Application of Steam Explosion as Pretreatment on Lignocellulosic

Review pubs.acs.org/IECR

Application of Steam Explosion as Pretreatment on Lignocellulosic Material: A Review N. Jacquet,*,† G. Maniet,† C. Vanderghem,† F. Delvigne,‡ and A. Richel† †

Department of Industrial Biological Chemistry and ‡Unité de Bio-industries/CWBI, University of Liège−Gembloux Agro-Bio Tech, Passage des Déportés No. 2, B-5030 Gembloux, Belgium ABSTRACT: Steam explosion is a thermo-mechanicochemical pretreatment which allows the breakdown of lignocellulosic structural components by the action of heating, formation of organic acids during the process, and shearing forces resulting in the expansion of the moisture. Two distinct stages compose the steam-explosion process: vapocracking and explosive decompression which include modification of the material components: hydrolysis of hemicellulosic components (mono- and oligosaccharides released), modification of the chemical structure of lignin, and modification of the cellulose crystallinity index, etc. These effects allow the opening of lignocellulosic structures and influence the enzymatic hydrolysis yield of the material.

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INTRODUCTION In the economic and energetic context of our society, it is universally recognized that an alternative to fossil fuels and oil based products will be needed in the nearest future. A potential solution is to develop second-generation biofuels and biobased products that utilize nonfood plant materials. The major component of these materials is lignocellulose, which is a complex composed by widely available biological polymers such as cellulose, hemicelluloses, and lignin. To make the conversion, these raw materials must be subjected to pretreatments which open the structure of the biomass and allow easier release of fermentable monosaccharides. For Grous et al.,1 three main factors facilitate the release of fermentable sugars. The first factor includes the separation of hemicelluloses, which increases the accessibility of the cellulose fraction by creation of large pores in the fiber structure, resulting in an increase of the number of sites available for hydrolysis reactions2 The second factor is the crystallinity of the cellulose. Various studies show that thermochemical treatments tend to increase the crystallinity index of the cellulose fraction, resulting in a decrease of the accessibility of the substrate. Finally, the accessibility to the cellulose fibers is strongly limited by the presence of the lignin matrix, surrounding the cellulose fraction. Lignin removal is essential for the achievement of efficient (enzymatic or chemical) hydrolysis.1 Several types of pretreatments allow the opening of lignocellulosic materials: acids and alkali process, hot water cracking, steam explosion, and high pressure treatment, etc. The main asset of steam-explosion pretreatment is its low energy consumption. Holtzapple et al.3 show that conventional milling techniques, applied to aspen wood, require higher energy (70%) than steam explosion to reach a comparable size reduction. The environmental impact of steam explosion is also more limited because this technology does not use any (or very little) chemical agent. This review, focused specifically on the steam-explosion technology, highlights the principles of this technique and its effects on various constituents of lignocellulosic material. © 2015 American Chemical Society

PROCESS DESCRIPTION The steam-explosion process was originally developed in 1924 by W. H. Mason to realize the production of chipboard panels. Its application was subsequently extended to the production of feed for ruminants during the second half of the 20th century.4 Technically, the steam-explosion installation is composed of a steam generator that supplies a reactor, which is subjected to a sudden depressurization. During depressurization, the material is ejected from the reactor and is recovered in the explosion tank (Figure 1). Description of the technology shows that two factors influence the efficiency of the process: the retention time and the pressure. Several studies show that hydrolysis of the hemicellulose fraction is correlated to the residence time of the biomass in the reactor. High residence time allows the complete hydrolysis of the hemicellulose fraction, which promotes downstream processes such as fermentation.5 Although hydrolysis products (mono- and oligosaccharides) are relatively stable in acidic conditions, they may undergo further reactions such as dehydration, fragmentation, and condensation. These subsequent reactions generate a variety of products such as furfural, hydroxymethylfurfural, levulinic and formic acid, and also various aromatic compounds which are fermentation inhibitors. An increase of the retention time is correlated with an increase of the amount of these degradation products, which must be absolutely minimized. Pressure plays also a major role in the process. Pressure is correlated to temperature and has an impact on hydrolysis of cellulose fractions and the kinetics of the production of degradation products. Furthermore, the pressure difference between the reactor and the atmospheric pressure is proportional to the intensity of the shearing forces applied to the biomass during the explosive release.6 Received: Revised: Accepted: Published: 2593

