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1.
Tadashi Toyama Noritaka Maeda Manabu Murashita Yong-Cheol Chang Shintaro Kikuchi 《Biodegradation》2010,21(2):157-165
A novel bacterium capable of utilizing 2-sec-butylphenol as the sole carbon and energy source, Pseudomonas sp. strain MS-1, was isolated from freshwater sediment. Within 30 h, strain MS-1 completely degraded 1.5 mM 2-sec-butylphenol in basal salt medium, with concomitant cell growth. A pathway for the metabolism of 2-sec-butylphenol by strain MS-1 was proposed on the basis of the identification of 3 internal metabolites—3-sec-butylcatechol, 2-hydroxy-6-oxo-7-methylnona-2,4-dienoic acid, and 2-methylbutyric acid—by gas chromatography-mass spectrometry
analysis. Strain MS-1 degraded 2-sec-butylphenol through 3-sec-butylcatechol along a meta-cleavage pathway. Degradation experiments with various alkylphenols showed that the degradability of alkylphenols by strain
MS-1 depended strongly on the position (ortho ≫ meta = para) of the alkyl substitute, and that strain MS-1 could degrade 2-alkylphenols with various sized and branched alkyl chain (o-cresol, 2-ethylphenol, 2-n-propylphenol, 2-isopropylphenol, 2-sec-butylphenol, and 2-tert-butylphenol), as well as a dialkylphenol (namely, 6-tert-butyl-m-cresol). 相似文献
2.
Park EY Ito Y Nariyama M Sugimoto T Lies D Kato T 《Applied microbiology and biotechnology》2011,91(5):1315-1326
We generated a high riboflavin-producing mutant strain of Ashbya gossypii by disparity mutagenesis using mutation of DNA polymerase δ in the lagging strand, resulting in loss of DNA repair function
by the polymerase. Among 1,353 colonies generated in the first screen, 26 mutants produced more than 3 g/L of riboflavin.
By the second screen and single-colony isolation, nine strains that produced more than 5.2 g/L of riboflavin were selected
as high riboflavin-producing strains. These mutants were resistant to oxalic acid and hydrogen peroxide as antimetabolites.
One strain (W122032) produced 13.7 g/L of riboflavin in a 3-L fermentor using an optimized medium. This represents a ninefold
improvement on the production of the wild-type strain. Proteomic analysis revealed that ADE1, RIB1, and RIB5 proteins were
expressed at twofold higher levels in this strain than in the wild type. DNA microarray analysis showed that purine and riboflavin
biosynthetic pathways were upregulated, while pathways related to carbon source assimilation, energy generation, and glycolysis
were downregulated. Genes in the riboflavin biosynthetic pathway were significantly overexpressed during both riboflavin production
and stationary phases, for example, RIB1 and RIB3 were expressed at greater than sixfold higher levels in this strain compared
to the wild type. These results indicate that the improved riboflavin production in this strain is related to a shift in carbon
flux from β-oxidation to the riboflavin biosynthetic pathway. 相似文献
3.
Gosset G 《Microbial cell factories》2005,4(1):14
The application of metabolic engineering in Escherichia coli has resulted in the generation of strains with the capacity to produce metabolites of commercial interest. Biotechnological
processes with these engineered strains frequently employ culture media containing glucose as the carbon and energy source.
In E. coli, the phosphoenolpyruvate:sugar phosphotransferase system (PTS) transports glucose when this sugar is present at concentrations
like those used in production fermentations. This protein system is involved in phosphoenolpyruvate-dependent sugar transport,
therefore, its activity has an important impact on carbon flux distribution in the phosphoenolpyruvate and pyruvate nodes.
