共查询到20条相似文献,搜索用时 93 毫秒
1.
Ethanol production from steam-explosion pretreated wheat straw 总被引:1,自引:0,他引:1
Ignacio Ballesteros Ma José Negro José Miguel Oliva Araceli Cabañas Paloma Manzanares Mercedes Ballesteros 《Applied biochemistry and biotechnology》2006,130(1-3):496-508
Bioconversion of cereal straw to bioethanol is becoming an attractive alternative to conventional fuel ethanol production
from grains. In this work, the best operational conditions for steam-explosion pretreatment of wheat straw for ethanol production
by a simultaneous saccharification and fermentation process were studied, using diluted acid [H2SO4 0.9% (w/w)] and water as preimpregnation agents. Acid-or water-impregnated biomass was steam-exploded at different temperatures
(160–200°C) and residence times (5, 10, and 20 min). Composition of solid and filtrate obtained after pretreatment, enzymatic
digestibility and ethanol production of pretreated wheat straw at different experimental conditions was analyzed. The best
pretreatment conditions to obtain high conversion yield to ethanol (approx 80% of theoretical) of cellulose-rich residue after
steam-explosion were 190°C and 10 min or 200°C and 5 min, in acid-impregnated straw. However, 180°C for 10 min in acid-impregnated
biomass provided the highest ethanol yield referred to raw material (140 L/t wheat straw), and sugars recovery yield in the
filtrate (300 g/kg wheat straw). 相似文献
2.
Gong-Yuan Wei You-Jung Lee Yi-Joon Kim Il-Hyuck Jin Jai-Heon Lee Chung-Han Chung Jin-Woo Lee 《Applied biochemistry and biotechnology》2010,162(5):1471-1482
The production of fermentable sugars from rice hull was studied by dilute acid pretreatment and enzymatic saccharification.
Rice hull (15%, w/v) was pretreated by 1% (v/v) sulfuric acid at high temperature (120∼160 °C) for 15, 30, 45, and 60 min, respectively. The maximum sugar concentration
from rice hull in the prehydrolysate was obtained at 140 °C for 30 min, but the enzymatic saccharification yield from the
corresponding pretreated rice hull is not high. To another aspect, the maximum enzymatic saccharification yield was achieved
at 160 °C for 60 min, while the recovery of fermentable sugars was the poorest. To take account of fermentable sugars from
pretreatment and enzymatic saccharification, the maximum yield of sugars was obtained only when rice hull was treated at 140 °C
for 30 min. Under this condition, 72.5% (w/w) of all sugars generated from the raw material can be recovered. The kinetic study on the enzymatic saccharification of dilute
acid pretreated rice hull was also performed in this work by a modified Michaelis–Menten model and a diffusion-limited model.
After calculation by a linear and a non-linear regression analysis, both models showed good relation with the experimental
results. 相似文献
3.
Barley is an abundant crop in Europe, which makes its straw residues an interesting cellulose source for ethanol production.
Steam pretreatment of the straw followed by enzymatic hydrolysis converts the cellulose to fermentable sugars. Prior to pretreatment
the material is impregnated with a catalyst, for example, H2SO4, to enhance enzymatic digestibility of the pretreated straw. Different impregnation techniques can be applied. In this study,
soaking and spraying were investigated and compared at the same pretreatment condition in terms of overall yield of glucose
and xylose. The overall yield includes the soluble sugars in the liquid from pretreatment, including soluble oligomers, and
monomer sugars obtained in the enzymatic hydrolysis. The yields obtained differed for the impregnation techniques. Acid-soaked
barley straw gave the highest overall yield of glucose, regardless of impregnation time (10 or 30 min) or acid concentration
(0.2 or 1.0 wt%). For xylose, soaking gave the highest overall yield at 0.2 wt% H2SO4. An increase in acid concentration resulted in a decrease in xylose yield for both acid-soaked and acid-sprayed barley straw.
Optimization of the pretreatment conditions for acid-sprayed barley straw was performed to obtain yields using spraying that
were as high as those with soaking. For acid-sprayed barley straw the optimum pretreatment condition for glucose, 1.0 wt%
H2SO4 and 220°C for 5 min, gave an overall glucose yield of 92% of theoretical based on the composition of the raw material. Pretreatment
with 0.2wt% H2SO4 at 190°C for 5 min resulted in the highest overall xylose yield, 67% of theoretical based on the composition of the raw material. 相似文献
4.
