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1.
Studies have been carried out using immobilized Z.mobilis in fluidized-bed bioreactors and have emphasized operation during high productivity and conversion. The bacteria are immobilized
within small uniform beads (~1 to 1.5-mm diam) of K-carrageenan at cell loadings of 15-50 g (dry wt)/L. Conversion and productivity
were measured under a variety of conditions, including feedstocks, flow rates, temperature, pH, and column sizes (up to 2.5
m tall). Volumetric productivities of 50-120 g EtOH/h-L reactor volume have been achieved. Productivities of 60 g/h-L are
demonstrated from a 15% feed with residual glucose concentrations of less than 0.1% and 7.4% EtOH in the tallest fermentor.
Among feeds of 10, 15, and 20% dextrose, the 15% gave the highest productivity and avoided substrate inhibition. A temperature
of 30°C and pH 5 were the optimum conditions. The ethanol yield was shown to be nearly constant at 0.49 g EtOH/g glucose,
or 97% of the theoretical under a variety of conditions and transients. The biocatalyst beads have been shown to remain active
for two months. Nonsterile feed has been used for weeks without detrimental contamination. The advantages of this advanced
bioreactor system over conventional batch technology are discussed. 相似文献
2.
Sun May Y. Nghiem Nhuan P. Davison Brian H. Webb Oren F. Bienkowski Paul R. 《Applied biochemistry and biotechnology》1998,(1):429-439
The production of ethanol from starch was studied in a fluidized-bed reactor (FBR) using co-immobilizedZymomonas mobilis and glucoamylase. The FBR was a glass column of 2.54 cm in diameter and 120 cm in length. TheZ. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of κ-carrageenan. The substrate for
ethanol production was a soluble starch. Light steep water was used as the complex nutrient source. The experiments were performed
at 35κC and pH range of 4.0-5.5. The substrate concentrations ranged from 40 to 185 g/L, and the feed rates from 10 to 37
mL/min. Under relaxed sterility conditions, the FBR was successfully operated for a period of 22 d, during which no contamination
or structural failure of the biocatalyst beads was observed. Volumetric productivity as high as 38 g ethanol/(Lh), which was
74% of the maximum expected value, was obtained. Typical ethanol volumetric productivity was in the range of 15-20 g/(Lh).
The average yield was 0.49 g ethanol/g substrate consumed, which was 90% of the theoretical yield. Very low levels of glucose
were observed in the reactor, indicating that starch hydrolysis was the rate-limiting step. 相似文献
3.
4.
Escobar Jose M. Rane Kishore D. Cheryan Munir 《Applied biochemistry and biotechnology》2001,91(1-9):283-296
Pilot plant trials were conducted in a corn wet mill with a 7000-L membrane recycle bioreactor (MRB) that integrated ceramic
microfiltration membranes in a semi-closed loop configuration with a stirred-tank reactor. Residence times of 7.5–10 h with
ethanol outputs of 10–11.5% (v/v) were obtained when the cell concentration was 60–100 g/L drywt of yeast, equivalent to about
109−1010 cells/mL. The performance of the membrane was dependent on the startup mode and pressure management techniques. A steady
flux of 70 L/(m2·h) could be maintained for several days before cleaning was necessary. The benefits of the MRB include better productivity;
a clear productstream containing no particulates or yeast cells, which should improve subsequent stripping and distillation
operations; and substantially reduced stillage handling. The capital cost of the MRB is $21–$34/(m3·yr) ($0.08–$0.13/[gal·yr]) of ethanol capacity. Operating cost, including depreciation, energy, membrane replacement, maintenance,
labor, and cleaning, is $4.5–9/m3 ($0.017–$0.034/gal) of ethanol. 相似文献
5.
R. D. Waldron J. L. Vega E. C. Clausen J. L. Gaddy 《Applied biochemistry and biotechnology》1988,18(1):127-142
The bacteriumZymomonas mobilis may be utilized to produce ethanol from glucose in a cross-linked immobilized cell reactor. Reactor startup is much more
rapid with cross-linkedZymomonas than with the yeastSaccharomyces cerevisiae. Volumetric ethanol productivities (based on liquid holdup) three times those obtained with cross-linked yeast, and comparable
to those obtained withZymomonas immobilized by other methods, are possible. 相似文献
6.
