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1.
To have all-year-round available feedstock, whole-crop maize is harvested premature, when it still contains enough moisture
for the anaerobic ensiling process. Silage preparation is a well-known procedure for preserving plant material. At first,
this method was applied to obtain high-quality animal feed. However, it was found that such ensiled crops are very suitable
for bioenergy production. Maize silage, which consists of hardly degradable lignocellulosic material, hemicellulosic material,
and starch, was evaluated for its potential as a feedstock in the production of bioethanol. It was pretreated at low severity
(185 °C, 15 min) giving very high glucan (∼100%) and hemicellulose recoveries (<80%)—as well as very high ethanol yield in
simultaneous saccharification and fermentation experiments (98% of the theoretical production based on available glucan in
the medium). The theoretical ethanol production of maize silage pretreated at 185 °C for 15 min without oxygen or catalyst
was 392 kg ethanol per ton of dry maize silage. 相似文献
2.
Downregulated lignin transgenic black cottonwood ( Populus trichocarpa) was used to elucidate the effect of lignin and xylan content on enzymatic saccharification. The lignin contents of three transgenic samples (4CL1-1, 4CL1-4, and CH8-1-4) were 19.3, 16.7, and 15.0?%, respectively, as compared with the wild type (21.3?%). The four pretreatments were dilute acid (0.1?% sulfuric acid, 185?°C, 30?min), green liquor (6?% total titratable alkali, 25?% sulfidity based on TTA, 185?°C, and 15?min.), autohydrolysis (185?°C, 30?min), and ozone delignification (25?°C, 30?min). Following the pretreatment, enzymatic saccharification was carried out using an enzyme charge of 5?FPU/g of substrates. The removal of lignin and hemicellulose varies with both the types of pretreatments and the lignin content of the transgenic trees. Due to the greatest removal of lignin, green liquor induced the highest sugar production and saccharification efficiency, followed by acid, ozone, and autohydrolysis in descending order. The results indicated that lignin is the main recalcitrance of biomass degradation. At a given lignin content, pretreatment with ozone delignification had lower saccharification efficiency than the other pretreatment methods due to higher xylan content. 相似文献
3.
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 [H 2SO 4 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
4.
After harvesting season, large amounts of durian peels were produced and uselessly disposed of by combustion or landfilling leading to environmental pollution and human health hazards. Proper management of these wastes is necessary to reduce not only an environmental problem but also to create value-added products. Herein, we optimized sulfuric acid pretreatment to promote enzymatic saccharification of durian peels and convert fermentable sugars to bioethanol. Three pretreatment parameters were optimized based on Response Surface Methodology (RSM), including acid concentration (0.5%–3.5%), temperature (60–140 °C), and time (20–100 min). At optimal pretreatment condition using 2.75% H 2SO 4, at 127.14 °C for 74.13 min, 0.53 g/g-biomass of reducing sugars were produced, which is 1.88 folds higher than the untreated durian peel. The pretreatment liquor and biomass hydrolysate were analyzed by Gas Chromatograph-Mass spectrometer (GC-MS), and fermentation inhibitors, i.e. acetic acid, furfural, and furan methanol, were identified in those fractions. Due to pretreatment at the optimal condition, a higher yield of reducing sugar was observed, and the production of ethanol from the pretreated biomass was 5.70 g/L (equivalent to 87.43% of theoretical yields). These findings demonstrated the potential of using durian waste in the biorefinery concept to achieve a concept of the green economy. 相似文献
5.
Corn stover silage (CSS) is regarded as a promising feedstock for bioethanol production. The two-step pretreatment using a sequential non-ionic surfactant and ferric nitrate pretreatment was investigated for improving the enzymatic hydrolysis of CSS. The first-step pretreatment using non-ionic surfactant (Tween-80, 2.0 wt.%) at 60 °C for 60 min achieved 30.48% the removal of lignin. Compared with the raw material, the cellulose content of first-step treated CSS increased by 15.86%. The second step using ferric nitrate resulted in 94.56% hemicellulose removal and achieved 72.53% cellulose purity at 130 °C for 30 min, while the yields of furfural and HMF were only 0.36 and 0.32 g/100 g dry material, respectively. The maximum enzymatic digestibility of the two-step treated CSS was 90.98% with a low cellulose dosage (15 FPU/g-glucan), which was approximately 32.07% higher than that of the first-step pretreatment only with Tween-80. 相似文献
6.
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% H 2SO 4) 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
7.
