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Oxygen Uptake Rate (oxygen + uptake_rate)
Kinds of Oxygen Uptake Rate Selected AbstractsAddition of activated carbon to batch activated sludge reactors in the treatment of landfill leachate and domestic wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001Özgür Akta Abstract Leachate from a municipal landfill was combined with domestic wastewater and was treated in batch activated sludge systems. The effectiveness and applicability of the addition of Powdered Activated Carbon (PAC) to activated sludge reactors was investigated. Isotherm tests were carried out with PAC in order to estimate the extent of adsorption of organic matter onto PAC. Then, in activated sludge reactors COD (Chemical Oxygen Demand) removal and nitrification were studied both in the absence and presence of PAC for comparison purposes. In both cases, Oxygen Uptake Rates (OUR) were measured with respect to time in order to investigate substrate removal and change in microbial activity. Addition of PAC to activated sludge increased COD removal by removing mainly the non-biodegradable fraction in leachate. The COD decreases in batch reactors were best expressed by a first-order kinetic model that incorporated this non-biodegradable leachate fraction. With added PAC, nitrification was also enhanced. But in all of the batch runs a significant accumulation of NO2 -N took place, indicating that the second step of nitrification was still inhibited. © 2001 Society of Chemical Industry [source] Intrinsic Oxygen Use Kinetics of Transformed Plant Root CultureBIOTECHNOLOGY PROGRESS, Issue 3 2001Patrick T. Asplund Root meristem oxygen uptake, root tip extension rate, and specific growth rate are assessed as a function of dissolved oxygen level for three transformed root cultures. The influence of hydrodynamic boundary layer was considered for all measurements to permit correlation of oxygen-dependent kinetics with the concentration of oxygen at the surface of the root meristem. Oxygen uptake rate is shown to be saturated at ambient conditions, and a saturation level of approximately 300 ,mole O2/(cm3 tissue·hr) was observed for all three of these morphologically diverse root types. In nearly all cases, the observation of a minimum oxygen pressure, below which respiration, extension, or root growth would not occur, could be accounted for as a boundary layer mass transfer resistance. The critical oxygen pressure below which respiration declines is below saturated ambient oxygen conditions. In contrast, critical oxygen pressures for root tip extension were much higher; extension was nearly linear for the two thicker root types (Hyoscyamus muticus, henbain; Solanum tuberosum, potato) above ambient oxygen levels. The performance of the thinnest root, Brassica juncea (Indian mustard) was consistent with reduced internal limitations for oxygen transport. Extension rates did not correlate with biomass accumulation. The fastest growing henbain culture (, = 0.44 day,1) displayed the slowest extension rate (0.16 mm/hr), and the slowest growing mustard culture (, = 0.22 day,1) had the fastest tip extension rate (0.3 mm/hr). This apparent paradox is explained in terms of root branching patterns, where the root branching ratio is shown to be dependent upon the oxygen-limited mersitem extension rate. The implications of these observations on the performance of root culture in bioreactors is discussed. [source] Hydrogel-Perfluorocarbon Composite Scaffold Promotes Oxygen Transport to Immobilized CellsBIOTECHNOLOGY PROGRESS, Issue 2 2008Kyuongsik Chin Cell encapsulation provides cells a three-dimensional structure to mimic physiological conditions and improve cell signaling, proliferation, and tissue organization as compared to monolayer culture. Encapsulation devices often encounter poor mass transport, especially for oxygen, where critical dissolved levels must be met to ensure both cell survival and functionality. To enhance oxygen transport, we utilized perfluorocarbon (PFC) oxygen vectors, specifically perfluorooctyl bromide (PFOB) immobilized in an alginate matrix. Metabolic activity of HepG2 liver cells encapsulated in 1% alginate/10% PFOB composite system was 47,104% higher than alginate systems lacking PFOB. A cubic model was developed to understand the oxygen