共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Eliana V. Canettieri João B. Almeida E. Silva Maria G. A. Felipe 《Applied biochemistry and biotechnology》2001,94(2):159-168
This study deals with the bioconversion of xylose into xylitol by Candida guilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtained by acid hydrolysis. The influence of various parameters (ammonium
sulfate, rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on
multivariate statistical concepts, with the application of factorial design techniques to identify the most important variables
in the process. The levels of these variables were quantified by the response surface methodology, which permitted the establishment
of a significant mathematical model with a coefficient determination of R
2=0.92. The best results (xylitol=10.0 g/L, yield factor=0.2 g/g, and productivity=0.1 g/[L·h]) were attained with hydrolysate
containing ammonium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentration of 60.0 g/L), after 72 h of
fermentation. The pH of fermentation was adjusted to 8.0 and the inoculum level utilized was 3 g/L. 相似文献
3.
Sene L. Vitolo M. Felipe M. G. A. Silva S. S. 《Applied biochemistry and biotechnology》2000,84(1-9):371-380
The effects of environmental conditions, namely initial pH (2.5–7.0) and temperature (25 and 35°C), on xylose reductase and
xylitol dehydrogenase levels, as well as on xylitol production, were evaluated. Although the fermentative parameter values
increased with an increase in pH and temperature (the maximum YP/s and Q
p
were 0.75 g/g and 0.95 g/[L·h], respectively, both attained at pH 6.0, 35°C), the highest xylose reductase activities (nearly
900 1U/mg of protein) were observed at an initial pH varying from 4.0 to 6.0. Xylitol dehydrogenase was favored by an increase
in both initial pH and temperature of the medium. The highest xylitol dehydrogenase specific activity was attained at pH 6.5
and 35°C (577 1U/mg of protein). 相似文献
4.
Rodrigues Denise C. G. A. Da Silva Silvio S. Almeida E Silva J. B. Vitolo Michele 《Applied biochemistry and biotechnology》2002,98(1-9):875-883
Xylose reductase activity of Candida guilliermondii FTI 20037 was evaluated during xylitol production by fed-batch fermentation of sugarcane bagasse hydrolysate. A 24-1 fractional factorial design was used to select process variables. The xylose concentrations in the feeding solution (S
F
) and in the fermentor (S
0), the pH, and the aeration rate were selected for optimization of this process, which will be undertaken in the near future.
The best experimental result was achieved at S
F
=45 g/L, S
0=40 g/L, pH controlled at 6.0, and aeration rate of 1.2 vvm. Under these conditions, the xylose reductase activity was 0.81
U/mg of protein and xylitol production was 26.3 g/L, corresponding to a volumetric productivity of 0.55 g/(L·h) and a xylose
xylitol yield factor of 0.68 g/g. 相似文献
5.
Martínez Ernesto Acosta Silva Silvio S. Felipe Maria G. A. 《Applied biochemistry and biotechnology》2000,84(1-9):633-641
The effect of the oxygen transfer coefficient on the production of xylitol by biocon version of xylose present in sugarcane
bagasse hemicellulosic hydrolysate using the yeast Candiada guilliermondii was investigated. Continuous cultivation was carried out in a 1.25-L fermentor at 30°C, pH 5.5, 300 rpm, and a dilution rate
of 0.03/h, using oxygen transfer coefficients of 10,20, and 30/h. The results showed that the microbial xylitol production
(11 g/L) increased by 108% with the decrease in the oxygen volumetric transfer coefficient from 30 to 20/h. The maximum values
of xylitol productivity (0.7g/[L…h]) and yield (0.58 g/g) were obtained at k
L
a 20/h. 相似文献
6.
Mayerhoff Zea D. V. L. Roberto Inês C. Franco Telma T. 《Applied biochemistry and biotechnology》2001,91(1-9):729-737
Xylose reductase (XR) activity was evaluated in extracts of Candida mogii grown in media containing different concentrations of rice straw hydrolysate. Results of X Ractivity were compared to xylitol
production and a similar behavior was observed for these parameters. Highest values of specific production and productivity
were found for xylose reductase (35 U/g of cell and 0.97 U/[g of cell·h], respectively) and for xylitol (5.63 g/g of cell
and 0.13 g/[g of cell·h]) in fermentation conducted in medium containing 49.2 g of xylose/L. The maximum value of XR:XD ratio
(1.82) was also calculated under this initial xylose concentration with 60 h of fermentation. 相似文献
7.
