共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Effect of glucose on xylose utilization in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> harboring the xylose reductase gene 总被引:1,自引:0,他引:1
We have constructed recombinant Saccharomyces cerevisiae JH1 harboring a xylose reductase gene (xyl1) isolated from Pichia stipitis. However, JH1 still utilizes glucose more easily than xylose. Therefore, in this study, we characterized the effect of a
glucose supplement on xylose utilization, the expression level of xylose reductase as a recombinant gene in JH1, and the expression
levels of two hexose transporters (Hxt4 and Hxt7) due to co-fermentation of different concentrations of glucose and xylose.
Co-fermentation using 20 g/l of glucose increased xylose consumption up to 11.7 g/l, which was 7.9-fold that of xylose fermentation
without a glucose supplement. In addition, we found xyl1 mRNA levels dramatically increased as cells grew under co-fermentation conditions with supplementary glucose; this result
is consistent with a significant decrease in the xylose concentration 48 h after cultivation. In addition, the expression
levels of Hxt4 and Hxt7 were strongly activated by the presence of glucose and xylose; in particular, Hxt7 showed a 2.9-fold
increased expression relative to that of recombinant S. cerevisiae JHM with only a backbone vector, pYES2. The results of this study suggest that xylose utilization would be improved by activation
of hexose transporters induced by glucose (rather than xylose) reductase expression. 相似文献
3.
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
4.
Novel additives that act as substratum for attachment of the yeast cells, increased ethanol production in Saccharomyces cerevisiae. The addition of 2 g rice husk, straw, wood shavings, plastic pieces or silica gel to 100 ml medium enhanced ethanol production by 30–40 (v/v). Six distillery strains showed an average enhancement of 34 from 4.1 (v/v) in control to 5.5 (v/v) on addition of rice husk. The cell wall bound glycogen increased by 40–50 mg g –1 dry yeast while intracellular glycogen decreased by 10–12 mg g–1 dry yeast in cells grown in presence of substratum 相似文献
5.
The goal of this investigation was to determine the effect of a xylose transport system on glucose and xylose co-consumption as well as total xylose consumption in Saccharomyces cerevisiae. We expressed two heterologous transporters from Arabidopsis thaliana in recombinant xylose-utilizing S. cerevisiae cells. Strains expressing the heterologous transporters were grown on glucose and xylose mixtures. Sugar consumption rates and ethanol concentrations were determined and compared to an isogenic control strain lacking the A. thaliana transporters. Expression of the transporters increased xylose uptake and xylose consumption up to 46% and 40%, respectively. Xylose co-consumption rates (prior to glucose depletion) were also increased by up to 2.5-fold compared to the control strain. Increased xylose consumption correlated with increased ethanol concentration and productivity. During the xylose/glucose co-consumption phase, strains expressing the transporters had up to a 70% increase in ethanol production rate. It was concluded that in these strains, xylose transport was a limiting factor for xylose utilization and that increasing xylose/glucose co-consumption is a viable strategy for improving xylose fermentation. 相似文献
6.
Yoshida H Hara KY Kiriyama K Nakayama H Okazaki F Matsuda F Ogino C Fukuda H Kondo A 《Applied microbiology and biotechnology》2011,91(4):1001-1006
We developed a novel enzymatic glutathione (GSH) production system using Saccharomyces cerevisiae as a whole-cell biocatalyst, and improved its GSH productivity by metabolic engineering. We demonstrated that the metabolic
engineering of GSH pathway and ATP regeneration can significantly improve GSH productivity by up to 1.7-fold higher compared
with the parental strain, respectively. Furthermore, the combination of both improvements in GSH pathway and ATP regeneration
is more effective (2.6-fold) than either improvement individually for GSH enzymatic production using yeast. The improved whole-cell
biocatalyst indicates its great potential for applications to other kinds of ATP-dependent bioproduction. 相似文献
7.
8.
