Operating at High Solid Content

Operating at high solid content in the enzymatic hydrolysis process is crucial for large-scale development of bioproduct and biofuel production processes. The aim of utilizing high solid content is to reach high sugar concentrations and subse­quently high concentrations of fermentation products, such as ethanol (Jprgensen et al. 2007a; Hodge et al. 2009). Furthermore, maintaining high substrate con­centrations throughout the conversion process is important for the energy balance and economic viability of biofuels production. Obtaining high concentration of fermentation product reduces global production cost since downstream processing and water consumption can be lowered. In case of ethanol production, distillation increases significantly the energy demand of the process, especially when ethanol concentrations are below 4 % (Ohgren et al. 2006).

In general, higher substrate loadings results in higher concentration of sugars. However, it has been shown that enzyme performance gradually decreases as substrate concentration increased. This can be attributed to enzyme inhibition by end products or toxics, presence of high concentrations of lignin and mass transfer limitations (Jprgensen et al. 2007a; Kristensen et al. 2009). In addition, some recent studies have reported a decrease in the adsorption capacity of cellulase enzymes to cellulose at high substrate loadings due to the effect of hydrolysis products (Kristensen et al. 2009; Wang et al. 2011). To overcome these barriers, different process configurations and strategies have been suggested to increase solids concentration in bioconversion processes.

Operating at high initial solids content (above 10-15 % (w/w)) involves tech­nical barriers. Viscosity of the pretreated materials is usually very high, which implies mass transfer limitations and mixing difficulties. Operating fed-batch processes by adding fresh substrate when viscosity decreases has been shown as an effective strategy to increase substrate concentrations in fermentations processes (Ballesteros et al. 2002; Varga et al. 2004). Another possibility is carrying out a prehydrolysis prior to initiate the simultaneous saccharification and fermentation (SSF) process. Using this strategy, the enzymes act at optimum temperature and reduce viscosity, which can result in higher substrates loadings (Rosgaard et al. 2007; Manzanares et al. 2011). A recent advance for operating at high consistency is the development of novel bioreactors with improved mixing capacity and low energy consumption (Jprgensen et al. 2007b; Zhang et al. 2009).

Another problem when operating at high substrate concentration is product inhibition. Cellobiose, glucose, and hemicellulose-derived sugars have been shown to inhibit the enzymes action (Xiao et al. 2004). In SSF processes, sugars released by the action of the enzymes are converted directly to ethanol by the fermenting microorganism, which reduces end-product inhibition (Ballesteros et al. 1994; Olsson et al. 2006). Constant removal of glucose during the process has been also proposed (Andric et al. 2010).

Degradation compounds originated from carbohydrates and lignin during the pretreatment affect the enzymatic hydrolysis (Tengborg et al. 2001; Ganna-Aparicio et al. 2006) and the fermenting microorganisms (Palmqvist and Hahn-Hagerdal 2000a; Oliva et al. 2003; Oliva et al. 2004). At high substrate loadings, the concentration of these compounds increases, therefore their influence in the bioconversion process can become more significant. Washing the pretreated material has been typically employed to eliminate toxic compounds and increase enzymatic hydrolysis and fermentation yields. To avoid washing and use the whole slurries, detoxification strategies such as laccase treatments have been studied to reduce the concentration of phenolic compounds and increase substrate concentrations in fermentation (Moreno et al. 2012).

Different articles reported the utilization of high substrate concentrations for ethanol production. Using wet oxidized and steam exploded corn stover, a sub­strate consistency of 15 % and 10-30 % dry matter (DM) in fermentation experiments, respectively, was studied (Varga et al. 2004; Lu et al. 2010). Using corn stover pretreated by combination of stream explosion and alkaline hydrogen peroxide, it was reached a solids loading of 30 % (Yang et al. 2010). With hydrothermal pretreated and steam pretreated wheat straw, it was possible to carry out hydrolysis and SSF at high substrate concentrations up to 20-30 % (Jprgensen 2009; Ballesteros et al. 2011), and with steam pretreated spruce it could be reached a consistency of 14 % (Hoyer et al. 2010).

6.4 Conclusion

Efficient utilization of lignocellulosic materials in a biorefinery depends on the advances in pretreatment technologies, enzyme saccharification, and fermentation of sugars to fuels and chemicals. Optimization of pretreatment and enzymatic hydrolysis processes is crucial to make bioconversion processes from lignocellu — losic biomass viable and cost-effective. The aim of the pretreatment is increasing the digestibility of carbohydrates while minimizing degradation of sugars and generation of toxic compounds. The pretreatment has to be adapted to the different raw materials and should be validated at large scale. The cost and efficiency of enzyme products still represents a major bottleneck to improve the economy of industrial biorefineries. To reduce costs of enzymatic hydrolysis processes, it is required the optimization of enzymatic mixtures in order to increase sugars pro­duction yields, reduce pretreatment severity, and decrease enzyme dosages. Complexity of lignocellulosic substrates involves that enzyme cocktails should be adapted for each raw material and type of pretreatment. In addition, operating at high solid content should be considered as a key issue for biofuels production. Finally, the integration of all the process steps has a remarkable importance to increase overall process efficiency and promote large-scale development. The type of biomass and pretreatment determines the process configuration requirements for hydrolysis and fermentation as each step has a large impact on all subsequent stages.

