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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.
The fadBA operon in the fatty acid β-oxidation pathway of P. putida KCTC1639 was blocked to induce a metabolic flux of the intermediates to the biosynthesis of medium chain-length PHA (mcl-PHA).
Succinate at 150 mg l−1 stimulated cell growth and also the biosynthesis of medium chain-length-polyhydroxyalkanoate. pH-stat fed-batch cultivation
of the fadA knockout mutant P. putida KCTC1639 was carried out for 60 h, in which mcl-PHA reached 8 g l−1 with a cell dry weight of 10.3 g l−1. 相似文献
3.
4.
Production of <Emphasis Type="SmallCaps">l</Emphasis>-alanine by metabolically engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> 总被引:2,自引:0,他引:2
Zhang X Jantama K Moore JC Shanmugam KT Ingram LO 《Applied microbiology and biotechnology》2007,77(2):355-366
Escherichia coli W was genetically engineered to produce l-alanine as the primary fermentation product from sugars by replacing the native d-lactate dehydrogenase of E. coli SZ194 with alanine dehydrogenase from Geobacillus stearothermophilus. As a result, the heterologous alanine dehydrogenase gene was integrated under the regulation of the native d-lactate dehydrogenase (ldhA) promoter. This homologous promoter is growth-regulated and provides high levels of expression during anaerobic fermentation.
Strain XZ111 accumulated alanine as the primary product during glucose fermentation. The methylglyoxal synthase gene (mgsA) was deleted to eliminate low levels of lactate and improve growth, and the catabolic alanine racemase gene (dadX) was deleted to minimize conversion of l-alanine to d-alanine. In these strains, reduced nicotinamide adenine dinucleotide oxidation during alanine biosynthesis is obligately
linked to adenosine triphosphate production and cell growth. This linkage provided a basis for metabolic evolution where selection
for improvements in growth coselected for increased glycolytic flux and alanine production. The resulting strain, XZ132, produced
1,279 mmol alanine from 120 g l−1 glucose within 48 h during batch fermentation in the mineral salts medium. The alanine yield was 95% on a weight basis (g
g−1 glucose) with a chiral purity greater than 99.5% l-alanine.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
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
6.
Durban MA Silbersack J Schweder T Schauer F Bornscheuer UT 《Applied microbiology and biotechnology》2007,74(3):634-639
Twenty-two Bacillus cereus strains were screened for phospholipase C (PLC, EC 3.1.4.3) activity using p-nitrophenyl phosphorylcholine as a substrate. Two strains (B. cereus SBUG 318 and SBUG 516) showed high activity at elevated temperatures (>70°C) at acidic pH (pH 3.5–6) and were selected for
cloning and functional expression using Bacillus subtilis. The genes were amplified from B. cereus DNA using primers based on a known PLC sequence and cloned into the expression vector pMSE3 followed by transformation into
B. subtilis WB800. On the amino acid level, one protein (PLC318) was identical to a PLC described from B. cereus, whereas PLC516 contained an amino acid substitution (E173D). PLC production using the recombinant strains was performed
by an acetoin-controlled expression system. For PLC516, 13.7 U g−1 wet cell weight was determined in the culture supernatant after 30 h cultivation time. Three purification steps resulted
in pure PLC516 with a specific activity of 13,190 U mg−1 protein. 相似文献
7.
Rosa María Camacho Juan Carlos Mateos Orfil González-Reynoso Lilia Arely Prado Jesús Córdova 《Journal of industrial microbiology & biotechnology》2009,36(7):901-909
The present study was conducted to investigate the capability of Haloarcula marismortui to synthesize esterases and lipases, and the effect of physicochemical conditions on the growth and the production of esterases
and lipases. Finally, the effect of NaCl concentration and temperature on esterase and lipase activities was studied using
intracellular crude extracts. In order to confirm the genomic prediction about the esterase and lipase synthesis, H. marismortui was cultured on a rich medium and the crude extracts (intra- or extracellular) obtained were assayed for both activities
using p-nitrophenyl esters and triacylglycerides as substrates. Studies on the kinetics of growth and production of esterase and
lipase of H. marismortui were performed, reaching a maximum growth rate of 0.053 h−1 and maximal productions of intracellular esterase and lipase of 2.094 and 0.722 U l−1 using p-nitrophenyl valerate and p-nitrophenyl laurate, respectively. Both enzymes were produced as growth-associated metabolites. The effects of temperature,
pH, and NaCl concentration on the growth rate and production of enzymes were studied by using a Box–Behnken response surface
design. The three response variables were significantly influenced by the physicochemical factors and an interaction effect
between temperature and NaCl concentration was also evidenced. The surface response method estimated the following maximal
values for growth rate and productions of esterase and lipase: 0.086 h−1 (at 42.5°C, pH 7.4, and 3.6 mol l−1 NaCl), 2.3 U l−1 (at 50°C, pH 7.5, and 4.3 mol l−1 NaCl), and 0.58 U l−1 (at 50°C, pH 7.6, and 4.5 mol l−1 NaCl), respectively. Esterases were active at different salt concentrations, showing two optimal activities (at 0.5 and 5 mol l−1 NaCl), which suggested the presence of two different esterases. Interestingly, in the absence of salt, esterase retained
50% residual activity. Esterases and lipase activities were maximal at 45°C and inactive at 75°C. This study represents the
first report evidencing the synthesis of esterase and lipase by H. marismortui. 相似文献
8.
