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1.
The effect of agitation and aeration on the growth and antibiotic production by Xenorhabdus nematophila YL001 grown in batch cultures were investigated. Efficiency of aeration and agitation was evaluated through the oxygen mass
transfer coefficient (K
L
a). With increase in K
L
a, the biomass and antibiotic activity increased. Activity units of antibiotic and dry cell weight were increased to 232 U ml−1 and 19.58 g l−1, respectively, productivity in cell and antibiotic was up more than 30% when K
L
a increased from 115.9 h−1 to 185.7 h−1. During the exponential growth phase, DO concentration was zero, the oxygen supply was not sufficient. So, based on process
analysis, a three-stage oxygen supply control strategy was used to improved the DO concentration above 30% by controlling
the agitation speed and aeration rate. The dry cell weight and activity units of antibiotic were further increased to 24.22 g l−1 and 249 U ml−1, and were improved by 24.0% and 7.0%, compared with fermentation at a constant agitation speed and a constant aeration rate
(300 rev min−1, 2.5 l min−1). 相似文献
2.
Domínguez-Bocanegra AR Ponce-Noyola T Torres-Muñoz JA 《Applied microbiology and biotechnology》2007,75(4):783-791
Phaffia rhodozyma (now Xanthophyllomyces dendrorhous) and Haematococcus pluvialis are known as the major prominent microorganisms able to synthesize astaxanthin natural pigment. Important research efforts
have been made to determine optimal conditions for astaxanthin synthesis. When the focus is on astaxanthin production, the
maximal reported value of 9.2 mg/g cell is obtained within H. pluvialis grown on BAR medium, under continuous illumination (345 μmol photon m−2 s−1) and without aeration. Whereas fermentation by mutated R1 yeast grown on coconut milk produced 1,850 μg/g yeast. However,
when looking at astaxanthin productivity, the picture is slightly different. The figures obtained with P. rhodozyma are rather similar to those of H. pluvialis. Maximal reported values are 170 μg/g yeast per day with a wild yeast strain and 370 μg/g yeast per day with mutated R1 yeast.
In the case of H. pluvialis, maximal values ranged from 290 to 428 μg/g cell per day depending on the media (BG-11 or BAR), light intensity (177 μmol
photon m−2 s−1), aeration, etc. The main aim of this work was to examine how astaxanthin synthesis, by P. rhodozyma and H. pluvialis, could be compared. The study is based on previous works by the authors where pigment productions have been reported. 相似文献
3.
In Escherichia coli, Vitreoscilla hemoglobin (VHb) protects against oxidative stress, perhaps, in part, by oxidizing OxyR. Here this protection, specifically
VHb-associated effects on superoxide dismutase (SOD) and catalase levels, was examined. Exponential or stationary phase cultures
of SOD+ or SOD−
E. coli strains with or without VHb and oxyR antisense were treated with 2 mM hydrogen peroxide without sublethal peroxide induction, and compared to untreated control
cultures. The hydrogen peroxide treatment was toxic to both SOD+ and SOD− cells, but much more to SOD− cells; expression of VHb in SOD+ strains enhanced this toxicity. In contrast, the presence of VHb was generally associated in the SOD+ background with a modest increase in SOD activity that was not greatly affected by oxyR antisense or peroxide treatment. In both SOD+ and SOD− backgrounds, VHb was associated with higher catalase activity both in the presence and absence of peroxide. Contrary to its
stimulatory effects in stationary phase, in exponential phase oxyR antisense generally decreased VHb levels. 相似文献
4.
