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1.
Corn stover, the most abundant agricultural residue in Hungary, is a potential raw material for the production of fuel ethanol
as a result of its high content of carbohydrates, but a pretreatment is required for its efficient hydrolysis. In this article,
we describe the results using various chemicals such as dilute H2SO4, HCl, and NaOH separately as well as consecutively under relative mild conditions (120°C, 1h). Pretreatment with 5% H2SO4 or 5% HCl solubilized 85% of the hemicellulose fraction, but the enzymatic conversion of pretreated materials increased only
two times compared to the untreated corn stover. Applying acidic pretreatment following a 1-d soaking in base achieved enzymatic
conversion that was nearly the theoretical maximum (95.7%). Pretreatment with 10% NaOH decreased the lignin fraction >95%,
increased the enzymatic conversion more than four times, and gave a 79.4% enzymatic conversion. However, by increasing the
reaction time, the enzymatic degradability could also be increased significantly, using a less concentrated base. When the
time of pretreatment was increased three times (0.5% NaOH at 120°C), the amount of total released sugars was 47.9 g from 100
g (dry matter) of untreated corn stover. 相似文献
2.
Optimization of dilute-acid pretreatment of corn stover using a high-solids percolation reactor 总被引:1,自引:0,他引:1
Yongming Zhu Y. Y. Lee Richard T. Elander 《Applied biochemistry and biotechnology》2005,124(1-3):1045-1054
We have previously demonstrated that pretreatment of corn stover with dilute sulfuric acid can achieve high digestibility
and efficient recovery of hemicellulose sugars with high yield and concentration. Further improvement of this process was
sought in this work. A modification was made in the operation of the percolation reactor that the reactor is preheated under
atmospheric pressure to remove moisture that causes autohydrolysis. This eliminated sugar decomposition during the preheating
stage and led to a considerable improvement in overall sugar yield. In addition, liquid throughput was minimized to the extent
that only one reactor void volume of liquid was collected. This was done to attain a high xylose concentration in the hydrolyzate.
The optimum reaction and operating conditions were identified wherein near quantitative enzymatic digestibilities are obtained
with enzyme loading of 15 FPU/g glucan. With a reduced enzyme loading of 5 FPU/g glucan, the enzymatic digestibility was decreased,
but still reached a level of 92%. Decomposition of carbohydrates was extremely low as indicated by the measured glucan and
xylan mass closures (recovered sugar plus unreacted) which were 98% and 94%, respectively. The data obtained in this work
indicate that the digestibility is related to the extent of xylan removal. 相似文献
3.
Optimization of steam pretreatment of corn stover to enhance enzymatic digestibility 总被引:5,自引:0,他引:5
Among the available agricultural byproducts, corn stover, with its yearly production of 10 million t (dry basis), is the most
abundant promising raw material for fuel ethanol production in Hungary. In the United States, more than 216 million to fcorn
stover is produced annually, of which a portion also could possibly be collected for conversion to ethanol. However, a network
of lignin and hemicellulose protects cellulose, which is the major source of fermentable sugars in corn stover (approx 40%
of the dry matter [DM]). Steam pretreatment removes the major part of the hemicellulose from the solid material and makes
the cellulose more susceptible to enzymatic digestion. We studied 12 different combinations of reaction temperature, time,
and pH during steam pretreatment. The best conditions (200°C, 5 min, 2% H2SO4) increased the enzymatic conversion (from cellulose to glucose) of corn stover more then four times, compared to untreated
material. However, steam pretreatment at 190°C for 5 min with 2% sulfuric acid resulted in the highest overall yield of sugars,
56.1 g from 100 g of untreated material (DM), corresponding to 73% of the theoretical. The liquor following steam explosion
was fermented using Saccharomyces cerevisiae to investigate the inhibitory effect of the pretreatment. The achieved ethanol yield was slightly higher than that obtained
with a reference sugar solution. This demonstrates that baker's yeast could adapt to the pretreated liquor and ferment the
glucose to ethanol efficiently. 相似文献
4.