Axial dispersion and phase holdup measurements were made using electroconductivity in a fermenting fluidized-bed bioreactor
(FBR) and in a model nonfermenting three-phase FBR. Multiple axial conductivity probes were used to nonintrusively monitor
the bed conductivity. The gas phase holdup was estimated from a ratio of the average bed conductivity and bulk conductivity.
The solid fraction in the three-phase FBR can be estimated from the two-phase liquid-solid FBR. The response to a salt pulse
was used to estimate the liquid axial dispersion coefficient. Particle Peclet numbers on the order of 10-2 were estimated as a function of flowrates and compared to literature correlations. 相似文献
7.
Capillary gas chromatography was used to study noncovalent sorption ofn-butyl,n-hexyl, andn-octyl acetates from aqueous solutions by corn starch cryotextures. In the concentration range of 0.5–15.0 mmol L−1, about 38%n-butyl acetate, 70%n-hexyl acetate, and 98%n-octyl acetate are extracted from aqueous solutions. The sorption of the alkyl acetates depends on the alkyl chain length,
indicating the hydrophobic character of their interaction with the corn starch cryotexture. No competitive sorption between
acetates in the mixture was observed. Binding of alkyl acetates occurs during the cryosponge formation, due probably to the
templation at the stage of starch sol, fixation in the cryosponge, and sorption on the surface of its walls.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1943–1945, October, 1998. 相似文献
8.
The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free
(CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose
plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the
products varied hyperbolically with time according to the equations (GA)=t(GA)max/(WGA +t), (SOR)=t (SOR)max/(WSor+t), vGA=[WGA (GA)max]/(WGA+t)2 and VSOR=[WSOR (SOR)max]/(WSOR+t)2. Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)max= 541 g/L, (SOR)max=552 g/L, WGA=4.8h, WSOR=4.9h, υGA=112.7 g/L· and υSOR=112.7 g/L·. 相似文献
9.
The operational characterization of a fluidized-bed bioreactor for ethanol fermentation using Ca-alginate immobilized yeast
cells is described. An additional air stream is supplied to the fermenter to ensure and maintain satisfactory fluidization
behavior of beads and to avoid slug formation. The influence of physical properties such as bead density and liquid density
on the fluidization quality and stability are discussed. 相似文献
10.
The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have
shown that the strain ZM4(pZB5) was capable of converting a mixture o 65 g/L of glucose and 65 g/L of xylose to 62 g/L of
ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose
utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition
studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose
under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane
bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of
50 g/L, an ethanol productivity of approx 5 g/(L·h), and a yield (Y
p/s) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state
(40–60 h); a slow bleed of concentrated cells may be required to overcome this problem. 相似文献
11.
Giordano Raquel L. C. Hirano Paulo C. Gonçalves Luciana R. B. Netto Willibaldo Schmidell 《Applied biochemistry and biotechnology》2000,84(1-9):643-654
This article presents a detailed study on the conditions for achieving a stable biocatalyst to be used in the production of
ethanol from starch. Different pellets were used depending on which characteristic of the biocatalyst was being studied: (a)
Saccharomyces cerevisiae entrapped in pectin or calcium alginate gel particles; (b) silica containing immobilized glucoamylase entrapped in pectin
gel particles; or (c) pectin gel particles, with the silicaenzyme derivative and yeast coimmobilized. The influence of several
variables on the mechanical resistance of the particle, on the viability of the microorganism, and on the rate of substrate
hydrolysis was studied with biocatalyst. The best conditions found were 6% pectin gel, 2-mm particle diameter, and curein
0.2 M CaCl2·2H2O/60 mM acetate buffer, pH 4.2, for gel preparation; and 6.0 g/L of CaCl2·2H2O in the fermentation medium. Biocatalyst (c) was successfully tested for the production of ethanol from liquefield manioc
flour syrup. 相似文献
12.