transport mechanism in the alginate/PFOB composite system. The theoretical flux enhancement in alginate systems containing 10% PFOB was 18% higher than in alginate-only systems. Oxygen uptake rates (OURs) of HepG2 cells were enhanced with 10% PFOB addition under both 20% and 5% O2 boundary conditions, by 8% and 15%, respectively. Model predictions were qualitatively and quantitatively verified with direct experimental OUR measurements using both a perfusion reactor and oxygen sensing plate, demonstrating a greater OUR enhancement under physiological O2 boundary conditions (i.e., 5% O2). Inclusion of PFCs in an encapsulation matrix is a useful strategy for overcoming oxygen limitations and ensuring cell viability and functionality both for large devices (>1 mm) and over extended time periods. Although our results specifically indicate positive enhancements in metabolic activity using the model HepG2 liver system encapsulated in alginate, PFCs could be useful for improving/stabilizing oxygen supply in a wide range of cell types and hydrogels. [source] 2,4,6-Trichlorophenol and phenol removal in methanogenic and partially-aerated methanogenic conditions in a fluidized bed bioreactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2005Claudio Garibay-Orijel Abstract A fluidized bed bioreactor (FBBR) was operated for more than 575 days to remove 2,4,6-trichlorophenol (TCP) and phenol (Phe) from a synthetic toxic wastewater containing 80 mg L,1 of TCP and 20 mg L,1 of Phe under two regimes: Methanogenic (M) and Partially-Aerated Methanogenic (PAM). The mesophilic, laboratory-scale FBBR consisted of a glass column (3 L capacity) loaded with 1 L of 1 mm diameter granular activated carbon colonized by an anaerobic consortium. Sucrose (1 g COD L,1) was used as co-substrate in the two conditions. The hydraulic residence time was kept constant at 1 day. Both conditions showed similar TCP and Phe removal (99.9 + %); nevertheless, in the Methanogenic regime, the accumulation of 4-chlorophenol (4CP) up to 16 mg L,1 and phenol up to 4 mg L,1 was observed, whereas in PAM conditions 4CP and other intermediates were not detected. The specific methanogenic activity of biomass decreased from 1.01 ± 0.14 in M conditions to 0.19 ± 0.06 mmolCH4 h,1 gTKN,1 in PAM conditions whereas the specific oxygen uptake rate increased from 0.039 ± 0.008 in M conditions to 0.054 ± 0.012 mmolO2 h,1 gTKN,1, which suggested the co-existence of both methanogenic archaea and aerobic bacteria in the undefined consortium. The advantage of the PAM condition over the M regime is that it provides for the thorough removal of less-substituted chlorophenols produced by the reductive dehalogenation of TCP rather than the removal of the parent compound itself. Copyright © 2005 Society of Chemical Industry [source] The use of 3,3,,4,,5-tetrachlorosalicylanilide as a chemical uncoupler to reduce activated sludge yieldJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2004Ying Xu Chen Abstract To determine whether chemical additions can be used to reduce sludge production in biological wastewater treatment, 3,3,,4,,5-tetrachlorosalicylanilide (TCS) was added to activated sludge cultures as a metabolic uncoupler. Batch tests confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield at concentrations greater than 1.0 mg dm,3; a TCS concentration of 1.0 mg dm,3 reduced sludge yield by approximately 50%. Substrate removal capability and effluent nitrogen concentration were not affected adversely by the presence of TCS when dosed every other day in a range of 2.0,3.6 mg dm,3 during the 40-day operation of activated sludge batch cultures. Such sludge growth reduction was associated with the enhancement of microbial activities in terms of the specific oxygen uptake rate and dehydrogenase activity. Sludge settleability of the treated and control samples was qualitatively comparable and not significantly different. Filamentous bacteria continued to grow in sludge flocs only in the control reactor at the end of the 40-day trial. These results suggest that TCS treatment of activated sludge systems may reduce excess sludge yield. Copyright © 2003 Society of Chemical Industry [source] Mitochondrial proline oxidation is affected by hyperosmotic stress in durum wheat seedlingsANNALS OF APPLIED BIOLOGY, Issue 1 2010M. Soccio