Daniel J. Schell Jody Farmer Millie Newman James D. McMillan 《Applied biochemistry and biotechnology》2003,105(1-3):69-85
Corn stover is a domestic feedstock that has potential to produce significant quantities of fuel ethanol and other bioenergy
and biobased products. However, comprehensive yield and carbon mass balance information and validated kinetic models for dilute-sulfuric
acid (H2SO4) pretreatment of corn stover have not been available. This has hindered the estimation of process economics and also limited
the ability to perform technoeconomic modeling to guide research. To better characterize pretreatment and assess its kinetics,
we pretreated corn stover in a continuous 1 t/d reactor. Corn stover was pretreated at 20% (w/w) solids concentration over
a range of conditions encompassing residence times of 3–12 min, temperatures of 165–195°C, and H2SO4 concentrations of 0.5–1.4% (w/w). Xylan conversion yield and carbon mass balance data were collected at each run condition.
Performance results were used to estimate kinetic model parameters assuming biphasic hemicellulose hydrolysis and a hydrolysis
mechanism incorporating formation of intermediate xylo-oligomers. In addition, some of the pretreated solids were tested in
a simultaneous saccharification and fermentation (SSF) process to measure the reactivity of their cellulose component to enzymatic
digestion by cellulase enzymes. Monomeric xylose yields of 69–71% and total xylose yields (monomers and oligomers) of 70–77%
were achieved with performance level depending on pretreatment severity. Cellulose conversion yields in SSF of 80–87% were
obtained for some of the most digestible pretreated solids. 相似文献
5.
Ammonia fiber explosion treatment of corn stover 总被引:1,自引:0,他引:1
Farzaneh Teymouri Lizbeth Laureano-Pérez Hasan Alizadeh Bruce E. Dale 《Applied biochemistry and biotechnology》2004,115(1-3):951-963
Optimizing process conditions and parameters such as ammonia loading, moisture content of biomass, temperature, and residence
time is necessary for maximum effectiveness of the ammonia fiber explosion process. Approximate optimal pretreatment conditions
for corn stover were found to be temperature of 90°C, ammonia: dry corn stover mass ratio of 1∶1, moisture content of corn
stover of 60% (dry weight basis), and residence time (holding at target temperature), of 5 min. Approximately 98% of the theoretical
glucose yield was obtained during enzymatic hydrolysis of the optimal treated corn stover using 60 filter paper units (FPU)
of cellulase enzyme/g of glucan (equal to 22 FPU/g of dry corn stover). The ethanol yield from this sample was increased up
to 2.2 times over that of untreated sample. Lowering enzyme loading to 15 and 7.5 FPU/g of glucan did not significantly affect
the glucose yield compared with 60 FPU, and any differences between effects at different enzyme levels decreased as the treatment
temperature increased. 相似文献
6.
Impact of fluid velocity on hot water only pretreatment of corn stover in a flowthrough reactor 总被引:1,自引:0,他引:1
Flowthrough pretreatment with hot water only offers many promising features for advanced pretreatment of biomass, and a better
understanding of the mechanisms responsible for flowthrough behavior could allow researchers to capitalize on key attributes
while overcoming limitations. In this study, the effect of fluid velocity on the fate of total mass, hemicellulose, and lignin
was evaluated for hot water only pretreatment of corn stover in tubular flow through reactors. Increasing fluid velocity significantly
accelerated solubilization of total mass, hemicellulose, and lignin at early times. For example, when fluid velocity was increased
from 2.8 to 10.7 cm/min, xylan removal increased from 60 to 82% for hot water only pretreatment of corn stover at 200°C after
8 min. At the same time, lignin removal increased from 30 to 46%. Dissolved hemicellulose was almost all in oligomeric form,
and solubilization of hemicellulose was always accompanied by lignin release. The increase in removal of xylan and lignin
with velocity, especially in the early reaction stage, suggests that chemical reaction is not the only factor controlling
hemicellulose hydrolysis and that mass transfer and other physical effects may also play an important trole in hemicellulose
and lignin degradation and removal. 相似文献
7.
Pretreatment of corn stover by dilute sulfuric acid was investigated using a laboratory percolation (flowthrough) reactor
operated under high-solids conditions. The effects of reaction conditions and operating parameters on the performance of the
percolation reactor were investigated seeking the optimal range in which acceptable levels of yield and sugar concentration
could be attained. It was demonstrated that 70–75% recovery of xylose and 6 to 7% (w/w) xylose concentration were attainable.