M. J. Mert S. H. Rose D. C. la Grange T. Bamba T. Hasunuma A. Kondo W. H. van Zyl 《Journal of industrial microbiology & biotechnology》2017,44(10):1459-1470
The yeast Saccharomyces cerevisiae cannot utilize xylose, but the introduction of a xylose isomerase that functions well in yeast will help overcome the limitations of the fungal oxido-reductive pathway. In this study, a diploid S. cerevisiae S288c[2n YMX12] strain was constructed expressing the Bacteroides thetaiotaomicron xylA (XI) and the Scheffersomyces stipitis xyl3 (XK) and the changes in the metabolite pools monitored over time. Cultivation on xylose generally resulted in gradual changes in metabolite pool size over time, whereas more dramatic fluctuations were observed with cultivation on glucose due to the diauxic growth pattern. The low G6P and F1,6P levels observed with cultivation on xylose resulted in the incomplete activation of the Crabtree effect, whereas the high PEP levels is indicative of carbon starvation. The high UDP-d-glucose levels with cultivation on xylose indicated that the carbon was channeled toward biomass production. The adenylate and guanylate energy charges were tightly regulated by the cultures, while the catabolic and anabolic reduction charges fluctuated between metabolic states. This study helped elucidate the metabolite distribution that takes place under Crabtree-positive and Crabtree-negative conditions when cultivating S. cerevisiae on glucose and xylose, respectively. 相似文献
9.
Karhumaa K Fromanger R Hahn-Hägerdal B Gorwa-Grauslund MF 《Applied microbiology and biotechnology》2007,73(5):1039-1046
Xylose fermentation performance was studied of a previously developed Saccharomyces cerevisiae strain TMB 3057, carrying high xylose reductase (XR) and xylitol dehydrogenase (XDH) activity, overexpressed non-oxidative
pentose phosphate pathway (PPP) and deletion of the aldose reductase gene GRE3. The fermentation performance of TMB 3057 was significantly improved by increased ethanol production and reduced xylitol
formation compared with the reference strain TMB 3001. The effects of the individual genetic modifications on xylose fermentation
were investigated by comparing five isogenic strains with single or combined modifications. All strains with high activity
of both XR and XDH had increased ethanol yields and significantly decreased xylitol yields. The presence of glucose further
reduced xylitol formation in all studied strains. High activity of the non-oxidative PPP improved the xylose consumption rate.
The results indicate that ethanolic xylose fermentation by recombinant S. cerevisiae expressing XR and XDH is governed by the efficiency by which xylose is introduced in the central metabolism. 相似文献
10.
Background
The NAD(P)H-dependent Pichia stipitis xylose reductase (PsXR) is one of the key enzymes for xylose fermentation, and has been cloned into the commonly used ethanol-producing yeast Saccharomyces cerevisiae. In order to eliminate the redox imbalance resulting from the preference of this enzyme toward NADPH, efforts have been made to alter the coenzyme specificity of PsXR by site-directed mutagenesis, with limited success. Given the industrial importance of PsXR, it is of interest to investigate further ways to create mutants of PsXR that prefers NADH rather than NADPH, by the alternative directed evolution approach. 相似文献11.
Ethanol production by Clostridium thermocellum ATCC 35609 and Saccharomyces cerevisiae ATCC 26603 was improved in an electrochemical bioreactor system. It was increased by 61% with Cl. thermocellum and 12% with S. cerevisiae in the presence of -1.5 V of electric potential. These increases were attributed to high production rates due to regeneration and availability of increased reduced equivalents in the presence of electric potential. The electric current caused considerable shift in the metabolite concentrations on a molar basis in Cl. thermocellum fermentation but less in S. cerevisiae fermentation. Increasing electric potential in Cl. thermocellum fermentation resulted in less acetate and more lactate production. Acetate production was also reduced with increased electric potential in S. cerevisiae fermentation. The high electric potential of -5 V adversely affected the Cl. thermocellum fermentation, but not the S. cerevisiae fermentation even at a high electric potential of -10 V. 相似文献
12.
