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1.
Lima LH das Graças de Almeida Felipe M Vitolo M Torres FA 《Applied microbiology and biotechnology》2004,65(6):734-738
The first two steps in xylose metabolism are catalyzed by NAD(P)H-dependent xylose reductase (XR) (EC 1.1.1.21) and NAD(P)-dependent xylitol dehydrogenase (XDH) (EC 1.1.1.9), which lead to xylosexylitolxylulose conversion. Xylitol has high commercial value, due to its sweetening and anticariogenic properties, as well as several clinical applications. The acid hydrolysis of sugarcane bagasse allows the separation of a xylose-rich hemicellulosic fraction that can be used as a substrate for Candida guilliermondii to produce xylitol. However, the hydrolysate contains acetic acid, an inhibitor of microbial metabolism. In this study, the effect of acetic acid on the activities of XR and XDH and on xylitol formation by C. guilliermondii were studied. For this purpose, fermentations were carried out in bagasse hydrolysate and in synthetic medium. The activities of XR and XDH were higher in the medium containing acetic acid than in control medium. Moreover, none of the fermentative parameters were significantly altered during cell culture. It was concluded that acetic acid does not interfere with xylitol formation since the increase in XR activity is proportional to XDH activity, leading to a greater production of xylitol and its subsequent conversion to xylulose. 相似文献
2.
Priscila Vaz de Arruda Rita de Cássia Lacerda Brambilla Rodrigues Débora Danielle Virgínio da Silva Maria das Graças de Almeida Felipe 《Biodegradation》2011,22(4):815-822
The evaluation of hexose and pentose in pre-cultivation of Candida guilliermondii FTI 20037 yeast on xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes activities was performed during fermentation in sugarcane bagasse hemicellulosic hydrolysate. The xylitol production was evaluated by using cells previously growth in 30.0 gl?1 xylose, 30.0 gl?1 glucose and in both sugars mixture (30.0 gl?1 xylose and 2.0 gl?1 glucose). The vacuum evaporated hydrolysate (80 gl?1) was detoxificated by ion exchange resin (A-860S; A500PS and C-150-Purolite®). The total phenolic compounds and acetic acid were 93.0 and 64.9%, respectively, removed by the resin hydrolysate treatment. All experiments were carried out in Erlenmeyer flasks at 200 rpm, 30°C. The maximum XR (0.618 Umg Prot ?1 ) and XDH (0.783 Umg Prot ?1 ) enzymes activities was obtained using inoculum previously growth in both sugars mixture. The highest cell concentration (10.6 gl?1) was obtained with inoculum pre-cultivated in the glucose. However, the xylitol yield and xylitol volumetric productivity were favored using the xylose as carbon source. In this case, it was observed maximum xylose (81%) and acetic acid (100%) consumption. It is very important to point out that maximum enzymatic activities were obtained when the mixture of sugars was used as carbon source of inoculum, while the highest fermentative parameters were obtained when xylose was used. 相似文献
3.
This paper evaluates the fermentative potential of Kluyveromyces marxianus grown in sugarcane bagasse cellulosic and hemicellulosic hydrolysates obtained by acid hydrolysis. Ethanol was obtained from a single glucose fermentation product, whereas xylose assimilation resulted in xylitol as the main product and ethanol as a by-product derived from the metabolism of this pentose. Fermentation performed in a simulated hydrolysate medium with a glucose concentration similar to that of the hydrolysate resulted in ethanol productivity (Qp?=?0.86 g L?1 h?1) that was tenfold higher than the one observed in the cellulosic hydrolysate. However, the use of hemicellulosic hydrolysate favored xylose assimilation in comparison with simulated medium with xylose and glucose concentrations similar to those found in this hydrolysate, without toxic compounds such as acetic acid and phenols. Under this condition, xylitol yield was 53.8 % higher in relation to simulated medium. Thus, the total removal of toxic compounds from the hydrolysate is not necessary to obtain bioproducts from lignocellulosic hydrolysates. 相似文献
4.
Mário A. Alves da Cunha Attilio Converti Júlio C. dos Santos Silvio S. da Silva 《World journal of microbiology & biotechnology》2006,22(1):65-72
Summary A new PVA-hydrogel matrix for yeast cell immobilization for xylitol bioproduction from sugarcane bagasse was studied. Five
repeated-batch fermentation runs were carried out in medium based on sugarcane bagasse hemicellulosic hydrolysate with reuse
of the entrapped biocatalyst. The system performance as well as the metabolic behaviour of cells entrapped into the matrix
were evaluated. The biocatalyst remained stable and exhibited a similar fermentative profile in all the successive batches,
demonstrating the viability of the system. At the end of the run, an average xylitol production was observed of 35.1 g l−1 and average xylitol yield and productivity of 0.58 g g−1 and 0.49 g l−1 h−1, respectively. 相似文献
5.