Eva Joachimsthal Kevin D. Haggett Peter L. Rogers 《Applied biochemistry and biotechnology》1999,77(1-3):147-157
The fermentation characteristics of two recombinant strains of Zymomonas mobilis, viz. CP4 (pZB5) and ZM4 (pZB5), capable of converting both glucose and xylose to ethanol, have been characterized in batch
and continuous culture studies. The strain ZM4 (pZB5) was found to be capable of converting a mixture of 65 g/L glucose and
65 g/L xylose to 62 g/L ethanol in 48h with a yield of 0.46 g/g. Higher sugar concentrations resulted in incompletexylose
utilization (80h) presumably owing to ethanol inhibition of xylose assimilation or metabolism. The fermentation results with
ZM4 (pZB5) show a significant improvement over results published previously for recombinant yeasts and other bacteria capable
of glucose and xylose utilization. 相似文献
13.
Continuous Production of Ethanol from Starch Using Glucoamylase and Yeast Co-Immobilized in Pectin Gel 总被引:1,自引:0,他引:1
This work presents a continuous simultaneous saccharification and fermentation (SSF) process to produce ethanol from starch
using glucoamylase and Saccharomyces cerevisiae co-immobilized in pectin gel. The enzyme was immobilized on macroporous silica, after silanization and activation of the
support with glutaraldehyde. The silica–enzyme derivative was co-immobilized with yeast in pectin gel. This biocatalyst was
used to produce ethanol from liquefied manioc root flour syrup, in three fixed bed reactors. The initial reactor yeast load
was 0.05 g wet yeast/ml of reactor (0.1 g wet yeast/g gel), used in all SSF experiments. The enzyme concentration in the reactor
was defined by running SSF batch assays, using different amount of silica–enzyme derivative, co-immobilized with yeast in
pectin gel. The chosen reactor enzyme concentration, 3.77 U/ml, allowed fermentation to be the rate-limiting step in the batch
experiment. In this condition, using initial substrate concentration of 166.0 g/l of total reducing sugars (TRS), 1 ml gel/1 ml
of medium, ethanol productivity of 8.3 g/l/h was achieved, for total conversion of starch to ethanol and 91% of the theoretical
yield. In the continuous runs, feeding 163.0 g/l of TRS and using the same enzyme and yeast concentrations used in the batch
run, ethanol productivity was 5.9 g ethanol/l/h, with 97% of substrate conversion and 81% of the ethanol theoretical yield.
Diffusion effects in the extra-biocatalyst film seemed to be reduced when operating at superficial velocities above 3.7 × 10−4 cm/s. 相似文献
14.
Golovnya R. V. Yuryev V. P. Kalistratova E. N. Wasserman L. A. Terenina M. B. Krikunova N. I. Misharina T. A. 《Russian Chemical Bulletin》2001,50(2):300-303
Supramolecular complexes of organic odorants (n-octanol and n-octyl acetate) with polysaccharides of corn starch, its cryotextures, and waxy corn starch cryotextures were studied by differential scanning microcalorimetry. It was shown that complexes are formed with amylose-containing starch and no complexes are formed with amylopectin starch. The melting enthalpies of the complexes were determined. It was shown that complexes of the odorants with native corn starch and its cryotextures have different thermodynamic characteristics. 相似文献
15.
Anderson W. Silva da Henriques Aline C. da Costa Tito L. M. Alves Enrique L. Lima 《Applied biochemistry and biotechnology》1999,77(1-3):277-291
A hybrid neural model was developed for the alcoholic fermentation by Zymomonas mobilis. This model is composed by the mass-balance equations of the process and neural networks, which describe the kinetic rates.
Strategies that combines scarce experimental data with approximate models of the process were used to generate new data for
the training of the networks, minimizing the number of experiments required. The proposed hybrid neural methodology uses all
the information avail able about the process to deal with the difficulties in the development of the model. 相似文献
16.