August 7, 2014 January 23, 2015 February 4, 2015 February 4, 2015 DOI: 10.1021/ie503151g Ind. Eng. Chem. Res. 2015, 54, 2593−2598

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Industrial & Engineering Chemistry Research

Figure 1. ULg−Gembloux Agro-Bio Tech steam-explosion pilot plant: (1) high pressure pump, (2) heaters, (3) gauges of steam boilers, (4) gauges of reactor, (5) isolation valve, (6) charging valve, (7) safety steam boiler valve, (8) safety reactor valve, (9) explosion valve, (10) purge valve, (11) recovery valves, and (12) gauge of explosion tank.

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SEVERITY FACTOR In relation to the important number of studies focused on the steam-explosion application on biomass, Chornet and Overend5 show that it was imperative to determine a representative factor to compare different parameters of the process. The results of the first studies realized on steam explosion indicate that a relationship could be established between the temperature of the process, the retention time, and the accessibility of the substrate, resulting in an improvement of the hydrolysis yields.5 From these observations, the authors develop a model that defines the severity of pretreatment based on the cumulative relation between temperature and retention time effects. This model is based on the hypothesis that process kinetics is of first order and obeys the Arrhenius law.5 ⎧ S = log⎨ ⎩

∫0

t

After considering the efficiency of a pilot-scale steamexplosion plant, it was shown that a significant time is required to reach the different target pressures. In these cases, the treatment severity must include the time necessary to reach the target pressure and the severity factor is calculated by the integral form ⎧ S = log⎨ ⎩

∫t

t1 2

⎛ T (t ) − 100 ⎞ ⎫ ⎟ dt ⎬ exp⎜ ⎝ 14.75 ⎠ ⎭

where t1 and t2 are the times at the start and the end of reaction, respectively. If the hypothesis which assumes that the temperature increases linearly with every increment in pressure (0.1 MPa), the severity factor can be calculated by the following integral form:

⎛ T (t ) − 100 ⎞ ⎫ ⎟ dt ⎬ exp⎜ ⎝ 14.75 ⎠ ⎭

⎧ ⎪ S = log⎨ ∑ ⎪ ⎩

where S = severity factor, T(t) = process temperature (°C), t = retention time (min), and 14.75 = activation energy value in the conditions where process kinetics are of first order and obey the Arrhenius law. When the volume of the steam-explosion reactor is small, the steam pressure can reach the target value in a very short time. In this case, the severity factor can be calculated by the following equation:

∫t

tn − 1 n

⎛ ⎜ Tn + exp⎜ ⎜ ⎝

(

Tn + 1 − Tn tn + 1 − tn

⎫

)(t − t ) − 100 ⎞⎟⎟ dt ⎪⎬ n

14.75

⎟ ⎠

⎪ ⎭

or the equation ⎧ 14.75(tn + 1 − tn) S = log⎨ ∑ Tn + 1 − Tn ⎩ ⎡ ⎛ T + 1 − 100 ⎞ ⎛ Tn − 100 ⎞⎤⎫ ⎟ − exp⎜ ⎟ ⎥⎬ × ⎢exp⎜ n ⎠ ⎝ 14.75 ⎠⎦⎭ ⎣ ⎝ 14.75

⎡ ⎛ T − 100 ⎞⎤ ⎟ S = log⎢t exp⎜ ⎝ 14.75 ⎠⎥⎦ ⎣

(1)

where tn and tn+1 are the initial times for increments n and n + 1 and Tn and Tn+1 are the process temperatures for times tn and tn+1, respectively.8,9

where T is the process temperature (°C).7 2594

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Industrial & Engineering Chemistry Research Chornet and Overend5 show that this model can be used to describe results presented in the literature. The amount of sugars obtained by Belkacemi10 and Heitz et al.11 on different lignocellulosic substrates can be correlated to the severity factor. However, Kaar et al.12 show that the Chornet and Overend model5 cannot be applied to all substrates and that the glucose yields obtained by the enzymatic hydrolysis of a pretreated bagasse are not constant for a given severity factor, indicating that the model must be adapted to the lignocellulosic substrate variety.