References

Agrawal P, Verma D, Daniell H (2011) Expression of Trichoderma reesei b-mannanase in tobacco chloroplasts and its utilization in lignocellulosic woody biomass hydrolysis. PLOS ONE 6(12):e29302. doi:10.1371/journal. pone.0029302

Alvira P, Tomas-Pejo E, Ballesteros M, Negro MJ (2010) Pretreatment technologies for an efficient bioethanol production process based on enzymatic hydrolysis: a review. Bioresour Technol 101:4851-4861

Alvira P, Negro MJ, Ballesteros M (2011a) Effect of endoxylanase and alpha-arabinofuranosidase supplementation on the enzymatic hydrolysis of steam exploded wheat straw. Bioresour Technol 102:4552-4558

Alvira P, Tomas-Pejo E, Negro MJ, Ballesteros M (2011b) Strategies of xylanase supplemen­tation for an efficient saccharification and cofermentation process from pretreated wheat straw. Biotechnol Prog 27:944-950

Andric P, Meyer AS, Jensen PA, Dam-Johansen K (2010) Effect and modelling of glucose inhibition and in situ glucose removal during enzymatic hydrolysis of pretreated wheat straw. Appl Biochem Biotechnol 160:280-297

Bajpai P (2004) Biological bleaching of chemical pulps. Crit Rev Biotechnol 24:1-58

Baker JO, King MR, Adney WS, Decker SR, Vinzant TB, Lantz SE, Nieves RE, Thomas SR, Li LC, Cosgrove DJ, Himmel ME (2000) Investigation of the cell-wall loosening protein expansin as a possible additive in the enzymatic saccharification of lignocellulosic biomass. Appl Biochem Biotechnol 84-86:217-223

Ballesteros I, Negro MJ, Oliva JM, Cabanas A, Manzanares P, Ballesteros M (2006) Ethanol production from steam-explosion pretreated wheat straw. Appl Biochem Biotechnol 130:496­508

Ballesteros I, Negro MJ, Oliva JM, Saez F, Manzanares P, Ballesteros M (2011) Increased ethanol concentration in saccharification and fermentation media of steam-exploded cereal straw. XIX. In: International symposium on alcohol fuels (ISAF), Development and utilization of alcohols fuels, to promote sustainability

Ballesteros I, Oliva JM, Carrasco JE, Ballesteros M (1994) Effect of media supplementation of ethanol production by simultaneous saccharification and fermentation process. Appl Biochem Biotechnol 45-46:283-294

Ballesteros I, Oliva JM, Negro MJ, Manzanares P, Ballesteros M (2002) Ethanol production from paper material using a simultaneous saccharification and fermentation system in a fed-batch basis. World J Microb Biot 18(6):559-561

Ballesteros M (2010) Enzymatic hydrolysis of lignocellulosic biomass. In: Waldron K (ed) Bioalcohol production. Biochemical conversion of lignocellulosic biomass. Woodhead Publishing, UK, pp 159-177

Banerjee G, Scott-Craig JS, Walton JD (2010) Improving enzymes for biomass conversion: a basic research perspective. Bioenerg Res 3:82-92 Bayer EA, Henrissat B, Lamed R (2008) The cellulosome: a natural bacterial strategy to combat biomass recalcitrance. In: Himmel ME (ed) Biomass recalcitrance. Deconstructing the plant cell wall for bioenergy. Blackwell Publishing, USA, pp 407-435 Bayer EA, Belaich JP, Shoham Y, Lamed R (2004) The cellulosomes: multienzyme machines for degradation of plant cell wall polysaccharides. Annu Rev Microbiol 58:521-554 Beg QK, Kapoor M, Mahajan L, Hoondal GS (2001) Microbial xylanases and their industrial applications: a review. Appl Microbiol Biotechnol 56:326-338 Benko Z, Siika-aho M, Viikari L, Reczey K (2008) Evaluation of the role of xyloglucanase in the enzymatic hydrolysis of lignocellulosic substrates. Enzyme Microb Technol 43:109-114 Berlin A, Gilkes N, Kilburnn D, Bura R, Markov A, Okunev O, Gusarov A, Maximenko V, Gregg D, Saddler J (2005) Evaluation of novel fungal cellulase prepration for ability to hydrolyze softwood substrate-evidence of the role of accessory enzymes. Enzyme Microb Technol 37:175-184