The high sugar concentration was obtained as a result of dense packing of dry corn stover and the low liquid throughput. Xylose
was mostly unreacted, rather than decomposed. The cellulose and the unreacted xylan of treated corn stover were both effectively
hydrolyzed by a “cellulase” enzyme preparation that also exhibits some activity on xylan. The xylose yield was affected significantly
by the flow rate under the same reaction time and conditions. This behavior appears to be related to sugar decomposition,
mass transfer resistance, and the fact that acid is neutralized by the buffering components of the biomass. 相似文献
8.
Ballesteros I. Oliva J. M. Navarro A. A. González A. Carrasco J. Ballesteros M. 《Applied biochemistry and biotechnology》2000,84(1-9):97-110
Although considerable progress has been made in technology for converting lignocellulosic biomass into ethanol, substantial
opportunities still exist toreduce production costs. In biomass pretreatment, reducing milling power is a technological improvement
that will substantially lower production costs for ethanol. Improving sugar yield from hemicellulose hydrolysis would also
reduce ethanol production costs. Thus, it would be desirable to test innovative pretreatment conditions to improve the economics
by reducing electrical power of the milling stage and by optimizing pretreatment recovery of hemicellulose, as well as to
enhance cellulose hydrolysis. The objective of this study was to evaluate the effect of chip size (2–5, 5–8, and 8–12 mm)
on steam-explosion pretreatment (190 and 210°C, 4 and 8 min) of softwood (Pinus pinater). 相似文献
9.
Nguyen Quang A. Tucker Melvin P. Keller Fred A. Eddy Fannie P. 《Applied biochemistry and biotechnology》2000,84(1-9):561-576
Whole treechips obtained from softwood forest thinnings were pretreated via single-and two-stage dilute-sulfuric acid pretreatment.
Whole-tree chips were impregnated with dilute sulfuric acid and steam treated in a 4-L steam explosion reactor. In single-stage
pretreatment, wood chips were treated using a wide range of severity. In two-stage pretreatment, the first stage was carried
out at low severity tomaximize hemicellulose recovery. Solubilized sugars were recovered from the first-stage prehydrolysate
by washing with water. In the second stage, water-insoluble solids from first-stage prehydrolysate were impregnated with dilute
sulfuric acid, then steam treated at more severe conditions to hydrolyze a portion of the remaining cellulose to glucose and
to improve the enzyme digestibility. The total sugar yields obtained after enzymatic hydrolysis of two-stage dilute acid-pretreated
samples were compared with sugar yields from single-stage pretreatment. The overall sugar yield from two-stage dilute-acid
pretreatment was approx 10% higher, and the net enzyme requirement was reduced by about 50%. Simultaneous saccharification
and fermentation using an adapted Saccharomyces cerevisiae yeast strain further improved cellulose conversion yield and lowered the enzyme requirement. 相似文献
10.
Karin Öhgren Mats Galbe Guido Zacchi 《Applied biochemistry and biotechnology》2005,124(1-3):1055-1067
In this study, corn stover with a dry matter content of 20% was impregnated with SO2 and then steam pretreated for various times at various temperatures. The pretreatment was evaluated by enzymatic hydrolysis
of the solid material and analysis of the sugar content in the liquid. The maximum overall yield of glucose, 89% of the theoretical
based on the glucan in the raw material, was achieved when the corn stover was pretreated at 200°C for 10 min. The maximum
overall yield of xylose, 78%, was obtained with pretreatment at 190°C for 5 min. 相似文献
11.
We have studied rapid calibration models to predict the composition of a variety of biomass feedstocks by correlating near-infrared
(NIR) spectroscopic data to compositional data produced using traditional wet chemical analysis techniques. The rapid calibration
models are developed using multivariate statistical analysis of the spectroscopic and wet chemical data. This work discusses
the latest versions of the NIR calibration models for corn stover feedstock and dilute-acid pretreated corn stover. Measures
of the calibration precision and uncertainty are presented. No statistically significant differences (p = 0.05) are seen between NIR calibration models built using different mathematical pretreatments. Finally, two common algorithms
for building NIR calibration models are compared; no statistically significant differences (p = 0.05) are seen for the major constituents glucan, xylan, and lignin, but the algorithms did produce different predictions
for total extractives. A single calibration model combining the corn stover feedstock and dilute-acid pretreated corn stover
samples gave less satisfactory predictions than the separate models. 相似文献
12.
