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1.
Sirisansaneeyakul S Luangpipat T Vanichsriratana W Srinophakun T Chen HH Chisti Y 《Journal of industrial microbiology & biotechnology》2007,34(5):381-391
Production of lactic acid from glucose by immobilized cells of Lactococcus lactis IO-1 was investigated using cells that had been immobilized by either entrapment in beads of alginate or encapsulation in
microcapsules of alginate membrane. The fermentation process was optimized in shake flasks using the Taguchi method and then
further assessed in a production bioreactor. The bioreactor consisted of a packed bed of immobilized cells and its operation
involved recycling of the broth through the bed. Both batch and continuous modes of operation of the reactor were investigated.
Microencapsulation proved to be the better method of immobilization. For microencapsulated cells at immobilized cell concentration
of 5.3 g l−1, the optimal production medium had the following initial concentrations of nutrients (g l−1): glucose 45, yeast extract 10, beef extract 10, peptone 7.5 and calcium chloride 10 at an initial pH of 6.85. Under these
conditions, at 37 °C, the volumetric productivity of lactic acid in shake flasks was 1.8 g l−1 h−1. Use of a packed bed of encapsulated cells with recycle of the broth through the bed, increased the volumetric productivity
to 4.5 g l−1 h−1. The packed bed could be used in repeated batch runs to produce lactic acid. 相似文献
2.
Joong Kon Park Yong Biao Jin Hyung Woo Park 《Biotechnology and Bioprocess Engineering》1997,2(2):132-135
We prepared capsules containingSaccharomyces cerevisiae andZoogloea ramigera cells for the removal of lead (II) and cadmium ions. Microbial cells were encapsulated and cultured in the growth medium.
TheS. cerevisiae cells grown in the capsule did not leak through the capsule membrane. The dried cell density reached to 250 g/l on the basis
of the inner volume of the 2.0 mm diameter capsule after 36 hour cultivation. The dry whole cell exopolymer density of encapsulatedZ. ramigera reached to 200 g/L. The capsule was crosslinked with triethylene tetramine and glutaric dialdehyde solutions. The cadmium
uptake of encapsulated whole cell exopolymer ofZ. ramigera was 55 mg Cd/g biosorbent. The adsorption line followed well Langmuir isotherm. The lead uptake of the encapsulatedS. cerevisiae was about 30 mg Pb/g biomass. The optimum pH of the lead uptake using encapsulatedS. cerevisiae was found to be 6. Freundlich model showed a little better fit to the adsorption data than Langmuir model. 95 percent of
the lead adsorbed on the encapsulated biosorbents was desorbed by the 1 M HCl solution. The capsule was reused 50 batches
without loosing the metal uptake capacity. And the mechanical strength of the crosslinked capsule was retained after 50 trials. 相似文献
3.
The biochemical oxygen demand (BOD) value is still a key parameter that can determine the level of organics, particularly
the content of biodegradable organics in water. In this work, the effects of sample dilution, which should be done inevitably
to get appropriate dissolved oxygen (DO) depletion, on the measurement of 5-day BOD (BOD5), was investigated with and without seeding using natural and synthetic water. The dilution effects were also evaluated for
water samples taken in different seasons such as summer and winter because water temperature can cause a change in the types
of microbial species, thus leading to different oxygen depletion profiles during BOD testing. The predation phenomenon between
microbial cells was found to be dependent on the inorganic nutrients and carbon sources, showing a change in cell populations
according to cell size after 5-day incubation. The dilution of water samples for BOD determination was linked to changes in
the environment for microbial growth such as nutrition. The predation phenomenon between microbial cells was more important
with less dilution. BOD5 increased with the specific amount of inorganic nutrient per microbial mass when the natural water was diluted. When seeding
was done for synthetic water samples, the seed volume also affected BOD due to the rate of organic uptake by microbes. BOD5 increased with the specific bacterial population per organic source supplied at the beginning of BOD measurement. For more
accurate BOD measurements, specific guidelines on dilution should be established. 相似文献
4.