R. V. Golovnya M. V. Grishin A. G. Filatova B. R. Shub 《Russian Chemical Bulletin》2000,49(8):1471-1472
The microstructure of a corn starch sol was studied by scanning tunneling microscopy. The influence ofn-octyl acetate on the microstructure was found. The original starch sol contains compact anisodiametric particles 500–800
nm in size. The addition ofn-octyl acetate produces friable oval associates consisting of fine spherical particles 50–20 nm in size.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1478–1480, August, 2000. 相似文献
17.
Immobilization of Zymomonas mobilis by different methods was investigated. Experiments were performed order to choose the most appropriate support for the immobilization
of the cells. The most advantageous option was to use permeabilized cells in the bore of microporous hollow fibers. Whereas
the reaction rate was about 33 g of gluconate/ (g of protein·h) using hollow fibers, which is comparable to that observed
by using free cells, the calcium alginate immobilized cells presented a reaction rate of 4 g of gluconate/ (g of protein·h).
These results can be explained by the mass transfer resistance effect, which, indeed, was much lower in the case of hollow-fiber
membranes than in the alginate gel beads. A loss of enzymatic activity during the reaction was observed in all experiments,
which was attributed to the lactone produced as an intermediate of the reaction. 相似文献
18.
Tardioli Paulo W. Zanin Gisella M. de Moraes Flávio F. 《Applied biochemistry and biotechnology》2000,84(1-9):1003-1019
Cyclodextrin-glycosyl-transferase (EC2.4.1.19), produced by Wacker (Munich, Germany), was purified by biospecific affinity
chromatography with β-cyclodextrin (β-CD) as ligand, and immobilized into controlled pore silica particles (0.42 mm). This
immobilized enzyme (IE) had 4.7 mg of protein/g of support and a specific activity of 8.6 μmol of β-CD/(min·gIF) at 50°C, pH 8.0. It was used in a fluidized-bed reactor (FBR) at the same conditions for producing cyclodextrins (CDs) with
10% (w/v) maltodextrin solution as substrate. Bed expansion was modeled by the Richardson and Zaki equation, giving a good
fit in two distin ctranges of bed porosities. The minimum fluidization velocity was 0.045 cm/s, the bed expansion coefficient
was 3.98, and the particle terminal velocity was 2.4 cm/s. The FBR achieved high productivity, reaching in only 4 min of residence
time the same amount of CDs normally achieved in a batch reactor with free enzyme after 24h of reaction, namely, 10.4 mM β-CD
and 2.3 mM γ-CD. 相似文献
19.
A. G. Filatova I. O. Volkov N. I. Krikunova T. A. Misharina R. V. Golovnya 《Russian Chemical Bulletin》2000,49(2):314-316
The surface composition and surface microtopography of corn starch cryogels obtained from a 3% starch sol containing organic
flavoring agents were studied by X-ray photoelectron spectroscopy and scanning electron microscopy. The cryogels withn-octanol,n-octyl methyl ketone, andn-octyl acetate have a well-developed microtopography and their surface layer (5–20 nm) is enriched in sorbed compounds.n-Octyl acetate, unliken-butyl acetate, influences the composition and microstructure of the cryogel surface. The sorbedn-octyl acetate occupies 20–25% of the surface, which has a well-developed topography and a porous structure. Drying and evacuation
do not change the concentration of the organic sorbates having a C8 alkyl group in the surface layer.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 312–314, February 2000. 相似文献
20.
Beker M. J. Shvinka J. E. Pankova L. M. Laivenieks M. G. Mezhbarde I. N. 《Applied biochemistry and biotechnology》1990,(1):265-274
Two biotechnological systems were developed for sucrose conversion into levan and ethanol withZymomonas mobilis, ensuring a 66.7% transfer of substrate carbon in a batch and 61% carbon transfer in a continuous culture. The effect of
glucose, ethanol, and medium pH on sucrose conversion byZ. mobilis was studied. The addition of ethanol to the fermentation medium, in the final conc. of 100 g/L, uncoupled levan synthesis
from ethanol fermentation. For a continuous culture, the most efficient conversion of substrate carbon into levan was reached
at pH 4.8, giving 64.2 g/L levan, with the levan yield of 0.22 g/g and the productivity of 3.2 g/L/h. 相似文献