Berlin AB, Maximenko V, Gilkes N, Saddler J (2006) Optimization of enzymes complexes for lignocellulose hydrolysis. Biotechnol Bioeng 97(2):287-296 Bourbonnais R, Paice MG (1990) Oxidation of non-phenolic substrates. An expanded role for laccase in lignin biodegradation. FEBS Lett 267:99-102 Carvalheiro F, Duarte LC, Gfrio FM (2008) Hemicellulose biorefineries: a review on biomass pretreatments. J Sci Ind Res 67:849-864

Chandra RP, Bura R, Mabee WE, Berlin A, Pan X, Saddler JN (2007) Substrate pretreatment: the key to effective enzymatic hydrolysis of lignocellulosics? Adv Biochem Eng/Biotechnol 108:67-93

Cosgrove DJ (2000) Loosening of plant cell walls by expansins. Nature 407:321-326 Crepin VF, Faulds CB, Connerton IF (2004) Functional classification of microbial feruloyl esterases. Appl Microbiol Biotechnol 63:647-652 Dahlman O, Jacobs A, Berg J (2003) Molecular properties of hemicelluloses located in the surface and inner layers of hardwood and softwood pulps. Cellulose 10:325-334 Decker SR, Siika-Aho M, Viikari L (2008) Enzymatic depolymerization of plant cell wall hemicellulases. In: Himmel ME (ed) Biomass Recalcitrance. Deconstructing the Plant Cell Wall for Bioenergy. Blackwell Publishing, USA, pp 407-435 Dias AA, Freitas GS, Marques GSM, Sampaio A, Fraga IS, Rodrigues MAM, Evtuguin DV, Bezerra RMF (2010) Enzymatic saccharification of biologically pretreated wheat straw with white-rot fungi. Bioresour Technol 101:6045-6050 DOE. US Department of Energy (2003) Energy information agency. Available from: http:// www. exxonmobil. com/corportae/energy_outlook. aspx Eriksson T, Karlsson J, Tjerneld F (2002) A model explaining declining rate in hydrolysis of lignocellulose substrates with cellobiohydrolase I (Cel 7A) and endoglucanase I (Cel7B) of Trichoderma reesei. Appl Biochem Biotechnol 101:41-60 Esteghlalian AR, Svivastava V, Gilkes N, Gregg DJ, Saddler JN (2001) An overview of factors influencing the enzymatic hydrolysis of lignocellulosic feedstocks. In: Himmel ME, Baker W, Saddler JN (eds) Glycosyl hydrolases for biomass conversion. ACS, USA, pp 100-111 Faulds CB, Mandalari G, Curco RB, Bisignano G, Christakopoulos P, Waldron KW (2006) Synergy between xylanases from glycoside hydrolase family 10 and family 11 and a feruloyl esterase in the release of phenolic acids from cereal arabinoxylan. Appl Microbiol Biotechnol 71:622-629

Foreman PK, Brown D, Dankmeyer L, Dean R, Diener S, Dunn-Coleman NS, Goedegebuur F, Houfek TD, England GJ, Kelley AS, Meerman HJ, Mitchell T, Mitchinson C, Olivares HA, Teunissen PJ, Yao J, Ward M (2003) Transcriptional regulation of biomass-degrading enzymes in the filamentous fungus Trichoderma reesei. J Biol Chem 278:31988-31997 Garaa-Aparicio MP, Ballesteros I, Gonzalez A, Oliva JM, Ballesteros M, Negro MJ (2006) Effect of inhibitors release during steam-explosion pretreatement of barley straw on enzymatic hydrolysis. Appl Biochem Biotechnol 129:278-288 Garaa-Aparicio MP, Ballesteros M, Manzanares P, Ballesteros I, Gonzalez A, Negro MJ (2007) Xylanase contribution to the efficiency of cellulose enzymatic hydrolysis of barley straw. Appl Biochem Biotechnol 136-140:353-366

Gfrio FM, Fonseca C, Carvalheiro F, Duarte LC, Marques S, Bogel-Lukasik R (2010) Hemicelluloses for fuel ethanol: a review. Bioresour Technol 101:4775-4800 Guillen F, Martmez AT, Martmez MJ (1992) Substrate specificity and properties of the aryl — alcohol oxidase from the ligninolytic fungus Pleurotus eryngii. Eur J Biochem 209:603-611 Guillen F, Martmez MJ, Munoz C, Martmez AT (1997) Quinone redox cycling in the ligninolytic fungus Pleurotus eryngii leading to extracellular production of superoxide anion radical. Arch Biochem Biophys 339:190-199

