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1.
Diffusivities of sulfuric acid in Aspen wood were experimentally determined at various diffusional temperatures and fitted to Arrhenius equations. These equations were subsequently incorporated into a theoretical model to establish the effect of transient acid concentration gradients within a solid substrate during acid-catalyzed hydrolysis of hemicellulose. Total xylose yield was found to decrease for increasing chip size, and this effect was intensified by increasing reaction temperature. Quantitative criteria were established for assessment of transient acid concentration effects upon xylose yield and reaction time at various reaction conditions.
相似文献2.
Xylan is the major component of hemicellulose, which consists of up to one-third of the lignocellulosic biomass. When the
zinc chloride solution was used as a pretreatment agent to facilitate cellulose hydrolysis, hemicellulose was hydrolyzed during
the pretreatment stage. In this study, xylan was used as a model to study the hydrolysis of hemicellulose in zinc chloride
solution. The degradation of xylose that is released from xylan was reduced by the formation of zinc-xylose complex. The xylose
yield was >90% (w/w) at 70°C. The yield and rate of hydrolysis were a function of temperature and the concentration of zinc
chloride. The ratio of zinc chloride can be decreased from 9 to 1.3 (w/w). At this ratio, 76% of xylose yield was obtained.
When wheat straw was pretreated with a concentrated zinc chloride solution, the hemicellulose hydrolysate contained only xylose
and trace amounts of arabinose and oligosaccharides. With this approach, the hemicellulose hydrolysate can be separated from
cellulose residue, which would be hydrolyzed subsequently to glucose by acid or enzymes to produce glucose. This production
scheme provided a method to produce glucose and xylose in different streams, which can be fermented in separated fermenters. 相似文献
3.
Neureiter Markus Danner Herbert Thomasser Christiane Saidi Bamusi Braun Rudolf 《Applied biochemistry and biotechnology》2002,98(1-9):49-58
Sugarcane bagasse, a byproduct of the cane sugar industry, is an abundant source of hemicellulose that could be hydrolyzed
to yield a fermentation feedstock for the production of fuel ethanol and chemicals. The effects of sulfuric acid concentration,
temperature, time, and dry matter concentration on hemicellulose hydrolysis were studied with a 20-L batch hydrolysis reactor
using a statistical experimental design. Even at less severe conditions considerable amounts (>29%) of the hemicellulose fraction
could be extracted. The percentage of soluble oligosaccharides becomes very low in experiments with high yields in monosaccharides,
which indicates that the cellulose fraction is only slightly affected. For the sugar yields, acid concentration appears to
be the most important parameter, while for the formation of sugar degradation products, temperature shows the highest impact.
It could be demonstrated that the dry matter concentration in the reaction slurry has a negative effect on the xylose yield
that can be compensated by higher concentrations of sulfuric acid owing to a positive interaction between acid concentration
and dry matter contents. 相似文献
4.
A thermochemical pretreatment of bagasse for the enzymatic hydrolysis has been carried out, in which pretreatment bagasse
was autoclaved with binary solvent, composed of Water and organic solvent having upper critical temperature (UCT) on the mutual
solubility curve. The pretreatment was named “UCT-solvent pretreatment.” The hydrophobic decomposition products from lignin
and hemicellulose, that dissolved in organic phase at room temperature, could be easily separated from the solid and sugars
in the aqueous phase. By using UCT-solvent instead of only water, the sugar recoveries from bagasse through the pretreatment
and the enzymatic hydrolysis were much improved. There exists an optimal mixing ratio between organic solvent and water to
maximize the effect of the pretreatment for enzymatic hydrolysis. The optimal ratio can be explained by the competitive effect
between the ability of water as a reagent for the hydrolysis and the ability of solvent for the extraction of the decomposition
product, and furthermore by the competitive effect between affinities of the solvent to hydrophilic hemicellulose and hydrophobic
lignin. Decomposition of hemicellulose at lower temperature than 190°C was decreased, and hence the degradation of xylose
during the pretreatment decreased. These favorable effects of UCT-solvent pretreatment are significantly attributed to the
formation of the homogeneous single phase of organic solvent and water at high temperature and the phase separation at room
temperature. 相似文献
5.