the increase of enzymatic hydrolysis yield is due to the removal of other biomass components such as hemicelluloses and lignin during the steam-explosion treatment.23 To explain the hydrolysis patterns, Jacquet et al.23 evidence that water retention and crystallinity properties of the cellulose steam-exploded samples must be considered simultaneously. Regarding crystallinity, results obtained for a moderate treatement (S < below 5.2) show a slight increase of the crystallinity of the steam-exploded samples with the increasing of treatment severity and contribute to an increase in the amount of very compact and resistant to enzymes regions which are less susceptible to enzymatic hydrolysis than amorphous regions.26−28 This increase of the crystallinity is attributed to a recrystallization of the amorphous cellulose induced by the rearrangement of the cellulose chains at high temperature and pressure.29 Atalla30 demonstrates in particular that a short high pressure treatment has more impact on the crystallinity than a long term treatment at a lower pressure. . Concerning water retention, the literature describes a continuous improvement of the water retention value with the severity factor applied (from 60% for a reference cellulose to 105% for treated C200 cellulose (S = 5.2)) leading to the decrease of fiber crystallinity combined with an increase in specific surface available for enzymatic hydrolysis.23,31 Studies indicate also that the separation of the cellulosic and hemicellulosic fractions (hydrophilic) and lignin (hydrophobic) greatly increments the number of hydroxyl groups available for making hydrogen bonds with water molecules. The results show that the water retention properties are related to the opening of the material structure. In a moderate range of steam-explosion treatment intensity (S < 5.2), the literature concludes that the increase of the amount of enzymatic binding sites induced by the improvement of water retention is counterbalanced by the crystallinity increase and the fact that a greater proportion of the substrate will be less accessible to enzymes.23 For higher severity treatment (S > 5.2), studies reveal that an important thermal degradation of cellulose occurred.9 This thermal degradation leads to an important change in substrate composition.32 Increasing amounts of degradation products in the sample induces a decrease of the quantity the cellulose available for hydrolysis and explains the decrease of the observed hydrolysis yield. Change in composition has also an impact on the physicochemical properties of the samples. The decrease in the cellulosic ratio of the samples is correlated to the decrease of the overall crystallinity and the large amount of degradation products (such as anhydrocellulose)33 combined with a significant disintegration of the material contributing to the higher water retention values observed.32 In addition to the recovery of the hemicellulosic sugars fraction and the improvement of the cellulosic fraction hydrolysis yields, the steam explosion induces important modifications in the structure of lignins. In the presence of organic acids, the hydroxyl groups of α carbons become reactive and lead to the formation of carbonium ions. At this time, two competitive reactions take place. First, the carbonium ions destabilize the β-4-O bond established between the various phenolic groups and induce the depolymerization of lignin units. On the other hand, the carbonium ions react with carbons 2 and 6 on the benzene rings and generate repolymerization.34−37