Hahn-Hagerdal B, Karhumaa K, Fonseca C, Spencer-Martins I, Gorwa-Grauslund MF (2007) Towards industrial pentose-fermenting yeast strains. Appl Microbiol Biotechnol 74:937-953 Harris PV, Welner D, McFarland KC, Re E, Navarro Poulsen JC, Brown K, Salbo R, Ding H, Vlasenko E, Merino S, Xu F, Cherry J, Larsen S, Lo Leggio L (2010) Stimulation of lignocellulosic biomass hydrolysis by proteins of glycoside hydrolase family 61: structure and function of a large, enigmatic family. Biochemistry 49:3305-3316 Hendriks ATWM, Zeeman G (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresour Technol 100:10-18

Henrissat B, Davies G (1997) Structural and sequences-based classification of glycoside hydrolases. Curr Opin Struct Biol 7:637-644

Himmel ME, Andey WS, Baker JO, Nieves RA, Thomas SR (1996) Cellulases: structure, function, and applications. In: Wyman CE (ed) Handbook on bioethanol production and utilization. Taylor and Francis, UK, pp 143-161 Himmel ME, Ding SY, Johnson DK, Adney WS, Nimlos MR, Brady JW, Foust TD (2007) Biomass recalcitrance: engineering plants and enzymes for biofuels production. Science 315:804-807

Himmel ME, Picataggio SK (2008) Our challenge is to acquire deeper understanding of biomass recalcitrance and conversion. In: Himmel ME (ed) Biomass recalcitrance. Deconstructing the Plant Cell Wall for Bioenergy. Blackwell Publishing, USA, pp 1-6 Hodge DB, Karim MN, Schell DJ, McMillan JD (2009) Model-based fed-batch for high-solids enzymatic cellulose hydrolysis. Appl Biochem Biotechnol 152(1):88-107 Hoyer K, Galbe M, Zacchi G (2010) Effects of enzyme feeding strategy on ethanol yield in fed — batch simultaneous saccharification and fermentation of spruce at high dry matter. Biotechnol Biofuels 3:14

Hu J, Arantes V, Saddler JN (2011) The enhancement of enzymatic hydrolysis of lignocellulosic substrates by the addition of accessory enzymes such as xylanase: is it an additive or synergistic effect? Biotechnol Biofuels 4:36

Igarashi K, Uchihashi T, Koivula A, Wada M, Kimura S, Okamoto T, Penttila M, Ando T, Samejima M (2011) Traffic jams reduce hydrolytic efficiency of cellulase on cellulose surface. Science 333:1279-1282

Jin M, Lau MW, Balan V, Dale BE (2010) Two-step SSCF to convert AFEX-treated switchgrass to ethanol using commercial enzymes and Saccharomyces cerevisiae 424A(LNH-ST). Bioresour Technol 101:8171-8178

J0rgensen H (2009) Effect of nutrients on fermentation of pretreated wheat straw at very high dry matter content by saccharomyces cerevisiae. Appl Biochem Biotechnol 153:44-57 J0rgensen H, Kristensen JB, Felby C (2007a) Enzymatic conversion of lignocellulose into fermentable sugars: challenges and opportunities. Biofuel Bioprod Bior 1:119-134

J0rgensen H, Olsson L (2006) Production of cellulases by Penicillium brasilianum IBT 20888- Effect of substrate on hydrolytic performance. Enzyme Microb Technol 38:381-390 J0rgensen H, Vibe-Pedersen J, Larsen J, Felby C (2007b) Liquefaction of lignocellulose at high — solids concentrations. Biotechnol Bioeng 96:862-870 Juhasz T, Szengyel Z, Reczey K, Siika-Aho M, Viikari L (2005) Characterization of cellulases and hemicellulases produced by Trichoderma reesei on various carbon sources. Process Biochem 40:3519-3525

Jurado M, Prieto A, Martmez-Alcala A, Martmez AT, Martmez MJ (2009) Laccase detoxification of steam-exploded wheat straw for second generation bioethanol. Bioresour Technol 100:6378-6384

Jonsson JL, Palmqvist E, Nilvebrant N-O, Hahn-Hagerdal B (1998) Detoxification of wood hydrolysates with laccase and peroxidase from the white-rot fungus Trametes versicolor. Appl Microbiol Biotechnol 49:691-697

Kalyani D, Dhiman SS, Kim H, Jeya M, Kim I-W, Lee J-K (2012) Characterization of a novel laccase from the isolated Coltricia perennis and its application to detoxification of biomass. Process Biochem 47:671-678