Jinxin Zhang Min Yang Shen Tian Yazhen Zhang Xiushan Yang 《Applied Biochemistry and Microbiology》2010,46(4):415-420
The inability oft Saccharomyces cerevisiae to utilize xylose is attributed to its inability to convert xylose to xylulose. Low xylose reductase (XR) and xylitol dehydrogenase
(XDH) activities in S. cerevisiae are regarded as the reason of blocking the pathway from xylose to xylulose. We had found that Candida shehatae could also be another source for XR gene except Pichia stipitis in the previous study. In this study, we tried to investigate if the expressed XR from C. shehatae could work with the over-expressed endogenous XDH together to achieve the same goal of converting xylose to ethanol in S. cerevisiae. The XR gene (XYL1) from C. shehatae and endogenous XDH gene (XYL2) were both cloned and over-expressed in host S. cerevisiae cell. The specific enzyme activities of XR and XDH were measured and the result of fermentation revealed that the new combination
of two enzymes from different sources other than P. stipitis could also coordinate and work with each other and confer xylose utilization ability to S. cerevisiae. 相似文献
13.
Stefan Krahulec Barbara Petschacher Michael Wallner Karin Longus Mario Klimacek Bernd Nidetzky 《Microbial cell factories》2010,9(1):16
Background
In spite of the substantial metabolic engineering effort previously devoted to the development of Saccharomyces cerevisiae strains capable of fermenting both the hexose and pentose sugars present in lignocellulose hydrolysates, the productivity of reported strains for conversion of the naturally most abundant pentose, xylose, is still a major issue of process efficiency. Protein engineering for targeted alteration of the nicotinamide cofactor specificity of enzymes catalyzing the first steps in the metabolic pathway for xylose was a successful approach of reducing xylitol by-product formation and improving ethanol yield from xylose. The previously reported yeast strain BP10001, which expresses heterologous xylose reductase from Candida tenuis in mutated (NADH-preferring) form, stands for a series of other yeast strains designed with similar rational. Using 20 g/L xylose as sole source of carbon, BP10001 displayed a low specific uptake rate q xylose (g xylose/g dry cell weight/h) of 0.08. The study presented herein was performed with the aim of analysing (external) factors that limit q xylose of BP10001 under xylose-only and mixed glucose-xylose substrate conditions. We also carried out a comprehensive investigation on the currently unclear role of coenzyme utilization, NADPH compared to NADH, for xylose reduction during co-fermentation of glucose and xylose. 相似文献14.
Efficient fermentation of xylose, which is abundant in hydrolysates of lignocellulosic biomass, is essential for producing
cellulosic biofuels economically. While heterologous expression of xylose isomerase in Saccharomyces cerevisiae has been proposed as a strategy to engineer this yeast for xylose fermentation, only a few xylose isomerase genes from fungi
and bacteria have been functionally expressed in S. cerevisiae. We cloned two bacterial xylose isomerase genes from anaerobic bacteria (Bacteroides stercoris HJ-15 and Bifidobacterium longum MG1) and introduced them into S. cerevisiae. While the transformant with xylA from B. longum could not assimilate xylose, the transformant with xylA from B. stercoris was able to grow on xylose. This result suggests that the xylose isomerase (BsXI) from B. stercoris is functionally expressed in S. cerevisiae. The engineered S. cerevisiae strain with BsXI consumed xylose and produced ethanol with a good yield (0.31 g/g) under anaerobic conditions. Interestingly, significant
amounts of xylitol (0.23 g xylitol/g xylose) were still accumulated during xylose fermentation even though the introduced
BsXI might not cause redox imbalance. We investigated the potential inhibitory effects of the accumulated xylitol on xylose fermentation.
Although xylitol inhibited in vitro BsXI activity significantly (K
I = 5.1 ± 1.15 mM), only small decreases (less than 10%) in xylose consumption and ethanol production rates were observed when
xylitol was added into the fermentation medium. These results suggest that xylitol accumulation does not inhibit xylose fermentation
by engineered S. cerevisiae expressing xylA as severely as it inhibits the xylose isomerase reaction in vitro. 相似文献
15.
Jin Hou Goutham N. Vemuri Xiaoming Bao Lisbeth Olsson 《Applied microbiology and biotechnology》2009,82(5):909-919
During growth of Saccharomyces cerevisiae on glucose, the redox cofactors NADH and NADPH are predominantly involved in catabolism and biosynthesis, respectively. A
deviation from the optimal level of these cofactors often results in major changes in the substrate uptake and biomass formation.