Two different high-cell-density cultivation processes based on the mutant Saccharomyces cerevisiae GE-2 for simultaneous production of glutathione and ergosterol were investigated. Compared with keeping the ethanol volumetric
concentration at a constant low level, feedback control of glucose feeding rate (F) by keeping the descending rate of ethanol volumetric concentration (ΔE/Δt) between −0.1% and 0.15% per hour was much more efficient to achieve a high glutathione and ergosterol productivity. This
bioprocess overcomes some disadvantages of traditional S. cerevisiae-based cultivation process, especially shortening cultivation period and making the cultivation process steady-going. A classical
on or off controller was used to manipulate F to maintain ΔE/Δt at its set point. The dry cell weight, glutathione yield and ergosterol yield reached 110.0 ± 2.6 g/l, 2,280 ± 76 mg/l, and
1,510 ± 28 mg/l in 32 h, respectively. 相似文献
5.
Motohiko Hikuma Hiroshi Suzuki Yakeo Yasuda Isao Karube Shuichi Suzuki 《Applied microbiology and biotechnology》1979,8(4):289-297
Summary A microbial electrode consisting of immobilized living whole cells of yeasts, porous membrane and an oxygen electrode was prepared for continuous estimation of biochemical oxygen demand (BOD). Immobilized Trichosporon cutaneum was employed for the microbial electrode sensor for BOD. When a sample solution containing the equivalent amount of glucose and glutamic acid was injected into the sensor system, the current of the electrode decreased markedly with time until steady state was reached. The response time was within 18 min. A linear relationship was observed between the current decrease and the concentration below 41 mg l
– of glucose and 41 mg l
– glutamic acid (5-day BOD 60 mg l
–). The current decrease was reproducible within ± 6% of the relative error when a sample solution containing 27 mg l
– of glucose and 27 mg l
– of glutamic acid (5-day BOD 40 mg l
–) was employed. The microbial electrode sensor was applied to untreated waste waters from a fermentation factory. Good comparative results were obtained between BOD estimated by the microbial electrode and that determined by the conventional 5-day method (regression coefficient was 1.2). Furthermore, the effect of various compounds on BOD estimation was also examined. The current output of the microbial electrode sensor was almost constant for 17 d and 400 tests. 相似文献
6.
Disposable sensor for biochemical oxygen demand 总被引:6,自引:0,他引:6
Disposable-type microbial sensors were prepared for the determination of biochemical oxygen demand (BOD). The yeast, Trichosporon cutaneum, was directly immobilized on the surface of miniature oxygen electrodes using an ultraviolet crosslinking resin (ENT-3400).
The oxygen electrodes (15 mm× 2 mm×0.4 mm) were made on silicon substrates using micromachining techniques. They were Clark-type
two-electrode systems with−1021 mV applied to the working electrode. Typical response times of the BOD sensors were in the
range of 7–20 min. At 20°C, the sensors’ dynamic range was from 0 to 18 mg/l BOD when a glucose/glutamate BOD standard solution
was used. The lower limit of detection was 0.2 mg/l BOD. This value was one order of magnitude lower than that of sensors
previously reported. The sensors’ operational lifetime of 3 days was satisfactory for a disposable type. The sensors’ responses
were reproducible to within 8% relative standard deviation. The BOD sensors’ were applied to untreated and treated waste waters
from industrial effluents and municipal sewage. BOD values determined using these sensors correlated well with those determined
by the conventional 5-day BOD determination method.
Received: 22 December 1995/Received revision: 19 February 1996/Accepted: 17 March 1996 相似文献
7.