Kersten PJ (1990) Glyoxal oxidase of Phanerochaete chrysosporium: Its characterization and activation by lignin peroxidase. Proc Natl Acad Sci USA 87:2936-2940 Kolb M, Sieber V, Amann M, Faulstich M, Schieder D (2012) Removal of monomer delignification products by laccase from Trametes versicolor. Bioresourc Technol 104:298­304

Kovacs K, Macrelli S, Szakacs G, Zacchi G (2009) Enzymatic hydrolysis of steam-pretreated lignocellulosic materials with Trichoderma viride enzymes produced in-house. Biotechnol Biofuels 2:14

Kristensen JB, Felby C, J0rgensen H (2009) Yield-determining factors in high-solids enzymatic hydrolysis of lignocellulose. Biotechnol Biofuels 2(1):11 Kubicek CP (1992) The cellulase proteins of Trichoderma reesei: structure, multiplicity, mode of action and regulation of formation. Adva Biochem Eng 45:1-27 Kuhar S, Nair LM, Kuhad RC (2008) Pretreatment of lignocellulosic material with fungi capable of higher lignin degradation and lower carbohydrate degradation improves substrate acid hydrolysis and the eventual conversion to ethanol. Can J Microbiol 54:305-313 Kumar P, Barrett DM, Delwiche MJ, Stroeve P (2009) Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Ind Eng Chem Res 48:3713-3729

Kumar R, Wyman CE (2008) Effect of enzyme supplementation at moderate cellulase loadings on initial glucose and xylose release from corn stover solids pretreated by leading technologies. Biotechnol Bioeng 102(2):457-467 Kumar R, Wyman CE (2009a) Does change in accessibility with conversion depend on both the substrate and pretreatment technology? Bioresour Technol 100:4193-4202 Kumar R, Wyman CE (2009b) Effect of xylanase supplementation of cellulase on digestion of corn stover solids prepared by leading pretreatment technologies. Bioresour Technol 100:4203-4213

Kumar R, Wyman CE (2009c) Effects of cellulase and xylanase enzymes on the deconstruction of solids from pretreatment of poplar by leading technologies. Biotechnol Prog 25:302-314 Kurasin M, Valjamae P (2011) Processivity of cellobiohydrolases is limited by the substrate. J Biol Chem 286:169-177

Laureano-Perez L, Teymouri F, Alizadeh H, Dale BE (2005) Understanding factors that limit enzymatic hydrolysis of biomass. Appl Biochem Biotechnol 121:1081-1099 Larsson S, Cassland P, Jonsson LF (2001) Development of a Saccharomyces cerevisiae strain with enhanced resistance to phenolic compounds inhibitors in lignocellulose hydrolysates by heterologous expression of laccase. Appl Environ Microbiol 67:1163-1170 Lu Y, Wang Y, Xu G, Chu J, Zhuang Y, Zhang S (2010) Influence of high solid concentration on enzymatic hydrolysis and fermentation of steam-exploded corn stover biomass. Appl Biochem Biotechnol 160:360-369

Mansfield SD, Mooney C, Saddler JN (1999) Substrate and enzyme characteristics that limit cellulose hydrolysis. Biotechnol Prog 15:804-816 Manzanares P, Negro MJ, Oliva JM, Saez F, Ballesteros I, Ballesteros M, Cara C, Castro E, Ruiz E (2011) Different process configurations for bioethanol production from pretreated olive pruning biomass. J Chem Technol Biotechnol 86(6):881-887 Martmez AT (2002) Molecular biology and structure-function of lignin-degrading heme peroxidases. Enz Microb Technol 30:425-444

Martmez AT, Speranza M, Ruiz-Duenas FJ, Ferreira P, Camarero S, Guillen F, Martmez MJ, Gutierrez A, del Rfo JC (2005) Biodegradation of lignocellulosics: Microbiological, chemical and enzymatic aspects of fungal attack to lignin. Intern Microbiol 8:195-204 Martinez D, Berka RM, Henrissat B, Saloheimo M, Arvas M, Baker SE, Chapman J, Chertkov O, Coutinho PM, Cullen D, Danchin EGJ, Grigoriev IV, Harris P, Jackson M, Kubicek CP, Han CS, Ho I, Larrondo LF, De Leon AL, Magnuson JK, Merino S, Misra M, Nelson B, Putnam N, Robbertse B, Salamov AA, Schmoll M, Terry A, Thayer N, Westerholm-Parvinen A, Schoch CL, Yao J, Barabote R, Nelson MA, Detter C, Bruce D, Kuske CR, Xie G, Richardson P, Rokhsar DS, Lucas SM, Rubin EM, Dunn-Coleman N, Ward M, Brettin TS (2008) Genome sequencing and analysis of the biomass-degrading fungus Trichoderma reesei (syn. Hypocrea jecorina). Nature Biotechnol 26:553-560