Wei Liao Zhiyou Wen Sharon Hurley Yan Liu Chuanbin Liu Shulin Chen 《Applied biochemistry and biotechnology》2005,124(1-3):1017-1030
This study focused on the effect of hemicellulose and lignin on enzymatic hydrolysis of dairy manure and hydrolysis process
optimization to improve sugar yield. It was found that hemicellulose and lignin in dairy manure, similar to their role in
other lignocellulosic material, were major resistive factors to enzymatic hydrolysis and that the removal of either of them,
or for best performance, both of them, improved the enzymatic hydrolysis of manure cellulose. This result combined with scanning
electron microscope (SEM) pictures further proved that the accessibility of cellulose to cellulase was the most important
feature to the hydrolysis. Quantitatively, fed-batch enzymatic hydrolysis of fiber without lignin and hemicellulose had a
high glucose yield of 52% with respect to the glucose concentration of 17 g/L at a total enzyme loading of 1300 FPU/L and
reaction time of 160 h, which was better than corresponding batch enzymatic hydrolysis. 相似文献
6.
Efficient utilization of the pentosan fraction of hemicellulose from lignocellulosic feedstocks offers an opportunity to increase
the yield and to reduce the cost of producing fuel ethanol. During prehydrolysis (acid hydrolysis or autohydrolysis of hemicellulose),
acetic acid is formed as a consequence of the deacetylation of the acetylated moiety of hemicellulose. Recombinant Escherichia
coli B (ATCC 11303), carrying the plasmid pLO1297 with pyruvate decarboxylase and alcohol dehydrogenase II genes from Zymomonas
mobilis (CP4), converts xylose to ethanol with a product yield that approaches theoretical maximum. Although other pentose-utilizing
microorganisms are inhibited by acetic acid, the recombinant E. coli displays a high tolerance for acetic acid. In xylose
fermentations with a synthetic medium (Luria broth), where the pH was controlled at 7, neither yield nor productivity was
affected by the addition of 10.7 g/L acetic acid. Nutrient-supplemented, hardwood (aspen) hemicellulose hydrolysate (40.7
g/L xylose) was completely fermented to ethanol (16.3 g/L) in 98 h. When the acetic acid concentration was reduced from 5.6
to 0.8 g/L, the fermentation time decreased to 58 h. Overliming, with Ca(OH)2 to pH 10, followed by neutralization to pH 7 with sulfuric acid and removal of insolubles, resulted in a twofold increase
in volumetric productivity. The maximum productivity was 0.93 g/L/h. The xylose-to-ethanol conversion efficiency and productivity
in Ca(OH)2-treated hardwood prehydrolysate, fortified with only mineral salts, were 94% and 0.26 g/L/h, respectively. The recombinant
E. coli exhibits a xylose-to-ethanol conversion efficiency that is superior to that of other pentose-utilizing yeasts currently
being investigated for the production of fuel ethanol from lignocellulosic materials. 相似文献
7.
Converse A. O. Kwarteng I. K. Grethlein H. E. Ooshima H. 《Applied biochemistry and biotechnology》1989,(1):63-78
The results of an experimental study of the acid hydrolysis of hardwood are presented in the form of values for the three
parameters, activation energy, power on the acid concentration, and pre-exponen-tial factor, of the first order kinetic constants
for each of the following reaction participants: xylan remaining, glucan remaining, xylose formed, and xylose decomposed.
These are used as a base for a quantitative theory to predict the temperature, time, and acid concentrations needed for effective
pretreatment of the substrate for subsequent enzymatic hydrolysis of the glucan. This theory is based on the assumption that
successful pretreatment requires >90% removal of the xylan, <10% removal of the glucan, and >80% xylose yield. This theory
is compared with selected published data. 相似文献
8.