Furthermore, PTS has a very important role in carbon catabolite repression. The properties of PTS impose metabolic and regulatory
constraints that can hinder strain productivity. For this reason, PTS has been a target for modification with the purpose
of strain improvement. In this review, PTS characteristics most relevant to strain performance and the different strategies
of PTS modification for strain improvement are discussed. Functional replacement of PTS by alternative phosphoenolpyruvate-independent
uptake and phosphorylation activities has resulted in significant improvements in product yield from glucose and productivity
for several classes of metabolites. In addition, inactivation of PTS components has been applied successfully as a strategy
to abolish carbon catabolite repression, resulting in E. coli strains that use more efficiently sugar mixtures, such as those obtained from lignocellulosic hydrolysates. 相似文献
4.
S. Parvez M. I. Rajoka M. N. Ahmed F. Latif R. Shahid K. A. Malik 《Folia microbiologica》1998,43(1):59-62
Citric acid production from sugar cane molasses byAspergillus niger NIAB 280 was studied in a batch cultivation process. A maximum of 90 g/L total sugar was utilized in citric acid production
medium. From the parental strainA. niger, mutant strains showing resistance to 2-deoxyglucose in Vogal's medium containing molasses as a carbon source were induced
by γ-irradiation. Among the new series of mutant strains, strain RP7 produced 120 g/L while the parental strain produced 80
g/L citric acid (1.5-fold improvement) from 150 g/L of molasses sugars. The period of citric acid production was shortened
from 10 d for the wild-type strain to 6–7 d for the mutant strain. The efficiency of substrate uptake rate with respect to
total volume substrate consumption rate,Q
s (g per L per h) and specific substrate consumption rate,q
s (g substrate per g cells per h) revealed that the mutant grew faster than its parent. This indicated that the selected mutant
is insensitive to catabolite repression by higher concentrations of sugars for citric acid production. With respect to the
product yield coefficient (Y
p/x), volume productivity (Q
p) and specific product yields (q
p), the mutant strain is significantly (p≤0.05) improved over the parental strain. 相似文献
5.
Peng Wang Juan Li Li Wang Ming-li Tang Zeng-liang Yu Zhi-ming Zheng 《Journal of industrial microbiology & biotechnology》2009,36(11):1363-1368
Low-energy ion beam irradiation (10–200 keV) has been proved to have a wide range of biological effects in recent years. When
Rhizopus oryzae PW352 was irradiated with a 15-keV low-energy ion beam an l(+)-lactic acid high-yield mutant, RQ4015, was obtained. When 150 g/l glucose was used as the sole carbon source, l(+)-lactic acid of RQ4015 reached 121 g/l after 36 h shake-flask cultivation. However, the highest lactic acid concentration
74 g/l was obtained when 100 g/l xylose was present in the medium as the sole carbon source. When mixed xylose (25 g/l) and
glucose (75 g/l) were present in a bubble column, l(+)-lactic acid production of RQ4015 reached 83 g. A high mutation rate and a wide mutation spectrum of low-energy ion implantation
were observed in the experiment, suggesting that ion implantation can be a highly efficient mutagenic means for microorganism
breeding in many commercial applications. 相似文献
6.
Rhamnolipid biosurfactant production by Pseudomonas nitroreducens isolated from petroleum-contaminated soil was investigated. The effects of carbon, nitrogen and carbon to nitrogen ratio
on biosurfactant production were examined using mineral salts medium as the growth medium. The tenso-active properties (surface
activity and critical micelle concentrations of the produced biosurfactant were also evaluated. The best carbon source, nitrogen
source were glucose and sodium nitrate giving rhamnolipid yields of 5.28 and 4.38 g l−1, respectively. The maximum rhamnolipid production of 5.46 g l−1 was at C/N (glucose/sodium nitrate) of 22. The rhamnolipid biosurfactant reduced the surface tension of water from 72 to
~37 mN/m. It also has critical micelle concentration of ~28 mg l−1. Thus, the results presented in our reports show that the produced rhamnolipid can find wide applications in various bioremediation
activities such as enhanced oil recovery and petroleum degradation. 相似文献
7.