Mayer AM, Staples RC (2002) Laccase: new functions for an old enzyme. Phytochem 60:551­565

Medve J, Karlsson J, Lee D, Tjerneld F (1998) Hydrolysis of microcrystalline cellulose by cellobiohydrolase I and endoglucanase II from Trichoderma reesei: adsorption, sugar production pattern, and synergism of the enzymes. Biotechnol Bioeng 59(5):621-634 Merino ST, Cherry J (2007) Progress and challenges in enzyme development for biomass utilization. Adv Biochem Eng Biotechnol 108:95-120 Moilanen U, Kellock M, Galkin S, Viikari L (2011) The laccase-catalyzed modification of lignin for enymatic hydrolysis. Enzyme Microb Technol 49:492-498 Moreno AD, Ibarra D, Fernandez JL, Ballesteros M (2012) Different laccase detoxification strategies for ethanol production from lignocellulosic biomass by the thermotolerant yeast Kluyveromyces marxianus CECT 10875. Bioresour Technol 106:101-109 Mukhopadhyay M, Kuila A, Tuli D, Banerjee R (2011) Enzymatic depolymerization of Ricinus communis, a potential lignocellulosic for improved saccharification. Biomass Bioenerg 35:3584-3591

Mosier N, Wyman CE, Dale BD, Elander RT, Lee YY, Holtzapple M, Ladisch CM (2005) Features of promising technologies for pretreatment of lignocellulosic biomass. Bioresour Technol 96:673-686

Numan MT, Bhosle NB (2006) Alpha-L-arabinofuranosidases: the potential applications in biotechnology. J Ind Microbiol Biotechnol 33:247-260 Ohgren K, Rudolf A, Galbe M, Zacchi G (2006) Fuel ethanol production from steam-pretreated corn stover using SSF at higher dry matter content. Biomass Bioenerg 30:863-869 Oliva JM, Ballesteros I, Negro MJ, Manzanares P, Cabanas A, Ballesteros M (2004) Effect of binary combinations of selected toxic compounds on growth and fermentation of Kluyver­omyces marxianus. Biotechnol Prog 20:715-720 Oliva JM, Saez F, Ballesteros I, Gonzalez A, Negro MJ, Manzanares P, Ballesteros M (2003) Effect of lignocellulosic degradation compounds in the steam explosion pretreatment on ethanol fermentation by thermotolerant yeast Kluyveromyces marxianus. Appl Biochem Biotechnol 105-108:141-153

Olsson L, Soerensen HR, Dam BP, Christensen H, Krogh KM, Meyer AS (2006) Separate and simultaneous enzymatic hydrolysis and fermentation of wheat hemicellulose with recombinant xylose utilizing Saccharomyces cerevisiae. Appl Microbiol Biotechnol 129­132:117-129

Olsson L, J0rgensen H, Krogh KBR, Roca C (2004) Bioethanol production from lignocellulosic material. In: Dumitriu S (ed) Polysaccharides: structural diversity and functional versatility. CRC Press, USA, pp 957-993

Palmqvist E, Hahn-Hagerdal B (2000a) Fermentation of lignocellulosic hydrolysates. II: inhibitors and mechanism of inhibition. Bioresour Technol 74:25-33 Palmqvist E, Hahn-Hagerdal B (2000b) Fermentation of lignocellulosic hydrolysates. I: inhibition and detoxification. Bioresour Technol 74:17-24

Palonen H, Viikari L (2004) Role of oxidative enzymatic treatments on enzymatic hydrolysis of softwood. Biotechnol Bioeng 86:550-557

Pan XJ, Gilkes N, Saddler JN (2006) Effect of acetyl groups on enzymatic hydrolysis of cellulosic substrates. Olzforschung 60:398-401

Pan X, Xie D, Gilkes N, Gregg DJ, Saddler JN (2005) Strategies to enhance the enzymatic hydrolysis of pretreated softwood with high residual lignin content. Appl Biochem Biotechnol 124:1069-1079

Panagiotou G, Olsson L (2007) Effect of compounds released during pre-treatment of wheat straw on microbial growth and enzymatic hydrolysis rates. Biotechnol Bioeng 96:250-258 Perez JA, Ballesteros I, Ballesteros M, Saez F, Negro MJ, Manzanares P (2008) Optimizing liquid hot water pretreatment conditions to enhance sugar recovery from wheat straw for fuel — ethanol production. Fuel 87:3640-3647

Persson I, Tjerneld F, Hahn-Hagerdal B (1991) Fungal cellulolytic enzyme production: a review. Process Biochem 26:65-74

