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1.
Franco Cotana Gianluca Cavalaglio Mattia Gelosia Valentina Coccia Alessandro Petrozzi Andrea Nicolini 《Applied biochemistry and biotechnology》2014,174(1):156-167
The study investigated the production of bioethanol from softwood, in particular pine wood chip. The steam explosion pretreatment was largely investigated, evaluating also the potential use of a double-step process to increase ethanol production through the use of both solid and liquid fraction after the pretreatment. The pretreatment tests were carried out at different conditions, determining the composition of solid and liquid fraction and steam explosion efficiency. The enzymatic hydrolysis was carried out with Ctec2 enzyme while the fermentation was carried out using Saccharomyces Cerevisiae yeast “red ethanol”. It was found that the best experimental result was obtained for a single-step pretreated sample (10.6 g of ethanol/100 g of initial biomass dry basis) for a 4.53 severity. The best double-step overall performance was equal to 8.89 g ethanol/100 g of initial biomass dry basis for a 4.27 severity. The enzymatic hydrolysis strongly depended on the severity of the pretreatment while the fermentation efficiency was mainly influenced by the concentration of the inhibitors. The ethanol enhancing potential of a double-step steam explosion could slightly increase the ethanol production compared to single-step potential. 相似文献
2.
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
3.
In biomass-to-ethanol processes a physico-chemical pretreatment of the lignocellulosic biomass is a critical requirement for enhancing the accessibility of the cellulose substrate to enzymatic attack. This report evaluates the efficacy on barley and wheat straw of three different pretreatment procedures: acid or water impregnation followed by steam explosion versus hot water extraction. The pretreatments were compared after enzyme treatment using a cellulase enzyme system, Celluclast 1.5 L from Trichoderma reesei, and a beta-glucosidase, Novozyme 188 from Aspergillus niger. Barley straw generally produced higher glucose concentrations after enzymatic hydrolysis than wheat straw. Acid or water impregnation followed by steam explosion of barley straw was the best pretreatment in terms of resulting glucose concentration in the liquid hydrolysate after enzymatic hydrolysis. When the glucose concentrations obtained after enzymatic hydrolyses were related to the potential glucose present in the pretreated residues, the highest yield, approximately 48% (g g-1), was obtained with hot water extraction pretreatment of barley straw; this pretreatment also produced highest yields for wheat straw, producing a glucose yield of approximately 39% (g g-1). Addition of extra enzyme (Celluclast 1.5 L+Novozyme 188) during enzymatic hydrolysis resulted in the highest total glucose concentrations from barley straw, 32-39 g L-1, but the relative increases in glucose yields were higher on wheat straw than on barley straw. Maldi-TOF MS analyses of supernatants of pretreated barley and wheat straw samples subjected to acid and water impregnation, respectively, and steam explosion, revealed that the water impregnated + steam-exploded samples gave a wider range of pentose oligomers than the corresponding acid-impregnated samples. 相似文献
4.
Schell D. J. Torget R. Power A. Walter P. J. Grohmann K. Hinman N. D. 《Applied biochemistry and biotechnology》1991,(1):87-97
Lignocellulosic biomass is one of the most plentiful and potentially cheapest feedstocks for ethanol production. The cellulose
component can be broken down into glucose by enzymes and then converted to ethanol by yeast. However, hydrolysis of cellulose
to glucose is difficult, and some form of pretreatment is necessary to increase the susceptibility of cellulose to enzymatic
attack. An analysis has been completed of two pretreatment options, dilute sulfuric acid hydrolysis and sulfur dioxide impregnated
steam explosion, for two feedstocks, wheat straw and aspen wood chips. Detailed process flow sheets and material and energy
balances were used to generate equipment cost information. A technical and economic analysis compared the two feedstocks for
each of the two pretreatments. For the same pretreatment, sugars produced from aspen wood hydrolysis were cheaper because
of the higher carbohydrate content of aspen, whereas dilute acid pretreatment is favored over acid-catalyzed steam explosion. 相似文献
5.