Jian Zhang Wen-Xue Zhang Jian Yang Yue-Hong Liu Xia Zhong Zheng-Yun Wu Kenji Kida Yu Deng 《Applied biochemistry and biotechnology》2012,166(7):1856-1870
Ethanol conversion from rice straw using butanone and acetaldehyde dilute solution explosions was evaluated based on the optimization
of pure water explosion. To decrease residual inhibitor content, the exploded slurry was dried and investigated at different
temperature. Using a 0.9-mol/L butanone solution explosion, with the explosion pressure set at 3.1 MPa, the residence time
at 7 min, the dried rice straw-to-water ratio at 1:3 (w/w), and the exploded slurry drying temperuture at 90 °C for 8 h, the yields of total sugar, glucose, and xylose were 85%, 88%,
82% (w/w), respectively, and the ethanol productivity was 26.0 g/100 g rice straw dry matter. Moreover, 0.5-mol/L acetaldehyde dilute
solution explosion improved the efficiency of enzymatic hydrolysis (EH) and simultaneous saccharification and co-fermentation
(SSCF), and the residual inhibitors had negligible effects on EH and SSCF after detoxification by drying. The results suggested
that compared with pure water explosions, the use of butanone and of acetaldehyde dilute solution explosions lowered the explosive
temperature and improved the sugar yield, although relative crystallinity of the rice straw dry matter was increased after
the explosion. 相似文献
5.
The present work presents an alternative approach to ethanol production from sweet sorghum: without detoxification, acid-impregnated
fresh sweet sorghum stem which contains soluble (glucose and sucrose) and insoluble carbohydrates (cellulose and hemicellulose)
was steam pretreated under mild temperature of 100 °C. Simultaneous saccharification and fermentation experiments were performed
on the pretreated slurries using Saccharomyces cerevisiae. Experimentally, ground fresh sweet sorghum stem was combined with H2SO3 at dosages of 0.25, 0.50, and 0.75 g/g dry matter (DM) and steam pretreated by varying the residence time (60, 120, or 240 min).
According to enzymatic hydrolysis results and ethanol yields, H2SO3 was a powerful and mild acid for improving enzymatic digestibility of sorghum stem. At a solid loading of 10% (w/v) and acid dosage of 0.25 g/g DM H2SO3 at 100 °C for 120 min, 44.5 g/L ethanol was obtained after 48 ± 4 h of simultaneous saccharification and fermentation. This
corresponded to an overall ethanol yield of 110% of the theoretical one, based on the soluble carbohydrates in the fresh sweet
sorghum stem. The concentrations of hydroxymethylfurfural and furfural of the sulfurous acid pretreated samples were below
0.4 g/L. Ethanol would not inhibit the cellulase activity, at least under the concentration of 34 g/L. 相似文献
6.
Agricultural residues were pretreated by steam explosion and the cellulosic component of these substrates were converted to
ethanol using a combined enzymatic hydrolysis and fermentation (CHF) process. The enzymatic hydrolysis was carried out using
culture filtrates ofTrichoderma harzianum E58 while the liberated sugars were fermented to ethanol byS. cerevisiae.
Initially, pretreatment conditions were optimized to ensure that the substrates were readily hydrolyzed and fermented. The
agricultural residues were steamed for various times between 30 and 120 s at approximately 240‡C prior to rapid decompression
(explosion) in a small masonite-type gun. The various substrates were selectively extracted by water and alkali to see whether
the enzymatic hydrolysis and fermentability of the substrates were enhanced. A comparison between the overall conversion of
wheat and barley straw was made since these are the two most readily available agricultural residues in Canada.
Steam explosion did not affect the hexosan content of the residues, although the pentosan content of the substrates decreased
with increasing duration of steaming. The hexosan (cellulose) content of wheat straw was 50.7% of the total substrate while
a slightly higher 52.9% cellulose content was detected in the barley straw. Wheat straw was more efficiently hydrolyzed after
it had been steamed for 90 s while optimum hydrolysis of the barley straw was detected after 60 s.
Steam exploded wheat and barley straw that was subsequently extracted with water was readily hydrolyzed to their component
sugars.S. cerevisiae could almost quantitatively convert these sugars to ethanol. This indicated that water washing not only enhanced the enzymatic
hydrolysis of the steam exploded substrates, it also removed inhibitory material that restricted the growth of S.cerevisiae.
