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Query: UMLS:C0085631 (agitation)
 12,064 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Laminaria japonica gametophytic cells were cultivated in a photobioreactor under continuous shear stress (0-1000 r/min) in 60 hours and the following static cultivation within 23.5 days. The content of chlorophyll a reached the maximum value of 2.36 mg/L at the end of continuous shear stress when the agitation speed was 90 r/min, while the chlorophyll a (chl a) concentration decreased quickly and nitrogen and phosphorus were released under high shear force (270-1000 r/min). The cell injury ratio at 1000r/min was as 18 times as that of the control. During the recovery course, gametophytic cells showed themselves distinct recovery capability at all agitation speeds. Furthermore, the content of chl a is a more exact index as biomass than dry cells weight (DCW). Besides cell injury ratio, the liberation of phosphorus demonstrates the cells injury.
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PMID:[Effects of short-term continuous shear stress on cells growth and recovery of Laminaria japonica gametophytic cells in photobioreactor]. 1805 78

Today we use many drugs produced by microorganisms. However, when these drugs were discovered it was found that the yields were low and a substantial effort had to be put in to develop commercially viable processes. A key part of this endeavor was the studies of the nutritional and the engineering parameters. In this chapter, the basic principles of optimizing the nutritional and engineering aspect of the production process are described with appropriate examples. It was found that two critical components of nutritional medium, carbon and nitrogen source regulated the synthesis of the compounds of interest. Rapidly utilizable carbon source such as glucose supported the growth but led to catabolite repression and alternative carbon sources or methods of addition had to be devised. Inorganic nitrogen sources led to undesirable changes in pH of the medium. Organic nitrogen sources could influence the yields positively or negatively and had to be chosen carefully. Essential nutrients like phosphates often inhibited the synthesis and its concentration had to be maintained below the inhibitory levels. On many occasions, trace nutrients like metal ions and vitamins were found to be critical for good production. Temperature and pH were important environmental variables and their optimum values had to be determined. The media were designed and optimized initially with 'one variable at a time' approach and later with experimental design based on statistics. The latter approach is preferred because it is economical, considers interactions between medium components and allows rapid optimization of the process. The engineering aspects like aeration, agitation, medium sterilization, heat transfer, process monitoring and control, become critical as the process is scaled-up to the production size. Aeration and agitation are probably the most important variables. In many processes dissolved oxygen concentration had to be maintained above a critical value to obtain the best yields. The rheological properties of fermentation broth significantly affect the aeration and mixing efficiency. The removal of heat from the large fermentors can be difficult under certain conditions. However, new designs of impellers, availability of sensors to monitor important physiological and process variables and advent of computers have facilitated successful scale-up of fermentation processes.
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PMID:Nutritional and engineering aspects of microbial process development. 1808 19

The cell-associated vaccine strain CVI 988, which is the active component of several commercial Marek's disease vaccines, normally is frozen and stored in liquid nitrogen. In order to ascertain good efficacy of the vaccine, it is crucial that the right procedures are followed for thawing and diluting of the virus. In the study presented here, ampoules containing the frozen product were taken from storage in liquid nitrogen and were thawed in a water bath at 27 C, which is similar to a lukewarm bath, and in a water bath at 37 C, with and without agitation. The effect of the thawing procedure on the live virus titer of the vaccine was investigated. Samples of thawed vaccine were diluted in diluent with different temperatures, and live virus titers were determined directly after dilution and after incubation of the diluted vaccine at different temperatures. The results show that directly after thawing in the water baths at 27 C and 37 C, with or without agitation, the live virus titers for CVI 988 were all in the same range. After incubation of the thawed virus at both temperatures for 15 min, the live virus titers were still in the same range. Decreases in live virus titers were observed after incubation for 4 hr. Live virus titration of the vaccine in diluent in different temperatures revealed that the highest titers were found with diluent at a temperature of 30 C to 37 C and the lowest titers in diluent at a temperature of 5 C. In addition, a combination product containing cell-associated CVI 988 and cell-associated herpesvirus of turkeys (HVT) was tested. For this combination product, the titers for HVT also were highest in diluent with a high temperature (i.e., 37 C), whereas the titers for CVI were highest in diluent at a temperature of 22 C. Both strains had relatively low titers in diluent at 5 C. After incubation of the diluted vaccine at the various temperatures for several hours, again, live virus titrations were done. Live virus titers were most stable with diluent at temperatures of 22 C. Vaccine virus diluted in diluent at 37 C could be stabilized by placing the diluted vaccine at 5 C directly after diluting. After evaluation of these data, the following is recommended. For thawing of the vaccine, a water bath at approximately 27 C, which is similar to a lukewarm bath, is preferred. For diluting the vaccine, diluent should be used at a temperature of 22 C or higher. If diluted in diluent at temperatures higher than 22 C, the diluted vaccine should be stored under cooling in order to avoid titer losses.
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PMID:Determination of optimal conditions for thawing and diluting cell-bound CVI 988 Marek's disease vaccine and stability of the diluted vaccine. 1825 10