Kameshnee Naidoo Manimaran Ayyachamy Kugen Permaul Suren Singh 《Bioprocess and biosystems engineering》2009,32(5):689-695
Xanthomonas campestris pv phaseoli produced an extracellular endoinulinase (9.24 ± 0.03 U mL−1) in an optimized medium comprising of 3% sucrose and 2.5% tryptone. X. campestris pv. phaseoli was further subjected to ethylmethanesulfonate mutagenesis and the resulting mutant, X. campestris pv. phaseoli KM 24 demonstrated inulinase production of 22.09 ± 0.03 U mL−1 after 18 h, which was 2.4-fold higher than that of the wild type. Inulinase production by this mutant was scaled up using
sucrose as a carbon source in a 5-L fermenter yielding maximum volumetric (21,865 U L−1 h−1) and specific (119,025 U g−1 h−1) productivities of inulinase after 18 h with an inulinase/invertase ratio of 2.6. A maximum FOS production of 11.9 g L−1 h−1 and specific productivity of 72 g g−1 h−1 FOS from inulin were observed in a fermenter, when the mutant was grown on medium containing 3% inulin and 2.5% tryptone.
The detection of mono- and oligosaccharides in inulin hydrolysates by TLC analysis indicated the presence of an endoinulinase.
This mutant has potential for large-scale production of inulinase and fructooligosaccharides. 相似文献
5.
Cardoso PG Ribeiro JB Teixeira JA de Queiroz MV de Araújo EF 《Journal of industrial microbiology & biotechnology》2008,35(3):159-166
The pectin lyase (PL) is an industrially important enzyme since it is used for maceration and clarification in the process
of fruit juice production in food industries. In order to increase the yields of pectin lyase we cloned the plg1 (pectin lyase 1) from Penicillium griseoroseum gene under the control of the strong constitutive promoter of the glyceraldehyde-3-phosphate dehydrogenase gene (gpdA) and the terminator region of the tryptophan synthetase (trpC) gene from Aspergillus nidulans (plasmid pAN52-Plg1) and transformed this construct into the P. griseoroseum strain PG63. One of the pAN52-Plg1 multi-copy transformants (strain 105) grown in culture medium containing glucose or sugar
cane juice showed PL activities of 4,804 or 5,202 U ml−1 respectively, which represented 57- and 132-fold increases. In addition, the apparent specific activity of PL produced by
this strain was much higher than the one observed for a commercial pectinase preparation. Evaluation of the extracellular
proteins in the culture supernatant of strain 105 by SDS-PAGE showed the presence of a clear and strong band of approximately
40 kDa that probably corresponds to PL. The enzyme yields reported here demonstrate that the system we developed is able to
express pectin lyase at levels comparable to, or exceeding, previously reported data. 相似文献
6.
The effect of pH, aeration and mixing on the growth and production of carbonyl reductase by Candida viswanathii was investigated in a 6.6-l fermentor. Controlling the pH at 8.0 had a very significant effect on the enzyme production.
Aeration and agitation influenced the dissolved oxygen concentration which in turn affected growth as well as enzyme production.
A maximum carbonyl reductase activity (53 Umg−1) was attained in 24 h under the optimal cultivation conditions of controlled pH at 8.0, aeration rate 1 vvm and an agitation
speed of 250 rpm at 25°C. The enzyme activity was twice as high (56 Umg−1) in the fermentor as compared to a shake flask. Further, the duration of growth and enzyme production in the fermentor was
shortened. Cells cultivated under the optimized conditions were used for the preparative scale reduction of N, N-dimethyl-(3-keto)-2-thienyl-propanamine
to (S)-N, N-dimethyl-(3-hydroxy)-2-thienyl-propanamine, a key intermediate in the production of the important antidepressant drug
(S)-duloxetine. 相似文献
7.
Acid phosphatase production by recombinant Arxula adeninivorans was carried out in submerged fermentation. Using the Plackett–Burman design, three fermentation variables (pH, sucrose concentration,
and peptone concentration) were identified to significantly affect acid phosphatase and biomass production, and these were
optimized using response surface methodology of central composite design. The highest enzyme yields were attained in the medium
with 3.9% sucrose and 1.6% peptone at pH 3.8. Because of optimization, 3.86- and 4.19-fold enhancement in enzyme production
was achieved in shake flasks (17,054 U g−1 DYB) and laboratory fermenter (18,465 U g−1 DYB), respectively. 相似文献
8.