The important role of plant mitochondria in the adaptation to environmental stresses at subcellular level has recently emerged. In particular, an important mitochondrial mechanism involved in the resistance to environmental stresses is the inhibition of proline oxidation. In order to study this physiological mechanism, we used both washed and purified durum wheat (Triticum durum) mitochondria (DWM) isolated from early seedlings germinated in two different NaCl solutions leading to either moderate or severe damage to growth. To assess the contribution of the osmotic component of stress, a parallel investigation was performed using hyperosmotic mannitol solutions. Comparison of the oxygen uptake rate in the course of proline oxidation, with that of the malate plus glutamate substrate pair and that of succinate showed that an early inhibition of proline oxidation occurs under stress. The drop of the proline-dependent oxygen uptake rate was as a result of a heavy inhibition of proline dehydrogenase (ProDH); on the other hand, malate plus glutamate-dependent and succinate-dependent oxidations were less inhibited, being the maintenance of oxygen uptake rate not dependent on alternative oxidase (AOX) pathway; in fact, DWM-AOX activity did not show any increase under our experimental stress conditions. The selective inhibition of proline oxidation should be considered a mitochondrial adaptation to stress rather than damage to mitochondrial oxidative properties. This result was achieved by means of a novel approach based on the comparison between oxygen uptake rates of washed and purified organelles. [source] Modeling the partial nitrification in sequencing batch reactor for biomass adapted to high ammonia concentrationsBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006V. Pambrun Abstract Partial nitrification has proven to be an economic way for treatment of industrial N-rich effluent, reducing oxygen and external COD requirements during nitrification/denitrification process. One of the key issues of this system is the intermediate nitrite accumulation stability. This work presents a control strategy and a modeling tool for maintaining nitrite build-up. Partial nitrification process has been carried out in a sequencing batch reactor at 30°C, maintaining strong changing ammonia concentration in the reactor (sequencing feed). Stable nitrite accumulation has been obtained with the help of an on-line oxygen uptake rate (OUR)-based control system, with removal rate of 2 kg NH -N,·,m,3/day and 90%,95% of conversion of ammonium into nitrite. A mathematical model, identified through the occurring biological reactions, is proposed to optimize the process (preventing nitrate production). Most of the kinetic parameters have been estimated from specific respirometric tests on biomass and validated on pilot-scale experiments of one-cycle duration. Comparison of dynamic data at different pH confirms that NH3 and NO should be considered as the true substrate of nitritation and nitratation, respectively. The proposed model represents major features: the inhibition of ammonia-oxidizing bacteria by its substrate (NH3) and product (HNO2), the inhibition of nitrite-oxidizing bacteria by free ammonia (NH3), the INFluence of pH. It appears that the model correctly describes the short-term dynamics of nitrogenous compounds in SBR, when both ammonia oxidizers and nitrite oxidizers are present and active in the reactor. The model proposed represents a useful tool for process design and optimization. © 2006 Wiley Periodicals, Inc. [source] Production of L(+)-lactic acid from glucose and starch by immobilized cells of Rhizopus oryzae in a rotating fibrous bed bioreactorBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2002Abdullatif Tay Abstract A rotating fibrous-bed bioreactor (RFB) was developed for fermentation to produce L(+)-lactic acid from glucose and cornstarch by Rhizopus oryzae. Fungal mycelia were immobilized on cotton cloth in the RFB for a prolonged period to study the fermentation kinetics and process stability. The pH and dissolved oxygen concentration (DO) were found to have significant effects on lactic acid productivity and yield, with pH 6 and 90% DO being the optimal conditions. A high lactic acid yield of 90% (w/w) and productivity of 2.5 g/L·h (467 g/h·m2) was