Kalebina TS Farkas V Laurinavichiute DK Gorlovoy PM Fominov GV Bartek P Kulaev IS 《Antonie van Leeuwenhoek》2003,84(3):179-184
It is shown that the deletion of BGL2 gene leads to increase in chitin content in the cell wall of Saccharomyces cerevisiae. A part of the additional chitin can be removed from the bgl2Δ cell wall by alkali or trypsin treatment. Chitin synthase 1 (Chs1) activity was increased by 60 % in bgl2Δ mutant. No increase in chitin synthase 3 (Chs3) activity in bgl2Δ cells was observed, while they became more sensitive to Nikkomycin Z. The chitin level in the cell walls of a strain lacking
both BGL2 and CHS3 genes was higher than that in chs3Δ and lower than that in bgl2Δ strains. Together these data indicate that the deletion of BGL2 results in the accumulation and abnormal incorporation of chitin into the cell wall of S. cerevisiae, and both Chs1 and Chs3 take part in a response to BGL2 deletion in S. cerevisiae cells.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Okino S Suda M Fujikura K Inui M Yukawa H 《Applied microbiology and biotechnology》2008,78(3):449-454
In mineral salts medium under oxygen deprivation, Corynebacterium glutamicum exhibits high productivity of l-lactic acid accompanied with succinic and acetic acids. In taking advantage of this elevated productivity, C. glutamicum was genetically modified to produce d-lactic acid. The modification involved expression of fermentative d-lactate dehydrogenase (d-LDH)-encoding genes from Escherichia coli and Lactobacillus delbrueckii in l-lactate dehydrogenase (l-LDH)-encoding ldhA-null C. glutamicum mutants to yield strains C. glutamicum ΔldhA/pCRB201 and C. glutamicum ΔldhA/pCRB204, respectively. The productivity of C. glutamicum ΔldhA/pCRB204 was fivefold higher than that of C. glutamicum ΔldhA/pCRB201. By using C. glutamicum ΔldhA/pCRB204 cells packed to a high density in mineral salts medium, up to 1,336 mM (120 g l−1) of d-lactic acid of greater than 99.9% optical purity was produced within 30 h. 相似文献
9.
Cadmium induces a heterogeneous and caspase-dependent apoptotic response in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> 总被引:1,自引:0,他引:1
Nargund AM Avery SV Houghton JE 《Apoptosis : an international journal on programmed cell death》2008,13(6):811-821
The toxic metal cadmium is linked to a series of degenerative disorders in humans, in which Cd-induced programmed cell death
(apoptosis) may play a role. The yeast, Saccharomyces cerevisiae, provides a valuable model for elucidating apoptosis mechanisms, and this study extends that capability to Cd-induced apoptosis.
We demonstrate that S. cerevisiae undergoes a glucose-dependent, programmed cell death in response to low cadmium concentrations, which is initiated within
the first hour of Cd exposure. The response was associated with induction of the yeast caspase, Yca1p, and was abolished in
a yca1Δ mutant. Cadmium-dependent apoptosis was also suppressed in a gsh1Δ mutant, indicating a requirement for glutathione. Other apoptotic markers, including sub-G1 DNA fragmentation and hyper-polarization of mitochondrial membranes, were also evident among Cd-exposed cells. These responses
were not distributed uniformly throughout the cell population, but were restricted to a subset of cells. This apoptotic subpopulation
also exhibited markedly elevated levels of intracellular reactive oxygen species (ROS). The heightened ROS levels alone were
not sufficient to induce apoptosis. These findings highlight several new perspectives to the mechanism of Cd-dependent apoptosis
and its phenotypic heterogeneity, while opening up future analyses to the power of the yeast model system. 相似文献
10.
