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1.
Hesham El-Enshasy Karsten Hellmuth Ursula Rinas 《Applied biochemistry and biotechnology》1999,81(1):1-11
The effect of culture conditions such as medium composition and shear stress on the fungal pellet morphology in shake-flask
cultures and its relation to glucose oxidase (GOD) excretion by recombinant Aspergillus niger NRRL 3 (GOD 3–18) was investigated. It was shown that culture conditions resulting in the formation of smaller fungal pellets
with an increased mycelial density result in higher yields of exocellular GOD. The pellets obtained in shake-flask cultures
showed distinct layers of mycelial density with only the thin outer layer consisting of a dense mycelial network. The performance
of the recombinant strain and the process of pellet formation was also analyzed during batch cultivation in a stirred-tank
bioreactor. It was shown that the process of pellet formation occurred in two steps: (1) aggregation of free spores to spore
clusters with subsequent germination and formation of small aggregates surrounded by a loose hyphal network, and (2) aggregation
of the primary aggregates to the final full-size pellets. The fungal pellets formed during bioreactor cultivation were smaller,
did not show large differences in mycelial density, and were more efficient with respect to the production of exocellular
GOD. The decreasing pellet size also correlated with an increased mycelial density, indicating an improvement of the transport
of nutrients to the inner parts of the pellet. 相似文献
2.
3.
An aquatic weed biomass, Eicchornia crassipes, present in abundance and leading to a threatening level of water pollution was used as substrate for cellulase and β-glucosidase
production using wild-type strain Aspergillus niger RK3 that was isolated from decomposing substrate. Alkali treatment of the biomass (10%) resulted in a 60–66% increase in
endoglucanase, exoglucanase, and β-glucosidase production by the A. niger RK3 strain in semi-solid-state fermentation. Similarly, the alkali-treated biomass led to a 45–54% increase in endo- and
exoglucanase and a higher (98%) increase in β-glucosidase production by Trichoderma reesei MTCC164 under similar conditions. However, the cocultivation of A. niger RK3 and T. reesei MTCC164 at a ratio of 3:1 showed a 20–24% increase in endo- and exoglucanase activities and about a 13% increase in the β-glucosidase
activity over the maximum enzymatic activities observed under single culture conditions. Multistep physical (ultraviolet)
and chemical (N-methyl-N′-nitrosoguanidine, sodium azide, colchicine) mutagenesis of the A. niger RK3 strain resulted in a highly cellulolytic mutant, UNSC-442, having an increase of 136, 138, and 96% in endoglucanase,
exoglucanase, and β-glucosidase, activity, respectively. The cocultivation of mutant UNSC-442 along with T. reesei MTCC164 (at a ratio of 3:1) showed a further 10–11% increase in endo- and exoglucanase activities and a 29% increase in β-glucosidase
activity in semi-solid-state fermentation. 相似文献
4.
The production of yeast cell wall mannan degrading -mannosidase was studied in shake flask experiments as well as in a highly instrumented, computer-coupled bioreactor. The enzyme is predominantly excreted into the culture liquid upon submerged cultivation on yeast mannan. Only low activities were detected with mannose or glucose as carbon source whereas the enzyme formation was totally repressed by glycerol. The amount of enzyme produced is proportional to the microbial biomass formed.Carbon-unlimited cultivation on mannose, the primary product of enzymic digestion, resulted in a specific growth rate of 0.10h–1, a specific oxygen uptake rate
·h and a respiratory quotient ofRQ=1.0. Addition of yeast mannan (0.5%) to nutrient-depleted bacterial cells resulted in an almost complete utilization of this substrate, with 55% of substrate carbon being converted to biomass and 37% to carbon dioxide. The yield coefficient on mannan wasY
x/s
=0.51 (g/g). Enzyme formation started with a delay of 30–40 min and stopped with termination of growth. Due to the increased production of mannose by the action of the enzyme the specific growth rate increased from 0.05 to 0.10 h–1, thus enabling computations of maintenance and yield coefficients for oxygen and carbon dioxide metabolism. 相似文献
5.