Palonen H Thomsen AB Tenkanen M Schmidt AS Viikari L 《Applied biochemistry and biotechnology》2004,117(1):1-17
The wet oxidation pretreatment (water, oxygen, elevated temperature, and pressure) of softwood (Picea abies) was investigated for enhancing enzymatic hydrolysis. The pretreatment was preliminarily optimized. Six different combinations
of reaction time, temperature, and pH were applied, and the compositions of solid and liquid fractions were analyzed. The
solid fraction after wet oxidation contained 58–64% cellulose, 2–16% hemicellulose, and 24–30% lignin. The pretreatment series
gave information about the roles of lignin and hemicellulose in the enzymatic hydrolysis. The temperature of the pretreatment,
the residual hemicellulose content of the substrate, and the type of the commercial cellulase preparation used were the most
important factors affecting the enzymatic hydrolysis. The highest sugar yield in a 72-h hydrolysis, 79% of theoretical, was
obtained using a pretreatment of 200°C for 10 min at neutral pH. 相似文献
9.
Ozlem Akpinar Okan Levent Şeyda Bostanci Ufuk Bakir Levent Yilmaz 《Applied biochemistry and biotechnology》2011,163(2):313-325
Cotton stalk, a lignocellulosic waste material, is composed of xylose that can be used as a raw material for production of
xylitol, a high-value product. There is a growing interest in the use of lignocellulosic wastes for conversion into various
chemicals because of their low cost and the fact that they are renewable and abundant. The objective of the study was to determine
the effects of H2SO4 concentration, temperature, and reaction time on the production of sugars (xylose, glucose, and arabinose) and on the reaction
by-products (furfural and acetic acid). Response surface methodology was used to optimize the hydrolysis process in order
to obtain high xylose yield and selectivity. The optimum reaction temperature, reaction time, and acid concentration were
140 °C, 15 min, and 6%, respectively. Under these conditions, xylose yield and selectivity were found to be 47.88% and 2.26 g
g−1, respectively. 相似文献
10.
Xylitol is a five-carbon sugar alcohol with established commercial use as an alternative sweetener and can be produced from
hemicellulose hydrolysate. However, there are difficulties with microbiological growth and xylitol biosynthesis on hydrolysate
because of the inhibitors formed from hydrolysis of hemicellulose. This research focused on the effect of furfural, vanillin,
and syringaldehyde on growth of Candida guilliermondii and xylitol accumulation from xylose in a semi-synthetic medium in microwell plate and bioreactor cultivations. All three
compounds reduced specific growth rate, increased lag time, and reduced xylitol production rate. In general, increasing concentration
of inhibitor increased the severity of inhibition, except in the case of 0.5 g vanillin per liter, which resulted in a faster
late batch phase growth rate and increased biomass yield. At concentrations of 1 g/l or higher, furfural was the least inhibitory
to growth, followed by syringaldehyde. Vanillin most severely reduced specific growth rate. All three inhibitors reduced xylitol
production rate approximately to the same degree. 相似文献
11.
Ferrer Alexis Byers Floyd M. Sulbarán-de-Ferrer Betzabé Dale Bruce E. Aiello Cateryna 《Applied biochemistry and biotechnology》2000,84(1-9):163-179
An ammonia pressurization/depressurization process was investigated to evaluate the potential of producing reducing sugars
from dwarf elephant grass, a warm-season forage. Moisture, temperature, and ammonia loading affected sugar yield (p<0.0001). At optimal conditions, ammonia processing solubilized 50.9% of the hemicellulose and raised the sugar yield (percentage
of theoretical) from 18 to 83%. Glucose and xylose production were increased 3.2-and 8.2-fold, respectively. The mild processing
conditions of the ammonia treatment (90–100°C, 5 min), the low enzyme loading (2 international filter paper units/g), and
the short hydrolysis time (24 h), greatly enhance the potential of using for ages to produce sugars valuable for several applications. 相似文献
12.