Rupali M. Khadake Prabhakar K. Ranjekar Abhay M. Harsulkar 《Molecular biotechnology》2009,42(2):168-174
The Δ12 desaturase represents a diverse gene family in plants and is responsible for conversion of oleic acid (18:1) to linoleic
acid (18:2). Several members of this family are known from plants like Arabidopsis and Soybean. Using primers from conserved C- and N-terminal regions, we have cloned a novel Δ12 desaturase gene amplified
from flax genomic DNA, denoted as LuFAD2-2. This intron-less gene is 1,149-base pair long encoding 382 amino acids—putative membrane-bound Δ12 desaturase protein. Sequence
comparisons show that the novel sequence has 85% similarity with previously reported flax Δ12 desaturase at amino acid level
and shows typical features of membrane-bound desaturase such as three conserved histidine boxes along with four membrane-spanning
regions that are universally present among plant desaturases. The signature amino acid sequence ‘YNNKL’ was also found to
be present at the N terminus of the protein, which is necessary and sufficient for ER localization of enzyme. Neighbor-Joining
tree generated from the sequence alignment grouped LuFAD2-2 among the other FAD2 sequences from Ricinus, Hevea, Jatropha, and Vernicia. When LuFAD2-2 and LuFAD2 were expressed in Saccharomyces cerevisiae, they could convert the oleic acid to linoleic acid, with an average conversion rate of 5.25 and 8.85%, respectively. However,
exogenously supplied linoleic acid was feebly converted to linolenic acid suggesting that LuFAD2-2 encodes a functional FAD2 enzyme and has substrate specificity similar to LuFAD2. 相似文献
11.
Suzuki T Tamura S Nakanishi H Tashiro M Nishizawa NK Yoshimura E 《Biological trace element research》2007,120(1-3):257-263
The budding yeast Saccharomyces cerevisiae secretes 2-isopropylmalic acid (2-iPMA), an intermediate in leucine biosynthesis. Because 2-iPMA binds Al(III) in the culture
medium, it is thought to reduce toxicity by Al(III). The effects of 2-iPMA and malic acid (MA) on Al toxicity were investigated
in a medium with a low pH and low concentrations of phosphates and magnesium. The reduction in the growth of S. cerevisiae observed in the presence of 100 μM Al(III) ions was relieved more by the addition of 1.0 mM 2-iPMA than by 1.0 mM MA, indicating
that 2-iPMA possesses superior Al(III)-ion detoxification ability. Investigations using the wild type and the Δleu4 and Δleu9 mutant strains indicated that secretion of a sufficient level of 2-iPMA was required to enhance the Al tolerance. It is thought
that 2-iPMA secreted from the yeast cells chelates Al ions and prevents them from entering the cells, resulting in Al tolerance.
Suzuki and Tamura contributed equally to this work. 相似文献
12.
Shumiao Zhao Ling Deng Nan Hu Bin Zhao Yunxiang Liang 《World journal of microbiology & biotechnology》2008,24(12):2859-2863
A novel simple solid state fermentation method, netting bag bioreactor (Φ 120 × 800 mm), was developed and used to cultivate
Bacillus licheniformis as probiotics. High spore yield (1.2 × 1011 CFU/g dry substrate) has been obtained by using this method. Comparing to the tray bioreactor and the packed bed bioreactor
for Bacillus fermentation, the netting bag method was more cost-effective, time- and space-saving and the material cost is also as low
as ca. US $293 per 1,000 kg spores. Thus, netting bag SSF can be widely applied to produce probiotic bacteria in developing
areas. 相似文献
13.
Bracesco N Candreva EC Keszenman D Sánchez AG Soria S Dell M Siede W Nunes E 《Radiation and environmental biophysics》2007,46(4):401-407
Checkpoints are components of signalling pathways involved in genome stability. We analysed the putative dual functions of
Rad17 and Chk1 as checkpoints and in DNA repair using mutant strains of Saccharomyces cerevisiae. Logarithmic populations of the diploid checkpoint-deficient mutants, chk1Δ/chk1Δ and rad17Δ/rad17Δ, and an isogenic wild-type strain were exposed to the radiomimetic agent bleomycin (BLM). DNA double-strand breaks (DSBs)
determined by pulsed-field electrophoresis, surviving fractions, and proliferation kinetics were measured immediately after
treatments or after incubation in nutrient medium in the presence or absence of cycloheximide (CHX). The DSBs induced by BLM
were reduced in the wild-type strain as a function of incubation time after treatment, with chromosomal repair inhibited by
CHX. rad17Δ/rad17Δ cells exposed to low BLM concentrations showed no DSB repair, low survival, and CHX had no effect. Conversely, rad17Δ/rad17Δ cells exposed to high BLM concentrations showed DSB repair inhibited by CHX. chk1Δ/chk1Δ cells showed DSB repair, and CHX had no effect; these cells displayed the lowest survival following high BLM concentrations.