Zahir Ahmad Zahir Usman Ghani Muhammad Naveed Sajid Mahmood Nadeem Hafiz Naeem Asghar 《Archives of microbiology》2009,191(5):415-424
Ethylene synthesis is accelerated in response to various environmental stresses like salinity. Ten rhizobacterial strains
isolated from wheat rhizosphere taken from different salt affected areas were screened for growth promotion of wheat under
axenic conditions at 1, 5, 10 and 15 dS m−1. Three strains, i.e., Pseudomonas putida (N21), Pseudomonas aeruginosa (N39) and Serratia proteamaculans (M35) showing promising performance under axenic conditions were selected for a pot trial at 1.63 (original), 5, 10 and 15 dS m−1. Results showed that inoculation was effective even in the presence of higher salinity levels. P. putida was the most efficient strain compared to the other strains and significantly increased the plant height, root length, grain
yield, 100-grain weight and straw yield up to 52, 60, 76, 19 and 67%, respectively, over uninoculated control at 15 dS m−1. Similarly, chlorophyll content and K+/Na+ of leaves also increased by P. putida over control. It is highly likely that under salinity stress, 1-aminocyclopropane-1-carboxylic acid-deaminase activity of
these microbial strains might have caused reduction in the synthesis of stress (salt)-induced inhibitory levels of ethylene.
The results suggested that these strains could be employed for salinity tolerance in wheat; however, P. putida may have better prospects in stress alleviation/reduction. 相似文献
9.
Meiru Li Hongqing Li Huawu Jiang Xiaoping Pan Guojiang Wu 《Plant Cell, Tissue and Organ Culture》2008,92(2):173-181
Jatropha curcas contains high amounts of oil in its seed and has been considered for bio-diesel production. A transformation procedure for
J. curcas has been established for the first time via
Agrobacterium tumefaciens infection of cotyledon disc explants. The results indicated that the efficiency of transformation using the strain LBA4404
and phosphinothricin for selection was an improvement over that with the strain EHA105 and hygromycin. About 55% of the cotyledon
explants produced phosphinothricin-resistant calluses on Murashige and Skoog (MS) medium supplemented with 1.5 mg l−1 benzyladenine (BA), 0.05 mg l−1 3–indolebutyric acid (IBA), 1 mg l−1 phosphinothricin and 500 mg l−1 cefotaxime after 4 weeks. Shoots were regenerated following transfer of the resistant calli to shoot induction medium containing
1.5 mg l−1 BA, 0.05 mg l−1 IBA, 0.5 mg l−1 gibberellic acid (GA3), 1 mg l−1 phosphinothricin and 250 mg l−1 cefotaxime, and about 33% of the resistant calli differentiated into shoots. Finally, the resistant shoots were rooted on
1/2 MS media supplemented with 0.3 mg l−1 IBA at a rate of 78%. The transgenic nature of the transformants was demonstrated by the detection of β-glucuronidase activity
in the primary transformants and by PCR and Southern hybridization analysis. 13% of the total inoculated explants produced
transgenic plants after approximately 4 months. The procedure described will be useful for both, the introduction of desired
genes into J. curcas and the molecular analysis of gene function. 相似文献
10.
11.
T. Zhang 《In vitro cellular & developmental biology. Plant》2007,43(2):91-94
This study investigated the factors affecting in vitro flowering of Perilla frutescens. The shoots regenerated from cotyledonary and hypocotyl explants cultured on Murashige and Skoog (MS) medium supplemented
with benzyladenine (BA) and indole-3-acetic acid, each at 0.5 mg l−1, were excised and transferred to MS medium containing 30 g l−1 of sucrose, 8.25 g l−1 of ammonium nitrate, and 1.0 mg l−1 of BA. After 40 d of culture, 86.2% of shoots flowered and most of which self-fertilized in vitro and produced mature fruits with viable seeds. These seeds were germinated and plants were grown to maturity and flowered
in soil under greenhouse conditions. The in vitro flowering system reported in this study may facilitate rapid breeding of P. frutescens and offers a model system for studying the physiological mechanism of flowering. 相似文献
12.