Mingjia Zhang Rongxin Su Wei Qi Zhimin He 《Applied biochemistry and biotechnology》2010,160(5):1407-1414
To enhance the conversion of the cellulose and hemicellulose, the corncob pretreated by aqueous ammonia soaking was hydrolyzed
by enzyme complexes. The saturation limit for cellulase (Spezyme CP) was determined as 15 mg protein/g glucan (50 filter paper
unit (FPU)/g glucan). The accessory enzymes (β-glucosidase, xylanase, and pectinase) were supplemented to hydrolyze cellobiose
(cellulase-inhibiting product), hemicellulose, and pectin (the component covering the fiber surfaces), respectively. It was
found that β-glucosidase (Novozyme 188) loading of 1.45 mg protein/g glucan [30 cellobiase units (CBU)/g glucan] was enough
to eliminate the cellobiose inhibitor, and 2.9 mg protein/g glucan (60 CBU/g glucan) was the saturation limit. The supplementation
of xylanase and pectinase can increase the conversion of cellulose and hemicellulose significantly. The yields of glucose
and xylose enhanced with the increasing enzyme loading, but the increasing trend became low at high loading. Compared with
xylanase, pectinase was more effective to promote the hydrolysis of cellulose and hemicellulose. The supplementation of pectinase
with 0.12 mg protein/g glucan could increase the yields of glucose and xylose by 7.5% and 29.3%, respectively. 相似文献
13.
Michel Brienzo Walter Carvalho Adriane M. F. Milagres 《Applied biochemistry and biotechnology》2010,162(4):1195-1205
Sugarcane bagasse hemicellulose was isolated in a one-step chemical extraction using hydrogen peroxide in alkaline media. The polysaccharide containing 80.9% xylose and small amounts of l-arabinose, 4-O-methyl-d-glucuronic acid and glucose, was hydrolyzed by crude enzymatic extracts from Thermoascus aurantiacus at 50?°C. Conditions of enzymatic hydrolysis leading to the best yields of xylose and xylooligosaccharides (DP 2-5) were investigated using substrate concentration in the range 0.5–3.5% (w/v), enzyme load 40–80 U/g of the substrate, and reaction time from 3 to 96 h, applying a 22 factorial design. The maximum conversion to xylooligosaccharides (37.1%) was obtained with 2.6% of substrate and xylanase load of 60 U/g. The predicted maximum yield of xylobiose by a polynomial model was 41.6%. Crude enzymatic extract of T. aurantiacus generate from sugarcane bagasse hemicellulose 39% of xylose, 59% of xylobiose, and 2% of other xylooligosaccharides. 相似文献
14.
Tae-Su Jeong Byung-Hwan Um Jun-Seok Kim Kyeong-Keun Oh 《Applied biochemistry and biotechnology》2010,161(1-8):22-33
Biological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars prior to fermentation. Hydrolysis can be performed enzymatically or with mineral acids. In this study, dilute sulfuric acid was used as a catalyst for the pretreatment of rapeseed straw. The purpose of this study is to optimize the pretreatment process in a 15-mL bomb tube reactor and investigate the effects of the acid concentration, temperature, and reaction time. These parameters influence hemicellulose removal and production of sugars (xylose, glucose, and arabinose) in the hydrolyzate as well as the formation of by-products (furfural, 5-hydroxymethylfurfural, and acetic acid). Statistical analysis was based on a model composition corresponding to a 33 orthogonal factorial design and employed the response surface methodology to optimize the pretreatment conditions, aiming to attain maximum xylan, mannan, and galactan (XMG) extraction from hemicellulose of rapeseed straw. The obtained optimum conditions were: H2SO4 concentration of 1.76% and temperature of 152.6 °C with a reaction time of 21 min. Under these optimal conditions, 85.5% of the total sugar was recovered after acid hydrolysis (78.9% XMG and 6.6% glucan). The hydrolyzate contained 1.60 g/L glucose, 0.61 g/L arabinose, 10.49 g/L xylose, mannose, and galactose, 0.39 g/L cellobiose, 0.94 g/L fructose, 0.02 g/L 1,6-anhydro-glucose, 1.17 g/L formic acid, 2.94 g/L acetic acid, 0.04 g/L levulinic acid, 0.04 g/L 5-hydroxymethylfurfural, and 0.98 g/L furfural. 相似文献
15.
