共查询到20条相似文献,搜索用时 218 毫秒
1.
Zhou H Liao X Liu L Wang T Du G Chen J 《Journal of industrial microbiology & biotechnology》2011,38(9):1219-1227
The l-phenylalanine (l-Phe) production by Escherichia
coli WSH-Z06 (pAP-B03) was frequently prevented by bacteriophage BP-1 infestation. To cope with the bacteriophage BP-1 problem
for an improved l-Phe production, one bacteriophage BP-1-resistant mutant, E. coli BR-42, was obtained from 416 mutant colonies of E. coli WSH-Z06 after N-methyl-N’-nitro-N-nitrosoguanidine (NTG) mutagenesis by selection for resistance to bacteriophage BP-1. The recombinant E. coli BR-42-carrying plasmid pAP-B03 had a high capacity in l-Phe production and a remarkable tolerance to 1 × 1010 pfu (plaque-forming unit)/ml bacteriophage stock. For an enhanced l-Phe production by E. coli BR-42 (pAP-B03), the effects of different feeding strategies including pH–stat, constant rate feeding, linear decreasing
rate feeding, and exponential feeding on l-Phe production were investigated; and a two-stage feeding strategy, namely exponential feeding at μ
set = 0.18 h−1 in the first 20 h and a following linear varying rate feeding with F = (−0.55 × t + 18.6) ml/h, was developed to improve l-Phe production. With this two-stage feeding approach, a maximum l-Phe titer of 57.63 g/l with a high l-Phe productivity (1.15 g/l/h) was achieved, which was 15% higher than the highest level (50 g/l) reported so far according
to our knowledge. The recombinant E. coli BR-42 (pAP-B03) is a potential l-Phe over-producer in substantial prevention of bacteriophage BP-1 infestation compared to its parent strain WSH-Z06 (pAP-B03). 相似文献
2.
Yoshihiro Ojima Mizuho Komaki Motomu Nishioka Shintaro Iwatani Nobuharu Tsujimoto Masahito Taya 《Biotechnology letters》2009,31(4):525-530
A stress-responsive gene, yggG, was introduced into an l-phenylalanine producer, Escherichia coli AJ12741. In shake-flask culture, the yggG-containing recombinant strain (named AJ12741/pHYGG) produced 6.4 g l-phenylalanine l−1 at the end of culture and its yield on glucose was 0.16 g l-phenylalanine g glucose−1. These values are much higher than those of the original AJ12741 strain (3.7 g l-phenylalanine l−1 and 0.09 g l-phenylalanine g glucose−1, respectively). On the other hand, AJ12741/pHYGG strain produced only 4.5 g acetic acid l−1 and its yield on glucose was about a half of that of the AJ12741 culture. Analysis of gene expression revealed that in late
growth phase, the expression levels of genes involved in acetic acid production (pta, ackA, and poxB) were relatively low in AJ12741/pHYGG cells. In particular, the level of poxB expression in AJ12741/pHYGG strains was one-seventh of that of the original strain. These results suggest that the formation
of a bottleneck for acetic acid production brings about a metabolic flow favorable to l-phenylalanine synthesis in the recombinant strain over-expressing the yggG gene.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Muñoz AJ Hernández-Chávez G de Anda R Martínez A Bolívar F Gosset G 《Journal of industrial microbiology & biotechnology》2011,38(11):1845-1852
l-3,4-dihydroxyphenylalanine (l-DOPA) is an aromatic compound employed for the treatment of Parkinson's disease. Metabolic engineering was applied to generate
Escherichia coli strains for the production of l-DOPA from glucose by modifying the phosphoenolpyruvate:sugar phosphotransferase system (PTS) and aromatic biosynthetic pathways.
