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1.
Cellulase retention and sugar removal by membrane ultrafiltration during lignocellulosic biomass hydrolysis 总被引:1,自引:0,他引:1
Technologies suitable for the separation and reuse of cellulase enzymes during the enzymatic saccharification of pretreated
corn stover are investigated to examine the economic and technical viability of processes that promote cellulase reuse while
removing inhibitory reaction products such as glucose and cellobiose. The simplest and most suitable separation is a filter
with relatively large pores on the order of 20–25 mm that retains residual corn stover solids while passing reaction products
such as glucose and cellobiose to form a sugar stream for a variety of end uses. Such a simple separation is effective because
cellulase remains bound to the residual solids. Ultrafiltration using 50-kDa polyethersulfone membranes to recover cellulase
enzymes in solution was shown not to enhance further the saccharification rate or overall conversion. Instead, it appears
that the necessary cellulase enzymes, including β-glucosidase, are tightly bound to the substrate; when fresh corn stover
is contacted with highly washed residual solids, without the addition of fresh enzymes, glucose is generated at a high rate.
When filtration was applied multiple times, the concentration of inhibitory reaction products such as glucose and cellobiose
was reduced from 70 to 10 g/L. However, an enhanced saccharification performance was not observed, most likely because the
concentration of the inhibitory products remained too high. Further reduction in the product concentration was not investigated,
because it would make the reaction unnecessarily complex and result in a product stream that is much too dilute to be useful.
Finally, an economic analysis shows that reuse of cellulase can reduce glucose production costs, especially when the enzyme
price is high. The most economic performance is shown to occur when the cellulase enzyme is reused and a small amount of fresh
enzyme is added after each separation step to replace lost or deactivated enzyme. 相似文献
2.
To improve the enzymatic hydrolytic efficiency and reduce the supplementation of enzymes, the mixture designed experimental
approach was used to optimize the composition of enzyme mixture and promote the hydrolysis of ball-milled corn stover. From
the experimental results, a synergistic effect was found when combinations of the three enzymes, two kinds of cellulases and
a kind of xylanase, were used. The optimal hydrolysis of pretreated corn stover accorded with enzymes activity ration of FPU/CMCase/β-glucosidase/xylanase = 4.4:1:75:829,
and the hydrolysis efficiency of corn stover increased significantly compared with using individual enzyme. The results indicated
that the mixture design experiment could be an effective tool for optimized enzyme mixture for lignocellulose hydrolysis. 相似文献
3.
Anahita Dehkhoda Eckard Kasiviswanathan Muthukumarappan William Gibbons 《Applied biochemistry and biotechnology》2012,167(2):377-393
Extrusion processing has shown potential to be used as a pretreatment method for second-generation bioethanol production. Furthermore, surfactants have been shown to reduce enzyme deactivation and increase the efficiency of hydrolysis. Therefore, a sequential pretreatment technique was developed for corn stover (CS) and prairie cordgrass (PCG) in which a single screw extruder was used for the first pretreatment according to a previously optimized condition using 70?C180?°C for feed, barrel, and die zones with 65?C155?rpm screw speed. The second pretreatment was optimized in this study at 45?C55?°C, 1?C4?h, 0.15?C0.6?g Tween 20/g glucan according to response surface methodology. Optimization of surfactant pretreatment facilitated the estimation of interaction and higher-order effects for major factors involved in surfactant treatment (temperature, time, surfactant loading). Using 8.6?FPU/g glucan cellulase, the optimum conditions found by fitting appropriate quadratic models to the data increased glucose and xylose yield by 27.5 and 33?% for CS and by 21.5 and 27?% for PCG, respectively. Tween 20 concentrations and pretreatment temperature were the most significant factors affecting sugar yield (p value <0.05). Studies of SDS concentration at and beyond critical micelle concentration (5.2?C100?mM) demonstrated a decrease in sugar yield compared to control. 相似文献
4.