Polizeli ML, Rizzatti AC, Monti R, Terenzi HF, Jorge JA, Amorim DS (2005) Xylanases from fungi: properties and indusrtial applications. Appl Microbiol Biotechnol 67(5):577-591 Poutanen K, Puls J (1989) The xylanolytic enzyme system of Trichoderma reesei. In: Lewis G, Paice M (eds) Biogenesis and biodegradation of plant cell wall polymers. ACS, USA, pp 630­640

Qi B, Chen X, Su Y, Wan Y (2011) Enzyme adsorption and recycling during hydrolysis of wheat straw lignocellulose. Bioresour Technol 102:2881-2889 Qi B, Luo J, Chen G, Chen X, Wan Y (2012) Application of ultrafiltration and nanofiltration for recycling cellulase and concentrating glucose from enzymatic hydrolyzate of steam exploded wheat straw. Bioresour Technol 104:466-472

Qing Q, Yang B, Wyman CE (2010) Xylooligomers are strong inhibitors of cellulose hydrolysis by enzymes. Bioresour Technol 101:9624-9630 Ragauskas AJ, Williams CK, Davison BH, Britovsek G, Cairney J, Eckert CA, Frederick WJ, Hallett JP, Leak DJ, Liotta CL, Mielenz JR, Murphy R, Templer R, Tschaplinski T (2006) The path forward for biofuels and biomaterials. Science 311:484-489 Raweesri P, Riangrungrojana P, Pinphanichakarn P (2008) Alpha-L-arabinofuranosidase from Streptomyces sp. PC22: purification, characterization and its synergistic action with xylanolytic enzymes in the degradation of xylan and agricultural residues. Bioresour Technol 99:8981-8986

Remond C, Aubry N, Cronier D, №ё! S, Martel F, Roge B, Rakotoarivonina H, Debeire P, Chabbert B (2010) Combination of ammonia and xylanase pretreatments: impact on enzymatic xylan and cellulose recovery from wheat straw. Bioresour Technol 101:6712-6717 Rosgaard L, Andric P, Dam-Johansen K, Pedersen S, Meyer AS (2007) Effects of substrate loading on enzymatic hydrolysis and viscosity of pretreated barley straw. Appl Biochem Biotechnol 143:27-40

Ruiz-Duenas FJ, Martmez AT (2009) Microbial degradation of lignin: How a bulky recalcitrant polymer is efficiently recycled in nature and how we can take advantage of this. Microbial Biotechnol 2:164-177

Ruiz-Duenas FJ, Martmez MJ, Martmez AT (1999) Molecular characterization of a novel peroxidise isolated from the ligninolytic fungus Pleurotus eryngii. Mol Microbiol 31:223-235 Saha BC (2000) Alpha-L-arabinofuranosidases: biochemistry, molecular biology and application in biotechnology. Biotechnol Adv 18:403-423 Saha BC (2003) Hemicellulose bioconversion. J Ind Microbiol Biotechnol 30:279-291 Saloheimo M, Paloheimo M, Hakola S, Pere J, Swanson B, Nyyssonen E, Bhatia A, Ward M, Penttila M (2002) Swollenin, a Trichoderma reesei protein with sequence with sequence

similary to the plant expansins, exhibits disruption activity on cellulosic materials. Eur J Biochem 269:4202-4211

Salvachua D, Prieto A, Lopez-Abelairas M, Lu-Chau T, Martinez AT, Martinez MJ (2011) Fungal pretreatment: An alternative in second-generation ethanol from wheat straw. Bioresour Technol 102:7500-7506

Sanchez OJ, Cardona CA (2008) Trends in biotechnological production of fuel ethanol from different feedstocks. Bioresour Technol 99:5270-5295 Selig MJ, Adney WS, Himmel ME, Decker SR (2009) The impact of cell wall acetylation on corn stover hydrolysis by cellulolytic and xylanolytic enzymes. Cellulose 16:711-722 Selig MJ, Knoshaug EP, Adney WS, Himmel ME, Decker SR (2008) Synergistic enhancement of cellobiohydrolase performance on pretreated corn stover by addition of xylanase and esterase activities. Bioresour Technol 99:4997-5005

Sipos B, Benko Z, Dienes D, Reczey K, Viikari L, Siika-Aho M (2010) Characterisation of specific activities and hydrolytic properties of cell-wall-degrading enzymes produced by Trichoderma reesei Rut C30 on different carbon sources. Appl Biochem Biotechnol 161:347­364

Sipos B, Szilagyi M, Sebestyen Z, Perazzini R, Dienes D, Jakab E, Crestini C, Reczey K (2011) Mechanism of the positive effect of poly(ethylene glycol) addition in enzymatic hydrolysis of steam pretreated lignocelluloses. C R Biol 334:812-823 Sun Y, Cheng J (2002) Hydrolysis of lignocellulosic materials for ethanol production: a review. Bioresour Technol 83:1-11