Fábio C. Sampaio Paolo Torre Flávia M. Lopes Passos Célia Alencar de Moraes Patrizia Perego Attilio Converti 《Applied biochemistry and biotechnology》2007,136(2):165-181
To obtain in-depth information on the overall metabolic behavior of the new good xylitol producer Debaryomyces hansenii UFV-170, batch bioconversions were carried out using semisynthetic media with compositions simulating those of typical acidic
hemicellulose hydrolysates of sugarcane bagasse. For this purpose, we used media containing glucose (4.3–6.5 g/L), xylose
(60.1–92.1 g/L), or arabinose (5.9–9.2 g/L), or binary or ternary mixtures of them in either the presence or absence of typical
inhibitors of acidic hydrolysates, such as furfural (1.0–5.0 g/L), hydroxymethylfurfural (0.01–0.30 g/L), acetic acid (0.5–3.0
g/L), and vanillin (0.5–3.0 g/L). D. hansenii exhibited a good tolerance to high sugar concentrations as well as to the presence of inhibiting compounds in the fermentation
media. It was able to produce xylitol only from xylose, arabitol from arabinose, and no glucitol from glucose. Arabinose metabolization
was incomplete, while ethanol was mainly produced from glucose and, to a lesser less extent, from xylose and arabinose. The
results suggest potential application of this strain in xyloseto-xylitol bioconversion from complex xylose media from lignocellulosic
materials. 相似文献
8.
Sene Luciane Felipe Maria G. A. Silva Silvio S. Vitolo Michele 《Applied biochemistry and biotechnology》2001,91(1-9):671-680
Candida guilliermondii FTI 20037 was cultured in sugarcane bagasse hydrolysate supplemented with 2.0 g/L of (NH4)2SO4, 0.1 g/L of CaCl2·2H2O, and 20.0 g/L of rice bran at 35°C; pH 4.0; agitation of 300 rpm; and aeration of 0.4, 0.6, or 0.8 vvm. The high xylitol
production (20.0 g/L) and xylose reductase (XR) activity (658.8 U/mg of protein) occurred at an aeration of 0.4 vvm. Under
this condition, the xylitol dehydrogenase (XD) activity was low. The apparent K
M for XR and XD against substrates and cofactors were as follows: for XR, 6.4×10−2
M (xylose) and 9.5×10−3 mM (NADPH); for XD, 1.6×10−1
M (xylitol) and 9.9×10−2 mM (NAD+). Because XR requires about 10-fold less xylose and cofactor than XD for the condition in which the reaction rate is
half of the V
max, some interference on the overall xylitol production by the yeast could be expected. 相似文献
9.
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
10.
Gimenes Maria Antonieta P. Carlos Luiz Cláudio S. Faria Luís F. F. Pereira Nei 《Applied biochemistry and biotechnology》2002,98(1-9):1049-1059
The global oxygen uptake rate (OUR) and specific oxygen uptake rates (SOUR) were determined for different values of the volumetric
oxygen mass transfer coefficient (15, 43, and 108 h−1), and for varying initial xylose concentrations (50, 100, 150, and 200 g/L) in shaking flasks. The initial cell concentration
was 4.0 g/L, and there was only significant growth in the fermentation with the highest oxygen availability. In this condition,
OUR increased proportionally to cell growth, reaching maximum values from 2.1 to 2.5 g of O2/(L·h) in the stationary phase when the initial substrate concentration was raised from 50 to 200 g/L, respectively. SOUR
showed different behavior, growing to a maximum value coinciding with the beginning of the exponential growth phase, after
which point it decreased. The maximum SOUR values varied from 265 to 370 mg of O2/(g of cell·h), indicating the interdependence of this parameter and the substrate concentration. Although the volumetric
productivity dropped slightly from 1.55 to 1.18 g of xylitol/(L·h), the strain producing capacity (γ
P/X
) rose from 9 to 20.6 g/g when the initial substrate concentration was increased from 50 to 200 g/L. As for the xylitol yield
over xylose consumed (γ
P/S
), there was no significant variation, resulting in a mean value of 0.76 g/g. The results are of interest in establishing
a strategy for controlling the dynamic oxygen supply to maximize volumetric productivity. 相似文献
11.