Synthetic biology seeks to reprogram microbial cells for efficient production of value-added compounds from low-cost renewable substrates. A great challenge of chemicals biosynthesis is the competition between cell metabolism and target product synthesis for limited cellular resource. Dynamic regulation provides an effective strategy for fine-tuning metabolic flux to maximize chemicals production. In this work, we created a tunable growth phase-dependent autonomous bifunctional genetic switch (GABS) by coupling growth phase responsive promoters and degrons to dynamically redirect the carbon flux for metabolic state switching from cell growth mode to production mode, and achieved high-level GABA production from low-value glycerol in Corynebacterium glutamicum. A ribosome binding sites (RBS)-library-based pathway optimization strategy was firstly developed to reconstruct and optimize the glycerol utilization pathway in C. glutamicum, and the resulting strain CgGly2 displayed excellent glycerol utilization ability. Then, the initial GABA-producing strain was constructed by deleting the GABA degradation pathway and introducing an exogenous GABA synthetic pathway, which led to 5.26 g/L of GABA production from glycerol. In order to resolve the conflicts of carbon flux between cell growth and GABA production, we used the GABS to reconstruct the GABA synthetic metabolic network, in which the competitive modules of GABA biosynthesis, including the tricarboxylic acid (TCA) cycle module and the arginine biosynthesis module, were dynamically down-regulated while the synthetic modules were dynamically up-regulated after sufficient biomass accumulation. Finally, the resulting strain G7-1 accumulated 45.6 g/L of GABA with a yield of 0.4 g/g glycerol, which was the highest titer of GABA ever reported from low-value glycerol. Therefore, these results provide a promising technology to dynamically balance the metabolic flux for the efficient production of other high value-added chemicals from a low-value substrate in C. glutamicum. 相似文献
8.
Thermophilic enzymes are in high demand for various applications due to their prolonged lifetimes and high reaction rates
at elevated temperatures. In this work, an open reading frame TM0295, which encodes a putative transaldolase (TAL) from a
hyper-thermophilic microorganism, Thermotoga maritima, was cloned and expressed in Escherichia coli. The enzyme activity of transaldolase at high temperatures (e.g., at 80 °C) was reported here for the first time. The recombinant
T. maritima transaldolase was extremely thermostable, with a half-life time of 198 and 13.0 h at 60 °C and 80 °C, respectively. The estimated
total turn-over number was 1.5 × 106 mol of product per mol of enzyme at 80 °C. This enzyme also exhibited high activities within a broad pH range of 6.0–9.0.
This ultra-thermostable TAL with high activity shows great potential for use in such applications as the production of enzymatic
biofuels production and the synthesis of high-value carbohydrates by cell-free synthetic pathway biotransformation. 相似文献
9.
Yin Liu Yong-Guang Zhang Ru-Bing Zhang Fan Zhang Jianhang Zhu 《Current microbiology》2011,62(1):152-158
Cosubstrates fermentation is such an effective strategy for increasing subject metabolic products that it could be available
and studied in propionic acid production, using glycerol and glucose as carbon resources. The effects of glycerol, glucose,
and their mixtures on the propionic acid production by Propionibacterium acidipropionici CGMCC1.2225 (ATCC4965) were studied, with the aim of improving the efficiency of propionic acid production. The propionic
acid yield from substrate was improved from 0.475 and 0.303 g g−1 with glycerol and glucose alone, respectively, to 0.572 g g−1 with co-fermentation of a glycerol/glucose mixture of 4/1 (mol/mol). The maximal propionic acid and substrate conversion
rate were 21.9 g l−1 and 57.2% (w/w), respectively, both significantly higher than for a sole carbon source. Under optimized conditions of fed-batch
fermentation, the maximal propionic acid yield and substrate conversion efficiency were 29.2 g l−1 and 54.4% (w/w), respectively. These results showed that glycerol/glucose co-fermentation could serve as an excellent alternative
to conventional propionic acid fermentation. 相似文献
10.