Increased popularity of attached-growth wastewater treatment systems (e.g. biological aerated filtration processes-BAF) has created the need for a rapid and reliable method of characterizing biofilms. In addition to the mass of the biofilm that may serve as a control parameter for attached-growth treatment systems, the nitrogen content of the biofilm is also of great interest with increasingly strict nitrogen removal guidelines. Existing methods that may be used to analyse biofilms in such processes involve complex sample preparation and microbiological expertise that limit their application in many biofilm wastewater treatment studies and at existing treatment facilities as a feasible method of monitoring the biofilm. This paper describes a simple technical procedure that enables biofilm samples attached to polystyrene beads to be characterized in terms of the biofilm mass and the nitrogen content of the biofilm. The proposed protocol incorporates an agitation procedure that demonstrates 99.9% removal of the biofilm from polystyrene beads; a modified TSS procedure that measures the removed biofilm mass; and subsequently a modified total Kjeldahl nitrogen (TKN) procedure that enables the nitrogen content of the biofilm to be measured directly on the filter. Moreover, this protocol allows numerous beads to be analysed with limited manipulation and without the loss of critical mass.
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PMID:Rapid and reliable quantification of biofilm weight and nitrogen content of biofilm attached to polystyrene beads. 1843 29

A Bacillus subtilis strain isolated from contaminated soil from a refinery has been screened for biosurfactant production in crystal sugar (sucrose) with different nitrogen sources (NaNO(3), (NH(4))(2)SO(4), urea, and residual brewery yeast). The highest reduction in surface tension was achieved with a 48-h fermentation of crystal sugar and ammonium nitrate. Optimization of carbon/nitrogen ratio (3, 9, and 15) and agitation rate (50, 150, and 250 rpm) for biosurfactant production was carried out using complete factorial design and response surface analysis. The condition of C/N 3 and 250 rpm allowed the maximum increase in surface activity of biosurfactant. A suitable model has been developed, having presented great accordance experimental data. Preliminary characterization of the bioproduct suggested it to be a lipopeptide with some isomers differing from those of a commercial surfactin.
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PMID:Optimizing carbon/nitrogen ratio for biosurfactant production by a Bacillus subtilis strain. 1847 10

The strain Saccharomyces cerevisiae W303-181, having the plasmid YEpPGK-G6P (built by coupling the vector YEPLAC 181 with the promoter phosphoglycerate kinase 1), was cultured by fed-batch process in order to evaluate its capability in the formation of glucose 6-phosphate dehydrogenase (EC.1.1.1.49). Two liters of culture medium (10.0 g/L glucose, 3.7 g/L yeast nitrogen broth (YNB), 0.02 g/L L-tryptophan, 0.02 g/L L-histidine, 0.02 g/L uracil, and 0.02 g/L adenine) were inoculated with 1.5 g dry cell/L and left fermenting in the batch mode at pH 5.7, aeration of 2.2 vvm, 30 degrees C, and agitation of 400 rpm. After glucose concentration in the medium was lower than 1.0 g/L, the cell culture was fed with a solution of glucose (10.0 g/L) or micronutrients (L-tryptophan, L-histidine, uracil, and adenine each one at a concentration of 0.02 g/L) following the constant, linear, or exponential mode. The volume of the culture medium in the fed-batch process was varied from 2 L up to 3 L during 5 h. The highest glucose 6-phosphate dehydrogenase activity (350 U/L; 1 U=1 micromol of NADP/min) occurred when the glucose solution was fed into the fermenter through the decreasing linear mode.
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PMID:Fed-batch production of glucose 6-phosphate dehydrogenase using recombinant Saccharomyces cerevisiae. 1847 28