Nghiem NP Montanti J Johnston DB Drapcho C 《Applied biochemistry and biotechnology》2011,164(8):1390-1404
A process was developed to fractionate and isolate the hemicellulose B component of corn fiber generated by corn wet milling.
The process consisted of pretreatment by soaking in aqueous ammonia followed by enzymatic cellulose hydrolysis, during which
the hemicellulose B was solubilized by cleavage into xylo-oligosaccharides and subsequently recovered by precipitation with
ethanol. The pretreatment step resulted in high retention of major sugars and improvement of subsequent enzymatic hydrolysis.
The recovered hemicellulose B was hydrolyzed by a cocktail of enzymes that consisted of β-glucosidase, pectinase, xylanase,
and ferulic acid esterase (FAE). Xylanase alone was ineffective, demonstrating yields of less than 2% of xylose and arabinose.
The greatest xylose and arabinose yields, 44% and 53%, respectively, were obtained by the combination of pectinase and FAE.
A mass balance accounted for 87% of the initially present glucan, 91% of the xylan, and 90% of the arabinan. The developed
process offered a means for production of corn fiber gum as a value-added co-product and C5 sugars, which could be converted
to other valuable co-products through fermentation in a corn wet-milling biorefinery. 相似文献
16.
A combined heat transfer/kinetic model was developed to quantify temperature variations in small tubular batch reactors and
estimate the effect of deviations from isothermal operation on the kinetics of biomass pretreatment. Assuming that heat transfer
was dominated by conduction in the radial direction, a classic parabolic time-dependent partial differential equation was
applied to describe the temperature in the system and dedimensionalized to provide a single solution for application to all
situations. A dimensionless expression for the reaction kinetics for xylan hydrolysis was then developed, and a single parameter
expressed as the dimensionless ratio of the first-order rate constant times the tube radius squared divided by the thermal
diffusivity was found to control the reaction rate. Three different characterizations of the deviation between the concentration
profile predicted for isothermal xylan hydrolysis and that based on the transient temperature were directly related to this
dimensionless rate constant parameter for both catalyzed and uncatalyzed hydrolysis kinetics. These results were then used
to project the relationship between deviations in yield from isothermal results and the tube radius and reaction time. 相似文献
17.
I. S. M. Rafiqul A. M. M. Sakinah M. R. Karim 《Applied biochemistry and biotechnology》2014,174(2):542-555
Xylitol production by bioconversion of xylose can be economically interesting if the raw material can be recovered from a cheap lignocellulosic biomass (LCB). Meranti wood sawdust (MWS) is a renewable and low-cost LCB that can be used as a promising and economic source of xylose, a starting raw material for the manufacture of several specialty chemicals, especially xylitol. This study aimed to optimize the hydrolysis process of MWS and to determine the influence of temperature, H2SO4 concentration, and residence time on xylose release and on by-product formation (glucose, arabinose, acetic acid, furfural, hydroxymethylfurfural (HMF), and lignin degradation products (LDPs)). Batch hydrolysis was conducted under various operating conditions, and response surface methodology was adopted to achieve the highest xylose yield. Xylose production was highly affected by temperature, acid concentration, and residence time. The optimum temperature, acid concentration, and time were determined to be 124 °C, 3.26 %, and 80 min, respectively. Under these optimum conditions, xylose yield and selectivity were attained at 90.6 % and 4.05 g/g, respectively. 相似文献
18.