Stenotrophomonas sp. RMSK capable of degrading acenaphthylene as a sole source of carbon and energy was isolated from coal sample. Metabolites
produced were analyzed and characterized by TLC, HPLC and mass spectrometry. Identification of naphthalene-1,8-dicarboxylic
acid, 1-naphthoic acid, 1,2-dihydroxynaphthalene, salicylate and detection of key enzymes namely 1,2-dihydroxynaphthalene
dioxygenase, salicylaldehyde dehydrogenase and catechol-1,2-dioxygenase in the cell free extract suggest that acenaphthylene
metabolized via 1,2-dihydroxynaphthalene, salicylate and catechol. The terminal metabolite, catechol was then metabolized
by catechol-1,2-dioxygenase to cis,cis-muconic acid, ultimately forming TCA cycle intermediates. Based on these studies, the proposed metabolic pathway in strain
RMSK is, acenaphthylene → naphthalene-1,8-dicarboxylic acid → 1-naphthoic acid → 1,2-dihydroxynaphthalene → salicylic acid → catechol → cis,cis-muconic acid. 相似文献
11.
Jiaheng Liu Huiling Li Hui Xiong Xixian Xie Ning Chen Guangrong Zhao Qinggele Caiyin Hongji Zhu Jianjun Qiao 《Biotechnology and bioengineering》2019,116(1):110-120
L -Threonine, a kind of essential amino acid, has numerous applications in food, pharmaceutical, and aquaculture industries. Fermentative l -threonine production from glucose has been achieved in Escherichia coli. However, there are still several limiting factors hindering further improvement of l -threonine productivity, such as the conflict between cell growth and production, byproduct accumulation, and insufficient availability of cofactors (adenosine triphosphate, NADH, and NADPH). Here, a metabolic modification strategy of two-stage carbon distribution and cofactor generation was proposed to address the above challenges in E. coli THRD, an l -threonine producing strain. The glycolytic fluxes towards tricarboxylic acid cycle were increased in growth stage through heterologous expression of pyruvate carboxylase, phosphoenolpyruvate carboxykinase, and citrate synthase, leading to improved glucose utilization and growth performance. In the production stage, the carbon flux was redirected into l -threonine synthetic pathway via a synthetic genetic circuit. Meanwhile, to sustain the transaminase reaction for l -threonine production, we developed an l -glutamate and NADPH generation system through overexpression of glutamate dehydrogenase, formate dehydrogenase, and pyridine nucleotide transhydrogenase. This strategy not only exhibited 2.02- and 1.21-fold increase in l -threonine production in shake flask and bioreactor fermentation, respectively, but had potential to be applied in the production of many other desired oxaloacetate derivatives, especially those involving cofactor reactions. 相似文献
12.
Fuhong Xie Yapeng Chao Zhiquan Xue Xiuqing Yang Guoqing Zhang Jiaji Shi Shijun Qian 《Journal of industrial microbiology & biotechnology》2009,36(5):739-746
In industry, fosfomycin is mainly prepared via chemical epoxidation of cis-propenylphosphonic acid (cPPA). The conversion yield of fosfomycin is less than 50% in the whole process and a large quantity
of waste is produced. Biotransformation by microorganisms is an alternative method of preparation. This kind of conversion
is more delicate, environmentally friendly, and the conversion yield of fosfomycin would be higher. In this work, an aerobic
bacterium capable of transforming cPPA to fosfomycin was isolated. The organism, designated as strain S101, was identified
as Bacillus simplex by morphological and physiological characteristics as well as by analysis of the gene encoding the 16S rRNA. Fosfomycin was
assayed by two means, bioassay and gas chromatography (GC). Glycerol was a good carbon source for growth and cPPA conversion
of strain S101. When cPPA was used as the sole carbon source, neither growth nor conversion to fosfomycin occurred. The optimum
cPPA concentration in the conversion medium was 2,000 μg ml−1. After 6 days of incubation, the concentration of fosfomycin reached its maximum level (1,838.2 μg ml−1), with a conversion ratio of 81.3%. Air was indispensable for the growth but not for the conversion to fosfomycin. Furthermore,
vanadium ions were found to be essential for the conversion. High concentrations of cPPA had fewer inhibitory effects on the
growth of strain S101. 相似文献
13.