Soybean hulls were subjected to thermo-mechanical extrusion pretreatment at various in-barrel moisture contents and screw
speeds. Extrusion degraded the lignocellulosic structure and enhanced enzymatic hydrolysis of soybean hulls, with up to 155%
increase in glucose yield as compared to untreated substrate. Greater glucose yields were observed at higher in-barrel moistures
(45% and 50%) and lower screw speed (280 and 350 rpm). Maximum 74% cellulose to glucose conversion resulted from using a two-enzyme
cocktail consisting of cellulase and β-glucosidase. Conversion increased to 87% when a three-enzyme cocktail having a cell
wall degrading enzyme complex was used for hydrolysis. Fermentation inhibitors, such as furfural, 5-(hydroxymethyl)-2-furaldehyde
(HMF), and acetic acid, were found in the extrusion pretreated soybean hulls and hydrolysate. However, their concentrations
were below the known thresholds for inhibition. Fermentation of hydrolysate by Saccharomyces cerevisiae led to high yields of ethanol, with concentration ranging from 13.04 to 15.44 g/L. 相似文献
5.
Pretreatment of biomass before subjecting it to enzyme saccharification is crucial with regards to facilitating access of
enzyme to biomass. Extrusion, as a continuous and cost-effective pretreatment method, combines heating with high shear and
mixing opening cell walls at the microscopic scale, thus largely increasing the specific surface area (SSA) of biomass for
enzyme adsorption. The objective of this study was to examine the effect of extrusion as a pretreatment method and the underlying
factors ruling the improvement of sugar yields. The optimum glucose, xylose, and combined sugar recoveries were 48.79%, 24.98%,
and 40.07%, respectively, at 27.5% moisture content and 80 rpm screw speed. These yields were 2.2, 6.6, and 2.6 times higher
than those for untreated corn stover. X-ray diffraction analysis showed that the crystallinity index was not a good indicator
of sugar yield. However, scanning electron microscopy showed that the cellulose network was exposed due to the destruction
of the lignin sheath. The Langmuir adsorption model was shown to be an effective tool for the estimation of the SSA of corn
stover. The SSA of pretreated samples was significantly amplified over the control, revealing that extrusion can open the
cell wall at the microscopic scale, which was especially favorable on sugar yields. 相似文献
6.
Claudia I. Ishizawa Tina Jeoh William S. Adney Michael E. Himmel David K. Johnson Mark F. Davis 《Cellulose (London, England)》2009,16(4):677-686
It has previously been shown that the improved digestibility of dilute acid pretreated corn stover is at least partially due
to the removal of xylan and the consequent increase in accessibility of the cellulose to cellobiohydrolase enzymes. We now
report on the impact that lignin removal has on the accessibility and digestibility of dilute acid pretreated corn stover.
Samples of corn stover were subjected to dilute sulfuric acid pretreatment with and without simultaneous (partial) lignin
removal. In addition, some samples were completely delignified after the pretreatment step using acidified sodium chlorite.
The accessibility and digestibility of the samples were tested using a fluorescence-labeled cellobiohydrolase (Trichoderma reesei Cel7A) purified from a commercial cellulase preparation. Partial delignification of corn stover during dilute acid pretreatment
was shown to improve cellulose digestibility by T. reesei Cel7A; however, decreasing the lignin content below 5% (g g−1) by treatment with acidified sodium chlorite resulted in a dramatic reduction in cellulose digestibility. Importantly, this
effect was found to be enhanced in samples with lower xylan contents suggesting that the near complete removal of xylan and
lignin may cause aggregation of the cellulose microfibrils resulting in decreased cellulase accessibility. 相似文献
7.
C. Karunanithy K. Muthukumarappan W. R. Gibbons 《Applied biochemistry and biotechnology》2012,167(1):81-99
Pretreatment is the first step to open up lignocellulose structure in the conversion of biomass to biofuels. Extrusion can be a viable pretreatment method due to its ability to simultaneously expose biomass to a range of disruptive conditions in a continuous flow process. Extruder screw speed, barrel temperature, and feedstock moisture content are important factors that can influence sugar recovery from biomass. Hence, the current study was undertaken to investigate the effects of these parameters on extrusion pretreatment of pine wood chips. Pine wood chip at 25, 35, and 45?% wb moisture content were pretreated at various barrel temperatures (100, 140, and 180?°C) and screw speeds (100, 150, and 200?rpm) using a screw with compression ratios of 3:1. The pretreated pine wood chips were subjected to standard enzymatic hydrolysis followed by sugar and byproducts quantification. Statistical analyses revealed the existence of significant differences in sugar recovery due to independent variables based on comparing the mean of main effects and interaction effects. Pine wood chips pretreated at a screw speed of 150?rpm and a barrel temperature of 180?°C with a moisture content of 25?% resulted in a maximum cellulose, hemicellulose, and total sugar recoveries of 65.8, 65.6, and 66.1?%, respectively, which was about 6.7, 7.9, and 6.8 fold higher than the control (unpretreated pine chips). Furthermore, potential fermentation inhibitors such as furfural, hydroxyl methyl furfural, and acetic acid were not found in any of the treatment combinations. 相似文献
8.