obtained from glucose in fed-batch fermentation. When cornstarch was used as the substrate, the lactic acid yield was close to 100% (w/w) and the productivity was 1.65 g/L·h (300 g/h·m2). The highest concentration of lactic acid achieved in these fed-batch fermentations was 127 g/L. The immobilized-cells fermentation in the RFB gave a virtually cell-free fermentation broth and provided many advantages over conventional fermentation processes, especially those with freely suspended fungal cells. Without immobilization with the cotton cloth, mycelia grew everywhere in the fermentor and caused serious problems in reactor control and operation and consequently the fermentation was poor in lactic acid production. Oxygen transfer in the RFB was also studied and the volumetric oxygen transfer coefficients under various aeration and agitation conditions were determined and then used to estimate the oxygen transfer rate and uptake rate during the fermentation. The results showed that the oxygen uptake rate increased with increasing DO, indicating that oxygen transfer was limited by the diffusion inside the mycelial layer. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 1,12, 2002. [source] A Cyclical Semicontinuous Process for Production of Human ,1 -Antitrypsin Using Metabolically Induced Plant Cell Suspension CulturesBIOTECHNOLOGY PROGRESS, Issue 2 2005Melody M. Trexler Transgenic rice suspension cultures were utilized to produce a human therapeutic protein, recombinant ,1 -antitrypsin (rAAT), in a cyclical, semicontinuous operation. Recombinant protein production was induced by removing the carbon source from the cell culture medium. The transgenic rice cells secreted the rAAT into the medium, and therefore medium exchanges could be performed for consecutive growth and protein expression phases. The process consisted of three cycles over a 25,28 day period, with growth phases lasting 4,6 days each and protein expression phases lasting 2.5,5 days each. Biomass and sugar concentrations, oxygen uptake rate, cell viability, culture pH, total extracellular protein, and active rAAT were measured throughout the cyclical process. The data profiles were reproducible between separate cyclical runs where, following each induction period, cell growth and viability could be reestablished once sucrose was added back to the culture. Volumetric productivities ranged from 3 to 12 mg active rAAT/(L day) for individual cycles with overall volumetric productivities of 4.5 and 7.7 mg active rAAT/(L day). [source] Packed Bed Column Fermenter and Kinetic Modeling for Upgrading the Nutritional Quality of Coffee Husk in Solid-State FermentationBIOTECHNOLOGY PROGRESS, Issue 6 2001Débora Brand Studies were carried out to evaluate solid-state fermentation (SSF) for the upgradation of the nutritional quality of coffee husk by degrading the caffeine and tannins present in it. SSF was carried out by Aspergillus niger LPBx in a glass column fermenter using factorial design experiments and surface response methodology to optimize bioprocess parameters such as the substrate pH and moisture content and aeration rate. The first factorial design showed that the moisture content of the substrate and aeration rate were significant factors for the degradation of toxic compounds, which was confirmed by the second factorial design too. The kinetic study showed that the degradation of toxic compounds was related to the development of the mold and its respiration and also to the consumption of the reducing sugars present in coffee husk. From the values obtained experimentally for the oxygen uptake rate and CO2 evolved, the system determined a biomass yield (Yx/o) of 3.811 (g of biomass)·(g of consumed O2),1 and a maintenance coefficient (m) of 0.0031 (g of consumed O2)·(g biomass of biomass),1·h,1. The best results on the degradation of caffeine (90%) and tannins (57%) were achieved when SSF was carried out with a 30 mL·min,1 aeration rate using coffee husk having a 55% initial moisture content. The inoculation rate did not affect the metabolization of the toxic compounds by the fungal culture. After SSF, the protein content of the husk was increased to 10.6%, which was more than double that of the unfermented husk (5.2%). [source] Oxygen transfer effects in ,-lactamase fermentation by Bacillus licheniformis