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
6.
M. Walfridsson M. Anderlund X. Bao B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1997,48(2):218-224
Saccharomyces cerevisiae was transformed with the Pichia stipitis CBS 6054 XYL1 and XYL2 genes encoding xylose reductase (XR) and xylitol dehydrogenase (XDH) respectively. The XYL1 and XYL2 genes were placed under the control of the alcohol dehydrogenase 1 (ADH1) and phosphoglycerate kinase (PGK1) promoters in the yeast vector YEp24. Different vector constructions were made resulting in different specific activities
of XR and XDH. The XR:XDH ratio (ratio of specific enzyme activities) of the transformed S. cerevisiae strains varied from 17.5 to 0.06. In order to enhance xylose utilisation in the XYL1-, XYL2-containing S. cerevisiae strains, the native genes encoding transketolase and transaldolase were also overexpressed. A strain with an XR:XDH ratio
of 17.5 formed 0.82 g xylitol/g consumed xylose, whereas a strain with an XR:XDH ratio of 5.0 formed 0.58 g xylitol/g xylose.
The strain with an XR:XDH ratio of 0.06, on the other hand, formed no xylitol and less glycerol and acetic acid compared with
strains with the higher XR:XDH ratios. In addition, the strain with an XR:XDH ratio of 0.06 produced more ethanol than the
other strains.
Received: 12 March 1997 / Received revision: 17 April 1997 / Accepted: 27 April 1997 相似文献
7.
Matsushika A Watanabe S Kodaki T Makino K Inoue H Murakami K Takimura O Sawayama S 《Applied microbiology and biotechnology》2008,81(2):243-255
A recombinant Saccharomyces cerevisiae strain transformed with xylose reductase (XR) and xylitol dehydrogenase (XDH) genes from Pichia stipitis has the ability to convert xylose to ethanol together with the unfavorable excretion of xylitol, which may be due to cofactor
imbalance between NADPH-preferring XR and NAD+-dependent XDH. To reduce xylitol formation, we have already generated several XDH mutants with a reversal of coenzyme specificity
toward NADP+. In this study, we constructed a set of recombinant S. cerevisiae strains with xylose-fermenting ability, including protein-engineered NADP+-dependent XDH-expressing strains. The most positive effect on xylose-to-ethanol fermentation was found by using a strain
named MA-N5, constructed by chromosomal integration of the gene for NADP+-dependent XDH along with XR and endogenous xylulokinase genes. The MA-N5 strain had an increase in ethanol production and
decrease in xylitol excretion compared with the reference strain expressing wild-type XDH when fermenting not only xylose
but also mixed sugars containing glucose and xylose. Furthermore, the MA-N5 strain produced ethanol with a high yield of 0.49 g
of ethanol/g of total consumed sugars in the nonsulfuric acid hydrolysate of wood chips. The results demonstrate that glucose
and xylose present in the lignocellulosic hydrolysate can be efficiently fermented by this redox-engineered strain. 相似文献
8.
Xylitol production from corn fiber and sugarcane bagasse hydrolysates by Candida tropicalis 总被引:4,自引:0,他引:4
A natural isolate, Candida tropicalis was tested for xylitol production from corn fiber and sugarcane bagasse hydrolysates. Fermentation of corn fiber and sugarcane bagasse hydrolysate showed xylose uptake and xylitol production, though these were very low, even after hydrolysate neutralization and treatments with activated charcoal and ion exchange resins. Initial xylitol production was found to be 0.43 g/g and 0.45 g/g of xylose utilised with corn fiber and sugarcane bagasse hydrolysate respectively. One of the critical factors for low xylitol production was the presence of inhibitors in these hydrolysates. To simulate influence of hemicellulosic sugar composition on xylitol yield, three different combinations of mixed sugar control experiments, without the presence of any inhibitors, have been performed and the strain produced 0.63 g/g, 0.68 g/g and 0.72 g/g of xylose respectively. To improve yeast growth and xylitol production with these hydrolysates, which contain inhibitors, the cells were adapted by sub culturing in the hydrolysate containing medium for 25 cycles. After adaptation the organism produced more xylitol 0.58 g/g and 0.65 g/g of xylose with corn fiber hydrolysate and sugarcane bagasse hydrolysate respectively. 相似文献
9.