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PHYSICOCHEMICAL EFFECTS OF THE STEAM-EXPLOSION PROCESS ON LIGNOCELLULOSIC SUBSTRATE First applications of the steam-explosion technology to pretreat the biomass were conducted in the early 1980s. Iotech Corp. was the first to study the effect of the steam explosion on the aspen Populus tremula L.13 Results of this study show that xylose and glucose yields obtained after subsequent hydrolysis depend on both the pressure and retention time applied. The best hydrolysis performance for all monosaccharides (glucose + xylose) is obtained for a pressure of 35−40 bar (temperature, 250 °C) and a retention time of 40 s. Further, Wu et al.14 show also that a moderate treatment (severity factor, 3.5) gives the best compromise to recover, in one way, the hemicellulose fraction and to improve, in another way, the enzymatic hydrolysis of the cellulosic fraction. Similar studies indicate that the recovery of sugars from hemicellulosic fraction decreases when the severity of the process increases.15 The opposite effect is observed for the enzymatic hydrolysis properties of the cellulosic fraction.16 It is also found that, under relatively mild conditions (pressure, 15−25 bar; temperature, 200−220 °C; 1−5 min) that hemicellulosic fraction could be recovered as monomers and oligomers.6 Concerning the cellulosic fraction, many studies were conducted to determine the efficiency of steam-explosion treatment on the cellulose hydrolysis rate of different complex lignocellulosic substrates (hardwood chips, rice hulls, corn stalks, and sugar cane bagasse).17 Results show that application of the steam-explosion treatment at a pressure of 40 bar (250 °C) and a retention time of 1 min can significantly increase the enzymatic hydrolysis rates of the cellulosic fraction of the various substrates studied. Other studies using Onopordum nervosum L. (O. nervosum L.), a woody herbaceous species of the Iberian Peninsula, and Cyanara cardunculus L. (C. cardunculus L.), a thorny thistle, as raw materials showed that cellulose hydrolysis yield shift above 90% for steam-exploded samples of O. nervosum L. (pressure, 30 bar; temperature, 233 °C; retention time, 1−2 min) and C. cardunculus L. (pressure, 20 bars; temperature, 212 °C; retention time, 2−4 min).18 Treatment efficacy of steam explosion on cellulose enzymatic yield has been shown on eucalyptus,19 pine chips,20 rice straw,21 and Miscanthus × giganteus (M. × giganteus).22 In contrast to what has been observed with complex biomass resources, recent works achieved on pure cellulose fiber show that steam-explosion treatments do not improve the hydrolysis properties of pure cellulose fibers when the severity factor applied is less than 5.2. For higher intensities, results show even an important decrease of the hydrolysis yields.23 These results are widely opposed to the results obtained on various complex biomass described in many studies17,19,22,24,25 and suggest that 2595

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Industrial & Engineering Chemistry Research Studies indicate that repolymerization reactions are limited when operating parameters are moderate (pressure < 28 bar; retention time < 2 min).35,37 Under higher conditions, addition of a competitive inhibitor (phenol reagent such as 2-naphthol), which could react with the carbonium ion, will allow significant limitation of the repolymerization reactions and permit more easily the extraction of lignin with low molecular weight.34 Several studies have also investigated the possibilities for combining steam-explosion technology and other pretreatments. A study based on herbaceous plant Brassica carinata L., realized by Ballesteros et al.,38 shows that the efficiency of the steam-explosion pretreatment depends on the initial particle size of the substrate. The best hydrolysis yields are obtained when substrate particles’ dimensions are between 8 and 12 mm. Smaller particles have no significant effect on the improvement of the hydrolysis efficiency. Conversely, Jin and Chen39 show than an extremely fine grinding (210 °C), Lomax et al.44 shows that the browning could be attributed to the simultaneous reactions of depolymerization and repolymerization of the lignin. A determination of the elemental composition of the steamexploded samples has allowed a decrease of the O/C and H/C rations to be highlighted, in relation to the treatment temperature and the particle size of the material. Reduction of these ratios is induced by the condensation reactions which occurred in lignin structure during the steam-explosion treatment.44

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CONCLUSION

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AUTHOR INFORMATION

This literature review, which aims to present the effects of the application of steam-explosion pretreatment of lignocellulosic materials, incorporates the principles of the technology and its effects on the various constituents of biomass. First, it is shown that hemicellulosic fraction is easily hydrolyzed. According to the intensity of the pretreatment, hemicelluloses are hydrolyzed in oligo- or monosacharrides which can be degraded to furfural and hydroxymethylfurfural in drastic conditions. Further, steam-explosion technology induces changes in lignin structure. The control of the treatment conditions and the addition of inhibitor molecules which prevent repolymerization reaction can promote lignin extraction. This delignification, coupled to the hemicellulosic fraction hydrolysis, increases substantially the availability of the cellulosic fraction of the material, highlighted by an important increase of the kinetics of cellulosic fraction hydrolysis. In parallel, it is shown that steam explosion has an impact on the physicochemical properties of lignocellulosic materials. Crystallinity of the cellulose fraction is increased, which is a drawback of the technology since the hydrolysis operations are generally more difficult with high crystallinity. Coloring, elemental composition, and water retention properties of the materials are also modified by steam-explosion treatment. However, a major technical critical point encountered by the technology remains in its design. Actually, only batch design is currently available on the market. Batch facilities do not permit processing large volumes (limited by the size of the reactor volume) and are not useful. Further, continuous systems, currently in development (see the work of Foody and Anand45), encounters significant technical difficulties. The future of steam explosion will pass through the development of a continuous pilot plant that can be extrapolated and incorporated into the second-generation biorefinery.