Maximum hydrolysis (78.5%) and ethanol yields (10 mg/mL) were obtained when wheat straw was steamed for 90 s. Slightly lower
hydrolysis (76.0%) and ethanol yields (9.5 mg/mL) were obtained with barley straw that had been steamed for 120 s. 相似文献
7.
Mercedes Ballesteros Felicia Sáez Ignacio Ballesteros Paloma Manzanares Maria Jose Negro Jose Maria Martínez Rafael Castañeda Jose Miguel Oliva Dominguez 《Applied biochemistry and biotechnology》2010,161(1-8):423-431
In this work, the use of organic fraction from municipal solid waste (MSW) as substrate for ethanol production based on enzymatic hydrolysis was evaluated. MSW was subjected to a thermal pretreatment (active hygienization) at 160?°C from 5 to 50 min. The organic fiber obtained after 30 min was used as substrate in a simultaneous saccharification and fermentation (SSF) and fed-batch SSF process using cellulases and amylases. In a fed-batch mode with 25% (w/w) substrate loading, final ethanol concentration of 30 g/L was achieved (60% of theoretical). In these conditions, more than 160 L of ethanol per ton of dry matter could be produced from the organic fraction of MSW. 相似文献
8.
Statistical Optimization of Recycled-Paper Enzymatic Hydrolysis for Simultaneous Saccharification and Fermentation Via Central Composite Design 总被引:1,自引:0,他引:1
Qing Liu Ke-ke Cheng Jian-an Zhang Jin-ping Li Ge-hua Wang 《Applied biochemistry and biotechnology》2010,160(2):604-612
A central composite design of the response surface methodology (RSM) was employed to study the effects of temperature, enzyme
concentration, and stirring rate on recycled-paper enzymatic hydrolysis. Among the three variables, temperature and enzyme
concentration significantly affected the conversion efficiency of substrate, whereas stirring rate was not effective. A quadratic
polynomial equation was obtained for enzymatic hydrolysis by multiple regression analysis using RSM. The results of validation
experiments were coincident with the predicted model. The optimum conditions for enzymatic hydrolysis were temperature, enzyme
concentration, and stirring rate of 43.1 °C, 20 FPU g−1 substrate, and 145 rpm, respectively. In the subsequent simultaneous saccharification and fermentation (SSF) experiment under
the optimum conditions, the highest 28.7 g ethanol l−1 was reached in the fed-batch SSF when 5% (w/v) substrate concentration was used initially, and another 5% added after 12 h fermentation. This ethanol output corresponded
to 77.7% of the theoretical yield based on the glucose content in the raw material. 相似文献
9.
Silva NL Betancur GJ Vasquez MP Gomes Ede B Pereira N 《Applied biochemistry and biotechnology》2011,163(7):928-936
Current research indicates the ethanol fuel production from lignocellulosic materials, such as residual wood chips from the
cellulose industry, as new emerging technology. This work aimed at evaluating the ethanol production from hemicellulose of
eucalyptus chips by diluted acid pretreatment and the subsequent fermentation of the generated hydrolysate by a flocculating
strain of Pichia stipitis. The remaining solid fraction generated after pretreatment was subjected to enzymatic hydrolysis, which was carried out simultaneously
with glucose fermentation [saccharification and fermentation (SSF) process] using a strain of Saccharomyces cerevisiae. The acid pretreatment was evaluated using a central composite design for sulfuric acid concentration (1.0–4.0 v/v) and solid to liquid ratio (1:2–1:4, grams to milliliter) as independent variables. A maximum xylose concentration of 50 g/L
was obtained in the hemicellulosic hydrolysate. The fermentation of hemicellulosic hydrolysate and the SSF process were performed
in bioreactors and the final ethanol concentrations of 15.3 g/L and 28.7 g/L were obtained, respectively. 相似文献
10.
Maria José Negro Paloma Manzanares Ignacio Ballesteros Jose Miguel Oliva Araceli Cabañas Mercedes Ballesteros 《Applied biochemistry and biotechnology》2003,105(1-3):87-100
Pretreatment has been recognized as a key step in enzyme-based conversion processes of lignocellulose biomass to ethanol. The aim of this study is to evaluate two hydrothermal pretreatments (steam explosion and liquid hot water) to enhance ethanol production from poplar (Populus nigra) biomass by a simultaneous saccharification and fermentation (SSF) process. The composition of liquid and solid fractions obtained after pretreatment, enzymatic digestibility, and ethanol production of poplar biomass pretreated at different experimental conditions was analyzed. The best results were obtained in steam explosion pretreatment at 210°C and 4 min, taking into account cellulose recovery above 95%, enzymatic hydrolysis yield of about 60%, SSF yield of 60% of theoretical, and 41% xylose recovery in the liquid fraction. Large particles can be used for poplar biomass in both pretreatments, since no significant effect of particle size on enzymatic hydrolysis and SSF was obtained. 相似文献
11.