Two oligosaccharides, a heptasaccharide (HS) and an octasaccharide (OS), isolated from Paris polyphylla var. yunnanensis, stimulated the growth and saponin accumulation of Panax ginseng hairy roots at 5–30 mg l−1. HS and OS at 30 mg l−1, fed separately to hairy root cultures at 10 days post-inoculation, increased the root biomass dry weight by more than 70%
to ∼20 g l−1 from 13 g l−1 and the total saponin content of roots by more than 1-fold to ∼3.5% from 1.6% (w/w). The results suggest that the two oligosaccharides
may have plant growth-regulatory activity in plant tissue cultures. 相似文献
13.
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
14.
Previous work from our laboratory has shown that most of Bacillus thuringiensis strains possess the ability to produce melanin in the presence of l-tyrosine at elevated temperatures (42 °C). Furthermore, it was shown that the melanin produced by B. thuringiensis was synthesized by the action of tyrosinase, which catalyzed the conversion of l-tyrosine, via l-DOPA, to melanin. In this study, the tyrosinase-encoding gene (mel) from B. thuringiensis 4D11 was cloned using PCR techniques and expressed in Escherichia coli DH5 . A DNA fragment with 1179 bp which contained the intact mel gene in the recombinant plasmid pGEM1179 imparted the ability to synthesize melanin to the E. coli recipient strain. The nucleotide sequence of this DNA fragment revealed an open reading frame of 744 bp, encoding a protein of 248 amino acids. The novel mel gene from B.thuringiensis expressed in E. coli DH5 conferred UV protection on the recipient strain. 相似文献
15.
The cry8C-type gene designated cry8Ca2, which was cloned and sequenced from a Bacillus thuringiensis isolate HBF-1 in China, consisted of an open reading frame of 3483 bp encoding a protein of 1160 amino-acid residues. Sequence
analysis showed that the Cry8Ca2 protoxin of 130.5 kDa had 99.9% sequence homology with the previously reported Cry8Ca1 protein,
with one mismatch between the two amino-acid sequences. When the Cry8Ca2 toxin was expressed in a crystal-negative strain
of B. thuringiensis (HD-73−), elliptical crystals were produced. Cell extracts from this recombinant strain showed insecticidal activity against Anomala corpulenta larva. Mutant cry8Ca2 genes, produced by polymerase chain reaction amplification with Taq DNA polymerase, were used to develop recombinant B. thuringiensis strains. Mutants producing higher levels of insecticidal activity were identified by bioassay. Thirty-five mutants forming
crystals were characterized, and two of them showed significantly increased insecticidal activity against A. corpulenta larva. The 50% lethality concentrations (LC50) of the two mutants were 0.2334 × 108 and 0.2591 × 108 colony-forming units g−1, considerably lower than the LC50 of the wild-type strain HBF-1 (0.9583 × 108 CFU g−1) and that of B. thuringiensis serovar japonensis strain Buibui (1.0752 × 108 CFU g−1). 相似文献
16.
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
17.
