Steam explosion pretreatment

Index Entries Com stover pretreatment steam explosion hydrolysis bioethanol. 

In the present study, the fermentation of glucose and xylose model solutions and hydrolysate samples from steam-pretreated aspen was investigated. After the steam explosion, the obtained slurry was suspended in water to a solid-to-liquid ratio of 200 g/L of dry matter (DM) and enzymatically hydrolyzed with a mixture of cellulolytic and hemicellulolytic enzymes. Subsequently, the hydrolysate was detoxified using a two-step treatment through cationic and anionic resins. 

Steam explosion pretreatment was carried out in a continuous Staketech digester processing 150 kg/h of DM. Water was added to the chips to raise the intrinsic humidity to 50%. The severity of the steam explosion pretreatment was expressed through the logarithm of the semiem-pirical relation described in Eq. 1 (11) ... 

A typical wood-to-ethanol bioconversion process consists of at least three major steps pretreatment, hydrolysis, and fermentation. The pretreatment stage has been shown to be the key step to providing a substrate susceptible to the subsequent hydrolysis. Steam explosion is one of the most intensively studied pretreatment methods for bioconversion of softwood materials (6-10). 

Pretreatment screening experiments of partially air-dried DG were carried out in both a 4-L steam explosion reactor (18,19) and a 4-L... 

Pretreating wet DG with S02 (experiment 2) resulted in higher solubilization of residual carbohydrates than uncatalyzed steam explosion (experiment 1), however, higher yields and conversions are possible if homogeneous absorption of the acid gas can be accomplished. Careful examination of the S02-pretreated residue indicated nonhomogeneous pretreatment because the S02 appears to have been absorbed only at the surface of the particles and did not penetrate far into the interior. However, less expensive pretreatment reactors are possible if S02 is used as the catalyst, as opposed to dilute-acid pretreatment, because exotic alloys may not be needed. 

Dekker, R. F. H., and Wallis, A. F. A. 1983. Enzymic saccharification of sugarcane bagasse pretreated by autohydrolysis-steam explosion. Biotech. Bioeng., 25, 3027-3048. 

Dekker, R. F. H. 1991. Steam explosion an effective pretreatment method for use in the bioconversion of lignocellulosic materials. In Focher, B., Marzetti, A., and Crescenzi, V. (Eds.), Steam Explosion Techniques Fundamental Principles and Industrial Applications (pp. 277-305). Philadlphia PA Gordon and Breach Scientific Publishers-. 

Schell, D. J., Torget, R., Power, A., Walter, P. J., Grohmann, K., and Hinman, N. D., A technical and economic-analysis of acid-catalyzed steam explosion and dilute sulfuric-acid pretreatments using wheat straw or aspen wood chips. Appl Biochem Biotechnol 1991, 28-9, 87-97. 

Schultz, T. R, Blermann, C. J., and McGinnis, G. D., Steam explosion of mixed hardwood chips as a biomass pretreatment. Industrial Engineering Chem Product Res Dev 1983, 22 (2), 344-348. 

Schell, D., Nguyen, Q., Tucker, M., and Boynton, B., Pretreatment of softwood by acid-catalyzed steam explosion followed by alkali extraction. Appl Biochem Biotechnol 1998, 70-2, 17- 24. 

Chen C-L, Connors WJ (1974) New carbonyl compounds from the alkaline ferncyamde dehydrogenation of p cresol J Org Chem 39 3877-3880 Chum HL, Johnson DK, Ratcliff M, Black S, Schroeder HA, Wallace K (1985) Comparison between lignins produced by steam explosion and organosolv pretreatments Proc 1985 Int Symp Wood Pulp Chem, Vancouver, BC, Canada, August 26-30, 1985, Tech Pap 223-226... 

Digestion of lignocellulose, to render it susceptible to hydrolysis, can be performed in a number of ways [10, 13, 14] but few of these satisfy the green commandments. There seems to be a trend towards aqueous pretreatment, such as the steam explosion that is used by Iogen (Canada) [15, 16], followed by enzy-... 

In contrast, the energy gain of ethanol fermentation from a cellulose-based crop was estimated at only 10% [31]. A fife cycle assessment of bioethanol from wood came to a similar conclusion [32]. This unsatisfactory outcome mainly results from the energy-intensive pretreatment with steam explosion, such as is used by Iogen [16]. The replacement of the latter by COz explosion [33] may redress the energetic balance. 

Schultz, T. P., and McGinnis, G. D. (1984). Final Report, Evaluation of a Steam-Explosion Pretreatment for Alcohol Production from Biomass, USDA-SEA Grant No. 59-2281-1-2-098-0, September 15, 1981 to October 1, 1984. Mississppi State University, Mississippi State, MS. 

Biomass material (woodchips or wheat straw) is placed in a high-pressure stainless steel tube and exposed to steam under pressures ranging from 250-650 psi at 200 to 240°C for up to 20 min. The sudden pressure release causes an explosion of biomass material thereby disrupting the lignin and hemicellulose bonding toward cellulose. Many investigators (see [29] for review) have studied the steam explosion of biomass materials. The addition of SO2 enhances the pretreatment effect and also increases the recovery of hemicellulose [34-36]. A refinement of this pretreatment method has recently been reported by Stenberg et al. [37]. 

AFEX is the pretreatment method that utilizes steam explosion techniques using ammonia as the chemical reagent [38-41]. The intended biomass material is placed in a pressure vessel with liquid ammonia (1 1 basis) and treated... 

Because the hemicellulose fraction of biomass materials can be separated from lignin and cellulose by dilute acid treatment, cellulose becomes more reactive towards cellulase. Hemicellulose hydrolysis rates vary with acid concentration, temperature, and solid-to-liquid ratio. With most lignocellulosic materials, complete hemicellulose hydrolysis can be achieved in 5-10 min at 160°C or 30-60 min at 140 °C. Dilute acid hydrolysis forms the basis of many pretreatment processes for example, autohydrolysis and steam explosion are based on high-temperature dilute acid catalyzed hydrolysis of biomass. 

Carrasco et al. [58] analyzed the effect of dilute H2SO4 and steam explosion pretreatment on the fractionation and kinetics of several biomass materials. 

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