Domínguez JM Cruz JM Roca E Domínguez H Parajó JC 《Applied biochemistry and biotechnology》1999,81(2):119-130
Debaryomyces hansenii cells were entrapped in Ca-alginate beads and used for producing xylitol from wood hydrolyzates. Batch experiments showed
that bioconversion was severely hindered when Ca-alginate beads were hardened with Al3+ solutions. As an alternative to Al3+ hardening, the improvements in both mechanical stability of bioparticles and fermenting ability of the immobilized system
derived from using increased concentrations of sodium alginate were assessed. The best results were obtained using a 4% (w/v)
Na-alginate solution in the gelification step. This concentration was selected to perform continuous fermentations in a packed-bed
reactor using raw or charcoal-treated hydrolyzates (15.5 g of xylose/L) with two different yeasts: Candida guilliermondii and Debaryomyces hansenii. With a final cell concentration of about 50 g of cells/L (0.075 g of cells/g of beads), the volumetric productivities reached
with these yeasts in media made from charcoal-treated hydrolyzates were 0.58 and 0.91 g/L·h, respectively. 相似文献
12.
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
13.
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
14.
Cao Ning-Jun Tang Rentian Gong C. S. Chen L. F. 《Applied biochemistry and biotechnology》1994,(1):515-519
The rate of xylitol production from D-xylose increased with increasing yeast cell density. The optimal temperature for xylitol
production is 36‡ C, and the optimal pH range is from 4.0 to 6.0. At high initial yeast cell concentration of 26 mg/mL, 210
g/L of xylitol was produced from 260 g/L of D-xylose after 96 h of incubation with an indicated yield of 81% of the theoretical
value. 相似文献
15.
The effects of oxygen limitation on xylose fermentation of Neurospora crassa AS3.1602 were studied using batch cultures. The maximum yield of ethanol was 0.34 g/g at oxygen transfer rate (OTR) of 8.4 mmol/L·h.
The maximum yield of xylitol was 0.33 g/g at OTR of 5.1 mmol/L·h. Oxygen limitation greatly affected mycelia growth and xylitol
and ethanol productions. The specific growth rate (μ) decreased 82% from 0.045 to 0.008 h−1 when OTR changed from 12.6 to 8.4 mmol/L·h. Intracellular metabolites of the pentose phosphate pathway, glycolysis, and tricarboxylic
acid cycle were determined at various OTRs. Concentrations of most intracellular metabolites decreased with the increase in
oxygen limitation. Intracellular enzyme activities of xylose reductase, xylitol dehydrogenase, and xylulokinase, the first
three enzymes in xylose metabolic pathway, decreased with the increase in oxygen limitation, resulting in the decreased xylose
uptake rate. Under all tested conditions, transaldolase and transketolase activities always maintained at low levels, indicating
a great control on xylose metabolism. The enzyme of glucose-6-phosphate dehydrogenase played a major role in NADPH regeneration,
and its activity decreased remarkably with the increase in oxygen limitation. 相似文献
16.
Faria Luis F. Figueiredo Gimenes Maria Antonieta P. Nobrega Ronaldo Pereira Nei 《Applied biochemistry and biotechnology》2002,98(1-9):449-458
Oxygen availability is the most important environmental parameter in the production of xylitol by yeasts, directly affecting
yields and volumetric productivity. This work evaluated the cell behavior in fermentations carried out with different dissolved
oxygen concentrations (0.5–30.0% of saturation), as well as a limited oxygen restriction (0% of saturation), at several oxygen
volumetric transfer coefficients (12 ≤ k
L
a ≤ 70 h−1). These experiments allowed us to establish the specific oxygen uptake rate limits to ensure high yields and volumetric productivity.
When oxygen availability was limited, the specific oxygen uptake rate values were between 12 and 26 mg of O2/of g cell·h, resulting in a yield of 0.71 g of xylitol/xylose consumed, and 0.85 g/[L·h] for the volumetric productivity.
According to the results, the effective control of the specific oxygen uptake rate makes it possible to establish complete
control over this fermentative process, for both cell growth and xylitol production. 相似文献
17.
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
18.