Tabka MG, Herpoёl-Gimbert I, Monod F, Asther M, Sigoillot JC (2006) Enzymatic saccharification of wheat straw for bioethanol production by a combined cellulase xylanase and feruloyl esterase treatment. Enzyme Microb Tech 39:897-902 Taherzadeh MJ, Karimi K (2008) Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review. Int J Mol Sci 9:1621-1651 Tengborg C, Galbe M, Zacchi G (2001) Reduced inhibition of enzymatic hydrolysis of steam — pretreated softwood. Enzyme Microb Tech 28:835-844 Tenkanen M, Makkonen M, Perttula M, Viikari L, Teleman A (1997) Action of Trichoderma reesei mannanase on galactoglucomannan in pine kraft pulp. J Biotech 57:191-204 Teter S, Xu F, Nedwin GE, Cherry (2010) Enzymes for biorefineries. In: Kamm B, Gruber PR, Kamm M (eds) Biorefineries-industrial processes and products. Wiley, USA, pp 357-383 Tomas-Pejo ME, Ballesteros M, Oliva JM, Olsson L (2010) Adaptation of the xylose fermenting yeast Saccharomyces cerevisiae F12 for improving ethanol production in different fed-batch SSF processes. J Ind Microbiol Biotechnol 37:1211-1220 Tomas-Pejo ME, Alvira P, Ballesteros M, Negro MJ (2011) Pretreatment technologies for lignocellulose-to-bioethanol conversion. In: Larroche C, Ricke SC, Dussap CG, Gnansounou E, Pandey A (eds) Biofuels: Alternative feedstocks and conversion processes. Academic, USA, pp 149-176

Tu M, Chandra RP, Saddler JN (2007) Evaluating the distribution of cellulases and the recycling of free cellulases during the hydrolysis of lignocellulosic substrates. Biotechnol Prog 23:398­406

Tu M, Saddler JN (2010) Potential enzyme cost reduction with the addition of surfactant during the hydrolysis of pretreated softwood. Appl Biochem Biotechnol 161:274-287 Varga E, Klinke HB, Reczey K, Thomsen AB (2004) High solid simultaneous saccharification and fermentation of wet oxidized corn stover to ethanol. Biotechnol Bioeng 88:567-574 Vries RP, Harry CMK, Charlotte HP, Jacques AEB, Jaap V (2000) Synergy between enzymes from Aspergillus involved in the degradation of plant cell wall polysaccharides. Carbohyd Res 327:401-410

Wang W, Kang L, Wei H, Arora R, Lee YY (2011) Study on the decreased sugar yield in enzymatic hydrolysis of cellulosic substrate at high solid loading. Appl Biochem Biotechnol 164:1139-1149

Wilson DB (2008) Aerobic microbial cellulase systems. In: Himmel ME (ed) Biomass recalcitrance. Deconstructing the plant cell wall for bioenergy. Blackwell Publishing, USA, pp 374-392

Wyman CE, Balan V, Dale BE, Elander RT, Falls M, Hames B, Holtzapple MT, Ladisch MR, Lee YY, Mosier N, Pallapolu VR, Shi J, Thomas SR, Warner RE (2011) Comparative data on effects of leading pretreatments and enzyme loadings and formulations on sugar yields from different switchgrass sources. Bioresour Technol 102:11052-11062

Xiao Z, Zhang X, Greff DJ, Saddler JN (2004) Effects of sugar inhibition on cellulases and b- glucosidase during enzymatic hydrolysis of softwood substrates. Appl Biochem Biotechnol 113-116:1115-1126

Yang M, Li W, Liu B, Li Q, Xing J (2010) High-concentration sugars production from corn stover based on combined pretreatments and fed-batch process. Bioresour Technol 101:4884­4888

Yang B, Wyman CE (2008) Pretreatment: the key to unlocking low-cost cellulosic ethanol. Biofuel Bioprod Bior 2:26-40

Yang R, Xu S, Wang Z, Yang W (2005) Aqueous extraction of corncob xylan and production of xylooligosaccharides. LWT-Food Sci Technol 38:677-682

Yang M, Zhang A, Liu B, Li W, Xing J (2011) Improvement of cellulose conversion caused by the protection of Tween-80 on the adsorbed cellulase. Biochem Eng J 56:125-129

Zhang J, Siika-aho M, Tenkanen M, Viikari L (2011) The role of acetyl xylan esterase in solubilisation of xylan and enzymatic hydrolysis of wheat straw and giant reed. Biotechnol Biofuels 4:60

Zhang X, Qin W, Paice MG, Saddler JN (2009) High consistency enzymatic hydrolysis of hardwood substrates. Bioresour Technol 100:5890-5897

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