Background
Metabolic engineering of Saccharomyces cerevisiae for xylose fermentation into fuel ethanol has oftentimes relied on insertion of a heterologous pathway that consists of xylose reductase (XR) and xylitol dehydrogenase (XDH) and brings about isomerization of xylose into xylulose via xylitol. Incomplete recycling of redox cosubstrates in the catalytic steps of the NADPH-preferring XR and the NAD+-dependent XDH results in formation of xylitol by-product and hence in lowering of the overall yield of ethanol on xylose. Structure-guided site-directed mutagenesis was previously employed to change the coenzyme preference of Candida tenuis XR about 170-fold from NADPH in the wild-type to NADH in a Lys274→Arg Asn276→Asp double mutant which in spite of the structural modifications introduced had retained the original catalytic efficiency for reduction of xylose by NADH. This work was carried out to assess physiological consequences in xylose-fermenting S. cerevisiae resulting from a well defined alteration of XR cosubstrate specificity. 相似文献10.
Cristina Martini Sâmia Maria Tauk-Tornisielo Carolina Brito Codato Reinaldo Gaspar Bastos Sandra Regina Ceccato-Antonini 《World journal of microbiology & biotechnology》2016,32(5):80
The search for new microbial strains that are able to withstand inhibitors released from hemicellulosic hydrolysis and are also still able to convert sugars in ethanol/xylitol is highly desirable. A yeast strain isolated from sugarcane juice and identified as Meyerozyma guilliermondii was evaluated for the ability to grow and ferment pentoses in synthetic media and in sugarcane bagasse hydrolysate. The yeast grew in xylose, arabinose and glucose at the same rate at an initial medium pH of 5.5. At pH 4.5, the yeast grew more slowly in arabinose. There was no sugar exhaustion within 60 h. At higher xylose concentrations with a higher initial cell concentration, sugar was exhausted within 96 h at pH 4.5. An increase of 350 % in biomass was obtained in detoxified hydrolysates, whereas supplementation with 3 g/L yeast extract increased biomass production by approximately 40 %. Ethanol and xylitol were produced more significantly in supplemented hydrolysates regardless of detoxification. Xylose consumption was enhanced in supplemented hydrolysates and arabinose was consumed only when xylose and glucose were no longer available. Supplementation had a greater impact on ethanol yield and productivity than detoxification; however, the product yields obtained in the present study are still much lower when compared to other yeast species in bagasse hydrolysate. By the other hand, the fermentation of both xylose and arabinose and capability of withstanding inhibitors are important characteristics of the strain assayed. 相似文献
11.
The xylose conversion into by Candida guilliermondii was evaluated in sugar cane bagasse hemicellulosic hydrolysate. The effect of air flow rates of 0.4, 0.6 and 0.8 vvm cn xylitol formation was studied. In addition, inoculum previously adapted to the hydrolysate was also tested in the fermentation carried out at 0.6 vvm. The results showed that xylitol production depends markedly on the aeration rate and on the previous adaptation of the yeast to the hydrolysate. When the highest productivity of xylitol was 0.39 g/l × h. However, during the fermentation carried out at an air flow rate of 0.6 vvm with adapted inoculum, the productivity increased to 0.65 g/l × h. Furthermore, the adapted cells performed quite well in the presencel of acetic concentrations of about 4.5 g/l in the medium. 相似文献
12.
Evaluation of xylitol production from corn cob hemicellulose hydrolysate by Candida parapsilosis 总被引:3,自引:0,他引:3
Candida parapsilosis was grown for 59 h in a medium containing corn cob hydrolysate consisting of 50 g xylose l–1, 3.0 g glucose l–1, 2.0 g arabinose l–1, and 0.9 g acetic acid l–1. A biomass of 9.1 g l–1 was produced with 36 g xylitol l–1 and 2.5 g ethanol l–1. In a medium containing 50 g xylose l–1 instead of corn cob hydrolysate, the concentrations of cells, xylitol, and ethanol were 8.6 g l–1, 33 g l–1, and 0.2 g l–1, respectively. The differences between two cultures were due to the glucose and arabinose in the corn cob hydrolysate stimulating growth and the low concentration of acetic acid stimulating xylitol production. 相似文献
13.
Raquel M. Cadete Monaliza A. Melo-Cheab Adriana L. Viana Evelyn S. Oliveira César Fonseca Carlos A. Rosa 《World journal of microbiology & biotechnology》2016,32(12):207
This study assessed the efficiency of Scheffersomyces amazonensis UFMG-CM-Y493T, cultured in xylose-supplemented medium (YPX) and rice hull hydrolysate (RHH), to convert xylose to xylitol under moderate and severe oxygen limitation. The highest xylitol yields of 0.75 and 1.04 g g?1 in YPX and RHH, respectively, were obtained under severe oxygen limitation. However, volumetric productivity in RHH was ninefold decrease than that in YPX medium. The xylose reductase (XR) and xylitol dehydrogenase (XDH) activities in the YPX cultures were strictly dependent on NADPH and NAD+ respectively, and were approximately 10% higher under severe oxygen limitation than under moderate oxygen limitation. This higher xylitol production observed under severe oxygen limitation can be attributed to the higher XR activity and shortage of the NAD+ needed by XDH. These results suggest that Sc. amazonensis UFMG-CM-Y493T is one of the greatest xylitol producers described to date and reveal its potential use in the biotechnological production of xylitol. 相似文献
14.