This study investigates the ability of sucrose to protect spermatozoa against mitochondrial damage, artificial cryoinduction of capacitation, and acrosome reaction. Spermatozoa were isolated using the swim-up procedure performed using three different media: (a) human tubal fluid (HTF, control) medium; (b) HTF with 1% human serum albumin (HSA); and (c) HTF with 1% HSA and 0.25 M sucrose. From each group, 30 mul suspensions of cells were dropped directly into liquid nitrogen and stored for at least 24 h. Cells were thawed by quickly submerging the spheres in HTF with 1% HSA at 37 degrees C with gentle agitation. Sperm motility, viability, mitochondrial membrane potential integrity, spontaneous capacitation, and acrosome reaction were investigated. Sperm viability, acrosome reaction, and capacitation were detected using the double fluorescence chlortetracycline-Hoechst 33258 staining technique. Mitochondrial function was evaluated using a unique fluorescent cationic dye, 5,5',6,6'-tetrachloro-1-1',3,3'-tetraethyl-benzamidazolocarbocyanin iodide, commonly known as JC-1. The number of progressively motile spermatozoa was significantly higher in the sucrose-supplemented medium group (57.1+/-3.2%, P<0.05) when compared with controls (19.4+/-1.9%). The combination of HSA and sucrose (65.2+/-2.6%) has a stronger cryoprotective effect on the integrity of mitochondrial membrane potential (P<0.05) compared with HSA alone (32.6+/-4.7%). In conclusion, vitrification of human spermatozoa with non-permeable cryoprotectants such as HSA and sucrose can effectively cryopreserve the cells without significant loss of important physiological parameters.
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PMID:Acrosomal status and mitochondrial activity of human spermatozoa vitrified with sucrose. 1848 75

A preliminary screening work selected Penicillium restrictum as a promising micro-organism for lipase production. The physiological response of the fungus towards cell growth and enzyme production upon variable carbon and nitrogen nutrition, specific air flow rate (Qa) and agitation (N) was evaluated in a 5-L bench-scale fermenter. In optimized conditions for lipase production meat peptone at 2% (w/v) and olive oil at 1% (w/v) were used in a growth medium with a C/N ratio of 9.9. Higher C/N ratios favored cell growth in detriment of enzyme production. Low extracellular lipase activities were observed using glucose as carbon source suggesting glucose regulation. Final lipase accumulation of 13,000 U/L was obtained, using optimized specific air flow rate (Qa) of 0.5 wm and an impeller speed (N) of 200 rpm. Agitation showed to be an important parameter to ensure nutrient availability in a growth medium having olive oil as carbon source.
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PMID:Lipase production by Penicillium restrictum in a bench-scale fermenter : effect of carbon and nitrogen nutrition, agitation, and aeration. 1857 99

Expression kinetics of the human Epidermal Growth Factor (hEGF) from the alpha-factor prepro region in a 2-mum based plasmid was studied in Saccharomyces cerevisiae. Production of hEGF was highly medium de pendent as a chemically defined, nonenriched media had a significantly lower yield than did enriched media. Also cells grown on yeast nitrogen base without amino acids with casamino acids degraded the hEGF after cell growth as opposed to a yeast extract, peptone, and dextrose (YEPD) medium, which elicited no measurable extracellular proteolysis of the hEGF. alpha-factor directed production kinetics of hEGF on the YEPD medium were growth associated, secretion limitations and extracellular degradation were negligible, and the hEGF was nearly 100% selectively secreted. With sufficient agitation, shake flask experiments were representative of aerated controlled batch fermentations. No effect of high cell density was observed on cell growth or hEGF production kinetics. The hollow fiber bioreactor had no direct effect on the substrate or protein yields of S. cerevisiae, however the low oxygen transfer capacity of the membrane was not sufficient to support respiration.
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PMID:alpha-Factor directed expression of the human epidermal growth factor in Saccharomyces cerevisiae. 1858 11

The efficiency of two different agitation systems (airlift and paddlewheel) in the biomass photoproduction of a nitrogen-fixing filamentous blue-green alga was evaluated outdoors, and the elemental and molecular composition of the cells grown with each system was analyzed. With the paddlewheel system, the productivity values achieved were over 30% higher than with the airlift system, both in summer and winter. In this last season, a conversion efficiency of total solar energy into stored biomass energy of 3.3% was estimated for the paddlewheel system. Moreover, the algal cells grown with this system exhibited a higher net protein (58.9% of dry weight) and nitrogen (11.3%) content than those grown with the airlift device, with an estimated nitrogen fixation rate of more than 2 g N m(-2) day(-1). These advantages of the paddlewheel system make this procedure more appropriate for the large-scale photoproduction of nitrogen-fixing blue-green algae outdoors.
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PMID:Analysis of the biomass quality and photosynthetic efficiency of a nitrogen-fixing cyanobacterium grown outdoors with two agitation systems. 1858 68


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