Débora Danielle Virgínio da Silva Maria das Graças de Almeida Felipe Ismael Maciel de Mancilha Sílvio Silvério da Silva 《Applied biochemistry and biotechnology》2005,121(1-3):427-437
The effect of glucose on xylose-xylitol metabolism in fermentation medium consisting of sugarcane bagasse hydrolysate was
evaluated by employing an inoculum of Candida guilliermondii grown in synthetic media containing, as carbon sources, glucose (30 g/L), xylose (30 g/L), or a mixture of glucose (2 g/L)
and xylose (30 g/L). The inoculum medium containing glucose promoted a 2.5-fold increase in xylose reductase activity (0.582
IU/mgprot) and a 2-fold increase in xylitol dehydrogenase activity (0.203 IU/mgprot) when compared with an inoculum-grown medium containing only xylose. The improvement in enzyme activities resulted in higher
values of xylitol yield (0.56 g/g) and productivity (0.46 g/[L·h]) after 48 h of fermentation. 相似文献
6.
Xylitol production by Debaryomyces hansenii NRRL Y-7426 was performed on synthetic medium varying the initial xylose concentration between 50 and 300 g/L. The experimental
results of these tests were used to investigate the effect of substrate level on xylose consumption by this yeast. Satisfactory
values of product yield on substrate (0.74–0.83 g/g) as well as volumetric productivity (0.481–0.694 g/L·h) were obtained
over a wide range of xylose levels (90–200 g/L), while a worsening of kinetic parameters took place at higher concentration,
likely due to a substrate inhibition phenomenon. The metabolic behavior of D. hansenii was studied, under these conditions, through a carbon material balance to estimate the fractions of xylose consumed by the
cell for different activities (xylitol production, biomass growth, and respiration) during the lag, exponential, and stationary
phases. 相似文献
7.
Production of laccase by immobilized cells of Agaricus sp. 总被引:1,自引:0,他引:1
Kaluskar VM Kapadnis BP Jaspers C Penninckx MJ 《Applied biochemistry and biotechnology》1999,76(3):161-170
Laccase was produced in the supernatant of culture of a local isolate of Agaricus sp. obtained from decaying Ficus religiosa wood. The enzyme was produced at a constitutive level when growing the fungus in a nitrogenlimited medium supplemented with
either glycerol, glucose, fructose, mannitol, arabinose, maltose, sacch arose, cellulose, or cellobiose. Atwo-to sixfold increase
in enzyme specific activity was observed when growing the strain in the presence of straw, xylan, xylose, lignosulfonate,
veratryl alcohol, and ferulic and veratric acid. Experimentsare consistent with the existence of an induction control on laccase
and the absence of a form of carbon catabolite repression mediated by noninducing carbon sources. Immobilization of the Agaricus sp. on several supports, including polyurethane foam, textilestrips, and straw, resulted in an increase of enzyme production
as compared to cultivation in liquid medium. 相似文献
8.
Mahesh S. Krishnan Nancy W. Y. Ho George T. Tsao 《Applied biochemistry and biotechnology》1999,78(1-3):373-388
Fermentation kinetics of ethanol production from glucose, xylose, and their mixtures using a recombinant Saccharomyces 1400 (pLNH33) are reported. Single-substrate kinetics indicate that the specific growth rate of the yeast and the specific
ethanol productivity on glucose as the substrate was greater than on xylose as a substrate. Ethanol yields from glucose and
xylose fermentation were typically 95 and 80% of the theoretical yield, respectively. The effect of ethanol inhibition is
more pronounced for xylose fermentation than for glucose fermentation. Studies on glucose-xylose mixtures indicate that the
recombinant yeast co-ferments glucose and xylose. Fermentation of a 52.8 g/L glucose and 56.3 g/L xylose mixture gave an ethanol
concentration of 47.9 g/L after 36 h. Based on a theoretical yield of 0.51 g ethanol/g sugars, the ethanol yield from this
experiment (for data up to 24 h) was calculated to be 0.46 g ethanol/g sugar or 90% of the theoretical yield. The specific
growth rate of the yeast on glucose-xylose mixtures was found to lie between the specific growth rate on glucose and the specific
growth rate on xylose. Kinetic studies were used to develop a fermentation model incorporating the effects of substrate inhibition,
product inhibition, and inoculum size. Good agreements were obtained between model predictions and experimental data from
batch fermentation of glucose, xylose, and their mixtures. 相似文献
9.
Ali Mohagheghi Karel Grohmann Charles E. Wyman 《Applied biochemistry and biotechnology》1988,17(1-3):263-277
Cellulase production by the RUT-C30 mutant of the fungusTrichoderma reesei was studied on mixtures of xylose and cellulose. In mixed substrates, the lag phase of the growth cycle was shorter and reached
the maximum of total productivity in a shorter time compared to growth on the single substrate, cellulose. A diauxic pattern
of utilization of the two carbon sources was observed as well: Xylose was utilized first to support growth, followed by cellulose
to induce the cellulase enzyme production and provide an additional carbon source for cellular metabolism. Of the various
mixtures of xylose and cellulose used in batch enzyme production, a ratio of 30∶30 g/L of xylose to cellulose was optimal.