Ruiz HA Ruzene DS Silva DP da Silva FF Vicente AA Teixeira JA 《Applied biochemistry and biotechnology》2011,164(5):629-641
The present work describes the delignification of wheat straw through an environmentally friendly process resulting from sequential
application of autohydrolysis and organosolv processes. Wheat straw autohydrolysis was performed at 180°C during 30 min with
a liquid–solid ratio of 10 (v/w); under these conditions, a solubilization of 44% of the original xylan, with 78% of sugars as xylooligosaccharides of the
sum of sugars solubilized in the autohydrolysis liquors generated by the hemicellulose fraction hydrolysis. The corresponding
solid fraction enrichment with 63.7% of glucan and 7.55% of residual xylan was treated with a 40% ethanol and 0.1% NaOH aqueous
solution at a liquid–solid ratio of 10 (v/w), with the best results obtained at 180°C during 20 min. The highest lignin recovery, measured by acid precipitation of the
extracted lignin, was 3.25 g/100 ml. The lignin obtained by precipitation was characterized by FTIR, and the crystallinity
indexes from the native cellulose, the cellulose recovered after autohydrolysis, and the cellulose obtained after applying
the organosolv process were obtained by X-ray diffraction, returning values of 21.32%, 55.17%, and 53.59%, respectively. Visualization
of the fibers was done for all the processing steps using scanning electron microscopy. 相似文献
12.
Rodrigues TH Rocha MV de Macedo GR Gonçalves LR 《Applied biochemistry and biotechnology》2011,164(6):929-943
In this work, the potential of microwave-assisted alkali pretreatment in order to improve the rupture of the recalcitrant
structures of the cashew able bagasse (CAB), lignocellulosic by-product in Brazil with no commercial value, is obtained from
cashew apple process to juice production, was studied. First, biomass composition of CAB was determined, and the percentage
of glucan and lignin was 20.54 ± 0.70% and 33.80 ± 1.30%, respectively. CAB content in terms of cellulose, hemicelluloses,
and lignin, 19.21 ± 0.35%, 12.05 ± 0.37%, and 38.11 ± 0.08%, respectively, was also determined. Results showed that, after
enzymatic hydrolysis, alkali concentration exerted influence on glucose formation, after pretreatment with 0.2 and 1.0 mo L−1 of NaOH (372 ± 12 and 355 ± 37 mg gglucan−1) when 2% (w/v) of cashew apple bagasse pretreated by microwave-assisted alkali pretreatment (CAB-M) was used. On the other hand, pretreatment
time (15–30 min) and microwave power (600–900 W) exerted no significant effect on hydrolysis. On enzymatic hydrolysis step,
improvement on solid percentage (16% w/v) and enzyme load (30 FPU gCAB-M−1) increased glucose concentration to 15 g L−1. The fermentation of the hydrolyzate by Saccharomyces cerevesiae resulted in ethanol concentration and productivity of 5.6 g L−1 and 1.41 g L−1 h−1, respectively. 相似文献
13.
Johanna Söderström Linda Pilcher Mats Galbe Guido Zacchi 《Applied biochemistry and biotechnology》2003,105(1-3):127-140
Fuel ethanol can be produced from softwood through hydrolysis in an enzymatic process. Prior to enzymatic hydrolysis of the
softwood, pretreatment is necessary. In this study, two-step steam pretreatment employing dilute H2SO4 impregnation in the first step and SO2 impregnation in the second step, to improve the overall sugar and ethanol yield, was investigated. The first pretreatment
step was performed under conditions of low severity (180°C, 10 min, 0.5% H2SO4) to optimize the amount of hydrolyzed hemicellulose. In the second step, the washed solid material from the first pretreatment
step was impregnated with SO2 and pretreated under conditions of higher severity to make the cellulose more accessible to enzymatic attack, as well as
to hydrolyze a portion of the cellulose. A wide range of conditions was used in the second step to determine the most favorable
combination. The temperatures investigated were between 190 and 230°C, the residence times were 2, 5, and 10 min; and the
SO2 concentration was 3%. The effect of pretreatment was assessed by both enzymatic hydrolysis of the solids and by simultaneous
saccharification and fermentation (SSF) of the whole slurry, after the second pretreatment step. For each set of pretreatment
conditions, the liquid fraction was also fermented to determine any inhibitory effects. Ethanol yield using the SSF configuration
reached 66% of the theoretical value for pretreatment conditions in the second step of 210°C and 5 min. The sugar yield using
the separate hydrolysis and fermentation configuration reached 71% for pretreatment conditions of 220°C and 5 min. 相似文献
14.