Selection of a large number of different strains of hyphal fungi of the genusAspergillus, capable of production of extracellular mannosidase and mannanase type enzymes, was carried out. Before cultivating the strains
on liquid synthetic medium containing 0.5%Saccharomyces cerevisiae mannan as the carbon source, they were adapted by multiple passage on solid synthetic media containingd-mannose,d-mannose and α-mannan and lastly only α-mannan. The extracellular enzymatic preparations of the mould fungi were tested for
their ability to hydrolyse three different substrates—Saccharomyces cerevisiae, Torulopsis ingeniosa andTorulopsis colliculosa mannan. The production of α-mannosidase was found to be specifically dependent on the character of the substrate used for
cultivation of the fungus. 相似文献
14.
Mannheimia succiniciproducens is a capnophilic gram-negative bacterium isolated from bovine rumen. Wild-type M. succiniciproducens can produce succinic acid as a major fermentation product with acetic, formic, and lactic acids as byproducts during the
anaerobic cultivation using several different carbon sources. Succinic acid is an important C4 building block chemical for
many applications. Here, we review the progress made with M. succiniciproducens for efficient succinic acid production; the approaches taken towards the development of an integrated process for succinic
acid production are described, which include strain isolation and characterization, complete genome sequencing and annotation,
development of genetic tools for metabolic engineering, strain development by systems approach of integrating omics and in
silico metabolic analysis, and development of fermentation and recovery processes. We also describe our current effort on
further improving the performance of M. succiniciproducens and optimizing the mid- and downstream processes. Finally, we finish this mini-review by discussing the issues that need
to be addressed to make this process of fermentative succinic acid production employing M. succiniciproducens to reach the industrial-scale process. 相似文献
15.
A bacterium growing on pyrazine-2-carboxylate broth was isolated, purified and identified as a strain of Stenotrophomonas sp. based on polyphasic taxonomic analyses and designated as strain HCU1. 16S rRNA gene sequence of strain HCU1 showed 98.7%
sequence similarity with the type strain of Stenotrophomonas maltophilia belonging to Gammaproteobacteria. Growth of strain HCU1 was demonstrated when pyrazine-2-carboxylate was used as a sole source of nitrogen. Ring reduction
of pyrazine-2-carboxylate was shown as increase in absorbance at 268 nm and the reduced product was confirmed as 1,2,5,6-tetrahydropyrazine-2-carboxylate,
while a ring opened product, 2-amino-2-hydroxy-3-(methylamino) propanoic acid (with a loss in carbon atom), indicated a reductive
degradation of pyrazine-2-carboxylate by strain HCU1. 相似文献
16.
β-Alanine is an important β-amino acid with a growing demand in a wide range of applications in chemical and food industries. However, current industrial production of β-alanine relies on chemical synthesis, which usually involves harmful raw materials and harsh production conditions. Thus, there has been increasing demand for more sustainable, yet efficient production process of β-alanine. In this study, we constructed Corynebacterium glutamicum strains for the highly efficient production of β-alanine through systems metabolic engineering. First, aspartate 1-decarboxylases (ADCs) from seven different bacteria were screened, and the Bacillus subtilis ADC showing the most efficient β-alanine biosynthesis was used to construct a β-alanine-producing base strain. Next, genome-scale metabolic simulations were conducted to optimize multiple metabolic pathways in the base strain, including phosphotransferase system (PTS)-independent glucose uptake system and the biosynthesis of key precursors, including oxaloacetate and L-aspartate. TCA cycle was further engineered for the streamlined supply of key precursors. Finally, a putative β-alanine exporter was newly identified, and its overexpression further improved the β-alanine production. Fed-batch fermentation of the final engineered strain BAL10 (pBA2_tr18) produced 166.6 g/L of β-alanine with the yield and productivity of 0.28 g/g glucose and 1.74 g/L/h, respectively. To our knowledge, this production performance corresponds to the highest titer, yield and productivity reported to date for the microbial fermentation. 相似文献
17.
