enzymes produced by different strains were used in the production of bleached wheat straw pulp. Pre-treatment with enzymes from Penicillium A10 and Aspergillus L22 at a xylanase dosage of 4 IU/g prior to pulping decreased pulp kappa number by 6.29% and 12.07% respectively as compared to the control. High cellulase activity in crude enzymes has a negative influence on pulping. Xylanase pre-bleaching reduced chlorine charge by 20–30%, or increased final brightness by approximately 4–5% ISO, and improved the pulp strength properties. Xylanase could substitute for alkali extraction in CEH sequence, and be used for treating chemical-bleached pulp, which resulted in higher strength properties for bleached pulp. Modification of bleached pulp with enzymes of 3 IU/g (on xylanase) increased pulp brightness and breaking length by 3–6% ISO and 160–790 m respectively, and decreased post color number and beating degree of pulp by 29–36% and 2.5–5.5 °SR respectively, as compared to the original pulp.

Background Liquid hot water (LHW) pretreatment is an effective and environmentally friendly method to produce bioethanol with lignocellulosic materials. In our previous study, high ethanol concentration and ethanol yield were obtained from water-insoluble solids (WIS) of reed straw and corn stover pretreated with LHW by using fed-batch semi-simultaneous saccharification and fermentation (S-SSF). However, high cellulase loading and the large amount of wash water possibly limit the practical application of LHW pretreatment. To decrease cellulase loading and the amount of wash water, we performed Tween 40 pretreatment before WIS was subjected to bioethanol fermentation. Results Results showed that the optimum conditions of Tween 40 pretreatment were as follows: Tween 40 concentration of 1.5%, WIS-to-Tween 40 ratio of 1:10 (w/v), and pretreatment time of 1 hour at ambient temperature. After Tween 40 pretreatment, cellulase loading could be greatly reduced. After Tween 40 pretreatment, the residual liquid could be recycled for utilization but slightly affected ethanol concentration and yield. The unwashed WIS could obtain a high ethanol concentration of 56.28 g/L (reed straw) and 52.26 g/L (corn stover) by Tween 40 pretreatment using fed-batch S-SSF. Ethanol yield reached a maximum of 69.1% (reed straw) and 71.1% (corn stover). Conclusions Tween 40 pretreatment was a very effective and less costly method with unwashed WIS. This pretreatment could greatly reduce cellulase loading and save wash water. Higher ethanol concentration was obtained almost without reducing ethanol yield.