Effect Of Oxygen Supply Research Articles

Electrochemical Reduction of Oxygen in Organic Solvents With and Without Li+ Cation – Effect of Oxygen Supply

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Effect of oxygen supply on biomass and helvolic acid production in submerged fermentation of Cordyceps taii

The entomogenous fungus Cordyceps taii, a traditional Chinese medicinal mushroom, exhibits potent important pharmacological effects and it has great potential for health foods and medicine. In this work, the effects of oxygen supply on production of biomass and bioactive helvolic acid were studied in shake-flask fermentation of C. taii mycelia. The value of initial volumetric oxygen transfer coefficient (KLa) within 10.1–33.8h−1 affected the cell growth, helvolic acid production and expression levels of biosynthetic genes. The highest cell concentration of 17.2g/L was obtained at 14.3h−1 of initial KLa. The highest helvolic acid production was 9.6mg/L at 10.1h−1 of initial KLa. The expression levels of three genes encoding hydroxymethylglutaryl-CoA synthase, hydroxymethylglutaryl-CoA reductase and squalene synthase were down-regulated on day 2 and day 8 but up-regulated on day 14 at an initial KLa value of 10.1h−1 vs. 33.8h−1, which well corresponded to the helvolic acid biosynthesis in those conditions. The information obtained would be helpful for improving the biomass and helvolic acid production in large-scale fermentation of C. taii.

Effects of Oxygen Supply and Mixed Sugar Concentration on D-Ribose Production by a Transketolase-Deficient Bacillus subtilis SPK1

D-Ribose is a value-added five-carbon sugar used for riboflavin production. To investigate the effects of oxygen supply and mixed sugar concentration on microbial production of D-ribose, a transketolase-deficient Bacillus subtilis SPK1 was cultured batch-wise using xylose and glucose. A change of agitation speed from 300 rpm to 600 rpm at 1 vvm of air supply increased both the xylose consumption rate and D-ribose production rate. Because the sum of the specific consumption rates for xylose and glucose was similar at all agitation speeds, metabolic preferences between xylose and glucose might depend on oxygen supply. Although B. subtilis SPK1 can take up xylose and glucose by the active transport mechanism, a high initial concentration of xylose and glucose was not beneficial for high D-ribose production.

Effect of Oxygen Supply on Glycogen Recovery and AMPK Protein Expression in Post-Exercise

Effect of Oxygen Supply on Glycogen Recovery and AMPK Protein Expression in Post-Exercise

Effects of oxygen supply on the biodegradation rate in oil hydrocarbons contaminated soil

Respirometry studies using the 10–chamber Micro-Oxymax respirometer (Columbus, Ohio) were conducted to determine the effect of biostimulation (by diverse ways of O2 supply) on enhancing biodegradation in soils contaminated with oil hydrocarbons. Soil was collected from a former military airport in Kluczewo, Poland. Oxygen was supplied by means of aerated water, aqueous solutions of H2O2 and KMnO4. The biodegradation was evaluated on the basis of O2 uptake and CO2 production. The O2 consumption and CO2 production rates during hydrocarbons biodegradation were estimated from the slopes of cumulative curve linear regressions. The pertinent intrinsic and enhanced biodegradation rates were calculated on the basis of mass balance equation and O2 uptake and CO2 production rates. The biodegradation rates of 5–7 times higher as compared to a control were observed when the aqueous solution of KMnO4 in concentration of 20 g L−1 was applied. Permanganate is known to readily oxidize alkene carbon – carbon double bonds; so it can be successfully applied in remediation technology for soils contaminated with oil hydrocarbons. While hydrocarbons are not completely mineralized by permanganate oxidation reactions, their structure is altered by polar functional groups providing vast improvements in aqueous solubility and availability for biodegradation. The 3% aqueous solution of H2O2 caused significant improvement of the biodegradation rates as compared to a control (on average about 260%). Aerobic biodegradation of hydrocarbons can benefit from the presence of oxygen released during H2O2 decomposition. Adding of aerated water resulted in an increase of biodegradation rates (about 114 – 229%) as compared to a control. The aerated water can both be the source of oxygen for microorganisms and determine the transport of substrate to bacteria cells.