Ballesteros I. Oliva J. M. Carrasco J. Cabañas A. Navarro A. A. Ballesteros M. 《Applied biochemistry and biotechnology》1998,(1):369-381
In this work, the effect of the addition of different concentrations of Tween-80 and three different zeolite-like products
on enzymatic hydrolysis, ethanol fermentation, and simultaneous saccharification and fermentation (SSF) process has been investigated.
The ability of these products to enhance the effectiveness of the SSF process to ethanol of steam-exploded poplar biomass
using the thermotolerant strainKluyveromyces marxianus EMS-26 has been tested.
Tween-80 (0.4 g/L) increased enzymatic hydrolysis yield by 20% when compared to results obtained in hydrolysis in absence
of the additive. Zeolite-like products (ZESEP-56 and ZECER-56) (2.5 g/L) improved rates of conversion and ethanol yields in
the fermentation of liquid fraction recovered from steam-exploded poplar. The periods required for the completion of fermentation
were approx 10 h in the presence of zeolite-like products and 24 h in the absence of additives. The probable mode of action
is through lowered levels of inhibitory substances because of adsorption by the additive. 相似文献
6.
The pretreatment of lignocellulosic materials prior to the enzymatic hydrolysis is essential to the sugar yield and bioethanol
production. Dilute acid hydrolysis of black spruce softwood chip was performed in a continuous high temperature reactor followed
with steam explosion and mechanical refining. The acid-soaked wood chips were pretreated under different feeding rates (60
and 92 kg/h), cooking screw rotation speeds (7.2 and 14.4 rpm), and steam pressures (12 and 15 bar). The enzymatic hydrolysis
was carried out on the acid-insoluble fraction of pretreated material. At lower feeding rate, the pretreatment at low steam
pressure and short retention time favored the recovery of hemicellulose. The pretreatment at high steam pressure and longer
retention time recovered less hemicellulose but improved the enzymatic accessibility. As a result, the overall sugar yields
became similar no matter what levels of the retention time or steam pressure. Comparing with lower feeding rate, higher feeding
rate resulted in consistently higher glucose yield in both liquid fraction after pretreatment and that released after enzymatic
hydrolysis. 相似文献
7.
Switchgrass was used as a model feedstock to determine the influence of pretreatment conditions and biomass quality on enzymatic hydrolysis using different enzyme products. Dilute sulfuric acid and soaking in aqueous ammonia pretreatments were used to produce biomass with varied levels of hemicellulose and lignin sheathing. Pretreated switchgrass solids were tested with simple enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) with three commercial enzyme products: Accellerase 1000 (Genencor), Spezyme CP (Genencor)/Novozyme 188 (Novozymes), and Celluclast/Novozyme 188 (Novozymes). Enzymes were loaded on a common activity basis (FPU/g cellulose and CBU/g cellulose). Despite identical enzyme loadings, glucose yields were significantly different for both acid and alkaline pretreatments but differences diminished as hydrolysis progressed for acid-pretreated biomass. Cellobiose concentrations in Accellerase treatments indicated an initial β-glucosidase limitation that became less significant over time. SSF experiments showed that differences in glucose and ethanol yields could not be attributed to enzyme product inhibition. Yield discrepancies of glucose or ethanol in acid pretreatment, alkaline pretreatment, and acid pretreatment/SSF were as much as 15%, 19%, and 5%. These results indicate that standardized protocols for measuring enzyme activity may not be adequate for assessing activity using pretreated biomass substrates. 相似文献
8.
Zhuang Zuo Shen Tian Zebing Chen Jia Li Xiushan Yang 《Applied biochemistry and biotechnology》2012,167(7):2088-2102
The production of ethanol and methane from corn stover (CS) was investigated in a biorefinery process. Initially, a novel soaking pretreatment (NaOH and aqueous-ammonia) for CS was developed to remove lignin, swell the biomass, and improve enzymatic digestibility. Based on the sugar yield during enzymatic hydrolysis, the optimal pretreatment conditions were 1?% NaOH?+?8?% NH4OH, 50°C, 48?h, with a solid-to-liquid ratio 1:10. The results demonstrated that soaking pretreatment removed 63.6?% lignin while reserving most of the carbohydrates. After enzymatic hydrolysis, the yields of glucose and xylose were 78.5?% and 69.3?%, respectively. The simultaneous saccharification and fermentation of pretreated CS using Pichia stipitis resulted in an ethanol concentration of 36.1?g/L, corresponding only to 63.3?% of the theoretical maximum. In order to simplify the process and reduce the capital cost, the liquid fraction of the pretreatment was used to re-soak new CS. For methane production, the re-soaked CS and the residues of SSF were anaerobically digested for 120?days. Fifteen grams CS were converted to 1.9?g of ethanol and 1337.3?mL of methane in the entire process. 相似文献
9.