Either the natural biodegradation process or the industrial hydrolytic process requires synergistic interactions between various
cellulases. However, it is sometimes impeded by low hydrolytic rate of existing cellulases and the lack of accessory enzymes.
Herein, the ability of a commercial cellulase (Spezyme CP, from Genencor) to degrade steam explosion-pretreated corn stover
was significantly improved. Firstly, a fungal cellulase producer, Aspergillus fumigatus ECU0811, was isolated from hundreds of soil samples. A 96-deep-well microscale-based platform was developed here to reduce
the labor-intensive screening work and proved to be consistent with macroscale screening work. After optimization of fermentation,
3% corn cob could induce A. fumigatus ECU0811 to yield the highest cellulase production. Based on the high activities of β-glucosidase and xylanase by A. fumigatus ECU0811, 0.91 and 125 U/mg protein, respectively, an enzyme cocktail was composed with a fixed dosage of Spezyme CP (CPCel)
at 14.2 filter paper units (FPU)/g glucan and varied dosages of A. fumigatus cellulase (AFCel). Consequently, the glucan-to-glucose conversion of corn stover was increased from 25.6% in the presence
of CPCel at a dosage of 14.2 FPU/g glucan to 99.5% in the presence of the enzyme cocktail (14.2 FPU CPCel plus 1.21 FPU AFCel
per gram of glucan). On the other side, it reduced the total protein amount of CPCel by as much as tenfold, which extremely
improved the hydrolytic rate of Spezyme CP and reduced its dosage. 相似文献
9.
Enhancing the Enzymatic Hydrolysis of Corn Stover by an Integrated Wet-milling and Alkali Pretreatment 总被引:1,自引:0,他引:1
Xun He Yelian Miao Xuejian Jiang Zidong Xu Pingkai Ouyang 《Applied biochemistry and biotechnology》2010,160(8):2449-2457
An integrated wet-milling and alkali pretreatment was applied to corn stover prior to enzymatic hydrolysis. The effects of
NaOH concentration in the pretreatment on crystalline structure, chemical composition, and reducing-sugar yield of corn stover
were investigated, and the mechanism of increasing reducing-sugar yield by the pretreatment was discussed. The experimental
results showed that the crystalline structure of corn stover was disrupted, and lignin was removed, while cellulose and hemicellulose
were retained in corn stover by the pretreatment with 1% NaOH in 1 h. The reducing-sugar yield from the pretreated corn stovers
increased from 20.2% to 46.7% when the NaOH concentration increased from 0% to 1%. The 1% NaOH pretreated corn stover had
a holocellulose conversion of 55.1%. The increase in reducing-sugar yield was related to the crystalline structure disruption
and delignification of corn stover. It was clarified that the pretreatment significantly enhanced the conversion of cellulose
and hemicellulose in the corn stover to sugars. 相似文献
10.
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
11.
Liang Zhang Xiaoqing Wang Zhenhua Ruan Ying Liu Xiaorui Niu Zhengbo Yue Zhimin Li Wei Liao Yan Liu 《Applied biochemistry and biotechnology》2014,172(2):1045-1054
Three pretreated corn stover (ammonia fiber expansion, dilute acid, and dilute alkali) were used as carbon source to culture Trichoderma reesei Rut C-30 for cellulase and xylanase production. The results indicated that the cultures on ammonia fiber expansion and alkali pretreated corn stover had better enzyme production than the acid pretreated ones. The consequent enzymatic hydrolysis was performed applying fungal enzymes on pretreated corn stover samples. Tukey’s statistical comparisons exhibited that there were significant differences on enzymatic hydrolysis among different combination of fungal enzymes and pretreated corn stover. The higher sugar yields were achieved by the enzymatic hydrolysis of dilute alkali pretreated corn stover. 相似文献
12.