Corresponding Author

*Tel.: +32 81 62 24 28. Fax: +32 81 60 17 67. E-mail: nicolas. [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Grous, W. R.; Converse, A. O.; Grethlein, H. E. Effect of Steam Explosion Pretreatment on Pore Size and Enzymatic Hydrolysis of Poplar. Enzyme Microb. Technol. 1986, 8, 274−280. (2) McMillan, J. D. Pretreatment of Lignocellulosic Biomass. In Enzymatic Conversion of Biomass for Fuels Production; Himmel, M. E., Baker, J. O., Overend, R. P., Eds.; ACS Symposium Series 566; American Chemical Society: Washington, DC, USA, 1994; pp 292− 324. (3) Holtzapple, M. T.; Humphrey, A. E.; Taylor, J. D. Energy requirements for the size reduction of poplar and aspen wood. Biotechnol. Bioeng. 1989, 33, 207−210. (4) Brecc, K.; Vellar, A.; Glasser, W. G. Steam-assisted biomass fractionation I. Process considerations and economic evaluation. Biomass Bioenergy 1998, 14, 205−218. (5) Chornet, E.; Overend, R. P. Phenomenological Kinetics and Reaction Engineering Aspects of Steam/Aqueous Treatments. Steam Explosion Techniques: Fundamentals and Industrial Applications, Proceedings of the International Workshop on Steam Explosion Technique; Gordon and Breach Science: New York, 1988; pp 2158