Carbon flow was directed to the biosynthesis of l-tyrosine (l-Tyr), an l-DOPA precursor, by transforming strains with compatible plasmids carrying genes encoding a feedback-inhibition resistant
version of 3-deoxy-d-arabino-heptulosonate-7-phosphate synthase, transketolase, the chorismate mutase domain from chorismate mutase-prephenate dehydratase
from E. coli and cyclohexadienyl dehydrogenase from Zymomonas mobilis. The effects on l-Tyr production of PTS inactivation (PTS− gluc+ phenotype), as well as inactivation of the regulatory protein TyrR, were evaluated. PTS inactivation caused a threefold increase
in the specific rate of l-Tyr production (q
l-Tyr), whereas inactivation of TyrR caused 1.7- and 1.9-fold increases in q
l-Tyr in the PTS+ and the PTS− gluc+ strains, respectively. An 8.6-fold increase in l-Tyr yield from glucose was observed in the PTS− gluc+
tyrR
− strain. Expression of hpaBC genes encoding the enzyme 4-hydroxyphenylacetate 3-hydroxylase from E. coli W in the strains modified for l-Tyr production caused the synthesis of l-DOPA. One of such strains, having the PTS− gluc+
tyrR
− phenotype, displayed the best production parameters in minimal medium, with a specific rate of l-DOPA production of 13.6 mg/g/h, l-DOPA yield from glucose of 51.7 mg/g and a final l-DOPA titer of 320 mg/l. In a batch fermentor culture in rich medium this strain produced 1.51 g/l of l-DOPA in 50 h. 相似文献
4.
5.
Kevin Michael Smith Kwang-Myung Cho James C. Liao 《Applied microbiology and biotechnology》2010,87(3):1045-1055
The production of isobutanol in microorganisms has recently been achieved by harnessing the highly active 2-keto acid pathways.
Since these 2-keto acids are precursors of amino acids, we aimed to construct an isobutanol production platform in Corynebacterium glutamicum, a well-known amino-acid-producing microorganism. Analysis of this host’s sensitivity to isobutanol toxicity revealed that
C. glutamicum shows an increased tolerance to isobutanol relative to Escherichia coli. Overexpression of alsS of Bacillus subtilis, ilvC and ilvD of C. glutamicum, kivd of Lactococcus lactis, and a native alcohol dehydrogenase, adhA, led to the production of 2.6 g/L isobutanol and 0.4 g/L 3-methyl-1-butanol in 48 h. In addition, other higher chain alcohols
such as 1-propanol, 2-methyl-1-butanol, 1-butanol, and 2-phenylethanol were also detected as byproducts. Using longer-term
batch cultures, isobutanol titers reached 4.0 g/L after 96 h with wild-type C. glutamicum as a host. Upon the inactivation of several genes to direct more carbon through the isobutanol pathway, we increased production
by ∼25% to 4.9 g/L isobutanol in a ∆pyc∆ldh background. These results show promise in engineering C. glutamicum for higher chain alcohol production using the 2-keto acid pathways. 相似文献
6.
7.
M. Helanto K. Kiviharju T. Granström M. Leisola A. Nyyssölä 《Applied microbiology and biotechnology》2009,83(1):77-83
l-Ribose is a rare and expensive sugar that can be used as a precursor for the production of l-nucleoside analogues, which are used as antiviral drugs. In this work, we describe a novel way of producing l-ribose from the readily available raw material l-arabinose. This was achieved by introducing l-ribose isomerase activity into l-ribulokinase-deficient Escherichia coli UP1110 and Lactobacillus plantarum BPT197 strains. The process for l-ribose production by resting cells was investigated. The initial l-ribose production rates at 39°C and pH 8 were 0.46 ± 0.01 g g−1 h−1 (1.84 ± 0.03 g l−1 h−1) and 0.27 ± 0.01 g g−1 h−1 (1.91 ± 0.1 g l−1 h−1) for E. coli and for L. plantarum, respectively. Conversions were around 20% at their highest in the experiments. Also partially purified protein precipitates
having both l-arabinose isomerase and l-ribose isomerase activity were successfully used for converting l-arabinose to l-ribose. 相似文献
8.