Present results indicate that Rad17 is essential for inducible DSB repair after low BLM-concentrations (low levels of oxidative
damage). The observations in the chk1Δ/chk1Δ mutant strain suggest that constitutive nonhomologous end-joining is involved in the repair of BLM-induced DSBs. The differential
expression of DNA repair and survival in checkpoint mutants as compared to wild-type cells suggests the presence of a regulatory
switch-network that controls and channels DSB repair to alternative pathways, depending on the magnitude of the DNA damage
and genetic background.
Nelson Bracesco and Ema C. Candreva have contributed equally to this article. 相似文献
14.
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
15.
Konstantin Schneider Verena Schütz Gernot Thomas John Elmar Heinzle 《Bioprocess and biosystems engineering》2010,33(5):541-547
We describe a new device with parallel optical measurement of dissolved oxygen (DO) and pH in up to nine shake flasks applicable
in any conventional shaking incubator. Measurement ranges are 0–500% of air saturation for oxygen and 5.5–8.5 for pH. It was
used to characterize growth profiles of different l-lysine producing strains of Corynebacterium glutamicum, of Saccharomyces cerevisiae and of Escherichia coli. Cultures in unbaffled flasks were highly reproducible. Oxygen limitation was indicated online which is particularly important
when cultivating fast growing cells as E. coli. C. glutamicum strains showed distinct characteristic patterns of DO and pH indicating biological events. During the cultivation of S. cerevisiae on glucose, fructose and galactose, oxygen uptake rate was determined using the predetermined value of k
L
a. pH measurement was used to determine the minimum buffer requirement for a culture of C. glutamicum. 相似文献
16.
The biochemical oxygen demand (BOD) test (BOD5) is a crucial environmental index for monitoring organic pollutants in waste water but is limited by the 5-day requirement
for completing the test. We have optimised a rapid microbial technique for measuring the BOD of a standard BOD5 substrate (150 mg glucose/l, 150 mg glutamic acid/l) by quantifying an equivalent biochemical mediator demand in the absence
of oxygen. Elevated concentrations of Escherichia coli were incubated with an excess of redox mediator, potassium hexacyanoferrate(III), and a known substrate for 1 h at 37 °C
without oxygen. The addition of substrate increased the respiratory activity of the microorganisms and the accumulation of
reduced mediator; the mediator was subsequently re-oxidised at a working electrode generating a current quantifiable by a
coulometric transducer. Catabolic conversion efficiencies exceeding 75% were observed for the oxidation of the standard substrate.
The inclusion of a mediator allowed a higher co-substrate concentration compared to oxygen and substantially reduced the incubation
time from 5 days to 1 h. The technique replicates the traditional BOD5 method, except that a mediator is substituted for oxygen, and we aim to apply the principle to measure the BOD of real waste
streams in future work.
Received: 2 August 1999 / Received revision: 6 December 1999 / Accepted: 12 December 1999 相似文献
17.
Kaulin YA Takemoto JY Schagina LV Ostroumova OS Wangspa R Teeter JH Brand JG 《Journal of bioenergetics and biomembranes》2005,37(5):339-399
Sphingolipids with long chain bases hydroxylated at the C4 position are a requisite for the yeast, Saccharomyces cerevisia, to be sensitive to the ion channel forming antifungal agent, syringomycin E (SRE). A mutant S. cerevisiae strain, Δsyr2, having sphingolipids with a sphingoid base devoid of C4-hydroxylation, is resistant to SRE. To explore the mechanism of
this resistance, we investigated the channel forming activity of SRE in lipid bilayers of varying composition. We found that
the addition of sphingolipid-rich fraction from Δsyr2 to the membrane-forming solution (DOPS/DOPE/ergosterol) resulted in lipid bilayers with lower sensitivity to SRE compared
with those containing sphingolipid fraction from wild-type S. cerevisiae. Other conditions being equal, the rate of increase of bilayer conductance was about 40 times slower, and the number of SRE
channels was about 40 times less, with membranes containing Δsyr2 versus wild-type sphingolipids. Δsyr2 sphingolipids altered neither SRE single channel conductance nor the gating charge but the ability of SRE channels to open
synchronously was diminished. The results suggest that the resistance of the Δsyr2 mutant to SRE may be partly due to the ability of sphingolipids without the C4 hydroxyl group to decrease the channel forming
activity of SRE. 相似文献
18.