2596

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Pinus pinaster wood after steam explosion pretreatment. Biomass Bioenergy 2003, 25, 301−308. (26) Yeh, A. I.; Huang, Y. C.; Chen, S. H. Effect of particle size on the rate of enzymatic hydrolysis of cellulose. Carbohydr. Polym. 2010, 79, 192−199. (27) Vanderghem, C.; Jacquet, N.; Danthine, S.; Blecker, C.; Paquot, M. Effect of physicochemical characteristics of cellulosic substrates on enzymatic hydrolysis by means of a multi-stage process for cellobiose production. Appl. Biochem. Biotechnol. 2012, 166, 1423−1432. (28) Jacquet, N.; Vanderghem, C.; Danthine, S.; Blecker, C.; Paquot, M. Influence of homogenization treatment on physico-chemical properties and enzymatic hydrolysis yield of pure cellulose fibers. Appl. Biochem. Biotechnol. 2013, 169, 1315−1328. (29) Excoffier, G.; Peguy, A.; Rinaudo, M.; Vignon, M. Evolution of lignocellulosic components during steam explosion potential applications. Steam Explosion Techniques: Fundamentals and Industrial Applications, Proceedings of the International Workshop on Steam Explosion Technique; Gordon and Breach Science: New York, 1988; pp 8395 (30) Atalla, R. H. 1988. Structural Transformations in Celluloses. Steam Explosion Techniques: Fundamentals and Industrial Applications, Proceedings of the International Workshop on Steam Explosion Technique; Gordon and Breach Science: New York, 1988; pp 7119 (31) Mantanis, G. I.; Young, R. A.; Rowell, R. M. Swelling of compressed cellulose fiber webs in organic liquids. Cellulose 1995, 2, 1−22. (32) Quievy, N.; Jacquet, N.; Sclavons, M.; Deroanne, C.; Paquot, M.; Devaux, J. Influence of homogenization and drying on the thermal stability of microfibrillated cellulose. Polym. Degrad. Stab. 2009, 95, 306−314. (33) Scheirs, J.; Camino, G.; Tumiatti, W. Overview of water evolution during the thermal degradation of cellulose. Eur. Polym. J. 2001, 37, 933−942. (34) Sun, X. F.; Xu, F.; Sun, R. C.; Wang, Y. X.; Fowler, P.; Baird, M. S. Characteristics of degraded lignins obtained from steam exploded wheat straw. Polym. Degrad. Stab. 2004, 86, 245−256. (35) Li, J.; Henriksson, G.; Gellerstedt, G. Lignin depolymerization/ repolymerization and its critical role for delignification of aspen wood by steam explosion. Bioresour. Technol. 2007, 98, 3061−3068. (36) Bonini, C.; D’Auria, M.; Di Maggio, P.; Ferri, R. Characterization and degradation of lignin from steam explosion of pine and corn stalk of lignin: The role of superoxide ion and ozone. Ind. Crops Prod. 2008, 27, 182−188. (37) Li, J.; Gellerstedt, G.; Toven, K. Steam explosion lignins; their extraction, structure and potential as feedstock for biodiesel and chemicals. Bioresour. Technol. 2009, 100, 2556−2561. (38) Ballesteros, I.; Oliva, J. M.; Negro, M. J.; Manzanares, P.; Ballesteros, M. Enzymatic hydrolysis of steam exploded herbaceous agricultural waste (Brassica carinata) at different particule sizes. Process Biochem. 2002, 38, 187−192. (39) Jin, S.; Chen, H. Superfine grinding of steam-exploded rice straw and its enzymatic hydrolysis. Biochem. Eng. J. 2006, 30, 225−230. (40) Morjanoff, P. J.; Gray, P. P. Optimization of steam explosion as method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification. Biotechnol. Bioeng. 1987, 29, 733−741. (41) Vignon, M. R.; Garcia-Jaldon, C.; Dupeyre, D. Steam explosion of woody hemp chénevotte. Int. J. Biol. Macromol. 1995, 17, 395−404. (42) Viola, E.; Cardinale, M.; Santarcangelo, R.; Villone, A.; Zimbardi, F. Ethanol from eel grass via steam explosion and enzymatic hydrolysis. Biomass Bioenergy 2008, 32, 613−618. (43) Ballesteros, I.; Oliva, J. M.; Navarro, A. A.; GonzSalez, A.; Carrasco, J.; Ballesteros, M. Effect of chip size on steam explosion pretreatment of softwood. Appl. Biochem. Biotechnol. 2000, 84, 97− 110. (44) Lomax, T. D.; Mackie, K. L.; Meder, R.; Croucher, M.; Burton, R. J. Steam explosion of Pinus radiata bark. J. Wood Chem. Technol. 1994, 14, 539−561.