Brevibacterium flavum ATCC14067 was engineered for l-valine production by overexpression of different ilv genes; the ilvEBNrC genes from B. flavum NV128 provided the best candidate for l-valine production. In traditional fermentation, l-valine production reached 30.08 ± 0.92 g/L at 31°C in 72 h with a low conversion efficiency of 0.129 g/g. To further improve
the l-valine production and conversion efficiency based on the optimum temperatures of l-valine biosynthesis enzymes (above 35°C) and the thermotolerance of B. flavum, the fermentation temperature was increased to 34, 37, and 40°C. As a result, higher metabolic rate and l-valine biosynthesis enzymes activity were obtained at high temperature, and the maximum l-valine production, conversion efficiency, and specific l-valine production rate reached 38.08 ± 1.32 g/L, 0.241 g/g, and 0.133 g g−1 h−1, respectively, at 37°C in 48 h fermentation. The strategy for enhancing l-valine production by overexpression of key enzymes in thermotolerant strains may provide an alternative approach to enhance
branched-chain amino acids production with other strains. 相似文献
9.
P Zheng M Liu XD Liu QY Du Y Ni ZH Sun 《World journal of microbiology & biotechnology》2012,28(3):1035-1043
Genome shuffling was used to improve the thermotolerance of l-glutamic acid-producing strain Corynebacteria glutamicum. Five strains with subtle improvements in high temperature tolerance and productivity were selected by ultraviolet irradiation
and diethyl sulfate mutagenesis. An improved strain (F343) was obtained by three rounds of genome shuffling of the five strains
as mentioned above. The cell density of F343 was four times higher than that of ancestor strains after 24 h of cultivation
at 44°C, and importantly, the yield of l-glutamic acid was increased by 1.8-times comparing with that of the ancestor strain at 38°C in a 5-L fermentor. With glucose
supplement and two-stage pH control, the l-glutamate acid concentration of F343 reached 119 g/L after fermentation for 30 h. The genetic diversity between F343 and
its ancestors was also evaluated by amplified fragment length polymorphism analysis. Results suggest that the phenotypes for
both thermotolerance and l-glutamic acid production in F343 were evolved. 相似文献
10.
Err-Cheng Chan Hsiu-Lan Tsai Shih-Lin Chen Due-Gang Mou 《Applied microbiology and biotechnology》1993,40(2-3):301-305
Classical mutagenesis could desensitize the feedback inhibition of l-tryptophan (l-Trp) biosynthesis. Among the mutants, a5-fluorotryptophan-resistant strain, Escherichia coli EMS4-C25 produced 3 g/l of l-Trp within 18 h. The feedback-resistant l-Trp operon gene (trp) prepared from E. coli EMS4-C25 was inserted into pUC19 and pHSG576 to generate pTC701 and pTC576, respectively. When pHSG576 and pTC701 were introduced into E. coli EMS4-C25, chromosomal integration occured through homologous recombination. By using Souther hybridization, we demostrated that the integrated plasmids existed as multicopies. The strains with integrated foreign trp operon gene had higher activities of anthranilate synthase and Trp synthase than those found for the host strain and produced 9.2 g/l of l-Trp with 13% conversion yield from d-glucose. The integration and implification of the trp-operon-beraing plasmid avoided the plasmid instability and increased l-TRp production.
Correspondence to: E.-C. Chan 相似文献
11.
Kim YS Lee JH Kim NH Yeom SJ Kim SW Oh DK 《Applied microbiology and biotechnology》2011,90(2):489-497
In the fed-batch culture of glycerol using a metabolically engineered strain of Escherichia coli, supplementation with glucose as an auxiliary carbon source increased lycopene production due to a significant increase in
cell mass, despite a reduction in specific lycopene content. l-Arabinose supplementation increased lycopene production due to increases in cell mass and specific lycopene content. Supplementation
with both glucose and l-arabinose increased lycopene production significantly due to the synergistic effect of the two sugars. Cell growth by the
consumption of carbon sources was related to endogenous metabolism in the host E. coli. Supplementation with l-arabinose stimulated only the mevalonate pathway for lycopene biosynthesis and supplementation with both glucose and l-arabinose stimulated synergistically only the mevalonate pathway. In the fed-batch culture of glycerol with 10 g l−1 glucose and 7.5 g l−1
l-arabinose, the cell mass, lycopene concentration, specific lycopene content, and lycopene productivity after 34 h were 42 g l−1, 1,350 mg l−1, 32 mg g cells−1, and 40 mg l−1 h−1, respectively. These values were 3.9-, 7.1-, 1.9-, and 11.7-fold higher than those without the auxiliary carbon sources,
respectively. This is the highest reported concentration and productivity of lycopene. 相似文献
12.
