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1.
Xylose reductase (XR) is a key enzyme in biological xylitol production, and most XRs have broad substrate specificities. During
xylitol production from biomass hydrolysate, non-specific XRs can reduce l-arabinose, which is the second-most abundant hemicellulosic sugar, to the undesirable byproduct arabitol, which interferes
with xylitol crystallization in downstream processing. To minimize the flux from l-arabinose to arabitol, the l-arabinose-preferring, endogenous XR was replaced by a d-xylose-preferring heterologous XR in Candida tropicalis. Then, Bacillus licheniformis
araA and Escherichia coli araB and araD were codon-optimized and expressed functionally in C. tropicalis for the efficient assimilation of l-arabinose. During xylitol fermentation, the control strains BSXDH-3 and KNV converted 9.9 g l-arabinose l−1 into 9.5 and 8.3 g arabitol l−1, respectively, whereas the recombinant strain JY consumed 10.5 g l-arabinose l−1 for cell growth without forming arabitol. Moreover, JY produced xylitol with 42 and 16% higher productivity than BSXDH-3
and KNV, respectively. 相似文献
2.
Kim JH Han KC Koh YH Ryu YW Seo JH 《Journal of industrial microbiology & biotechnology》2002,29(1):16-19
Xylitol, a functional sweetener, was produced from xylose by biological conversion using Candida tropicalis ATCC 13803. Based on a two-substrate fermentation using glucose for cell growth and xylose for xylitol production, fed-batch
fermentations were undertaken to increase the final xylitol concentration. The effects of xylose and xylitol on xylitol production
rate were studied to determine the optimum concentrations for fed-batch fermentation. Xylose concentration in the medium (100
g l−1) and less than 200 g l−1 total xylose plus xylitol concentration were determined as optimum for maximum xylitol production rate and xylitol yield.
Increasing the concentrations of xylose and xylitol decreased the rate and yield of xylitol production and the specific cell
growth rate, probably because of an increase in osmotic stress that would interfere with xylose transport, xylitol flux to
secretion to cell metabolism. The feeding rate of xylose solution during the fed-batch mode of operation was determined by
using the mass balance equations and kinetic parameters involved in the equations in order to increase final xylitol concentration
without affecting xylitol and productivity. The optimized fed-batch fermentation resulted in 187 g l−1 xylitol concentration, 0.75 g xylitol g xylose−1 xylitol yield and 3.9 g xylitol l−1 h−1 volumetric productivity. Journal of Industrial Microbiology & Biotechnology (2002) 29, 16–19 doi:10.1038/sj.jim.7000257
Received 15 October 2001/ Accepted in revised form 30 March 2002 相似文献
3.
The effects of glycerol and the oxygen transfer rate on the xylitol production rate by a xylitol dehydrogenase gene (XYL2)-disrupted mutant of Candida tropicalis were investigated. The mutant produced xylitol near the almost yield of 100% from d-xylose using glycerol as a co-substrate for cell growth and NADPH regeneration: 50 g d-xylose l−1 was completely converted into xylitol when at least 20 g glycerol l−1 was used as a co-substrate. The xylitol production rate increased with the O2 transfer rate until saturation and it was not necessary to control the dissolved O2 tension precisely. Under the optimum conditions, the volumetric productivity and xylitol yield were 3.2 g l−1 h−1 and 97% (w/w), respectively. 相似文献
4.