(6) Sun, X. F.; Xu, F.; Sun, R. C.; Geng, Z. C.; Fowler, P.; Baird, M. S. Characteristics of degraded hemicellulosic polymers obtained from steam exploded wheat straw. Carbohydr. Polym. 2005, 60, 15−26. (7) Overend, R. P.; Chornet, E.; Gascoigne, J. A. Fractionation of lignocellulosics by steam-aqueous pretreatments. Philos. Trans. R. Soc., A 1987, 523−536. (8) Li, H.; Chen, H. Detoxification of steam-exploded corn straw produced by an industrial-scale reactor. Process Biochem. 2008, 43, 1447−1451. (9) Jacquet, N.; Quiévy, N.; Vanderghem, C.; Janas, S.; Blecker, C.; Wathelet, B.; Devaux, J.; Paquot, M. Influence of steam explosion on the thermal stability of cellulose fibres. Polym. Degrad. Stab. 2011, 96, 1582−1588. (10) Belkacemi, K. Valorisation des déchets agricoles: Tiges de mais̈ et Stipa Tenacissima par voies d’hydrolyse acide et enzymatique, Thesis; Sherbrooke University, Quebec, Canada, 1989. (11) Heitz, M.; Capek-Menard, E.; Koeberle, P. G.; Gagne, J.; Chornet, E.; Overend, R. P.; Taylor, J. D.; Yu, E. Fractionation of Populus tremuloides at the pilot plant scale: Optimization of steam pretreatment conditions using the STAKE II technology. Bioresour. Technol. 1991, 35, 23−32. (12) Kaar, W. E.; Gutierrez, C. V.; Kinoshita, C. M. Steam Explosion of Sugarcane Bagasse as a Pretreatment for Conversion to Ethanol. Biomass Bioenergy 1998, 14, 277−287. (13) Foody, P. Optimization of Steam Explosion Pretreatment, Final Report to DOE, Contract AC02-79ET23050; Iotech: Ottawa, Ontario, Canada, 1980. (14) Wu, M.; Chang, K.; Gregg, D.; Boussaid, A.; Beatson, R.; Saddler, J. Optimization of Steam Explosion to Enhance Hemicellulose Recovery and Enzymatic Hydrolysis of Cellulose in Softwoods. Appl. Biochem. Biotechnol. 1999, 47, 77−79. (15) Shevchenko, S. M.; Chang, K.; Robinson, J.; Saddler, J. N. Optimization of monosaccharide recovery by post-hydrolysis of the water-soluble hemicellulose component after steam explosion of softwood chips. Bioresour. Technol. 2000, 72, 207−211. (16) Wang, K.; Jiang, J. X.; Xu, F.; Sun, R. C. Influence of steaming explosion time on the physic-chemical properties of cellulose from Lespedeza stalks (Lespedeza crytobotrya). Bioresour. Technol. 2009, 100, 5288−5294. (17) Schultz, T. P.; Templeton, M. C.; Biermann, C. J.; Mc Ginnis, G. D. Steam Explosion of Mixed Hardwood Chips, Rice Hulls, Corn Stalks, and Sugar Cane Bagasse. J. Agric. Food. Chem. 1984, 32, 1166− 1172. (18) Martinez, J.; Negro, M. J.; Saez, F.; Manero, J.; Saez, R.; Martin, C. Effect of Acid Steam Explosion on Enzymatic Hydrolysis of O. nervosum and C. cardunculus. Appl. Biochem. Biotechnol. 1990, 24, 127−134. (19) Nunes, A. P.; Pourquie, J. Steam Explosion Pretreatment and Enzymatic Hydrolysis of Eucalyptus Wood. Bioresour. Technol. 1996, 57, 107−110. (20) Martin, R. S.; Perez, C.; Briones, R. Simultaneous Production of Ethanol and Kraft Pulp from Pine (Pinus radiata) Using Steam Explosion. Bioresour. Technol. 1995, 53, 217−223. (21) Moniruzzaman, M. Saccharification and Alcohol Fermentation of Steam-Exploded Rice Straw. Bioresour. Technol. 1996, 55, 111−117. (22) Sorensen, A.; Teller, P. J.; Hilstrom, T.; Ahring, B. K. Hydrolysis of Miscanthus for bioethanol production using dilute acid presoaking combined with wet explosion pre-treatment and enzymatic treatment. Bioresour. Technol. 2008, 99, 6602−6607. (23) Jacquet, N.; Vanderghem, C.; Danthine, S.; Quiévy, N.; Blecker, C.; Devaux, J.; Paquot, M. Influence of steam explosion on physicochemical properties and hydrolysis yield of pure cellulose fibers. Bioresour. Technol. 2012, 121, 221−227. (24) Fernandez-Bolanos, J.; Felizon, B.; Heredia, A.; Rodriguez, R.; Guillen, R.; Jimenez, A. Steam-explosion of olive stones: Hemicellulose solubilization and enhancement of enzymatic hydrolysis of cellulose. Bioresour. Technol. 2001, 79, 53−61. (25) Negro, M. J.; Manzanares, P.; Oliva, J. M.; Ballesteros, I.; Ballesteros, M. Changes in various physical/chemical parameters of 2597

DOI: 10.1021/ie503151g Ind. Eng. Chem. Res. 2015, 54, 2593−2598

Review

Industrial & Engineering Chemistry Research (45) Foody, B.; Anand, V. Continuous flowing pre-treatment system with steam recovery. World Intellectual Property Organization, WO2006034590, 2006. (46) Jacquet, N.; Vanderghem, C.; Blecker, C.; Paquot, M. La steam explosion: Application en tant que prétraitement et effet sur la matière lignocellulosique. Biotechnol., Agron., Soc. Environ. (B.A.S.E.) 2010, 14, 561−566.

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