Effects of Oxygen Supply on Growth and Carotenoids Accumulation by Xanthophyllomyces dendrorhous

The effects of oxygen supply on growth and carotenoids accumulation by Xanthophyllomyces dendrorhous were studied. Initial volumetric oxygen transfer coefficients (K(L)a) within the range 21.5-148.5 h(-1) had significant effects on growth and carotenoids accumulation, and an increase of the initial K(L)a value led to higher carotenoids, astaxanthin and biomass yields by X. dendrorhous. At an initial K(L)a value of 148.5 h(-1), a maximal cell concentration of 19.37 g 1(-1) and optimal carotenoids and astaxanthin productions of 18.1 and 14.5 mg 1(-1) were obtained, as well as a maximal astaxanthin content of 0.8 mg g DCW(-1), respectively. A higher oxygen supply was advantageous to astaxanthin biosynthesis and the ratio of astaxanthin in the total carotenoids. An increasing initial K(L)a value gave stronger fluorescence intensities by X. dendrorhous, resulting in the maximal intensity of fluorescence at the K(L)a value 148.5 h(-1). The cell growth of X. dendrorhous was significantly inhibited when dissolved oxygen tension (DOT) was controlled at approximately 20% air saturation, which was due to the oxygen limitation in broth. The astaxanthin yield and content at approximately 50% DOT were higher than those at approximately 20% DOT.

Aerobic Methane Oxidation Coupled to Denitrification: Kinetics and Effect of Oxygen Supply

Aerobic methane oxidation coupled to denitrification (AME-D) is a process in which aerobic methanotrophs oxidize methane and release organic compounds that are used by coexisting denitrifiers as electron donors for denitrification. This process is potentially promising for denitrification of wastewater or landfill leachate poor in organic carbon using methane produced onsite as external electron donor. We studied the kinetics of an aerobic methane-oxidizing denitrifying culture and investigated the effect of dissolved oxygen (DO) concentration and air supply rate on AME-D using a batch reactor and a semicontinuous reactor setup. At methane concentrations of 18–33% in air and air flow rates of 15–35 mL air L−1 liquid min−1, the DO concentration was less than 0.01 mg L−1 and the nitrate removal reached a maximum value of 56.7 mg NO3–N g−1 VSS d−1 with 79% being attributed to denitrification. When the air supply rate was increased to 70 mL air L−1 liquid min−1 resulting in a drop in methane content to 10%, the DO concentration in the bioreactor rose to about 0.8–1.0 mg L−1 and the total nitrate removal dropped to about 10 mg NO3–N g−1 VSS d−1 with none of it being attributed to denitrification.

Enhancement of Candida parapsilosis catalyzing deracemization of (R,S)‐1‐phenyl‐1, 2‐ethanediol: agitation speed control during cell cultivation

AbstractBACKGROUND: Microbial cells have been used widely in biosynthesis of chiral alcohols. However, research concerning the effect of oxygen supply in cultivation on biocatalytic activity of whole cells in organic synthesis is limited. This study improved the reaction efficiency of Candida parapsilosis catalyzing (R,S)‐1‐phenyl‐1,2‐ethanediol (PED) deracemization by controlling agitation during cell cultivation.RESULTS: The increase of dissolved oxygen concentration by adjusting agitation speed from 200 to 300 rpm at aeration rate 1.5 vvm significantly improved the cell growth of C. parapsilosis and the activities of two key enzymes involved in deracemization. (S)‐PED with higher optical purity of 98.23%e.e. and yield of 82.94% was formed. Compared with the initial fermentation conditions at aeration rate 0.75 vvm and agitation speed 200 rpm, enhanced oxygen supply conditions afforded better cells for highly efficient conversion under higher substrate concentration.CONCLUSION: Oxygen supply had a significant effect on cell growth and catalytic activity of C. parapsilosis catalyzing asymmetric oxidoreduction. By conveniently controlling agitation in cultivation, cell activity and key enzymes production for a complex reaction of concurrent tandem oxidation and reduction processes can easily be conducted, which could help to cultivate cells catalyzing synthesis of interested chiral compounds. Copyright © 2008 Society of Chemical Industry

Effect of Oxygen Supply on Flavor Formation during Continuous Alcohol-Free Beer Production: A Model Study

The influence of oxygen supply on the formation and conversion of the most important flavor compounds during continuous, alcohol-free beer production was studied in a complex model medium. The medium contained inorganic salts, nutrients, and aldehydes (hexanal, 2-methyl propanal, 3-methyl butanal, and furfural) and mimicked real brewery wort, with the advantage of a constant composition. Fermentation experiments were carried out in a continuously operating gas-lift reactor, with brewing yeast immobilized on spent grains. The formation (ethanol, higher alcohols, esters, vicinal diketones, and acetaldehyde) and reduction (aldehydes) of flavor-active compounds at different aeration rates were observed. The results suggest that the oxygen supply represents an influential tool for controlling the degree of fermentation and flavor formation carried out by an immobilized biocatalyst. Under optimal oxygen supply conditions in the continuously operating gas-lift reactor, it was possible to obtain a fermented model medium with a composition approaching that of commercial alcohol-free beers produced by batch process.