Chang Geun Yoo Chao Wang Chenxu Yu Tae Hyun Kim 《Applied biochemistry and biotechnology》2013,169(5):1648-1658
Photocatalyst-assisted ammonia pretreatment was explored to improve lignin removal of the lignocellulosic biomass for effective sugar conversion. Corn stover was treated with 5.0–12.5 wt.% ammonium hydroxide, two different photocatalysts (TiO2 and ZnO) in the presence of molecular oxygen in a batch reactor at 60 °C. Various solid-to-liquid ratios (1:20–1:50) were also tested. Ammonia pretreatment assisted by TiO2-catalyzed photo-degradation removed 70 % of Klason lignin under the optimum condition (12.5 % ammonium hydroxide, 60 °C, 24 h, solid/liquid?=?1:20, photocatalyst/biomass?=?1:10 with oxygen atmosphere). The enzymatic digestibilities of pretreated corn stover were 85 % for glucan and 75 % for xylan with NH3-TiO2-treated solid and 82 % for glucan and 77 % for xylan with NH3-ZnO-treated solid with 15 filter paper units/g-glucan of cellulase and 30 cellobiase units/g-glucan of β-glucosidase, a 2–13 % improvement over ammonia pretreatment alone. 相似文献
13.
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
14.
Ball Milling Pretreatment of Corn Stover for Enhancing the Efficiency of Enzymatic Hydrolysis 总被引:2,自引:0,他引:2
Zengxiang Lin He Huang Hongman Zhang Lin Zhang Lishi Yan Jingwen Chen 《Applied biochemistry and biotechnology》2010,162(7):1872-1880
Ethanol can be produced from lignocellulosic biomass with the usage of ball milling pretreatment followed by enzymatic hydrolysis
and fermentation. The sugar yields from lignocellulosic feed stocks are critical parameters for ethanol production process.
The research results from this paper indicated that the yields of glucose and xylose were improved by adding any of the following
dilute chemical reagents: H2SO4, HCl, HNO3, CH3COOH, HCOOH, H3PO4, and NaOH, KOH, Ca(OH)2, NH3·H2O in the ball milling pretreatment of corn stover. The optimal enzymatic hydrolysis efficiencies were obtained under the conditions
of ball milling in the alkali medium that was due to delignification. The data also demonstrated that ball milling pretreatment
was a robust process. From the microscope image of ball milling-pretreated corn stover, it could be observed that the particle
size of material was decreased and the fiber structure was more loosely organized. Meanwhile, the results indicate that the
treatment effect of wet milling is better than that of dry milling. The optimum parameters for the milling process were ball
speed of 350 r/min, solid/liquid ratio of 1:10, raw material particle size with 0.5 mm, and number of balls of 20 (steel ball,
Φ = 10 mm), grinding for 30 min. In comparison with water milling process, alkaline milling treatment could increase the enzymatic
hydrolysis efficiency of corn stover by 110%; and through the digestion process with the combination of xylanase and cellulase
mixture, the hydrolysis efficiency could increase by 160%. 相似文献
15.
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
16.
Extraction and characterization of native heteroxylans from delignified corn stover and aspen 总被引:1,自引:0,他引:1
Radnaa Naran Stuart Black Stephen R. Decker Parastoo Azadi 《Cellulose (London, England)》2009,16(4):661-675
Dimethylsulfoxide-solubilized polysaccharides from delignified corn stover and aspen were characterized. The biomass was delignified
by two different techniques; a standard acid chlorite and a pulp and paper QPD technique comprising chelation (Q), peroxide
(P), and acid-chlorite (D). Major polysaccharides in all fractions were diversely substituted xylan. Xylan acetylation was
intact after chlorite delignification and, as expected, xylan from QPD-delignified fraction was de-acetylated by the alkaline
peroxide step. The study of DMSO-extractable xylans from chlorite-delignified biomass revealed major differences in native
acetylation patterns between corn stover and aspen xylan. Xylan from cell walls of corn stover contains 2-O- and 3-O-mono-acetylated xylan and [MeGlcA-α-(1 → 2)][3-OAc]-xylp units. In addition, aspen xylan also contains 2,3-di-O-acetylated xylose. 1,4-β-d-xylp residues substituted with MeGlcA at O-2 position are absent in chlorite-delignified aspen xylan. Sugar composition in accord with NMR-spectroscopic data indicated
that corn stover xylan is arabinosylated while aspen xylan is not. We have shown that corn stover xylan has similar structure
with xylans from other plants of Poales order. No evidence was found to indicate the presence of 1,4-β-d-[MeGlcA-α-(1 → 2)][Ara-α-(1 → 3)]-xylp in corn stover xylan fractions. 相似文献
17.