Nitraria retusa and Atriplex halimus (xero-halophytes) plants were grown in the range 0–800 mM NaCl while Medicago arborea (glycophyte) in 0–300 mM NaCl. Salt stress caused a marked decrease in osmotic potential and a significant accumulation of
Na+ and Cl− in leaves of both species. Moderate salinity had a stimulating effect on growth rate, net CO2 assimilation, transpiration and stomatal conductance for the xero-halophytic species. At higher salinities, these physiological
parameters decreased significantly, and their percentages of reduction were higher in A. halimus than in N. retusa whereas, in M. arborea they decreased linearly with salinity. Nitraria retusa PSII photochemistry and carotenoid content were unaffected by salinity, but a reduction in chlorophyll content was observed
at 800 mM NaCl. Similar results were found in A. halimus, but with a decrease in the efficiency of PSII (F′v/F′m) occurred at 800 mM. Conversely, in M. arborea plants we observed a significant reduction in pigment concentrations and chlorophyll fluorescence parameters. The marked
toxic effect of Na+ and/or Cl− observed in M. arborea indicates that salt damage effect could be attributed to ions’ toxicity, and that the reduction in photosynthesis is most
probably due to damages in the photosynthetic apparatus rather than factors affecting stomatal closure. For the two halophyte
species, it appears that there is occurrence of co-limitation of photosynthesis by stomatal and non-stomatal factors. Our
results suggest that both N. retusa and A. halimus show high tolerance to both high salinity and photoinhibition while M. arborea was considered as a slightly salt tolerant species. 相似文献
9.
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
10.
Constitutive expression of human angiostatin in <Emphasis Type="Italic">Pichia pastoris</Emphasis> by high-density cell culture 总被引:1,自引:0,他引:1
Zhang AL Zhang TY Luo JX Chen SC Guan WJ Fu CY Peng SQ Li HL 《Journal of industrial microbiology & biotechnology》2007,34(2):117-122
A high-density cell culture method to produce human angiostatin has been successfully established by constitutive expression
of the protein in Pichia pastoris. The fermentation was carried out in a 20 l bioreactor with a 10 l working volume, using a high-density cell culture method
by continuously feeding with 50% glycerol−0.8% PTM4 to the growing culture for 60 h at 30°C. Dissolved oxygen level was maintained
at 25–30% and pH was controlled at 5 by the addition of 7 M NH4OH. Angiostatin was constitutively expressed during the fermentation by linking its expression to the P. pastoris constitutive GAP promoter (pGAP). But after 36 h of fermentation, the peak biomass growth was 305 as measured by absorption
of 600 nm, while the peak angiostatin expression was 176 mg/l. Similar to the product expressed from inducible system [24], angiostatin produced from constitutive system also inhibited the angiogenesis on the CAM and suppressed the growth of B16
melanoma in C57BL/6J mouse. The above results suggest that GAP promoter is more efficient than AOX1 promoter for the expression
of angiostatin in P. pastoris by shake flask culture or high-density cell fermentation and is likely to be an alternative to AOX1 promoter in large-scale
expression of angiostatin and other heterologous proteins.
Supported by the Natural Science Foundation of China (39670013) and “225” Science and Technology Program of Guangzhou Municipal
Government of China (99-Z-004-001). 相似文献
11.
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
12.