Hot-compressed water (HCW) is among several cost-effective pretreatment processes of lignocellulosic biomass for enzymatic
hydrolysis. The present work investigated the characteristics of HCW pretreatment of rice straw including sugar production
and inhibitor formation in the liquid fraction and enzymatic hydrolysis of pretreated material. Pretreatment was carried out
at a temperature ranging from 140 to 240 °C for 10 or 30 min. Soluble oligosaccharides were found to constitute almost all
the components of total sugars in the liquid fraction. The maximal production of total glucose at 180 °C and below accounted
for 4.4–4.9% of glucan in raw material. Total xylose production peaked at 180 °C, accounting for 43.3% of xylan in raw material
for 10-min pretreatment and 29.8% for 30-min pretreatment. The production of acetic acid increased at higher temperatures
and longer treatment time, indicating more significant disruption of lignocellulosic structure, and furfural production achieved
the maximum (2.8 mg/ml) at 200 °C for both 10-min and 30-min processes. The glucose yield by enzymatic hydrolysis of pretreated
rice straw was no less than 85% at 180 °C and above for 30-min pretreatment and at 200 °C and above for 10-min pretreatment.
Considering sugar recovery, inhibitor formation, and process severity, it is recommended that a temperature of 180 °C for
a time of 30 min can be the most efficient process for HCW pretreatment of rice straw. 相似文献
8.
The fermentable sugars in lignocellulosic biomass are derived from cellulose and hemicellulose, which are not readily accessible
to enzymatic saccharification because of their recalcitrance. An ethanosolv pretreatment method was applied for the enzymatic
saccharification of barley straw with an inorganic acid. The effects of four process variables (temperature, time, catalyst
dose, and ethanol concentration) on the barley straw pretreatment were analyzed over a broad range using a small composite
design and a response surface methodology. The yield of the residual solid and composition of the solid fraction differed
as ethanosolv conditions varied within the experimental range. A glucan recovery, xylan recovery, and delignification were
85%, 14%, and 69% at center point conditions (170°C, 60 min, 1.0% ( w/ w) H 2SO 4, and 50% ( w/ w) ethanol), respectively. Ethanosolv pretreatment removed lignin effectively. Additionally, the highest enzymatic digestibility
of 85.3% was obtained after 72 h at center point conditions. 相似文献
9.
Steam treatment of an industrial process stream, denoted starch-free wheat fiber, was investigated to improve the formation
of monomeric sugars in subsequent enzymatic hydrolysis for further bioconversion into ethanol. The solid fraction in the process
stream, derived from a combined starch and ethanol factory, was rich in arabinose (21.1%), xylose (30.1%), and glucose (18.6%),
in the form of polysaccharides. Various conditions of steam pretreatment (170–220°C for 5–30 min) were evaluated, and their
effect was assessed by enzymatic hydrolysis with 2 g of Celluclast + Ultraflo mixture/ 100 g of starch-free fiber (SFF) slurry
at 5% dry matter (DM). The highest overall sugar yield for the combined steam pretreatment and enzymatic hydrolysis, 52g/100
g of DM of SFF, corresponding to 74% of the theoretical, was achieved with pretreatment at 190°C for 10 min followed by enzymatic
hydrolysis. 相似文献
10.
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
11.
Corn stover silage is an attractive raw material for the production of biofuels and chemicals due to its high content of carbohydrates
and easy degradability. The effects of Fe(NO 3) 3 pretreatment conditions on sugar yields were investigated for corn stover silage. In addition, a combined severity factor
was used to evaluate the effect of pretreatment conditions on the concentration of total sugars and inhibitors. Optimum pretreatment
condition was obtained at 150 °C for 10 min with 0.05 M Fe(NO 3) 3, at which the yields of soluble xylose and glucose in liquid achieved 91.80% of initial xylose, 96.74% of initial arabinose
and 19.09% of initial glucose, respectively, meanwhile, 91.84% of initial xylose, 98.24% of initial arabinose, and 19.91%
of initial glucose were removed. In addition, a severity analysis showed that the maximum sugar concentration of 33.48 g/l
was achieved at combined severity parameter value of 0.62, while the inhibitor concentration was only 0.03 g/l. Fe(NO 3) 3 is an effective catalyst to enhance hemicellulose hydrolysis in corn stover silage, the yields of monomeric xylose in the
liquid fraction reached as high as 91.06% of initial xylose and 96.22% of initial arabinose, respectively. 相似文献
12.
Aqueous dilute acid pretreatments of corncob were conducted using cylindrical pressure vessels in an oil bath. Pretreatments
were conducted in a temperature range of 160–190 °C with acid-solution-to-solid-corncob ratio of 2. The acid concentration
(v/v) in the pretreatment solution was varied from 0% to 0.7%, depending on temperature. This gives acid charge on ovendry-weight
corncob of 0–2.58%. It was found that optimal pretreatment temperature is between 160 and 170 °C based on total xylose and
glucose yields and thermal energy consumption in pretreatment. At 170 °C and acid charge of 2.2% on cob, total glucose yield
and xylose recovery were 97% and 75%, respectively, which resulted in an overall monomeric sugar recovery of about 88%. Xylose
concentration in the hydrolysate was about 12%, with xylose-to-acetic-acid ratio of 8 and to furan (furfural and hydroxymethylfurfural)
of about 15. 相似文献
13.