Development of sucrose-utilizing Escherichia coli K-12 strain by cloning β-fructofuranosidases and its application for l-threonine production 总被引:1,自引:0,他引:1
Jeong Wook Lee Sol Choi Jin Hwan Park Claudia E. Vickers Lars K. Nielsen Sang Yup Lee 《Applied microbiology and biotechnology》2010,88(4):905-913
Sucrose is one of the most promising carbon sources for industrial fermentation. To achieve sucrose catabolism, the sucrose
utilization operons have been introduced into microorganisms that are not able to utilize sucrose. However, the rates of growth
and sucrose uptake of these engineered strains were relatively low to be successfully employed for industrial applications.
Here, we report a practical example of developing sucrose-utilizing microorganisms using Escherichia coli K-12 as a model system. The sucrose utilizing ability was acquired by introducing only β-fructofuranosidase from three different
sucrose-utilizing organisms (Mannheimia succiniciproducens, E. coli W, and Bacillus subtilis). Among them, the M. succiniciproducens β-fructofuranosidase was found to be the most effective for sucrose utilization. Analyses of the underlying mechanism revealed
that sucrose was hydrolyzed into glucose and fructose in the extracellular space and both liberated hexoses could be transported
by their respective uptake systems in E. coli K-12. To prove that this system can also be applied for the production of useful metabolites, the M. succiniciproducens β-fructofuranosidase was introduced into the engineered l-threonine production strain of E. coli K-12. This recombinant strain was able to produce 51.1 g/L l-threonine by fed-batch culture, resulting in an overall yield of 0.284 g l-threonine per g sucrose. This simple approach to make E. coli K-12 to acquire sucrose-utilizing ability and its successful biotechnological application can be employed to develop sustainable
bioprocesses using renewable biomass. 相似文献
13.
Rolf Wichmann Christian Wandreg Joachim Große-Wiesmann 《Applied microbiology and biotechnology》1990,32(4):373-379
Summary Continuous production ofl-leucine was carried out withCorynebacterium glutamicum, strain ATCC 13032 starting from-ketoisocaproic acid as the precursor, glucose as the carbon source and ammonium sulphate as the nitrogen source, with biotin in a mineral medium. By means of cross-flow microfiltration or centrifugal separation for cell retention in continuous fermentation an increase in cell density was achieved and the product solution was obtained cell-free. The cells were concentrated to over 70 g cell dry mass/1. In experiments of up to 42 days, conversion rates of 85%–99% andl-leucine yields of 85%–93% were achieved. With a substrate residence time of 3.6 h, 114 mmol/1l-leucine was produced with a space-time yield of 97 g/1 per day. A scale-up of the fermentation volume from 4 to 1001 provided comparable results. 相似文献
14.
The excretion of the aromatic amino acid l-tyrosine was achieved by manipulating three gene targets in the wild-type Escherichia coli K12: The feedback-inhibition-resistant (fbr) derivatives of aroG and tyrA were expressed on a low-copy-number vector, and the TyrR-mediated regulation of the aromatic amino acid biosynthesis was
eliminated by deleting the tyrR gene. The generation of this l-tyrosine producer, strain T1, was based only on the deregulation of the aromatic amino acid biosynthesis pathway, but no
structural genes in the genome were affected. A second tyrosine over-producing strain, E. coli T2, was generated considering the possible limitation of precursor substrates. To enhance the availability of the two precursor
substrates phosphoenolpyruvate and erythrose-4-phosphate, the ppsA and the tktA genes were over-expressed in the strain T1 background, increasing l-tyrosine production by 80% in 50-ml batch cultures. Fed-batch fermentations revealed that l-tyrosine production was tightly correlated with cell growth, exhibiting the maximum productivity at the end of the exponential
growth phase. The final l-tyrosine concentrations were 3.8 g/l for E. coli T1 and 9.7 g/l for E. coli T2 with a yield of l-tyrosine per glucose of 0.037 g/g (T1) and 0.102 g/g (T2), respectively. 相似文献
15.
l-threo-3,4-Dihydroxyphenylserine (DOPS) is a chiral unnatural β-hydroxy amino acid used for the treatment of Parkinson disease.