High-cell-density production of recombinant growth hormone of Lateolabrax japonicus (rljGH) expressed intracellularly in Pichia pastoris was investigated. In the regular strategy of induction at a cell density of 160 g l−1, short duration of intracellular rljGH accumulation (17 h) resulted in a low final cell density of 226 g l−1. Thus, a novel strategy of induction at a cell density of 320 g l−1 was investigated. In this strategy, the preinduction glycerol-feeding scheme had a significant effect on the post-induction
production. Constant glycerol feeding led to a decrease of the specific rljGH production and specific production rate because
of low preinduction specific growth rate. This decrease was avoided by exponential glycerol feeding to maintain a preinduction
specific growth rate of 0.16 h−1. The results from exponential glycerol feeding indicated that the rljGH production depended on the preinduction specific
growth rate. Moreover, mixed feeding of methanol and glycerol during induction improved the specific production rate to 0.07 mg
g−1 h−1 from 0.043 mg g−1 h−1. Consequently, both high cell density (428 g l−1) and high rljGH production could be achieved by the novel strategy: growing the cells at the specific growth rate of 0.16 h−1 to the cell density of 320 g l−1 and inducing the expression by mixed feeding. 相似文献
13.
Ping Su Anders Henriksson Christina Nilsson Hazel Mitchell 《World journal of microbiology & biotechnology》2008,24(9):1837-1842
The aim of this study was to assess the effect of a commercial green tea extract (TEAVIGO™) on the microbial growth of three
probiotic strains (Lactobacillus and Bifidobacterium), as well as three pathogenic bacteria. MIC and co-culture studies were performed. The MICs of the green tea extract against
Staphylococcus aureus and Streptococcus pyogenes (100 μg ml−1) were considerably lower than those against the probiotic strains tested (>800 μg ml−1) and Escherichia coli (800 μg ml−1). In co-culture studies, a synergistic effect of the probiotic strains and the green tea extract was observed against both
Staph. aureus and Strep. pyogenes. Green tea extract in combination with probiotics significantly reduced the viable count of both pathogens at 4 h and by
24 h had completely abolished the recovery of viable Staph. aureus and Strep. pyogenes. These reductions were more significant than the reductions induced by probiotics or green tea extracts used separately.
These results demonstrate the potential for combined therapy using the green tea extract plus probiotics on microbial infections
caused by Staph. aureus and Strep. pyogenes. As probiotics and the green tea extract are derived from natural products, treatment with these agents may represent important
adjuncts to, or alternatives to, conventional antibiotic therapy. 相似文献
14.
Orlita A Sidwa-Gorycka M Malinski E Czerwicka M Kumirska J Golebiowski M Lojkowska E Stepnowski P 《Biotechnology letters》2008,30(3):541-545
Growth of Ruta graveolens shoots was induced when Bacillus sp. cell lysates were added to the culture medium. Elicitation of coumarin by this lysate was also very effective; the concentrations
of isopimpinelin, xanthotoxin and bergapten increased to 610, 2120 and 1460 μg g−1 dry wt, respectively. It also had a significant effect on the production of psoralen and rutamarin (680 and 380 μg g−1 dry wt) and induced the biosynthesis of chalepin, which was not detected in the control sample, up to 47 μg g−1 dry wt With lysates of the Pectobacterium
atrosepticum, their effect on growth was not so significant and had no effect on the induction of coumarin accumulation. But elicitation
with this lysate was much more effective for inducing the production of furoquinolone alkaloids; the concentrations of γ-fagarine,
skimmianine, dictamnine and kokusaginine rose to 99, 680, 172 and 480 μg g−1 dry wt, respectively. 相似文献
15.
K. Kapsopoulou A. Mourtzini M. Anthoulas E. Nerantzis 《World journal of microbiology & biotechnology》2007,23(5):735-739
Four mixed culture fermentations of grape must were carried out with Kluyveromyces thermotolerans strain TH941 and Saccharomyces cerevisiae strain SCM952. In the first culture, both yeasts were added together, whereas in the remaining three cultures S. cerevisiae was added 1, 2, and 3 days after the inoculation of K. thermotolerans. The growth and survival of the K. thermotolerans strain and the amount of the produced l-lactic acid depend on the time of inoculation of the S. cerevisiae strain and provided an effective acidification during alcoholic fermentation. The four cultures contained, respectively,
at the end of fermentation 0.18, 1.80, 4.28, and 5.13 g l-lactic acid l−1. The grape must with an initial pH of 3.50 was effectively acidified (70% increase in titratable acidity, 0.30 pH unit decrease)
by the production of 5.13 g l-lactic acid l−1. 相似文献
16.