Anjali Madhavan Sriappareddy Tamalampudi Aradhana Srivastava Hideki Fukuda Virendra S. Bisaria Akihiko Kondo 《Applied microbiology and biotechnology》2009,82(6):1037-1047
Previously, a Saccharomyces cerevisiae strain was engineered for xylose assimilation by the constitutive overexpression of the Orpinomyces xylose isomerase, the S. cerevisiae xylulokinase, and the Pichia stipitis SUT1 sugar transporter genes. The recombinant strain exhibited growth on xylose, under aerobic conditions, with a specific growth
rate of 0.025 h−1, while ethanol production from xylose was achieved anaerobically. In the present study, the developed recombinant yeast was
adapted for enhanced growth on xylose by serial transfer in xylose-containing minimal medium under aerobic conditions. After
repeated batch cultivations, a strain was isolated which grew with a specific growth rate of 0.133 h−1. The adapted strain could ferment 20 g l−1 of xylose to ethanol with a yield of 0.37 g g−1 and production rate of 0.026 g l−1 h−1. Raising the fermentation temperature from 30°C to 35°C resulted in a substantial increase in the ethanol yield (0.43 g g−1) and production rate (0.07 g l−1 h−1) as well as a significant reduction in the xylitol yield. By the addition of a sugar complexing agent, such as sodium tetraborate,
significant improvement in ethanol production and reduction in xylitol accumulation was achieved. Furthermore, ethanol production
from xylose and a mixture of glucose and xylose was also demonstrated in complex medium containing yeast extract, peptone,
and borate with a considerably high yield of 0.48 g g−1. 相似文献
5.
To construct Candida tropicalis strains that produce a high yield of xylitol with no requirement for co-substrates, we engineered the yeast with an attenuated
xylitol dehydrogenase (XDH) and then assessed the efficiency of xylitol production The mutants, strains XDH-5 (with only one
copy of the XDH gene), and ARSdR-16 (with a mutated XDH gene) showed 70 and 40% of wild type (WT) XDH activity, respectively.
Conversions of xylose to xylitol by WT, XDH-5, and ARSdR-16 were 62, 64, and 75%, respectively, with productivities of 0.52,
0.54, and 0.62 g l−1 h−1, respectively. The ARSdR-16 mutant strain produced xylitol with high yield and high productivity in a simple process that
required no co-substrates, such as glycerol. This strain represents a promising alternative for efficient and cost-effective
xylitol production. 相似文献
6.
Sachin Kumar Surendra P. Singh Indra M. Mishra Dilip K. Adhikari 《Journal of industrial microbiology & biotechnology》2009,36(12):1483-1489
A yeast strain Kluyveromyces sp. IIPE453 (MTCC 5314), isolated from soil samples collected from dumping sites of crushed sugarcane bagasse in Sugar Mill,
showed growth and fermentation efficiency at high temperatures ranging from 45°C to 50°C. The yeast strain was able to use
a wide range of substrates, such as glucose, xylose, mannose, galactose, arabinose, sucrose, and cellobiose, either for growth
or fermentation to ethanol. The strain also showed xylitol production from xylose. In batch fermentation, the strain showed
maximum ethanol concentration of 82 ± 0.5 g l−1 (10.4% v/v) on initial glucose concentration of 200 g l−1, and ethanol concentration of 1.75 ± 0.05 g l−1 as well as xylitol concentration of 11.5 ± 0.4 g l−1 on initial xylose concentration of 20 g l−1 at 50°C. The strain was capable of simultaneously using glucose and xylose in a mixture of glucose concentration of 75 g l−1 and xylose concentration of 25 g l−1, achieving maximum ethanol concentration of 38 ± 0.5 g l−1 and xylitol concentration of 14.5 ± 0.2 g l−1 in batch fermentation. High stability of the strain was observed in a continuous fermentation by feeding the mixture of glucose
concentration of 75 g l−1 and xylose concentration of 25 g l−1 by recycling the cells, achieving maximum ethanol concentration of 30.8 ± 6.2 g l−1 and xylitol concentration of 7.35 ± 3.3 g l−1 with ethanol productivity of 3.1 ± 0.6 g l−1 h−1 and xylitol productivity of 0.75 ± 0.35 g l−1 h−1, respectively. 相似文献
7.