We developed a continuous bioconversion system for DOPS production that uses whole-cell biocatalyst of recombinant Escherichia coli expressing l-threonine aldolase (l-TA) genes cloned from Streptomyces avelmitilis MA-4680. Maximum conversion rates were observed at 2 M glycine, 145 mM 3,4-dihydroxybenzaldehyde, 0.75% Triton-X, 5 g E. coli cells/l, pH 6.5 and 10°C. In the optimized condition, overall productivity was 8 g/l, which represents 40 times the synthesis
yield possible with no optimization of conditions. 相似文献
16.
Iris Eggeling Christiana Cordes Lothar Eggeling Hermann Sahm 《Applied microbiology and biotechnology》1987,25(4):346-351
Summary
Corynebacterium glutamicum ATCC 13 032 produces 13 g/l l-isoleucine from 200 mM -ketobutyrate as a synthetic precursor. In fed batch cultures up to 19 g/l l-isoleucine is formed. For optimal conversion the addition of 0.3 mM l-valine plus 0.3 mM l-leucine to the fermentation medium is required. The affinity constants for the acetohydroxy acid synthase (AHAS) were determined. (This enzyme directs the flow of -ketobutyrate plus pyruvate towards l-isoleucine and that of two moles of pyruvate to l-valine and l-leucine, respectively.) For -ketobutyrate the K
m is 4.8×10-3 M, and V
max 0.58 U/mg, for pyruvate the K
m is 8.4×10-3 M, and V
max 0.37 U/mg. Due to these characteristics the presence of high -ketobutyrate concentrations apparently results in a l-valine, l-leucine deficiency. This in turn leads to a derepression of the AHAS synthesis from 0.03 U/mg to 0.29 U/mg and high l-isoleucine production is favoured. The derepression of the AHAS synthesis induced by the l-valine, l-leucine shortage was directly proven with a l-valine, l-leucine, l-isoleucine auxotrophic mutant where the starvation of each amino acid resulted in an increased AHAS level. This is in accordance with the fact that only one AHAS enzyme could be verified by chromatographic and electrophoretic separations as being responsible for the synthesis of all three branched-chain amino-acids. 相似文献
17.
J. Netrval 《Folia microbiologica》1977,22(2):106-116
The effect of 18 amino acids and 7 organic acids on the production ofl-asparaginase EC-2 by a strain ofEscherichia coli in a chemically defined medium was investigated under moderate aeration. All the amino acids and some of the organic acids
stimulated the enzyme production. The specific activity without stimulants was about 0.16 nkat per mg dry weight, with stimulants
it lay between 1 and 6 nkat per mg dry weight but withl-leucine andl-methionine the values were 12 nkat and 17 nkat per mg, respectively. When two organic or amino acids were added simultaneously
at concentrations that were suboptimal for stimulation, the stimulating effects were cumulative in most cases. When cells
were grown under conditions approaching anaerobiosis, the specific activity reached, even in the absence of stimulants, values
as high as 5 nkat per mg; under these conditions, a further substantial increase in specific activity was only caused byl-leucine andl-methionine. Stimulating effects ofdl-lactate and of some amino acids were also found in other strains ofEscherichia coli. The ability to grow on a medium withl-asparagine as the sole source of both nitrogen and carbon was found in two strains; growth took place even when there was
no measurable activity ofl-asparaginase EC-2. 相似文献
18.