This mixture produced the highest maximal enzyme productivity of 122 IFPU/L h, and its total productivity reached a maximum
value of 55 IFPU/L h in less time than others. However, similar total productivities and higher enzyme titers were observed
for growth on cellulose alone. 相似文献
10.
Gao Qiang Zhang Min McMillan James D. Kompala Dhinakar S. 《Applied biochemistry and biotechnology》2002,98(1-9):341-355
Zymomonas mobilis has been metabolically engineered to broaden its substrate utilization range to include d-xylose and l-arabinose. Both genomically integrated and plasmid-bearing Z. mobilis strains that are capable of fermenting the pentose d-xylose have been created by incorporating four genes: two genes encoding xylose utilization metabolic enzymes (xylA/xylB) and two genes encoding pentose phosphate pathway enzymes (talB/tktA). We have characterized the activities of the four newly introduced enzymes for xylose metabolism, along with those of three
native glycolytic enzymes, in two different xylose-fermenting Z. mobilis strains. These strains were grown on glucose-xylose mixtures in computer-controlled fermentors. Samples were collected and
analyzed to determine extracellular metabolite concentrations as well as the activities of several intracellular enzymes in
the xylose and glucose uptake and catabolism pathways. These measurements provide new insights on the possible bottlenecks
in the engineered metabolic pathways and suggest methods for further improving the efficiency of xylose fermentation. 相似文献
11.
Balasubramanian Niru Seok Kim Jun Lee Y. Y. 《Applied biochemistry and biotechnology》2001,91(1-9):367-376
For optimum fermentation, fermenting xylose into acetic acid by Clostridium thermoaceticum (ATCC 49707) requires adaptation of the strain to xylose medium. Exposed to a mixture of glucose and xylose, it preferentially
consumesxylose over glucose. The initial concentration of xylose in the medium affects the final concentration and the yield
of acetic acid. Batch fermentation of 20 g/L of xylose with 5g/L of yeast extract as the nitrogen source results in a maximum
acetate concentration of 15.2 g/L and yield of 0.76 g of acid/g of xylose. Corn steep liquor (CLS) is a good substitute for
yeast extract and results in similar fermentation profiles. The organism consumes fructose, xylose, and glucose from a mixture
of sugars in batch fermentation. Arabinose, mannose, and galactose are consumed only slightly. This organism loses viability
on fed-batch operation, even with supplementation of all the required nutrients. In fed-batch fermentation with CSL supplementation,
d-xylulose (an intermediate in the xylose metabolic pathway) accumulates in large quantities. 相似文献
12.
Recombinant Zymomonas mobilis CP4:pZB5 was grown with pH control in batch and continuous modes with either glucose or xylose as the sole carbon and energy
source. In batch cultures in which the ratio of the final cell mass concentration to the amount of sugar in the medium was
constant (i.e., under conditions that promote “coupled growth”), maximum specific rates of glucose and xylose consumption
were 8.5 and 2.1 g/(g of cell…h), respectively; maximum specific rates of ethanol production for glucose and xylose were 4.1
and 1.0 g/(g of cell…h), respectively; and average growth yields from glucose and xylose were 0.055 and 0.034 g of dry cell
mass (DCM)/g of sugar respectively. The corresponding value of YATP for glucose and xylose was 9.9 and 5.1 g of DCM/mol of ATP, respectively. YATP for the wild-type culture CP4 with glucose was 10.4g of DCM/mol of ATP. For single substratechem ostat cultures in which
the growth rate was varied as the dilution rate (D), the maximum or “true” growth yield (max Ya/s) was calculated from Pirt plots as the inverse of the slope of the best-fit linear regression for the specific sugar utilization
rate as a function of D, and the “maintenance coefficient” (m) was determined as the y-axis intercept. For xylose, values of max Y
s/s and m were 0.0417g of DCM/g of xylose (YATP=6.25) and 0.04g of, xylose/(g of cell…h), respectively. However, with glucose there was an observed deviation from linearity,
and the data in the Pirt plot was best fit with a second-order polynomial in D. At D>0.1/h, YATP=8.71 and m=2.05g of glu/(g of cell…h) whereas at D<0.1/h, YATP=4.9g of DCM/mol of ATP and m=0.04g of glu/(g of cell…h). This observation provides evidence to question the validity of the unstructured growth model
and the assumption that Pirt's maintenance coefficient is a constant that is in dependent of the growth rate. Collectively,
these observations with individual sugars and the values assign ed to various growth and fermentation parameters will be useful
in the development of models to predict the behavior of rec Zm in mixed substrate fermentations of the type associated with
biomass-to-ethanol processes. 相似文献
13.