Production of extracellular bifidogenic growth stimulator by anaerobic and aerobic cultivations of several propionibacterial strains

Production of a bifidogenic growth stimulator (BGS) by propionic acid bacteria was investigated under anaerobic and aerobic culture conditions. To measure the concentration of extracellular BGS produced by propionic acid bacteria, we evaluated the effects of bioassay conditions using Bifidobacterium longum as a test microorganism on the formation of a growth-stimulation zone. The diameter of the growth-stimulation zone was significantly affected by both the component concentrations and the pH of a bioassay medium. The optimum component concentrations and pH of a bioassay medium were one-half of the normal values and 8.5, respectively. Using the bioassay method, we can measure the concentration of BGS produced by propionic acid bacteria ranging in concentrations from 0.1 microg/l to 1 mg/l using 1,4-dihydroxy-2-naphthoic acid (DHNA) and 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ) as standards. Of six dairy propionic acid bacterial strains tested, the four strains (Propionibacterium freudenreichii ET-3, P. shermanii PZ-3, P. acidipropionici JCM 6432, and P. jensenii JCM 6433) produced BGS at a concentration range of 4-23 mg/l under the anaerobic culture conditions. Analysis of high performance liquid chromatography (HPLC) showed that more than 70% of total BGS produced in supernatant samples was DHNA and no ACNQ was produced by the strains. The effect of oxygen supply on BGS production was investigated for the four BGS-producing strains. The aerobic conditions exerted in positive effects on BGS production by only P. acidipropionici JCM 6432. The concentration of BGS obtained in the aerobic cultivation of P. acidipropionici JCM 6432 was 1.3-fold than that in anaerobic cultivation. Different properties (BGS production as well as cell growth and glucose metabolism) occurring in response to the aerobic conditions were observed, depending on the propionic acid bacterial strain used. This paper is the first report on BGS production by propionibacterial strains except for P. freudenreichii.

Effects of Oxygen Supply on Microbial Xylitol Production from Corn Cobs by Candida Magnoliae

Effects of Oxygen Supply on Microbial Xylitol Production from Corn Cobs by Candida Magnoliae

Effect of oxygen supply on cell growth and saponin production in bioreactor cultures of Panax ginseng

The effects of oxygen supply within the range 20.8-50% (using pure oxygen and air), on cell cultures of Panax ginseng were investigated in a balloon-type bubble bioreactor (5L capacity, containing 4 L Murashige and Skoog medium, supplemented with 7.0 mgL(-1) indolebutyric acid, 0.5 mgL(-1) kinetin and 30 gL(-1) sucrose). A 40% oxygen supply was found to be optimal for the production of both cell mass and saponin yielding values of 12.8 g(DW)L(-1), 4.5mg(gDW)(-1) on day 25, respectively. Low (20.8%, 30%) and high (50%) oxygen concentration supplies were unfavorable to cell growth and saponin accumulation. The results indicate that oxygen supplementation to bioreactor-based ginseng cultures was beneficial for biomass accumulation and saponin production.

Perfusion of the isolated trout heart coronary circulation with red blood cells: effects of oxygen supply and nitrite on coronary flow and myocardial oxygen consumption

A method for perfusion of the isolated trout heart coronary circulation with red blood cells (RBCs) was developed. The method was used to analyse the influence of RBC perfusion on myocardial O(2) supply and O(2) consumption and to test the hypothesis that nitrite is converted to vasoactive nitric oxide in the RBC-perfused coronary circulation. Perfusion with RBCs significantly increased myocardial O(2) supply and O(2) consumption by increasing the incoming O(2) concentration and the O(2) extraction. Coronary flow did not differ between RBC perfusion and saline perfusion, but RBC perfusion established a strong linear increase in myocardial O(2) consumption with coronary flow. Nitric oxide was measured in the atrial effluent of the preparation. Perfusion with saline under hypoxic conditions was associated with NO production. The nitric oxide synthase inhibitor L-NA obliterated this NO production and significantly decreased coronary flow, showing that the NO was vasoactive and probably of endothelial origin. RBC perfusion at low P(O(2)) similarly caused an L-NA-inhibitable NO production. The change in NO production upon subsequent nitrite addition, by contrast, was not inhibited by L-NA. Nitrite entered trout erythrocytes independent of degree of oxygenation, but the O(2) saturation of RBCs showed a major decrease in the coronary circulation, and [NO(2)(-)] decreased while methaemoglobin rose, suggesting that deoxyHb-mediated reduction of nitrite to NO may have occurred. However, other possibilities (e.g. NO(2)(-)-->NO conversion in myocardial cells) cannot be excluded. The NO formation associated with nitrite had no effect on coronary flow, possibly because NO was produced after the resistance vessels.