Miho Sasaki Toru Jojima Masayuki Inui Hideaki Yukawa 《Applied microbiology and biotechnology》2010,86(4):1057-1066
Wild-type Corynebacterium glutamicum produced 0.6 g l−1 xylitol from xylose at a productivity of 0.01 g l−1 h−1 under oxygen deprivation. To increase this productivity, the pentose transporter gene (araE) from C. glutamicum ATCC31831 was integrated into the C. glutamicum R chromosome. Consequent disruption of its lactate dehydrogenase gene (ldhA), and expression of single-site mutant xylose reductase from Candida tenuis (CtXR (K274R)) resulted in recombinant C. glutamicum strain CtXR4 that produced 26.5 g l−1 xylitol at 3.1 g l−1 h−1. To eliminate possible formation of toxic intracellular xylitol phosphate, genes encoding xylulokinase (XylB) and phosphoenolpyruvate-dependent
fructose phosphotransferase (PTSfru) were disrupted to yield strain CtXR7. The productivity of strain CtXR7 increased 1.6-fold over that of strain CtXR4. A fed-batch
21-h CtXR7 culture in mineral salts medium under oxygen deprivation yielded 166 g l−1 xylitol at 7.9 g l−1 h−1, representing the highest bacterial xylitol productivity reported to date. 相似文献
8.
Analysis and optimization of a two-substrate fermentation for xylitol production using Candida tropicalis 总被引:1,自引:0,他引:1
Xylitol, a functional sweetener, was produced from xylose using Candida tropicalisATCC 13803. A two-substrate fermentation was designed in order to increase xylitol yield and volumetric productivity. Glucose
was used initially for cell growth followed by conversion of xylose to xylitol without cell growth and by-product formation
after complete depletion of glucose. High glucose concentrations increased volumetric productivity by reducing conversion
time due to high cell mass, but also led to production of ethanol, which, in turn, inhibited cell growth and xylitol production.
Computer simulation was undertaken to optimize an initial glucose concentration using kinetic equations describing rates of
cell growth and xylose bioconversion as a function of ethanol concentration. Kinetic constants involved in the equations were
estimated from the experimental results. Glucose at 32 g L−1 was estimated to be an optimum initial glucose concentration with a final xylose concentration of 86 g L−1 and a volumetric productivity of 5.15 g-xylitol L−1 h−1. The two-substrate fermentation was performed under optimum conditions to verify the computer simulation results. The experimental
results were in good agreement with the predicted values of simulation with a xylitol yield of 0.81 g-xylitol g-xylose−1 and a volumetric productivity of 5.06 g-xylitol L−1 h−1.
Received 16 June 1998/ Accepted in revised form 28 February 1999 相似文献
9.
Sebastián Sánchez Vicente Bravo Juan Francisco García Nicolás Cruz Manuel Cuevas 《World journal of microbiology & biotechnology》2008,24(5):709-716
The fermentation of d-glucose and d-xylose mixtures by the yeast Candida tropicalis NBRC 0618 has been studied under the most favourable operation conditions for the culture, determining the most adequate
initial proportion in these sugars for xylitol production. In all the experiments a synthetic culture medium was used, with
an initial total substrate concentration of 25 g L−1, a constant pH of 5.0 and a temperature of 30 °C. From the experimental results, it was deduced that the highest values of
specific rates of production and of overall yield in xylitol were achieved for the mixtures with the highest percentage of
d-xylose, specifically in the culture with the initial d-glucose and d-xylose concentrations of 1 and 24 g L−1, respectively, with an overall xylitol yield of 0.28 g g−1. In addition, the specific rates of xylitol production declined over the time course of the culture and the formation of
this bioproduct was favoured by the presence of small quantities of d-glucose. The sum of the overall yield values in xylitol and ethanol for all the experiments ranged from 0.26 to 0.56 g bioproduct/g
total substrate. 相似文献
10.
Feiwei Zhang Dairong Qiao Hui Xu Chong Liao Shilin Li Yi Cao 《Journal of microbiology (Seoul, Korea)》2009,47(3):351-357
Xylose reductase (XR) is a key enzyme in xylose metabolism because it catalyzes the reduction of xylose to xylitol. In order
to study the characteristics of XR from Candida tropicalis SCTCC 300249, its XR gene (xyll) was cloned and expressed in Escherichia coli BL21 (DE3). The fusion protein was purified effectively by Ni2+-chelating chromatography, and the kinetics of the recombinant XR was investigated. The Km values of the C. tropicalis XR for NADPH and NADH were 45.5 μM and 161.9 μM, respectively, which demonstrated that this XR had dual coenzyme specificity.