PVA-Hydrogel Entrapped <Emphasis Type="Italic">Candida Guilliermondii</Emphasis> for Xylitol Production from Sugarcane Hemicellulose Hydrolysate 总被引:1,自引:0,他引:1
da Cunha MA Converti A Santos JC Ferreira ST da Silva SS 《Applied biochemistry and biotechnology》2009,157(3):527-537
Viable cells of Candida guilliermondii were immobilized by inclusion into polyvinyl alcohol (PVA) hydrogel using the freezing–thawing method. Entrapment experiments
were planned according to a 23 full factorial design, using the PVA concentration (80, 100, and 120 g L−1), the freezing temperature (−10, −15, and −20 °C), and the number of freezing-thawing cycles (one, three, and five) as the
independent variables, integrated with three additional tests to estimate the errors. The effectiveness of the immobilization
procedure was checked in Erlenmeyer flasks as the pellet capability to catalyze the xylose-to-xylitol bioconversion of a medium
based on sugarcane bagasse hemicellulosic hydrolysate. To this purpose, the yield of xylitol on consumed xylose, xylitol volumetric
productivity, and cell retention yield were selected as the response variables. Cell pellets were then used to perform the
same bioconversion in a stirred tank reactor operated at 400 rpm, 30 °C, and 1.04 vvm air flowrate. At the end of fermentation,
a maximum xylitol concentration of 28.7 g L−1, a xylitol yield on consumed xylose of 0.49 g g−1 and a xylitol volumetric productivity of 0.24 g L−1 h−1 were obtained. 相似文献
19.
Lawford Hugh G. Rousseau Joyce D. Mohagheghi Ali McMillan James D. 《Applied biochemistry and biotechnology》1998,(1):353-367
The continuous cofermentation performance of xylose-fermentingZymomonas mobilis at 30°C and pH 5.5 was characterized using a pure-sugar feed solution that contained 8 g/L glucose and 40 g/L xylose. Successful
chemostat start up resulted in complete utilization of glucose and greater than 85% utilization of xylose, but was only reproducibly
achieved using initial dilution rates at or less than 0.04/h; once initiated, cofermentation could be maintained at dilution
rates of 0.04 to 0.10/h. Whereas xylose and cell-mass concentrations increased gradually with increasing dilution rate, ethanol
concentrations and ethanol yields on available sugars remained approximately constant at 20–22 g/L and 80–90% of theoretical,
respectively. Volumetric and specific ethanol productivities increased linearly with increasing dilution rate, rising from
approx 1.0 each (g/L/h or g/g/h) at a dilution rate of 0.04/h to approx 2.0 each (g/L/h or g/g/h) at a dilution rate of 0.10/h.
Similarly, specific sugar-utilization rates increased from approx 2.0 g/g/h at dilution rate 0.04/h to approx 3.5 g/g/h at
dilution rate of 0.10/h. The estimated values of 0.042 g/g for the maximum Z.mobilis cell-mass yield on substrate and 1.13 g/g/h for the minimum specific substrate utilization rate required for cellular maintenance
energy are within the range of values reported in the literature. Results are also presented which suggest that long-term
adaptation in continuous culture is a powerful technique for developing strains with higher tolerance to inhibitory hemicellulose
hydrolyzates. 相似文献
20.
In this study, the immobilization characteristics of Enterococcus faecalis RKY1 for succinate production were examined. At first, three natural polymers—agar, κ-carrageenan, and sodium alginate—were
tried as immobilizing matrices. Among these, sodium alginate was selected as the best gel for immobilization of E. faecalis RKY1. Efficient conditions for immobilization were established to be with a 2% (w/v) sodium alginate solution and 2-mm-diameter
bead. The bioconversion characteristics of the immobilized cellsat various pH values and temperatures were examined and compared
with those of free cells. The optimum pH and temperature of the immobilized cells were the same as for free cells, 7.0 and
38°C respectively, but the conversion ratio was higher by immobilization for all the other pH and temperature conditions tested.
When the seed volume of the immobilized cells was adjusted to 10% (v/v), 30 g/L of fumarate was completely converted tosuccinate
(0.973 g/g conversion ratio) after 12 h. In addition, the immobilized cells maintained a conversion ratio of >0.95 g/g during
4wk of storageat 4°C in a 2% (w/v) CaCl2 solution. In repetitive bioconversion experiments, the activity of the immobilized cells decreased linearly according to
the number of times of reuse. 相似文献