Effect of oxygen supply on passaging, stabilising and screening of recombinant Hansenula polymorpha production strains in test tube cultures.

Twenty-four Hansenula polymorpha transformants were passaged and stabilised in glucose medium and screened in glycerol medium for recombinant phytase in shaken test tubes. The cultivations were performed under either limited or non-limited oxygen supply. Maximum oxygen transfer capacities of test tubes were assessed by sulfite oxidation. Oxygen-limited glucose cultures resulted in a partially anaerobic metabolism and formation of 4.1 g ethanol l(-1), which was subsequently aerobically metabolised. Non-limited oxygen supply led to overflow metabolism and to accumulation of 2.1 g acetic acid l(-1), reducing the biomass yield. The use of glycerol in the screening main cultures prevented by-product formation irrespective of oxygen supply. Preculturing in glucose medium under non-limited oxygen supply resulted in a 20-h lag phase of the screening main culture. This lag phase was not observed when preculturing was performed under oxygen limitation. Phytase activity was on average 25% higher in cultures passaged, stabilised and screened under limited oxygen supply than in cultures under non-limited oxygen supply.

Role of oxygen supply in submerged fermentation of Ganoderma lucidum for production of Ganoderma polysaccharide and ganoderic acid

The effects of oxygen supply on the submerged fermentation of Ganoderma lucidum, a famous traditional Chinese medicinal mushroom, for simultaneous production of bioactive compounds— Ganoderma polysaccharide and ganoderic acid (GA) were studied. An initial volumetric oxygen transfer coefficient ( K La) value within the range of 16.4–96.0 h −1 had a significant effect on the cell growth, cellular morphology and metabolites biosynthesis. At an initial K La of 78.2 h −1, a maximal cell concentration of 15.62 g l −1 by dry weight was obtained, as well as a maximal intracellular polysaccharide (IPS) production of 2.19 g l −1 and its maximal productivity of 217 mg l −1 per day. An increase of initial K La led to a bigger size of mycelia aggregates and a higher production and productivity of GA. The GA production and productivity at an initial K La of 96.0 h −1 was 1.8-fold those at an initial K La of 16.4 h −1. Dissolved oxygen tension (DOT) also affected the fermentation process. The cell growth of G. lucidum was significantly inhibited when DOT was controlled ∼10% of air saturation, which was due to the oxygen limitation in mycelia aggregates. The production of extracellular polysaccharide (EPS) and contents of IPS and GA ∼10% of DOT were higher than those ∼25% of DOT. However, the total production and productivity of IPS and GA at a low DOT were lower than those at a high DOT. The fundamental information obtained in this study will be useful for submerged fermentation of G. lucidum on a large scale.

エラスターゼ高生産菌のロイシン要求性株による低臭納豆の開発

Since one of the natto flavor components, 3-methyl butanoate is a metabolite of leucine, two leucine-requiring mutants of elastase-producing Bacillus subtilis (natto) KFP 419 were obtained by ultra-violet irradiation to develop natto with weaker flavor. The natto manufactured with these mutants did not contain sticky materials at 41 deg C but turned to be viscous at 43 deg C on program A of the Automatic Natto Manufacturing Instrument. The optimum growth temperature of KFP 419 and the mutants coincided with that for manufacturing good quality of natto. The effect of oxygen supply on the quality of natto was not clarified by an experiment using a respiramy cup at the bottom of which an air-permeable plastic laminated film was spreaded. As the odor of natto made by both mutant was weak to characterize the natto, the volatile components of the head space gas of natto were analyzed by GLC. Although the odor of 3-methyl butanoate was smelled by sniffing at the retention fame of this component its peak was too small to determine quantitatively. It was suggested that the characteristics of the flavors of natto manufactured by the mutants were attributable to complicated quantitative ratio of many volatile components. The elastase activities of the natto of both mutants were lower than that of the parent strain when manufactured at 40 deg C, but were at the same level a the latter when manufactured at 43 deg C.