Dimitris Petroutsos Petros Katapodis Paul Christakopoulos Dimitris Kekos 《Journal of applied phycology》2007,19(5):485-490
The ability of Tetraselmis marina, a green coastal microalga, to remove chlorophenols under photoautotrophic conditions was investigated. T.marina was able to grow in the presence of 20 mg L−1 of the phenolic compounds tested. The EC50 (growth rate) value of p-chlorophenol (p-CP) to T.marina was found to be 25.5 mg L−1. The microalga was able to remove chlorophenols, showing higher efficiency for p-CP. The effect of photoregime and NaHCO3 concentration on p-CP removal was investigated. Under continuous illumination with 1 g L−1 NaHCO3 initial concentration T.marina removed 65% of 20 mg L−1 in a 10-day cultivation period. 相似文献
17.
The biokinetics of glucose metabolism were evaluated in Aeromonas hydrophila during growth in an anaerobic biosystem. After approx 34 h growth, A. hydrophila metabolized 5,000 mg glucose l−1 into the end-products ethanol, acetate, succinate and formate. The maximum growth rate, μ
m, half saturation coefficients, K
s, microbial yield coefficient, Y, cell mass decay rate coefficient, k
d, and substrate inhibition coefficient, K
si were 0.25 ± 0.03 h−1, 118 ± 31 mg glucose l−1, 0.12 μg DNA mg glucose−1, 0.01 h−1, and 3,108 ± 1,152 mg glucose l−1, respectively. These data were used to predict the performance of a continuous growth system with an influent glucose concentration
of 5,000 mg l−1. Results of the analysis suggest that A. hydrophila will metabolize glucose at greater than 95% efficiency when hydraulic retention times (HRTs) exceed 7 h, whereas the culture
is at risk of washing out at an HRT of 6.7 h. 相似文献
18.
Lakkana Laopaiboon Pornthap Thanonkeo Prasit Jaisil Pattana Laopaiboon 《World journal of microbiology & biotechnology》2007,23(10):1497-1501
Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations.
The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 108 cells ml−1 and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y
ps) and productivity (Q
p
) were 100 g l−1, 0.42 g g−1 and 1.67 g l−1 h−1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar
concentration of 24 °Bx was one-time substrate feeding, where P, Y
ps and Q
p
were 120 g l−1, 0.48 g g−1 and 1.11 g l−1 h−1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of
ethanol concentration and product yield. 相似文献
19.
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
20.
Meiru Li Hongqing Li Huawu Jiang Guojiang Wu 《Plant Cell, Tissue and Organ Culture》2008,93(3):249-255
Broussonetia papyrifera is well-known for its bark fibers, which are used for making paper, cloth, rope etc. This is the first report of a successful
genetic transformation protocol for B. papyrifera using Agrobacterium tumefaciens. Callus was initiated at a frequency of about 100% for both leaf and petiole explants. Shoots formed on these calli with
a success rate of almost 100%, with 14.08 and 8.36 shoots regenerating from leave-derived and petiole-derived callus, respectively.
For genetic transformation, leaf explants of B. papyrifera were incubated with A. tumefaciens strain LBA4404 harboring the binary vector pCAMBIA 1301 which contains the hpt gene as a selectable marker for hygromycin resistance and an intron-containing β-glucuronidase gene (gus-int) as a reporter gene. Following co-cultivation, leaf explants were cultured on Murashige and Skoog (Physiol Plant 15:473,
1962) (MS) medium supplemented with 1.5 mg l−1 benzyladenine (BA) and 0.05 mg l−1 indole-3-butyric acid (IBA) (CI medium) containing 5 mg l−1 hygromycin and 500 mg l−1 cefotaxime, in the dark. Hygromycin-resistant calli were induced from leaf explants 3 weeks thereafter. Regenerating shoots
were obtained after transfer of the calli onto MS medium supplemented with 1.5 mg l−1 BA, 0.05 mg l−1 IBA, and 0.5 mg l−1 gibberellic acid (GA3) (SI medium), 5 mg l−1 hygromycin and 250 mg l−1 cefotaxime under fluorescent light. Finally, shoots were rooted on half strength MS medium (1/2 MS) supplemented with 10 mg l−1 hygromycin. Transgene incorporation and expression was confirmed by PCR, Southern hybridisation and histochemical GUS assay.
Using this protocol, transgenic B. papyrifera plants containing desirable new genes can be obtained in approximately 3 months with a transformation frequency as high as
44%. 相似文献