The pentanol isomers 2-methyl-1-butanol and 3-methyl-1-butanol represent commercially interesting alcohols due to their potential application as biofuels. For a sustainable microbial production of these compounds, Corynebacterium glutamicum was engineered for producing 2-methyl-1-butanol and 3-methyl-1-butanol via the Ehrlich pathway from 2-keto-3-methylvalerate and 2-ketoisocaproate, respectively. In addition to an already available 2-ketoisocaproate producer, a 2-keto-3-methylvalerate accumulating C. glutamicum strain was also constructed. For this purpose, we reduced the activity of the branched-chain amino acid transaminase in an available C. glutamicum l-isoleucine producer (K2P55) via a start codon exchange in the ilvE gene enabling accumulation of up to 3.67 g/l 2-keto-3-methylvalerate. Subsequently, nine strains expressing different gene combinations for three 2-keto acid decarboxylases and three alcohol dehydrogenases were constructed and characterized. The best strains accumulated 0.37 g/l 2-methyl-1-butanol and 2.76 g/l 3-methyl-1-butanol in defined medium within 48 h under oxygen deprivation conditions, making these strains ideal candidates for additional strain and process optimization. 相似文献
19.
Characterization of salt-tolerant mutant for enhancement of l-threonine production in Escherichia coli 总被引:1,自引:0,他引:1
Escherichia coli strain HS3, metabolically engineered to have Met–, AHVr, IleL and AECr characteristics, produced 58.0 g/l of l-threonine, but it was neither salt-tolerant nor osmotolerant; and the growth and threonine production of the strain were
severely inhibited both by the addition of NaCl with a concentration higher than 2% and by the presence of glucose with a
concentration higher than 10%. Therefore, salt-tolerant mutants were isolated. The salt-tolerant mutants, HS454 and HS528
which were derived from strain HS3, were both tolerant to salt (2%) and hyperproductive. The growth and l-threonine production by the mutant strain HS454 were almost unaffected by a glucose concentration lower than 10%, but gradually
reduced with increasing glucose concentration, up to 15%. However, the mutant strain HS528 showed slightly enhanced growth
and l-threonine production with increasing glucose concentration, up to 10–12.5%. Strains HS454 and HS528 produced 69.8 g/l and
74.0 g/l of l-threonine, respectively in a 5-l jar fermentor.
Received: 21 January 2000 / Received revision: 31 March 2000 / Accepted: 5 May 2000 相似文献
20.
Simmons T Mozo J Wilson J Ahearn GA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2012,182(2):209-216
Purified epithelial brush border membrane vesicles (BBMV) were produced from the hepatopancreas of the Atlantic White shrimp,
Litopeneaus setiferus, using standard methods originally developed for mammalian tissues and previously applied to other crustacean and echinoderm
epithelia. These vesicles were used to study the cation dependency of sugar and amino acid transport across luminal membranes
of hepatopancreatic epithelial cells. 3H-d-glucose uptake by BBMV against transient sugar concentration gradients occurred when either transmembrane sodium or potassium
gradients were the only driving forces for sugar accumulation, suggesting the presence of a possible coupled transport system
capable of using either cation. 3H-l-histidine transport was only stimulated by a transmembrane potassium gradient, while 3H-l-leucine uptake was enhanced by either a sodium or potassium gradient. These responses suggest the possible presence of a
potassium-dependent transporter that accommodates either amino acid and a sodium-dependent system restricted only to l-leucine. Uptake of 3H-l-leucine was significantly stimulated (P < 0.05) by several metallic cations (e.g., Zn2+, Cu2+, Mn2+, Cd2+, or Co2+) at external pH values of 7.0 or 5.0 (internal pH 7.0), suggesting a potential synergistic role of the cations in the transmembrane
transfer of amino acids. 3H-l-histidine influxes (15 suptakes) were hyperbolic functions of external [zinc] or [manganese], following Michaelis–Menten
kinetics. The apparent affinity constant (e.g., K
m) for manganese was an order of magnitude smaller (K
m = 0.22 μM Mn) than that for zinc (K
m = 1.80 μM Zn), while no significant difference (P > 0.05) occurred between their maximal transport velocities (e.g., J
max). These results suggest that a number of cation-dependent nutrient transport systems occur on the shrimp brush border membrane
and aid in the absorption of these important dietary elements. 相似文献