Scale-up study on suspension cultures of Taxus chinensis cells for production of taxane diterpene.

Suspension cells of Taxus chinensis were cultivated in both shake flasks and bioreactors. The production of taxuyunnanine C (TC) was greatly reduced when the cell cultures were transferred from shake flasks to bioreactors. Oxygen supply, shear stress and stripping-off of gaseous metabolites were considered as potential factors affecting the taxane accumulation in bioreactors. The effects of oxygen supply on the cell growth and metabolism were investigated in a stirred tank bioreactor by altering its oxygen transfer rate (OTR). It was found that both the pattern and amount of TC accumulation were not much changed within the range of OTR as investigated. Comparative studies on the cell cultivation in low shear and high shear generating bioreactors suggest that the decrease of TC formation in bioreactors was not due to the different shear environments in different cultivation vessels. An incorporation of 2% CO(2) in the inlet air was beneficial for the cell growth, but did not improve the TC production in bioreactors. Furthermore, the effects of different levels of ethylene addition into the inlet air on the cell growth and TC production were investigated in a bubble column reactor. The average cell growth rate increased from 0.146 to 0.204 d(-1) as the ethylene concentration was raised from 0 to 50 ppm, and both the content and production of TC were also greatly improved by ethylene addition. At an ethylene concentration of 18 ppm, the highest TC content and volumetric production in the reactor reached 13.28 mg/(g DW) and 163.7 mg/L, respectively, which were almost the same as those in shake flasks. Compared with the control reactor (bubble column without ethylene supplementation), the maximum TC content was increased by 82% and the total production of TC was doubled. The results indicate that ethylene is a key factor in scaling up the process of the suspension cultures of T. chinensis from a shake flask to a bioreactor.

Theoretical Simulation of Oxygen Transport to Brain by Networks of Microvessels: Effects of Oxygen Supply and Demand on Tissue Hypoxia

Theoretical Simulation of Oxygen Transport to Brain by Networks of Microvessels: Effects of Oxygen Supply and Demand on Tissue Hypoxia

Theoretical Simulation of Oxygen Transport to Brain by Networks of Microvessels: Effects of Oxygen Supply and Demand on Tissue Hypoxia

Simulations of oxygen delivery by a three-dimensional network of microvessels in rat cerebral cortex were used to examine how the distribution of partial pressure of oxygen (PO2) in tissue depends on blood flow and oxygen consumption rates. Network geometry was deduced from previously published scanning electron micrographs of corrosion casts. A nonlinear least-squares method, using images obtained at three different angles, was used to estimate vessel locations. The network consisted of 50 segments in a region 140 microm x 150 microm x 160 microm. A Green's function method was used to predict the PO2 distribution. Effects of varying perfusion and consumption were examined, relative to a control state with consumption 10 cm3O2/100 g per min and perfusion 160 cm3/100 g per min. In the control state, minimum tissue PO2, was 7 mm Hg. A Krogh-type model with the same density of vessels, but with uniform spacing, predicted a minimum tissue PO2 of 23 mm Hg. For perfusion below 60% of control, tissue hypoxia (PO2 <1 mm Hg) was predicted. When perfusion was reduced by 75%, the resulting hypoxia could be eliminated by a 31% reduction in oxygen consumption rate. The simulations suggest that tissue hypoxia resulting from a severe decrease in brain perfusion, as can occur in stroke, may be avoided by a moderate decrease in oxygen consumption rate.

Effect of oxygen supply on metabolism of immobilized and suspended Escherichia coli

The effect of reduced oxygen supply on the production of a recombinant protein (plasmid-encoded beta-galactosidase) was investigated in Escherichia coli. A novel modified bubble tank reactor was used to provide a direct comparison between immobilized and suspended cells in identical environments except for the immobilization matrix. Decreased oxygen supply led to increased beta-galactosidase synthesis by both immobilized and suspended cells. Immobilized cells produced similar amounts of beta-galactosidase as the suspended cells. Lactose consumption and acetate production, on a per cell basis, were significantly higher in immobilized cells, suggesting that immobilized cells utilized fermentative metabolism. However, a transport analysis of the immobilized cell system showed that immobilized cells were not subject to either external or internal mass transfer gradients.