Pretreatment of corn stover using wet oxidation to enhance enzymatic digestibility 总被引:17,自引:0,他引:17
Corn stover is an abundant, promising raw material for fuel ethanol production. Although it has a high cellulose content,
without pretreatment it resists enzymatic hydrolysis, like most lignocellulosic materials. Wet oxidation (water, oxygen, mild
alkali or acid, elevated temperature and pressure) was investigated to enhance the enzymatic digestibility of corn stover.
Six different combinations of reaction temperature, time, and pH were applied. The best conditions (60g/L of corn stover,
195°C, 15 min, 12 bar O2, 2 g/L of Na2CO3) increased the enzymatic conversion of corn stover four times, compared to untreated material. Under these conditions 60%
of hemicellulose and 30% of lignin were solubilized, whereas 90% of cellulose remained in the solid fraction. After 24-h hydrolysis
at 50°C using 25 filter paper units (FPU)/g of dry matter (DM) biomass, the achieved conversion of cellulose to glucose was
about 85%. Decreasing the hydrolysis temperature to 40°C increased hydrolysis time from 24 to 72 h. Decreasing the enzyme
loading to 5 FPU/g of DM biomass slightly decreased the enzymatic conversion from 83.4 to 71%. Thus, enzyme loading can be
reduced without significantly affecting the efficiency of hydrolysis, an important economical aspect. 相似文献
13.
Fred A. Keller Jenny E. Hamilton Quang A. Nguyen 《Applied biochemistry and biotechnology》2003,105(1-3):27-41
Typical pretreatment requires high-energy (steam and electricity) and corrosion-resistant, high-pressure reactors. A review
of the literature suggests that fungal pretreatment could potentially lower the severity requirements of acid, temperature
and time. These reductions in severity are also expected to result in less biomass degradation and consequently lower inhibitor
concentrations compared to conventional thermochemical pretreatment. Furthermore, potential advantages of fungal pretreatment
of agricultural residues, such as corn stover, are suggested by its effectiveness in improving the cellulose digestibility
of many types of forage fiber and agricultural wastes. Our preliminary tests show a three- to five-fold improvement in enzymatic
cellulose digestibility of corn stover after pretreatment with Cyathus stercoreus; and a ten- to 100-fold reduction in shear force needed to obtain the same shear rate of 3.2 to 7 rev/s, respectively, after
pretreatment with Phanerochaete chrysosporium. 相似文献
14.
Melvin P. Tucker Nicholas J. Nagle Edward W. Jennings Kelly N. Ibsen Andy Aden Quang A. Nguyen Kyoung H. Kim Sally L. Noll 《Applied biochemistry and biotechnology》2004,115(1-3):1139-1159
Over the past three decades ethanol production in the United States has increased more than 10-fold, to approx 2.9 billion
gal/yr (mid-2003), with ethanol production expected to reach 5 billion gal/yr by 2005. The simultaneous coproduction of 7
million t/yr of distiller's grain (DG) may potentially drive down the price of DG as a cattle feed supplement. The sale of
residual DG for animal feed is an important part of corn dry-grind ethanol production economics; therefore, dry-grind ethanol
producers are seeking ways to improve the quality of DG to increase market penetration and help stabilize prices. One possible
improvement is to increase the protein content of DG by converting the residual starch and fiber into ethanol. We have developed
methods for steam explosion, SO2, and dilute-sulfuric acid pretreatment of DG for evaluation as a feedstock for ethanol production. The highest soluble sugar
yields (∼77% of available carbohydrate) were obtained by pretreatment of DG at 140°C for 20 min with 3.27 wt% H2SO4. Fermentation protocols for pretreated DG were developed at the bench scale and scaled to a working volume of 809 L for production
of hydrolyzed distiller's grain (HDG) for feeding trials. The pretreated DG was fermented with Saccharomyces cerevisiae D5A, with ethanol yields of 73% of theoretical from available glucans. The HDG was air-dried and used for turkey-feeding trials.