Weber JM Cernota WH Gonzalez MC Leach BI Reeves AR Wesley RK 《Applied microbiology and biotechnology》2012,93(4):1575-1583
The Saccharopolyspora erythraea mutB knockout strain, FL2281, having a block in the methylmalonyl-CoA mutase reaction, was found to carry a diethyl methylmalonate-responsive
(Dmr) phenotype in an oil-based fermentation medium. The Dmr phenotype confers the ability to increase erythromycin A (erythromycin)
production from 250–300% when the oil-based medium is supplemented with 15 mM levels of this solvent. Lower concentrations
of the solvent stimulated proportionately less erythromycin production, while higher concentrations had no additional benefit.
Although the mutB strain is phenotypically a low-level erythromycin producer, diethyl methylmalonate supplementation allowed it to produce
up to 30% more erythromycin than the wild-type (control) strain—a strain that does not show the Dmr phenotype. The Dmr phenotype
represents a new class of strain improvement phenotype. A theory to explain the biochemical mechanism for the Dmr phenotype
is proposed. Other phenotypes found to be associated with the mutB knockout were a growth defect and hyper-pigmentation, both of which were restored to normal by exposure to diethyl methylmalonate.
Furthermore, mutB fermentations did not significantly metabolize soybean oil in the presence of diethyl methylmalonate. Finally, a novel method
is proposed for the isolation of additional mutants with the Dmr phenotype. 相似文献
18.
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
19.
Spirulina produces γ-linolenic acid (GLA), an important pharmaceutical substance, in a relatively low level compared with fungi and
plants, prompting more research to improve its GLA yield. In this study, metabolic flux analysis was applied to determine
the cellular metabolic flux distributions in the GLA synthetic pathways of twoSpirulina strains, wild type BP and a high-GLA producing mutant Z19/2. Simplified pathways involving the GLA synthesis ofS. platensis formulated comprise of photosynthesis, gluconeogenesis, the pentose phosphate pathway, the anaplerotic pathway, the tricarboxylic
cycle, the GLA synthesis pathway, and the biomass synthesis pathway. A stoichiometric model reflecting these pathways contains
17 intermediates and 22 reactions. Three fluxes—the bicarbonate (C-source) uptake rate, the specific growth rate, and the
GLA synthesis rate—were measured and the remaining fluxes were calculated using linear optimization. The calculation showed
that the flux through the reaction converting acetyl-CoA into malonyl-CoA in the mutant strain was nearly three times higher
than that in the wild-type strain. This finding implies that this reaction is rate controlling. This suggestion was supported
by experiments, in which the stimulating factors for this reaction (NADPH and MgCl2) were added into the culture medium, resulting in an increased GLA-synthesis rate in the wild type strain. 相似文献
20.
Anita Rywińska Waldemar Rymowicz Barbara Żarowska Adam Skrzypiński 《World journal of microbiology & biotechnology》2010,26(7):1217-1224
A wild type strain A-101 of Y. lipolytica and its three acetate-negative mutants (Wratislavia 1.31, Wratislavia AWG7, and Wratislavia K1) were compared for the production
of citric acid from glucose and glycerol (pure and crude) in batch cultures. The substrates were used either as single carbon
sources or as mixtures of glucose and pure or crude glycerol. The kinetic parameters, i.e., the volumetric citric acid production
rate and yield obtained in the study show that the Wratislavia 1.31 and Wratislavia AWG7 strains produced the highest amount
of citric acid from glycerol, with a yield from 0.40 to 0.53 g g−1. This substrate was found to be a better carbon source for the biosynthesis of citric acid than glucose. The results obtained
with the same strains have shown low content of isocitric acid and polyols, such as erythritol and mannitol. Y. lipolytica A-101 strain produced the highest amount of isocitric acid, from 13.8 to 21% isocitric acid in the sum of citric acids. However,
the highest concentrations of erythritol were found in cultures with Y. lipolytica Wratislavia K1, from 18.1 to 30 g l−1, for glucose and pure glycerol, respectively. 相似文献