The pretreatment of lignocellulosic biomass is crucial for efficient subsequent enzymatic hydrolysis and ethanol fermentation. In this study, wet explosion (WEx) pretreatment was applied to cocksfoot grass and pretreatment conditions were tailored for maximizing the sugar yields using response surface methodology. The WEx process parameters studied were temperature (160–210 °C), retention time (5–20 min), and dilute sulfuric acid concentration (0.2–0.5 %). The pretreatment parameter set E, applying 210 °C for 5 min and 0.5 % dilute sulfuric acid, was found most suitable for achieving a high glucose release with low formation of by-products. Under these conditions, the cellulose and hemicellulose sugar recovery was 94 % and 70 %, respectively. The efficiency of the enzymatic hydrolysis of cellulose under these conditions was 91 %. On the other hand, the release of pentose sugars was higher when applying less severe pretreatment conditions C (160 °C, 5 min, 0.2 % dilute sulfuric acid). Therefore, the choice of the most suitable pretreatment conditions is depending on the main target product, i.e., hexose or pentose sugars. 相似文献
14.
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
15.
The overall objective in this European Union-project is to develop cost and energy effective production systems for coproduction
of bioethanol and electricity based on integrated biomass utilization. A pilot plan reactor for hydrothermal pretreatment
(including weak acid hydrolysis, wet oxidation, and steam pretreatment) with a capacity of 100 kg/h was constructed and tested
for pretreatment of wheat straw for ethanol production. Highest hemicellulose (C5 sugar) recovery and extraction of hemicellulose
sugars was obtained at 190°C whereas highest C6 sugar yield was obtained at 200°C. Lowest toxicity of hydrolysates was observed
at 190°C; however, addition of H 2O 2 improved the fermentability and sugar recoveries at the higher temperatures. The estimated total ethanol production was 223
kg/t straw assuming utilisation of both C6 and C5 during fermentation, and 0.5 g ethanol/g sugar. 相似文献
16.
Distillers’ grains and corn fiber are the coproducts of the corn dry grind and wet milling industries, respectively. Availability
of distillers’ grains and corn fiber at the ethanol plant and their high levels of lignocellulosic material make these coproducts
attractive feedstocks for conversion to ethanol. In this study, dilute sulfuric acid hydrolysis of these coproducts was investigated
in a multistage scheme. After the completion of each pretreatment stage, the liquid substrate was separated and reused in
the succeeding pretreatment stage with a fresh substrate. The substrate from each stage was also subjected to enzyme hydrolysis
in a separate experiment. The sulfuric acid concentration and the substrate loading were maintained at 1.0 vol% and 15.0 wt.%,
respectively, and the temperature was maintained at 120 °C in all the experiments. Experiments were also performed to study
the effect of removing oil from the samples prior to the pretreatment. The highest concentration of monomeric sugars (MS)
was observed when three stages of pretreatment were followed by the enzyme reaction. The enzyme hydrolysis of the three-stage
pretreated dried distillers’ grains and corn fiber yielded 122.6 ± 5.8 and 184.5 ± 4.1 mg/mL of MS, respectively. The formation
of inhibitory products was also monitored. 相似文献
17.
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
18.
The olive pulp fraction contained in the residue generated in olive oil extraction by a two-step centrifugation process can
be upgraded by using the cellulose fraction to produce ethanol and recovering high value phenols (tyrosol and hydroxytyrosol).
Olive pulp was pretreated in a laboratory scale stirred autoclave at different temperatures (150–250°C). Pretreatment was
evaluated regarding cellulose recovery, enzymatic hydrolysis effectiveness ethanol production by a simultaneous saccharification
and fermentation process (SSF), and phenols recovery in the filtrate. The pretreatment of olive pulp using water at temperatures
between 200°C and 250°C enhanced enzymatic hydrolysis. Maximum ethanol production (11.9 g/L) was obtained after pretreating
pulp at 210°C in a SSF fed-batch procedure. Maximum hydroxytyrosol recovery was obtained in the liquid fraction when pretreated
at 230°C. 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.
Oxidative lime pretreatment increases the enzymatic digestibility of lignocellulosic biomass primarily by removing lignin.
In this study, recommended pretreatment conditions (reaction temperature, oxygen pressure, lime loading, and time) were determined
for Dacotah switchgrass. Glucan and xylan overall hydrolysis yields (72 h, 15 FPU/g raw glucan) were measured for 105 different
reaction conditions involving three different reactor configurations (very short term, short term, and long term). The short-term
reactor was the most productive. At the recommended pretreatment condition (120 °C, 6.89 bar O 2, 240 min), it achieved an overall glucan hydrolysis yield of 85.2 g glucan hydrolyzed/100 g raw glucan and an overall xylan
yield of 50.1 g xylan hydrolyzed/100 g raw xylan. At this condition, glucan oligomers (1.80 g glucan recovered/100 g glucan
in raw biomass) and xylan oligomers (25.20 g xylan recovered/100 g xylan in raw biomass) were recovered from the pretreatment
liquor, which compensate for low pretreatment yields. 相似文献
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