Pretreatment and enzymatic saccharification of corn fiber 总被引:14,自引:0,他引:14
Corn fiber consists of about 20% starch, 14% cellulose, and 35% hemicellulose, and has the potential to serve as a low-cost
feedstock for production of fuel ethanol. Several pretreatments (hot water, alkali, and dilute, acid) and enzymatic saccharification
procedures were evaluated for the conversion of corn fiber starch, cellulose, and hemicellulose to monomeric sugars. Hot water
pretreatment (121°C, 1 h) facilitated the enzymatic sacch arification of starch and cellulose but not hemicellulose. Hydrolysis
of corn fiber pretreated with alkali un dersimilar conditions by enzymatic means gave similar results. Hemicellulose and starch
components were converted to monomeric sugars by dilute H2SO4 pretreatment (0.5–1.0%, v/v) at 121°C. Based on these findings, a method for pretreatment and enzymatic saccharification
of corn fiber is presented. It in volves the pretreatment of corn fiber (15% solid, w/v) with dilute acid (0.5% H2SO4, v/v) at 121°C for 1 h, neutralization to pH 5.0, then saccharification of the pretreated corn fiber material with commercial
cellulase and β-glucosidase preparations The yield of monomeric sugars from corn fiber was typically 85–100% of the theoretical
yield.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
15.
Jihane Zeghlouli Gwendoline Christophe Amine Guendouz Cherkaoui El Modafar Abdeljalil Belkamel Philippe Michaud Cdric Delattre 《Molecules (Basel, Switzerland)》2021,26(9)
Argan pulp is an abundant byproduct from the argan oil process. It was investigated to study the feasibility of second-generation bioethanol production using, for the first time, enzymatic hydrolysis pretreatment. Argan pulp was subjected to an industrial grinding process before enzymatic hydrolysis using Viscozyme L and Celluclast 1.5 L, followed by fermentation of the resulting sugar solution by Saccharomyces cerevisiae. The argan pulp, as a biomass rich on carbohydrates, presented high saccharification yields (up to 91% and 88%) and an optimal ethanol bioconversion of 44.82% and 47.16% using 30 FBGU/g and 30 U/g of Viscozyme L and Celluclast 1.5 L, respectively, at 10%w/v of argan biomass. 相似文献
16.
Steam-exploded corn stover biomass was used as the substrate for fed-batch separate enzymatic hydrolysis and fermentation
(SHF) to investigate the solid concentration ranging from 10% to 30% (w/w) on the lignocellulose enzymatic hydrolysis and fermentation. The treatment of washing the steam-exploded material was also
evaluated by experiments. The results showed that cellulose conversion changed little with increasing solid concentration,
and fermentation by Saccharomyces cerevisiae revealed a nearly same ethanol yield with the water-washed steam-exploded corn stover. For the washed material at 30% substrate
concentration, i.e., 30% water insoluble solids (WIS), enzymatic hydrolysis yielded 103.3 g/l glucose solution and a cellulose
conversion of 72.5%, thus a high ethanol level up to 49.5 g/l. With the unwashed steam-exploded corn stover, though a cellulose
conversion of 70.9% was obtained in hydrolysis at 30% solid concentration (27.9% WIS), its hydrolysate did not ferment at
all, and the hydrolysate of 20% solid loading containing 3.3 g/l acetic acid and 145 mg/l furfural already exerted a strong
inhibition on the fermentation and ethanol production. 相似文献
17.
Sugarcane Bagasse Mild Alkaline/Oxidative Pretreatment for Ethanol Production by Alkaline Recycle Process 总被引:1,自引:0,他引:1
Cheng KK Zhang JA Ping WX Ge JP Zhou YJ Ling HZ Xu JM 《Applied biochemistry and biotechnology》2008,151(1):43-50
In order to decrease the alkali and water consumptions in the sugarcane bagasse alkaline/oxidative pretreatment for ethanol
production, an alkaline recycle process was carried out. Two recycles of NaOH/H2O2 pretreatment did not decrease the pretreatment and enzymatic hydrolysis efficiencies and the consumptions of NaOH and water
would be saved by 26% and 40%, respectively. A simultaneous saccharification and fermentation (SSF) culture with pretreated
bagasse as substrate was developed giving 25 g ethanol l−1 with a yield of 0.2 g g−1 bagasse and productivity of 0.52 g l−1 h−1. 相似文献
18.