Ballesteros Ignacio Oliva José Miguel Negro Maria José Manzanares Paloma Ballesteros Mercedes 《Applied biochemistry and biotechnology》2002,98(1-9):717-732
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
10.
Ballesteros Ignacio Oliva Jose Miguel Saez Felicia Ballesteros Mercedes 《Applied biochemistry and biotechnology》2001,91(1-9):237-252
The recent implementation of a new two-step centrifugation process for extracting olive oil in Spain has substantially reduced
water consumption, thereby eliminating oil mill wastewater. However, a new high sugar content residue is still generated.
In this work the two fractions present in the residue (olive pulp and fragm ented stones) were assayed as substrate for ethanol
production by the simultaneous saccharification and fermentation (SSF) process. Pretreatment of fragmented olive stones by
sulfuric acid-catalyzed steam explosion was the most effective treatment for increasing enzymatic digestibility; however,
a pretreatment step was not necessary to bioconvert the olive pulp into ethanol. Theolive pulp and fragmented olive stones
were tested by the SSF process using a fed-batch procedure. By adding the pulp three times at 24-h intervals, 76% of the theoretical
SSF yield was obtained. Experiments with fed-batch pretreated olive stones provided SSF yields significantly lower than those
obtained at standard SSF procedure. The preferred SSF conditions to obtain ethanol from olives stones (61% of theoretical
yield) were 10% substrate and addition of cellulases at 15 filter paper units/g of substrate. 相似文献
11.
Evaluation and Characterization of Forage Sorghum as Feedstock for Fermentable Sugar Production 总被引:2,自引:0,他引:2
Corredor DY Salazar JM Hohn KL Bean S Bean B Wang D 《Applied biochemistry and biotechnology》2009,158(1):164-179
Sorghum is a tropical grass grown primarily in semiarid and drier parts of the world, especially areas too dry for corn. Sorghum
production also leaves about 58 million tons of by-products composed mainly of cellulose, hemicellulose, and lignin. The low
lignin content of some forage sorghums such as brown midrib makes them more digestible for ethanol production. Successful
use of biomass for biofuel production depends on not only pretreatment methods and efficient processing conditions but also
physical and chemical properties of the biomass. In this study, four varieties of forage sorghum (stems and leaves) were characterized
and evaluated as feedstock for fermentable sugar production. Fourier transform infrared spectroscopy and X-ray diffraction
were used to determine changes in structure and chemical composition of forage sorghum before and after pretreatment and the
enzymatic hydrolysis process. Forage sorghums with a low syringyl/guaiacyl ratio in their lignin structure were easy to hydrolyze
after pretreatment despite the initial lignin content. Enzymatic hydrolysis was also more effective for forage sorghums with
a low crystallinity index and easily transformed crystalline cellulose to amorphous cellulose, despite initial cellulose content.
Up to 72% hexose yield and 94% pentose yield were obtained using modified steam explosion with 2% sulfuric acid at 140 °C
for 30 min and enzymatic hydrolysis with cellulase (15 filter per unit (FPU)/g cellulose) and β-glucosidase (50 cellobiose
units (CBU)/g cellulose). 相似文献
12.
Lignocellulosic biomass, such as wood, grass, agricultural, and forest residues, are potential resources for the production of bioethanol. The current biochemical process of converting biomass to bioethanol typically consists of three main steps: pretreatment, enzymatic hydrolysis, and fermentation. For this process, pretreatment is probably the most crucial step since it has a large impact on the efficiency of the overall bioconversion. The aim of pretreatment is to disrupt recalcitrant structures of cellulosic biomass to make cellulose more accessible to the enzymes that convert carbohydrate polymers into fermentable sugars. This paper reviews several leading acidic, neutral, and alkaline pretreatments technologies. Different pretreatment methods, including dilute acid pretreatment (DAP), steam explosion pretreatment (SEP), organosolv, liquid hot water (LHW), ammonia fiber expansion (AFEX), soaking in aqueous ammonia (SAA), sodium hydroxide/lime pretreatments, and ozonolysis are intensively introduced and discussed. In this minireview, the key points are focused on the structural changes primarily in cellulose, hemicellulose, and lignin during the above leading pretreatment technologies. 相似文献
13.