A central composite experimental design leading to a set of 16 experiments with different combinations of pH and temperature was performed to attain the optimal activities of xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes from Candida mogii cell extract. Under optimized conditions (pH 6.5 and 38°C), the XR and XDH activities were found to be 0.48 U/ml and 0.22 U/ml, respectively, resulting in an XR to XDH ratio of 2.2. Stability, cofactor specificity and kinetic parameters of the enzyme XR were also evaluated. XR activity remained stable for 3 h under 4 and 38°C and for 4 months of storage at −18°C. Studies on cofactor specificity showed that only NADPH-dependent XR was obtained under the cultivation conditions employed. The XR present in C. mogii extracts showed a superior K
m value for xylose when compared with other yeast strains. Besides, this parameter was not modified after enzyme extraction by aqueous two-phase system. 相似文献
15.
Oskar Bengtsson Bärbel Hahn-Hägerdal Marie F Gorwa-Grauslund 《Biotechnology for biofuels》2009,2(1):9-10
Background
Xylose reductase (XR) and xylitol dehydrogenase (XDH) from Pichia stipitis are the two enzymes most commonly used in recombinant Saccharomyces cerevisiae strains engineered for xylose utilization. The availability of NAD+ for XDH is limited during anaerobic xylose fermentation because of the preference of XR for NADPH. This in turn results in xylitol formation and reduced ethanol yield. The coenzyme preference of P. stipitis XR was changed by site-directed mutagenesis with the aim to engineer it towards NADH-preference. 相似文献16.
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
17.
Efficient conversion of hexose and pentose (glucose and xylose) by a single strain is a very important factor for the production
of industrially important metabolites using lignocellulose as the substrate. The kinetics of growth and polyol production
by Debaryomyces nepalensis NCYC 3413 was studied under single and mixed substrate conditions. In the presence of glucose, the strain produced ethanol
(35.8 ± 2.3 g/l), glycerol (9.0 ± 0.2 g/l), and arabitol (6.3 ± 0.2 g/l). In the presence of xylose, the strain produced xylitol
(38 ± 1.8 g/l) and glycerol (18 ± 1.0 g/l) as major metabolites. Diauxic growth was observed when the strain was grown with
different combinations of glucose/xylose, and glucose was the preferred substrate. The presence of glucose enhanced the conversion
of xylose to xylitol. By feeding a mixture of glucose at 100 g/l and xylose at 100 g/l, it was found that the strain produced
a maximum of 72 ± 3 g/l of xylitol. A study of important enzymes involved in the synthesis of xylitol (xylose reductase (XR)
and xylitol dehydrogenase (XDH)), glycerol (glycerol-3-phosphate dehydrogenase (G3PDH)) and ethanol (alcohol dehydrogenase
(ADH)) in cells grown in the presence of glucose and xylose revealed high specific activity of G3PDH and ADH in cells grown
in the presence of glucose, whereas high specific activity of XR, XDH, and G3PDH was observed in cells grown in the presence
of xylose. To our knowledge, this is the first study to elaborate the glucose and xylose metabolic pathway in this yeast strain. 相似文献
18.
Metabolic engineering of Saccharomyces cerevisiae for xylose fermentation has often relied on insertion of a heterologous pathway consisting of nicotinamide adenine dinucleotide (phosphate) NAD(P)H-dependent xylose reductase (XR) and NAD+-dependent xylitol dehydrogenase (XDH). Low ethanol yield, formation of xylitol and other fermentation by-products are seen for many of the S. cerevisiae strains constructed in this way. This has been ascribed to incomplete coenzyme recycling in the steps catalyzed by XR and XDH. Despite various protein-engineering efforts to alter the coenzyme specificity of XR and XDH individually, a pair of enzymes displaying matched utilization of NAD(H) and NADP(H) was not previously reported. We have introduced multiple site-directed mutations in the coenzyme-binding pocket of Galactocandida mastotermitis XDH to enable activity with NADP+, which is lacking in the wild-type enzyme. We describe four enzyme variants showing activity for xylitol oxidation by NADP+ and NAD+. One of the XDH variants utilized NADP+ about 4 times more efficiently than NAD+. This is close to the preference for NADPH compared with NADH in mutants of Candida tenuis XR. Compared to an S. cerevisiae-reference strain expressing the genes for the wild-type enzymes, the strains comprising the gene encoding the mutated XDH in combination a matched XR mutant gene showed up to 50% decreased glycerol yield without increase in ethanol during xylose fermentation. 相似文献
19.
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
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