This study compared the anaerobic catabolism of glucose and xylose by a patented, recombinant ethanologenicEscherichia coli B 11303:pLOI297 in terms of overall yields of cell mass (growth), energy (ATP), and end product (ethanol). Batch cultivations
were conducted with pH-controlled stirred-tank bioreactors using both a nutritionally rich, complex medium (Luria broth) and
a defined salts minimal medium and growth-limiting concentrations of glucose or xylose. The value of YATP was determined to be 9.28 and 8.19 g dry wt cells/mol ATP in complex and minimal media, respectively. Assuming that the nongrowth-associated
energy demand is similar for glucose and xylose, the mass-based growth yield (Y
x/s
, g dry wt cells/g sugar) should be proportional to the net energy yield from sugar metabolism. The value ofY
x/s
was reduced, on average, by about 50% (from 0.096 g/g glu to 0.051 g/g xyl) when xylose replaced glucose as the growth-limiting
carbon and energy source. It was concluded that this observation is consistent with the theoretical difference in net energy
(ATP) yield associated with anaerobic catabolism of glucose and xylose when differences in the mechanisms of energy-coupled
transport of each sugar are taken into account. In a defined salts medium, the net ATP yield was determined to be 2.0 and
0.92 for glucose and xylose, respectively. 相似文献
14.
Assessment of various carbon sources and nutrient feeding strategies for Panax ginseng cell culture 总被引:1,自引:0,他引:1
Ginseng (root of Panax ginseng C. A. Meyer) cells were cultivated on medium supplemented with various carbohydrates including sucrose, glucose, and fructose,
at initial concentrations ranging from 10 to 110 g/L. Sucrose was shown to be the superior carbon source to the monosaccharides
for ginseng cell growth and the optimal concentration was between 30 and 50 g/L. An increase in the initial concentration
within this range increased the maximum cell density and growth index significantly, whereas much higher concentrations inhibited
cell growth. Feeding of sucrose and some other medium components during the growth (fed-batch mode) was more effective in
enhancing the cell growth and biomass productivity, increasing the growth index by more than 60–70% and biomass productivity
by more than 50%. 相似文献
15.
Jeong Gwi-Taek Park Don-Hee Ryu Hwa-Won Lee Woo-Tai Park Kyungmoon Kang Choon-Hyoung Hwang Baik Woo Je-Chang 《Applied biochemistry and biotechnology》2002,98(1-9):1129-1139
Panax ginseng hairy roots were transformed by Agrobacterium rhizogenes KTCT 2744. They showed an active branching pattern and fast growth in hormone-free medium, and good growth at 23°C, pH 5.8,
1/2 MS medium, and 3% sucrose. Sucrose provided the highest growth among seven carbon sources tested. Six complex media were
also tested. In the combined sugar study, hairy roots grew better on sucrose without glucose or fructose than with glucose
or fructose. In the 1/2 MS basal medium, 30 mM in nitrogen and 0.62 mM phosphate salt concentration was the optimum. The growth ratio was maximal at an inoculum size of 0.4% (w/v). Crude saponin
and polysaccharide levels were also measured. 相似文献
16.
Christina Bohlin Leif J. Jönsson Robyn Roth Willem H. van Zyl 《Applied biochemistry and biotechnology》2006,129(1-3):195-214
Convenient expression systems for efficient heterologous production of different laccases are needed for their characterization
and application. The laccase cDNAs lcc1 and lcc2 from Trametes versicolor were expressed in Pichia pastoris and Aspergillus niger under control of their respective glyceraldehyde-3-phosphate dehydrogenase promoters and with the native secretion signal
directing catalytically active laccase to the medium. P. pastoris batch cultures in shake-flasks gave higher volumetric activity (1.3 U/L) and a better activity to biomass ratio with glucose
than with glycerol or maltose as carbon source. Preliminary experiments with fed-batch cultures of P. pastoris in bioreactors yielded higher activity (2.8 U/L) than the shake-flask experiments, although the levels remained moderate
and useful primarily for screening purposes. With A. niger, high levels of laccase (2700 U/L) were produced using a minimal medium containing sucrose and yeast extract. Recombinant
laccase from A. nigher harboring the lcc2 cDNA was purified to homogeneity and it was found to be a 70-kDa homogeneous enzyme with biochemical and catalytic properties
similar to those of native T. versicolor laccase A. 相似文献
17.