Two cDNAs isolated from Cymodocea nodosa, CnSOS1A, and CnSOS1B encode proteins with high-sequence similarities to SOS1 plant transporters. CnSOS1A expressed in a yeast Na+-efflux mutant under the control of a constitutive expression promoter mimicked AtSOS1 from Arabidopsis; the wild type cDNA did not improve the growth of the recipient strain in the presence of Na+, but a cDNA mutant that expresses a truncated protein suppressed the defect of the yeast mutant. In similar experiments,
CnSOS1B was not effective. Conditional expression, under the control of an arabinose responsive promoter, of the CnSOS1A and CnSOS1B cDNAs in an Escherichia coli mutant defective in Na+ efflux was toxic, and functional analyses were inconclusive. The same constructs transformed into an E. coli K+-uptake mutant revealed that CnSOS1A was also toxic, but that it slightly suppressed defective growth at low K+. Truncation in the C-terminal hydrophilic tail of CnSOS1A relieved the toxicity and proved that CnSOS1A was an excellent
low-affinity K+ and Rb+ transporter. CnSOS1B mediated a transient, extremely rapid K+ or Rb+ influx. Similar tests with AtSOS1 revealed that it was not toxic and that the whole protein exhibited excellent K+ and Rb+ uptake characteristics in bacteria. 相似文献
18.
The vhb gene encoding Vitreoscilla haemoglobin (VHb) was transferred to barley with the aim of studying the role of oxygen availability in germination and growth.
Previous findings indicate that VHb expression improves the efficiency of energy generation during oxygen-limited growth,
and germination is known to be an energy demanding growth stage during which the embryos also suffer from oxygen deficiency.
When subjected to oxygen deficiency, the roots of vhb-expressing barley plants showed a smaller increase in alcohol dehydrogenase (ADH) activity than those of the control plants.
This indicates that VHb plants experienced less severe oxygen deficiency than the control plants, possibly due to the ability
of VHb to substitute ADH for recycling NADH and maintaining glycolysis. In contrast to previous findings, we found that constitutive
vhb expression did not improve the germination rate of barley kernels in any of the conditions studied. In some cases, vhb expression even slowed down germination slightly. VHb production also appeared to restrict root formation in young seedlings.
The adverse effects of VHb on germination and root growth may be related to its ability to scavenge nitric oxide (NO), an
important signal molecule in both seed germination and root formation. Because NO has both cytotoxic and stimulating properties,
the effect of vhb expression in plants may depend on the level and role of endogenous NO in the conditions studied. VHb production also affected
the levels of endogenous barley haemoglobin, which may explain the relatively moderate effects of VHb in this study. 相似文献
19.
An effective, simple, and convenient method to improve yeast’s multiple-stress tolerance, and ethanol production was developed.
After an ethanologenic Saccharomyces cerevisiae strain SC521 was treated by nine cycles of freeze-thaw, a mutant FT9-11 strain with higher multiple-stress tolerance was
isolated, whose viabilities under acetic acid, ethanol, freeze-thaw, H2O2, and heat-shock stresses were, respectively, 23-, 26-, 10- and 7-fold more than the parent strain at an initial value 2 × 107 c.f.u. per ml. Ethanol production of FT9-11 was similar (91.5 g ethanol l−1) to SC521 at 30°C with 200 g glucose l−1, and was better than the parent strain at 37°C (72.5 g ethanol l−1), with 300 (111 g ethanol l−1) or with 400 (85 g ethanol l−1) g glucose l−1. 相似文献
20.
Wen-Hao Chen Chun-Ming Xu Jian-Li Zeng Bing Zhao Xiao-Dong Wang Yu-Chun Wang 《World journal of microbiology & biotechnology》2007,23(10):1451-1458
At appropriate concentrations, polyamines promoted the callus growth and echinacoside content of Cistanche deserticola while Ag+ increased the content of echinacoside and acteoside. In a 20-day culture period, when putrescine (25 μM) and Ag+ (10 μM) were added on day 8 and day 16, respectively, the echinacoside production (1.7 g l−1) and acteoside production (0.4 g l−1) reached the maximum, which were 1.4-fold and 1.5-fold of those in single putrescine treatment, 1.6-fold and 1.4-fold of
those in single Ag+ treatment, respectively. Exogenous putrescine enhanced cell viability and antioxidant enzyme activity markedly, so increased
the final biomass. Ag+ addition increased H2O2 content and phenylalanine ammonia-lyase activity significantly which led to higher echinacoside and acteoside contents. 相似文献