Olivia Córdova Fabiana Passos Rolando Chamy 《Applied biochemistry and biotechnology》2018,185(1):114-126
Microalgae may be a potential feedstock for biogas production through anaerobic digestion. However, this process is limited by the hydrolytic stage, due to the complex and resistant microalgae cell wall components. This fact hinders biomass conversion into biogas, demanding the application of pretreatment techniques for inducing cell damage and/or lysis and organic matter solubilisation. In this study, sonication, thermal, ultrasound, homogeneizer, hydrothermal and steam explosion pretreatments were evaluated in different conditions for comparing their effects on anaerobic digestion performance in batch reactors. The results showed that the highest biomass solubilisation values were reached for steam explosion (65–73%) and ultrasound (33–57%). In fact, only applied energies higher than 220 W or temperatures higher than 80 °C induced cell wall lysis in C. sorokiniana. Nonetheless, the highest methane yields were not correlated to biogas production. Thermal hydrolysis and steam explosion showed lower methane yields in respect to non-pretreated biomass, suggesting the presence of toxic compounds that inhibited the biological process. Accordingly, these pretreatment techniques led to a negative energy balance. The best pretreatment method among the ones evaluated was thermal pretreatment, with four times more energy produced that demanded. 相似文献
14.
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
15.
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
16.
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
17.
Mohamed Amine Jmel Nico Anders Nesrine Ben Yahmed Christian Schmitz M. Nejib Marzouki Antje Spiess Issam Smaali 《Applied biochemistry and biotechnology》2018,184(3):777-793
Green macroalgae are an abundant and undervalued biomass with a specific cell wall structure. In this context, different pretreatments, namely ethanol organosolv (Org), alkaline, liquid hot water (LHW), and ionic liquid (IL) pretreatments, were applied to the green macroalgae Ulva lactuca biomass and then evaluated. Their effects on chemical composition, biomass crystallinity, enzymatic digestibility, and theoretical ethanol potential were studied. The chemical composition analysis showed that the Org and LHW pretreatments allowed the highest glucan recovery (80.8 ± 3.6 and 62.9 ± 4.4 g/100 g DM, respectively) with ulvan (80.0 and 99.1%) and hemicellulose (55.0 and 42.3%) removal. These findings were in agreement with both thermogravimetric analysis and scanning electron microscopy results that confirm significant structural changes of the pretreated biomasses. It was found that the employed pretreatments did not significantly affect the cellulose crystallinity; however, they both increased the whole crystallinity and the enzymatic digestibility. This later reached 97.5% in the case of LHW pretreatment. Our results showed high efficiency saccharification of Ulva lactuca biomass that will constitute the key step of the implementation of a biorefinery process. 相似文献
18.
K. C. Patrick Lee Millicent Bulls John Holmes John W. Barrier 《Applied biochemistry and biotechnology》1997,66(1):1-23
Because of the recalcitrant nature of lignocellulosic materials, it is important to pretreat the biomass in order to obtain
a suitable material for the bioconversion. In this study, two different types of pretreatments were performed. The first experiment
used a 2-gal Parr reactor operated at 140, 150,160, and 170‡C with sulfuric acid concentrations varying from 0.5 to 2%. A
second pretreatment was performed with a two-stage low-temperature process. The first-stage pretreatment was performed at
100 or 120‡C with sulfuric acid concentrations of 0.5, 2, and 5% followed by a secondstage pretreatment at 120‡C with 2% acid
concentration. The best residues for enzymatic hydrolysis and simultaneous saccharification and fermentations (SSF) came from
the higher temperature pretreatment with the Parr reactor. However, a large portion of the xylose fraction was degraded to
furfural and glucose was degraded to HMF. On the contrary, the two-stage low temperature pretreatment resulted in a very low
percentage of xylose degradation, and no glucose degradation. The residues from this two-stage pretreatment performed satisfactorily
toward the production of ethanol by SSFs. This study discusses the results obtained from these experiments. 相似文献
19.