Luís C. Duarte Florbela Carvalheiro Joana Tadeu Francisco M. Gírio 《Applied biochemistry and biotechnology》2006,130(1-3):461-475
The combined effects of inhibitors present in lignocellulosic hydrolysates was studied using a multivariate statistical approach.
Acetic acid (0–6 g/L), formic acid (0–4.6 g/L) and hydroquinone (0–3 g/L) were tested as model inhibitors in synthetic media
containing a mixture of glucose, xylose, and arabinose simulating concentrated hemicellulosic hydrolysates. Inhibitors were
consumed sequentially (acetic acid, formic acid, and hydroquinone), alongside to the monosaccharides (glucose, xylose, and
arabinose). Xylitol was always the main metabolic product. Additionally, glycerol, ethanol, and arabitol were also obtained.
The inhibitory action of acetic acid on growth, on glucose consumption and on all product formation rates was found to be
significant (p≤0.05), as well as formic acid inhibition on xylose consumption and biomass production. Hydroquinone negatively affected biomass
productivity and yield, but it significantly increased xylose consumption and xylitol productivity. Hydroquinone interactions,
either with acetic or formic acid or with both, are also statistically signficant. Hydroquinone seems to partially lessen
the acetic acid and amplify formic acid effects. The results clearly indicate that the interaction effects play an important
role on the xylitol bioprocess. 相似文献
18.
Rosa S. M. A. Felipe M. G. A. Silva S. S. Vitolo M. 《Applied biochemistry and biotechnology》1998,(1):127-135
The effect of pH, time of fermentation, and xylose and glucose concentration on xylitol production, cell growth, xylose reductase
(XR), and xylitol dehydrogenase (XD) activities ofCandida guilliermondii FTI 20037 were determined. For attaining XR and XD activities of 129-2190 U/mg of protein and 24-917 U/mg of protein, respectively,
the cited parameters could vary as follows: initial pH: 3.0-5.0; xylose: 15-60 g/L; glucose: 0-5 g/L; and fermentation time:
12-24 h. Moreover, the high XR and XD activities occurred when the xylitol production by the yeast was less than 19.0 g/L. 相似文献
19.
Zsófia Kádár Truus de Vrije Giel E. van Noorden Miriam A. W. Budde Zsolt Szengyel Kati Réczey Pieternel A. M. Claassen 《Applied biochemistry and biotechnology》2004,114(1-3):497-508
This study addressed the utilization of an industrial waste stream, paper sludge, as a renewable cheap feedstock for the fermentative
production of hydrogen by the extreme thermophile Caldicellulosiruptor saccharolyticus. Hydrogen, acetate, and lactate were produced in medium in which paper sludge hydrolysate was added as the sole carbon and
energy source and in control medium with the same concentration of analytical grade glucose and xylose. The hydrogen yield
was dependent on lactate formation and varied between 50 and 94% of the theoretical maximum. The carbon balance in the medium
with glucose and xylose was virtually 100%. The carbon balance was not complete in the paper sludge medium because the measurement
of biomass was impaired owing to interfering components in the paper sludge hydrolysate. Nevertheless, >85% of the carbon
could be accounted for in the products acetate and lactate. The maximal volumetric hydrogen production rate was 5 to 6 mmol/(L·h),
which was lower than the production rate in media with glucose, xylose, or a combination of these sugars (9–11 mmol/[L·h]).
The reduced hydrogen production rate suggests the presence of inhibiting components in paper sludge hydrolysate. 相似文献
20.
The glucose analog 2-deoxyglucose (2-DOG) has been used to obtain mutants depressed for pentose metabolism. Some researchers
have used 2-DOG alone whereas others have used it in the presence of a glucose-repressible carbon source. We examined both
methods and screened mutant strains for improved use of xylose in the presence of glucose. Pichia stipitis mutants selected for growth on d-xylose in the presence of 2-DOG used xylose from a 1∶1 glucose:xylose mixture more rapidly than did their parents. One of
these mutants, FPL-DX26, completely consumed xylose in the presence of glucose and produced 33g/L ethanol in 45h from 80 g/L
of this sugar mixture. Mutants selected for growth on 2-DOG alone did not show significant improvement. Selection for growth
on d-xylose in the presence of 2-DOG has been useful in developing parental strains for further genetic manipulation.
The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin-Madison. This article was prepared
by U.S. Goverment employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献