Laura L. G. Fuentes Sarita C. Rabelo Rubens Maciel Filho Aline C. Costa 《Applied biochemistry and biotechnology》2011,163(5):612-625
The objective of this work was to determine the optimum conditions of sugarcane bagasse pretreatment with lime to increase
the enzymatic hydrolysis of the polysaccharide component and to study the delignification kinetics. The first stage was an
evaluation of the influence of temperature, reaction time, and lime concentration in the pretreatment performance measured
as glucose release after hydrolysis using a 23 central composite design and response surface methodology. The maximum glucose yield was 228.45 mg/g raw biomass, corresponding
to 409.9 mg/g raw biomass of total reducing sugars, with the pretreatment performed at 90°C, for 90 h, and with a lime loading
of 0.4 g/g dry biomass. The enzymes loading was 5.0 FPU/dry pretreated biomass of cellulase and 1.0 CBU/dry pretreated biomass
of β-glucosidase. Kinetic data of the pretreatment were evaluated at different temperatures (60°C, 70°C, 80°C, and 90°C),
and a kinetic model for bagasse delignification with lime as a function of temperature was determined. Bagasse composition
(cellulose, hemicellulose, and lignin) was measured, and the study has shown that 50% of the original material was solubilized,
lignin and hemicellulose were selectively removed, but cellulose was not affected by lime pretreatment in mild temperatures
(60–90°C). The delignification was highly dependent on temperature and duration of pretreatment. 相似文献
18.
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
19.
Microbial lipid is a promising source of oil to produce biofuel if it can be generated from lignocellulosic materials. Mortierella isabellina is a filamentous fungal species featuring high content of oil in its cell biomass. In this work, M. isabellina was studied for lipid production from corn stover. The experimental results showed that M. isabellina could grow on different kinds of carbon sources including xylose and acetate, and the lipid content reached to 35 % at C/N ratio of 20. With dilution, M. isabellina could endure inhibition effects by dilute acid pretreatment of corn stover (0.3 g/L furfural, 1.2 g/L HMF, and 1 g/L 4-hydroxybenozic acid) and the strain formed pellets in the cell cultivations. An integrated process was developed combining the dilute acid pretreatment, cellulase hydrolysis, and cell cultivation for M. isabellina to convert corn stover to oil containing fungal biomass. With 7.5 % pretreated biomass solid loading ratio, the final lipid yield from sugar in pretreated biomass was 40 % and the final lipid concentration of the culture reached to 6.46 g/L. 相似文献
20.
Pretreatment of corn stover by soaking in aqueous ammonia 总被引:1,自引:0,他引:1
Soaking in aqueous ammonia (SAA) was investigated as a pretreatment method for corn stover. In this method, the feedstock
was soaked in aqueous ammonia over an extended period (10–60 d) at room temperature. It was done without agitation at atmospheric
pressure. SAA treatment removed 55–74% of the lignin, but retained nearly 100% of the glucan and 85% of the xylan. The xylan
remaining in the corn stover after SAA treatment was hydrolyzed along with the glucan by xylanase present in the Spezyme CP
enzyme. In the simultaneous saccharification and fermentation (SSF) test of SAA-treated corn stover, using S. cerevisiae (D5A), an ethanol yield of 73% of theoretical maximum was obtained on the basis of the glucan content in the treated corn stover.
The accumulation of xylose in the SSF appears to inhibit the cellulase activity on glucan hydrolysis, which limits the yield
of ethanol. In the simultaneous saccharification and co-fermentation (SSCF) test, using recombinant E. coli (KO11), both the glucan and xylose were effectively utilized, resulting in on overall ethanol yield of 77% based on the glucan
and xylan content of the substrate. When the SSCF process is used, the fact that the xylan fraction is retained during pretreatment
is a desirable feature since the overall bioconversion can be carried out in a single step without separate recovery of xylose
from the pretreatment liquid. 相似文献