Ho Nam Chang Byoung Jin Kim Jong Won Kang Chang Moon Jeong Nag-Jong Kim Joong Kon Park 《Biotechnology and Bioprocess Engineering》2008,13(2):123-135
An upflow packed-bed cell recycle bioreactor (IUPCRB) is proposed for obtaining a high cell density. The system is comprised
of a stirred tank bioreactor in which cells are retained partially by a packed-bed. A 1.3 cm (ID) × 48 cm long packed-bed
was installed inside a 2 L bioreactor (working volume 1 L). Continuous ethanol fermentation was carried out using a 100 g/L
glucose solution containing Saccharomyces cerevisiae (ATCC 24858). Cell retention characteristics were investigated by varying the void fraction (VF) of the packed bed by packing
it with particles of 0.8∼2.0 mm sized stone, cut hollow fiber pieces, ceramic, and activated carbon particles. The best results
were obtained using an activated carbon bed with a VF of 30∼35%. The IUPCRB yielded a maximum cell density of 87 g/L, an ethanol
concentration of 42 g/L, and a productivity of 21 g/L/h when a 0.5 h−1 dilution rate was used. A natural bleeding of cells from the filter bed occurred intermittently. This cell loss consisted
of an average of 5% of the cell concentration in the bioreactor when a high cell concentration (approximately 80 g/L) was
being maintained. 相似文献
19.
The anaerobic performance of gpd1Δ and gpd2Δ mutants of Saccharomyces cerevisiae was characterized and compared to that of a wild-type strain under well-controlled conditions by using a high-performance
bioreactor. There was a 40% reduction in glycerol level in the gpd2Δ mutant compared to the wild-type. Also the gpd1Δ mutant showed a slight decrease in glycerol formation but to a much lesser degree. As a consequence, ethanol formation in
the gpd2Δ mutant was elevated by 13%. In terms of growth, the gpd1Δ mutant and the wild-type were indistinguishable. The gpd2Δ mutant, on the other hand, displayed an extended lag phase as well as a reduced growth rate under the exponential phase.
Even though glycerol-3-phosphate dehydrogenase 2 (GPD2) is the important enzyme under anaerobic conditions it can, at least
in part, be substituted by GPD1. This was indicated by the higher expression level of GPD1 in the gpd2Δ mutant compared to the wild type. These results also show that the cells are able to cope and maintain redox balance under
anaerobic conditions even if glycerol formation is substantially reduced, as observed in the gpd2Δ mutant. One obvious way of solving the redox problem would be to make a biomass containing less protein, since most of the
excess NADH originates from amino acid biosynthesis. However, the gpd2Δ mutant did not show any decrease in the protein content of the biomass.
Received: 16 February 1998 / Received revision: 16 March 1998 / Accepted: 1 June 1998 相似文献
20.
Phlebiopsis gigantea fungus used in biological control of root rot is currently cultivated commercially in disposable, sterilizable plastic bags.
A novel packed bed bioreactor was designed for cultivating P. gigantea and compared to the plastic bag method and to a tray bioreactor. The spore viability of 5.4 × 106 c.f.u./g obtained with the packed bed bioreactor was of the same order of magnitude as the viabilities obtained with the
other cultivation methods. Furthermore, the packed bed bioreactor was less time and space consuming and easier to operate
than the tray bioreactor. 相似文献