Qining Sun Marcus Foston Daisuke Sawada Sai Venkatesh Pingali Hugh M. O’Neill Hongjia Li Charles E. Wyman Paul Langan Yunqiao Pu Art J. Ragauskas 《Cellulose (London, England)》2014,21(4):2419-2431
One commonly cited factor that contributes to the recalcitrance of biomass is cellulose crystallinity. The present study aims to establish the effect of several pretreatment technologies on cellulose crystallinity, crystalline allomorph distribution, and cellulose ultrastructure. The observed changes in the cellulose ultrastructure of poplar were also related to changes in enzymatic hydrolysis, a measure of biomass recalcitrance. Hot-water, organo-solv, lime, lime-oxidant, dilute acid, and dilute acid-oxidant pretreatments were compared in terms of changes in enzymatic sugar release and then changes in cellulose ultrastructure measured by 13C cross polarization magic angle spinning nuclear magnetic resonance and wide-angle X-ray diffraction. Pretreatment severity and relative chemical depolymerization/degradation were assessed through compositional analysis and high-performance anion-exchange chromatography with pulsed amperometric detection. Results showed minimal cellulose ultrastructural changes occurred due to lime and lime-oxidant pretreatments, which at short residence time displayed relatively high enzymatic glucose yield. Hot water pretreatment moderately changed cellulose crystallinity and crystalline allomorph distribution, yet produced the lowest enzymatic glucose yield. Dilute acid and dilute acid-oxidant pretreatments resulted in the largest increase in cellulose crystallinity, para-crystalline, and cellulose-Iβ allomorph content as well as the largest increase in cellulose microfibril or crystallite size. Perhaps related, compositional analysis and Klason lignin contents for samples that underwent dilute acid and dilute acid-oxidant pretreatments indicated the most significant polysaccharide depolymerization/degradation also ensued. Organo-solv pretreatment generated the highest glucose yield, which was accompanied by the most significant increase in cellulose microfibril or crystallite size and decrease in relatively lignin contents. Hot-water, dilute acid, dilute acid-oxidant, and organo-solv pretreatments all showed evidence of cellulose microfibril coalescence. 相似文献
20.
Effects of temperature and moisture on dilute-acid steam explosion pretreatment of corn stover and cellulase enzyme digestibility 总被引:3,自引:0,他引:3
Melvin P. Tucker Kyoung H. Kim Mildred M. Newman Quang A. Nguyen 《Applied biochemistry and biotechnology》2003,105(1-3):165-177
Corn stover is emerging as a viable feedstock for producing bioethanol from renewable resources. Dilute-acid pretreatment
of corn stover can solubilize a significant portion of the hemicellulosic component and enhance the enzymatic digestibility
of the remaining cellulose for fermentation into ethanol. In this study, dilute H2SO4 pretreatment of corn stover was performed in a steam explosion reactor at 160°C, 180°C, and 190°C, approx 1 wt% H2SO4, and 70-s to 840-s residence times. The combined severity (Log10 [R
o
] - pH), an expression relating pH, temperature, and residence time of pretreatment, ranged from 1.8 to 2.4. Soluble xylose
yields varied from 63 to 77% of theoretical from pretreatments of corn stover at 160 and 180°C. However, yields >90% of theoretical
were found with dilute-acid pretreatments at 190°C. A narrower range of higher combined severities was required for pretreatment
to obtain high soluble xylose yields when the moisture content of the acid-impregnated feedstock was increased from 55 to
63 wt%. Simultaneous saccharification and fermentation (SSF) of washed solids from corn stover pretreated at 190°C, using
an enzyme loading of 15 filter paper units (FPU)/g of cellulose, gave ethanol yields in excess of 85%. Similar SSF ethanol
yields were found using washed solid residues from 160 and 180°C pretreatments at similar combined severities but required
a higher enzyme loading of approx 25 FPU/g of cellulose. 相似文献