Moreover, this XR showed the highest catalytic efficiency (kcat=1.44×l04 min−1) for xylose among the characterized aldose reductases. Batch fermentation was performed with Saccharomyces serivisiae W303-lA:pYES2XR, and resulted in 7.63 g/L cell mass, 93.67 g/L xylitol, and 2.34 g/L · h xylitol productivity. This XR coupled
with its dual coenzyme specificity, high activity, and catalytic efficiency proved its utility in in vitro xylitol production. 相似文献
11.
Candida tropicalis, a strain isolated from the sludge of a factory manufacturing xylose, produced a high xylitol concentration of 131 g/l from
150 g/l xylose at 45 h in a flask. Above 150 g/l xylose, however, volumetric xylitol production rates decreased because of
a lag period in cell growth. In fed-batch culture, the volumetric production rate and xylitol yield from xylose varied substantially
with the controlled xylose concentration and were maximum at a controlled xylose concentration of 60 g/l. To increase the
xylitol yield from xylose, feeding experiments using different ratios of xylose and glucose were carried out in a fermentor.
The maximum xylitol yield from 300 g/l xylose was 91% at a glucose/xylose feeding ratio of 15%, while the maximum volumetric
production rate of xylitol was 3.98 g l−1 h−1 at a glucose/xylose feeding ratio of 20%. Xylitol production was found to decrease markedly as its concentration rose above
250 g/l. In order to accumulate xylitol to 250 g/l, 270 g/l xylose was added in total, at a glucose/xylose feeding ratio of
15%. Under these conditions, a final xylitol production of 251 g/l, which corresponded to a yield of 93%, was obtained from
270 g/l xylose in 55 h.
Received: 20 April 1998 / Received revision: 29 May 1998 / Accepted: 19 June 1998 相似文献
12.
Anne Usvalampi Kristiina Kiviharju Matti Leisola Antti Nyyssölä 《Journal of industrial microbiology & biotechnology》2009,36(10):1323-1330
Factors affecting the production of the rare sugar l-xylulose from xylitol using resting cells were investigated. An E. coli BPT228 strain that recombinantly expresses a gene for xylitol dehydrogenase was used in the experiments. The ratio of xylitol
to l-xylulose was three times lower in the cytoplasm than in the medium. The effects of pH, temperature, shaking speed, and initial
xylitol concentration on l-xylulose production were investigated in shaking flasks using statistical experimental design methods. The highest production
rates were found at high shaking speed and at high temperature (over 44°C). The optimal pH for both productivity and conversion
was between 7.5 and 8.0, and the optimal xylitol concentration was in the range 250–350 g l−1. A specific productivity of 1.09 ± 0.10 g g−1 h−1 was achieved in a bioreactor. The response surface model based on the data from the shake flask experiments predicted the
operation of the process in a bioreactor with reasonable accuracy. 相似文献
13.
Xylose utilisation by recombinant strains of Saccharomyces cerevisiae on different carbon sources 总被引:1,自引:0,他引:1
van Zyl WH Eliasson A Hobley T Hahn-Hägerdal B 《Applied microbiology and biotechnology》1999,52(6):829-833
Autoselective xylose-utilising strains of Saccharomyces cerevisiae expressing the xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) genes of Pichia stipitis were constructed by replacing the chromosomal FUR1 gene with a disrupted fur1::LEU2 allele. Anaerobic fermentations with 80 g l−1
d-xylose as substrate showed a twofold higher consumption of xylose in complex medium compared to defined medium. The xylose
consumption rate increased a further threefold when 20 g l−1
d-glucose or raffinose was used as co-substrate together with 50 g l−1
d-xylose. Xylose consumption was higher with raffinose as co-substrate than with glucose (85% versus 71%, respectively) after
82 h fermentations. A high initial ethanol concentration and moderate levels of glycerol and acetic acid accompanied glucose
as co-substrate, whereas the ethanol concentration gradually increased with raffinose as co-substrate with no glycerol and
much less acetic acid formation.
Received: 12 March 1999 / Received revision: 31 June 1999 / Accepted: 5 July 1999 相似文献
14.