The inclusion of HDG into turkey poult (as a model non-ruminant animal) diets at 5 and 10% levels, replacing corn and soybean
meal, showed weight gains in the birds similar to controls, whereas 15 and 20% inclusion levels showed slight decreases (−6%)
in weight gain. At the conclusion of the trial, no negative effects on internal organs or morphology, and no mortality among
the poults, was found. The high protein levels (58–61%) available in HDG show promising economics for incorporation of this
process into corn dry-grind ethanol plants. 相似文献
15.
Summary of findings from the Biomass Refining Consortium for Applied Fundamentals and Innovation (CAFI): corn stover pretreatment 总被引:1,自引:0,他引:1
Richard T. Elander Bruce E. Dale Mark Holtzapple Michael R. Ladisch Y. Y. Lee Colin Mitchinson John N. Saddler Charles E. Wyman 《Cellulose (London, England)》2009,16(4):649-659
The Biomass Refining Consortium for Applied Fundamentals and Innovation, with members from Auburn University, Dartmouth College,
Michigan State University, the National Renewable Energy Laboratory, Purdue University, Texas A&M University, the University
of British Columbia, and the University of California at Riverside, has developed comparative data on the conversion of corn
stover to sugars by several leading pretreatment technologies. These technologies include ammonia fiber expansion pretreatment,
ammonia recycle percolation pretreatment, dilute sulfuric acid pretreatment, flowthrough pretreatment (hot water or dilute
acid), lime pretreatment, controlled pH hot water pretreatment, and sulfur dioxide steam explosion pretreatment. Over the
course of two separate USDA- and DOE-funded projects, these pretreatment technologies were applied to two different corn stover
batches, followed by enzymatic hydrolysis of the remaining solids from each pretreatment technology using identical enzyme
preparations, enzyme loadings, and enzymatic hydrolysis assays. Identical analytical methods and a consistent material balance
methodology were employed to develop comparative sugar yield data for each pretreatment and subsequent enzymatic hydrolysis.
Although there were differences in the profiles of sugar release, with the more acidic pretreatments releasing more xylose
directly in the pretreatment step than the alkaline pretreatments, the overall glucose and xylose yields (monomers + oligomers)
from combined pretreatment and enzymatic hydrolysis process steps were very similar for all of these leading pretreatment
technologies. Some of the water-only and alkaline pretreatment technologies resulted in significant amounts of residual xylose
oligomers still remaining after enzymatic hydrolysis that may require specialized enzyme preparations to fully convert xylose
oligomers to monomers. 相似文献
16.
Bura Renata Mansfield Shawn D. Saddler John N. Bothast Rodney J. 《Applied biochemistry and biotechnology》2002,98(1-9):59-72
Corn fiber, a by-product of the corn wet-milling industry, represents a renewable resource that is readily available in significant
quantities and could potentially serve as a low-cost feedstock for the production of fuel-grade alcohol. In this study, we
used a batch reactor to steam explode corn fiber at various degrees of severity to evaluate the potential of using this feedstock
in the bioconversion process. The results indicated that maximum sugar yields (soluble and following enzymatic hydrolysis)
were recovered from corn fiber that was pretreated at 190°C for 5 min with 6% SO2. Sequential SO2-catalyzed steam explosion and enzymatic hydrolysis resulted in very high conversion (81%) of all polysaccharides in the corn
fiber to monomeric sugars. Subsequently, Saccharomyces cerevisiae was able to convert the resultant corn fiber hydrolysates to ethanol very efficiently, yielding 90–96% of theoretical conversion
during the fermentation process. 相似文献
17.
R. Eric Berson John S. Young Sarah N. Kamer Thomas R. Hanley 《Applied biochemistry and biotechnology》2005,124(1-3):923-934
A technique for the removal of acetic acid from an actual pretreated corn stover hydrolysate was investigated. A powdered
form of activated carbon previously shown to be effective in the removal of acetic acid from a synthetic hydrolysate was utilized.