Biotechnological Production of Xylitol: Enhancement of Monosaccharide Production by Post-Hydrolysis of Dilute Acid Sugarcane Hydrolysate 总被引:1,自引:0,他引:1
Boutros Fouad Sarrouh Ricardo de Freitas Branco Silvio Silvério da Silva 《Applied biochemistry and biotechnology》2009,153(1-3):163-170
Dilute-acid hydrolysis pretreatment of sugarcane bagasse resulted in release of 48% (18.4 g/L) of the xylan in the hemicellulose fraction into the hydrolysate as monomeric xylose. In order to enhance the recuperation of this monomer, a post-hydrolysis stage consisted of thermal treatment was carried out. This treatment resulted in an increase in xylose release of 62% (23.5 g/L) of the hemicellulose fraction. Original and post-hydrolysates were concentrated to the same levels of monomeric xylose in the fermentor feed. During the fermentation process, cellular growth was observed to be higher in the post-hydrolysate (3.5 g/L, Y x/s?=?0.075 g cells/g xylose) than in the original hydrolysate (2.9 g/L, Y x/s?=?0.068 g cells/g xylose). The post-treated hydrolysate required less concentration of sugars resulting in a lower concentration of fermentation inhibitors, which were formed primarily in the dilute acid hydrolysis step. Post-hydrolysis step led to a high xylose–xylitol conversion efficiency of 76% (0.7 g xylitol/g xylose) and volumetric productivity of 0.68 g xylitol/L h when compared to 71% (0.65 g xylitol/g xylose and productivity of 0.61 g xylitol/L h) for the original hemicellulosic hydrolysate. 相似文献
19.
Hanchar RJ Teymouri F Nielson CD McCalla D Stowers MD 《Applied biochemistry and biotechnology》2007,137(1-12):313-325
A process was developed to fractionate corn fiber into glucose- and pentose-rich fractions. Corn fiber was ammonia fiber explosion treated at 90 degrees C, using 1 g anhydrous ammonia pergram of drybiomass, 60% moisture, and 30-min residence time. Twenty four hour hydrolysis of ammonia fiber explosion-treated corn fiber with cellulase converted 83% of available glucanto-glucose. In this hydrolysis the hemicellulose was partially broken down with 81% of the xylan and 68% of the arabinan being contained in the hydrolysate after filtration to remove lignin and other insoluble material. Addition of ethanol was used to precipitate and recover the solubilized hemicellulose from the hydrolysate, followed by hydrolysis with 2% (v/v) sulfuric acid to convert the recovered xylan and arabinan to monomeric sugars. Using this method, 57% of xylose and 54% of arabinose available in corn fiber were recovered in a pentose-rich stream. The carbohydrate composition of the pentose-enriched stream was 5% glucose, 57% xylose, 27% arabinose, and 11% galactose. The carbohydrate composition of the glucose-enriched stream was 87% glucose, 5% xylose, 6% arabinose, and 1% galactose, and contained 83% of glucose available from the corn fiber. 相似文献
20.
Akio Kumagai Shinichiro Iwamoto Seung-Hwan Lee Takashi Endo 《Cellulose (London, England)》2014,21(4):2433-2444
Quartz crystal microbalance with dissipation (QCM-D) monitoring was performed to investigate the impact of steam treatment (ST) on the enzymatic hydrolysis of lignocellulosic nanofibrils (LCNFs). ST at mild temperatures up to 140 °C mainly affected the hemicellulose content of LCNFs. The hemicellulose constituents in the water-soluble fraction and the residual LCNF were quantified. The impact of changes in hemicellulose by ST on enzymatic hydrolysis was monitored by QCM-D using Acremonium cellulase as a source of multicomponent enzymes including hemicellulases. LCNFs without ST showed distinctive initial changes in frequency and energy dissipation, which differed from those of pure cellulose film, whereas these changes shifted toward typical changes of enzymatic hydrolysis of pure cellulosic films with increasing ST temperature. The QCM-D results suggested that hemicellulose located around cellulose microfibrils is rapidly decomposed, thus exposing the cellulose surface shortly after initial enzymatic hydrolysis, and then the main enzymatic hydrolysis of cellulose occurs. 相似文献