However, the metabolism of xylose by recombinant S. cerevisiae carrying xylose reductase and xylitol dehydrogenase from the fungal pathway requires both NADH and NADPH and creates cofactor
imbalance during growth on xylose. As one possible solution to overcoming this imbalance, the effect of overexpressing the
native NADH kinase (encoded by the POS5 gene) in xylose-consuming recombinant S. cerevisiae directed either into the cytosol or to the mitochondria was evaluated. The physiology of the NADH kinase containing strains
was also evaluated during growth on glucose. Overexpressing NADH kinase in the cytosol redirected carbon flow from CO2 to ethanol during aerobic growth on glucose and to ethanol and acetate during anaerobic growth on glucose. However, cytosolic
NADH kinase has an opposite effect during anaerobic metabolism of xylose consumption by channeling carbon flow from ethanol
to xylitol. In contrast, overexpressing NADH kinase in the mitochondria did not affect the physiology to a large extent. Overall,
although NADH kinase did not increase the rate of xylose consumption, we believe that it can provide an important source of
NADPH in yeast, which can be useful for metabolic engineering strategies where the redox fluxes are manipulated. 相似文献
16.
Fernanda Badotti Marcelo G Dário Sergio L AlvesJr Maria Luiza A Cordioli Luiz C Miletti Pedro S de Araujo Boris U Stambuk 《Microbial cell factories》2008,7(1):4
Background
Overflow metabolism is an undesirable characteristic of aerobic cultures of Saccharomyces cerevisiae during biomass-directed processes. It results from elevated sugar consumption rates that cause a high substrate conversion to ethanol and other bi-products, severely affecting cell physiology, bioprocess performance, and biomass yields. Fed-batch culture, where sucrose consumption rates are controlled by the external addition of sugar aiming at its low concentrations in the fermentor, is the classical bioprocessing alternative to prevent sugar fermentation by yeasts. However, fed-batch fermentations present drawbacks that could be overcome by simpler batch cultures at relatively high (e.g. 20 g/L) initial sugar concentrations. In this study, a S. cerevisiae strain lacking invertase activity was engineered to transport sucrose into the cells through a low-affinity and low-capacity sucrose-H+ symport activity, and the growth kinetics and biomass yields on sucrose analyzed using simple batch cultures. 相似文献17.
Nehme N Mathieu F Taillandier P 《Journal of industrial microbiology & biotechnology》2008,35(7):685-693
This study examines the interactions that occur between Saccharomyces cerevisiae and Oenococcus oeni strains during the process of winemaking. Various yeast/bacteria pairs were studied by applying a sequential fermentation strategy which simulated the natural winemaking process. First, four yeast strains were tested in the presence of one bacterial strain leading to the inhibition of the bacterial component. The extent of inhibition varied widely from one pair to another and closely depended on the specific yeast strain chosen. Inhibition was correlated to weak bacterial growth rather than a reduction in the bacterial malolactic activity. Three of the four yeast strains were then grown with another bacteria strain. Contrary to the first results, this led to the bacterial stimulation, thus highlighting the importance of the bacteria strain. The biochemical profile of the four yeast fermented media exhibited slight variations in ethanol, SO(2) and fatty acids produced as well as assimilable consumed nitrogen. These parameters were not the only factors responsible for the malolactic fermentation inhibition observed with the first bacteria strain. The stimulation of the second has not been reported before in such conditions and remains unexplained. 相似文献
18.
19.
K. Parvathi R. Naresh Kumar R. Nagendran 《World journal of microbiology & biotechnology》2007,23(5):671-676
Summary Biosorption of manganese from its aqueous solution using yeast biomass Saccharomyces cerevisiae and fungal biomass Aspergillus niger was carried out. Manganese biosorption equilibration time for A. niger and S. cerevisiae were found to be 60 and 20 min, with uptakes of 19.34 and 18.95 mg/g, respectively. Biosorption increased with rise in pH,
biomass, and manganese concentration. The biosorption equilibrium data fitted with the Freundlich isotherm model revealed
that A. niger was a better biosorbent of manganese than S. cerevisiae. 相似文献
20.
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