Wheat straw was pretreated by wet explosion using three different oxidizing agents (H2O2, O2, and air). The effect of the pretreatment was evaluated based on glucose and xylose liberated during enzymatic hydrolysis.
The results showed that pretreatment with the use of O2 as oxidizing agent was the most efficient in enhancing overall convertibility of the raw material to sugars and minimizing
generation of furfural as a by-product. For scale-up of the process, high dry matter (DM) concentrations of 15–20% will be
necessary. However, high DM hydrolysis and fermentation are limited by high viscosity of the material, higher inhibition of
the enzymes, and fermenting microorganism. The wet-explosion pretreatment method enabled relatively high yields from both
enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) to be obtained when performed on unwashed slurry
with 14% DM and a low enzyme loading of 10 FPU/g cellulose in an industrial acceptable time frame of 96 h. Cellulose and hemicellulose
conversion from enzymatic hydrolysis were 70 and 68%, respectively, and an overall ethanol yield from SSF was 68%. 相似文献
19.
A novel process using chemical, thermal, and enzymatic treatment for conversion of hulled barley into fermentable sugars was
developed. The purpose of this process is to convert both lignocellulosic polysaccharides and starch in hulled barley grains
into fermentable sugars simultaneously without a need for grinding and hull separation. In this study, hulled barley grains
were treated with 0.1 and 1.0 wt.-% sulfuric acid at various temperatures ranging from 110 to 170 °C in a 63-ml flow-through
packed-bed stainless steel reactor. After sulfuric acid pretreatment, simultaneous conversion of lignocellulose and starch
in the barley grains into fermentable sugars was performed using an enzyme cocktail, which included α-amylase, glucoamylase,
cellulase, and β-glucosidase. Both starch and non-starch polysaccharides in the pre-treated barley grains were readily converted
to fermentable sugars. The treated hulled barley grains, including their hull, were completely hydrolyzed to fermentable sugars
with recovery of almost 100% of the available glucose and xylose. The pretreatment conditions of this chemical, thermal, and
enzymatic (CTE) process for achieving maximum yield of fermentable sugars were 1.0 wt.% sulfuric acid and 110 °C. In addition
to starch, the acid pretreatment also retained most of the available proteins in solid form, which is essential for subsequent
production of fuel ethanol and high protein distiller’s dried grains with solubles co-product. 相似文献
20.
Söderström Johanna Pilcher Linda Galbe Mats Zacchi Guido 《Applied biochemistry and biotechnology》2002,98(1-9):5-21
Two-step steam pretreatment of softwood was investigated with the aim of improving the enzymatic digestibility for ethanol
production. In the first step, softwood was impregnated with SO2 and steam pretreated at different severities. The first step was performed at low severity to hydrolyze the hemicellulose
and release the sugars into the solution. The combination of time and temperature that yielded the highest amount of hemicellulosic
sugars in the solution was determined. In the second step, the washed solid material from the optimized first step was impregnated
once more with SO2 and steam pretreated under more severe conditions to enhance the enzymatic digestibility. The investigated temperature range
was between 180 and 220°C, and the residence times were 2, 5 and 10 min. The effectiveness of pretreatment was assessed by
both enzymatic hydrolysis of the solids and simultaneous saccharification and fermentation (SSF) of the whole slurry after
the second pretreatment step, in the presence of antibiotics. For each pretreatment combination, the liquid fraction was fermented
to determine any inhibiting effects. At low severity in the second pretreatment step, a high conversion of cellulose was obtained
in the enzymatic hydrolysis step, and at a high severity a high conversion of cellulose was obtained in the second pretreatment
step. This resulted in an overall yield of sugars that was nearly constant over a wide range of severity. Compared with the
one-step steam pretreatment, the two-step steam pretreatment resulted in a higher yield of sugar and in a slightly higher
yield of ethanol. The overall sugar yield, when assessed by enzymatic hydrolysis, reached 80%. In the SSF configuration, an
overall ethanol yield of 69% was attained. 相似文献