The method proved to be effective at lowering acetic acid levels while exhibiting minimal adsorption of the desired sugars
from the hydrolysate, although at a lower efficiency in the actual hydrolysate than in the synthetic hydrolysate. Results
are obtained for temperatures between 25 and 35°C and agitation rates between 150 and 350 rpm in shake flasks. Adsorption
isotherm and kinetic rate date are presented. Temperature differences over this range did not have an effect on adsorption
characteristics. Five stages of detoxification were necessary to lower acetic acid concentration to the maximum 2 g/L desired
for fermentation. 相似文献
18.
Biomechanics of wheat/barley straw and corn stover 总被引:3,自引:0,他引:3
Christopher T. Wright Peter A. Pryfogle Nathan A. Stevens Eric D. Steffler J. Richard Hess Thomas H. Ulrich 《Applied biochemistry and biotechnology》2005,121(1-3):5-19
The lack of understanding the mechanical characteristics of cellulosic feedstocks is a limiting factor in economically collecting
and processing crop residues, primarily wheat and barley stems and corn stover. Several testing methods—compression, tension,
and bend—were investigated to increase the understanding of the biomechanical behavior of cellulosic feedstocks. Biomechanical
data from these tests can provide required input to numerical models and help advance harvesting, handling, and processing
techniques. In addition, integrating the models with the complete data set from this study can identify potential tools for
manipulating the biomechanical properties of plant varieties in such a manner as to optimize their physical characteristics
to produce higher-value biomass and more energy-efficient harvesting practices. 相似文献
19.
Kim Sung Bae Um Byung Hwan Park Soon Chul 《Applied biochemistry and biotechnology》2001,91(1-9):81-94
The effect of pretreatment reagent and hydrogen peroxide on enzymatic digestibility of oak was investigated to compare pretreatment
performance. Pretreatment reagents used were ammonia, sulfuric acid, and water. These solutions were used without or in combination
with hydrogen peroxide in the percolation reactor. The reaction was carried out at 170°C for the predetermined reaction time.
Ammonia treatment showed the highest delignification but the lowest digestibility and hemicellulose removal among the three
treatments. Acid treatment proved to be a very effective method in terms of hemicellulose recovery and cellulose digestibility.
Hemicellulose recovery was 65–90% and digestibilities were >90% in the range of 0.01–0.2% acid concentration. In both treatments,
hydrogen peroxide had some effect on digestibility but decomposed soluble sugars produced during pretreatment. Unlike ammonia
and acid treatments, hydrogen peroxide in water treatment has a certain effect on hemicellulose recovery as well as delignification.
At 1.6% hydrogen peroxide concentration, both hemicellulose recovery and digestibility were about 90%, which were almost the
same as those of 0.2% sulfuric acid treatment. Also, digestibility was investigated as a function of hemicellulose removal
or delignification. It was found that digestibility was more directly related to hemicellulose removal rather than delignification. 相似文献
20.
Renata Bura Rodney J. Bothast Shawn D. Mansfield John N. Saddler 《Applied biochemistry and biotechnology》2003,106(1-3):319-335
A batch reactor was employed to steam explode corn fiber at various degrees of severity to evaluate the potential of using
this feedstock as part of an enzymatically mediated cellulose-to-ethanol process. Severity was controlled by altering temperature
(150–230°C), residence time (1–9 min), and SO2 concentration (0–6% [w/w] dry matter). The effects of varying the different parameters were assessed by response surface
modeling. The results indicated that maximum sugar yields (hemicellulose-derived water soluble, and cellulose-derived following
enzymatic hydrolysis) were recovered from corn fiber pretreated at 190°C for 5 minutes after exposure to 3% SO2. Sequential SO2-catalyzed steam explosion and enzymatic hydrolysis resulted in a conversion efficiency of 81% of the combined original hemicellulose
and cellulose in the corn fiber to monomeric sugars. An additional posthydrolysis step performed on water soluble hemicellulose
stream increased the concentration of sugars available for fermentation by 10%, resulting in the high conversion efficiency
of 91%. Saccharomyces cerevisiae was able to ferment the resultant corn fiber hydrolysates, perhydrolysate, and liquid fraction from the posthydrolysis steps
to 89, 94, and 85% of theoretical ethanol conversion, respectively. It was apparent that all of the parameters investigated
during the steam explosion pretreatment had a significant effect on sugar recovery, inhibitory formation, enzymatic conversion
efficiency, and fermentation capacity of the yeast. 相似文献