Fábio Coelho Sampaio Janaína Teles de Faria Jane Sélia R. Coimbra Flávia M. Lopes Passos Attilio Converti Luis Antônio Minin 《Bioprocess and biosystems engineering》2009,32(6):747-754
To develop a new enzymatic xylose-to-xylitol conversion, deeper knowledge on the regulation of xylose reductase (XR) is needed.
To this purpose, a new strain of Debaryomyces hansenii (UFV-170), which proved a promising xylitol producer, was cultivated in semi-synthetic media containing different carbon
sources, specifically three aldo-hexoses (d-glucose, d-galactose and d-mannose), a keto-hexose (d-fructose), a keto-pentose (d-xylose), three aldo-pentoses (d-arabinose, l-arabinose and d-ribose), three disaccharides (maltose, lactose and sucrose) and a pentitol (xylitol). The best substrate was lactose on which
cell concentration reached about 20 g l−1 dry weight (DW), while the highest specific growth rates (0.58–0.61 h−1) were detected on lactose, d-mannose, d-glucose and d-galactose. The highest specific activity of XR (0.24 U mg−1) was obtained in raw extracts of cells grown on d-xylose and harvested in the stationary growth phase. When grown on cotton husk hemicellulose hydrolyzates, cells exhibited
XR activities five to seven times higher than on semi-synthetic media. 相似文献
15.
Lactic acid production from xylose by the fungus Rhizopus oryzae 总被引:1,自引:1,他引:0
Lignocellulosic biomass is considered nowadays to be an economically attractive carbohydrate feedstock for large-scale fermentation of bulk chemicals such as lactic acid. The filamentous fungus Rhizopus oryzae is able to grow in mineral medium with glucose as sole carbon source and to produce optically pure l(+)-lactic acid. Less is known about the conversion by R. oryzae of pentose sugars such as xylose, which is abundantly present in lignocellulosic hydrolysates. This paper describes the conversion of xylose in synthetic media into lactic acid by ten R. oryzae strains resulting in yields between 0.41 and 0.71 g g−1. By-products were fungal biomass, xylitol, glycerol, ethanol and carbon dioxide. The growth of R. oryzae CBS 112.07 in media with initial xylose concentrations above 40 g l−1 showed inhibition of substrate consumption and lactic acid production rates. In case of mixed substrates, diauxic growth was observed where consumption of glucose and xylose occurred subsequently. Sugar consumption rate and lactic acid production rate were significantly higher during glucose consumption phase compared to xylose consumption phase. Available xylose (10.3 g l−1) and glucose (19.2 g l−1) present in a mild-temperature alkaline treated wheat straw hydrolysate was converted subsequently by R. oryzae with rates of 2.2 g glucose l−1 h−1 and 0.5 g xylose l−1 h−1. This resulted mainly into the product lactic acid (6.8 g l−1) and ethanol (5.7 g l−1). 相似文献
16.
Batch fermentations for xylitol production were conducted using Candida boidinii (BCRC 21432), C. guilliermondii (BCRC 21549), C. tropicalis (BCRC 20520), C. utilis (BCRC 20334), and P. anomala (BCRC 21359) together with a mixture of sugars simulating lignocellulosic hydrolysates as the carbon source. C. tropicalis had the highest bioconversion yield (YP/S) of 0.79 g g−1 (g xylitol·g xylose−1) over 48 h. Additional fermentations with C. tropicalis achieved YP/S values of 0.6 and 0.39 g g−1 after 96 and 72 h using urea and soybean meal as the nitrogen sources, respectively. Ethanol and arabitol were also produced
in all fermentation. Xylitol in the fermentation broth was recovered by cross-flow ultrafiltration. With prior application
of 2 mg polydiallyl dimethylammonium chloride l−1 on the membrane surface, protein in the permeate was reduced from 7.1 to 1.5 mg l−1 after 2 h. 相似文献
17.
Yang Guo Qiaojuan Yan Zhengqiang Jiang Chao Teng Xinlei Wang 《Journal of industrial microbiology & biotechnology》2010,37(11):1137-1143
The aim of this study is to investigate production of l-lactic acid from sucrose and corncob hydrolysate by the newly isolated R. oryzae GY18. R. oryzae GY18 was capable of utilizing sucrose as a sole source, producing 97.5 g l−1
l-lactic acid from 120 g l−1 sucrose. In addition, the strain was also efficiently able to utilize glucose and/or xylose to produce high yields of l-lactic acid. It was capable of producing up to 115 and 54.2 g l−1 lactic acid with yields of up to 0.81 g g−1 glucose and 0.90 g g−1 xylose, respectively. Corncob hydrolysates obtained by dilute acid hydrolysis and enzymatic hydrolysis of the cellulose-enriched
residue were used for lactic acid production by R. oryzae GY18. A yield of 355 g lactic acid per kg corncobs was obtained after 72 h incubation. Therefore, sucrose and corncobs could
serve as potential sources of raw materials for efficient production of lactic acid by R. oryzae GY18. 相似文献
18.
Eleonora Winkelhausen Ruzica Jovanovic-Malinovska Slobodanka Kuzmanova Maja Cvetkovska Christo Tsvetanov 《World journal of microbiology & biotechnology》2008,24(10):2035-2043
Hydrogels based on high molecular weight poly(ethylene oxide) were synthesized by u.v.-irradiation of aqueous solutions in
presence of the photoinitiator, (4-benzoylbenzyl)trimethylammonium chloride and different crosslinkers, poly(ethylene glycol),
diacrylates and N,N′-methylenebisacrylamide. Candida boidinii cells were immobilized in these hydrogels and the gels were characterized in regards to gel fraction yield, degree of equilibrium
swelling, shear storage and loss moduli. In addition, the number average molecular weight between crosslinks and the mesh
size were estimated. The incorporated yeast cells considerably affected the viscoelastic properties of the gels. Immobilized
C. boidinii cells were used for conversion of xylose to xylitol. Of the immobilized systems tested, only the system with poly(ethylene
oxide) crosslinked with N,N′-methylenebisacrylamide exhibited xylitol production. The operational stability of this system was evaluated by seven repeated-batch
runs performed in Erlenmeyer flasks in duration of 55 days. The progressive improvement of xylose consumption, up to 73.5%,
stopped in the fifth cycle, after which it dropped to 42.7%. Although xylitol concentration never reached more than 4.2 g l−1, xylitol was produced in each of the seven cycles. The cell leakage of 1.8 g l−1 during the first 45 days, indicated very good stability of the system. 相似文献
19.
M G A Felipe M Vitolo I M Mancilha S S Silva 《Journal of industrial microbiology & biotechnology》1997,18(4):251-254
The bioconversion of xylose to xylitol by Candida guilliermondii FTI 20037 cultivated in sugar cane bagasse hemicellulosic hydrolyzate was influenced by cell inoculum level, age of inoculum
and hydrolyzate concentration. The maximum xylitol productivity (0.75 g L−1 h−1) occurred in tests carried out with hydrolyzate containing 54.5 g L−1 of xylose, using 3.0 g L−1 of a 24-h-old inoculum. Xylitol productivity and cell concentration decreased with hydrolyzate containing 74.2 g L−1 of xylose.
Received 02 February 1996/ Accepted in revised form 15 November 1996 相似文献
20.
Candida peltata NRRL Y-6888 to ferment xylose to xylitol was evaluated under different fermentation conditions such as pH, temperature, aeration,
substrate concentration and in the presence of glucose, arabinose, ethanol, methanol and organic acids. Maximum xylitol yield
of 0.56 g g−1 xylose was obtained when the yeast was cultivated at pH 6.0, 28°C and 200 rpm on 50 g L−1 xylose. The yeast produced ethanol (0.41 g g−1 in 40 h) from glucose (50 g L−1) and arabitol (0.55 g g−1 in 87 h) from arabinose (50 g L−1). It preferentially utilized glucose > xylose > arabinose from mixed substrates. Glucose (10 g L−1), ethanol (7.5 g L−1) and acetate (5 g L−1) inhibited xylitol production by 61, 84 and 68%, respectively. Arabinose (10 g L−1) had no inhibitory effect on xylitol production.
Received 24 December 1998/ Accepted in revised form 18 March 1999 相似文献