in a glucose-based defined mediumJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2005nar Çal Abstract The effects of oxygen transfer on the ,-lactamase production by Bacillus licheniformis were investigated in a glucose-based defined medium. The experiments were conducted in 3.0 dm3 batch bioreactor systems at three different air inlet (QO/VR = 0.2, 0.5 and 1.0 vvm) and agitation rates (N = 250, 500 and 750 min,1). During the fermentation, the concentrations of the cell, glucose, by-products, ie organic and amino acids, oxygen transfer coefficients (KLa), yield coefficients, specific rates and oxygen uptake rates (OUR) were determined, in addition to ,-lactamase activities. The highest ,-lactamase activity was obtained at QO/VR = 0.5 vvm and N = 500 min,1 and at QO/VR = 0.2 vvm and N = 500 min,1 conditions, as caA = 90 U cm,3. The highest cell concentration was obtained as CX = 0.67 kg m,3 at QO/VR = 0.5 vvm and N = 750 min,1 and at QO/VR = 0.2 vvm and N = 750 min,1 conditions. The values of KLa increased with increasing agitation and aeration rates and varied between 0.007 and 0.044 s,1, and the OUR varied between 0.4 and 1.6 mol m,3 s,1. With increasing QO/VR and/or N, the Damköhler number (ie the oxygen transfer limitation) decreased owing to the increase in mass transfer coefficients (KLa). The highest instantaneous yield of cell on substrate (YX/S) and yield of cell on oxygen (YX/O) values were respectively obtained at 0.5 vvm and 500 min,1 conditions at t = 2 h as YX/S = 0.72 kg kg,1 and YX/O = 1.49 kg kg,1. The highest instantaneous yield of substrate on oxygen (YS/O) was obtained at 0.5 vvm and 750 min,1 conditions at t = 20 h as YS/O = 8.07 kg kg,1. Copyright © 2005 Society of Chemical Industry [source] Mitochondrial proline oxidation is affected by hyperosmotic stress in durum wheat seedlingsANNALS OF APPLIED BIOLOGY, Issue 1 2010M. Soccio The important role of plant mitochondria in the adaptation to environmental stresses at subcellular level has recently emerged. In particular, an important mitochondrial mechanism involved in the resistance to environmental stresses is the inhibition of proline oxidation. In order to study this physiological mechanism, we used both washed and purified durum wheat (Triticum durum) mitochondria (DWM) isolated from early seedlings germinated in two different NaCl solutions leading to either moderate or severe damage to growth. To assess the contribution of the osmotic component of stress, a parallel investigation was performed using hyperosmotic mannitol solutions. Comparison of the oxygen uptake rate in the course of proline oxidation, with that of the malate plus glutamate substrate pair and that of succinate showed that an early inhibition of proline oxidation occurs under stress. The drop of the proline-dependent oxygen uptake rate was as a result of a heavy inhibition of proline dehydrogenase (ProDH); on the other hand, malate plus glutamate-dependent and succinate-dependent oxidations were less inhibited, being the maintenance of oxygen uptake rate not dependent on alternative oxidase (AOX) pathway; in fact, DWM-AOX activity did not show any increase under our experimental stress conditions. The selective inhibition of proline oxidation should be considered a mitochondrial adaptation to stress rather than damage to mitochondrial oxidative properties. This result was achieved by means of a novel approach based on the comparison between oxygen uptake rates of washed and purified organelles. [source] Expression of merA, trxA, amoA, and hao in continuously cultured Nitrosomonas europaea cells exposed to cadmium sulfate additionsBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Tyler S. Radniecki Abstract The effects of CdSO4 additions on the gene expressions of a mercury reductase, merA, an oxidative stress protein, trxA, the ammonia-monooxygenase enzyme (AMO), amoA, and the hydroxylamine oxidoreductase enzyme (HAO), hao, were examined in continuously cultured N. europaea cells. The reactor was fed 50,mM NH4+ and was operated for 78 days with a 6.9 days hydraulic retention time. Over this period, six successive batch additions of CdSO4 were made with increasing maximum concentrations ranging from 1 to 60,µM Cd2+. The expression of merA was highly correlated with the level of Cd2+ within the reactor (Rs,=,0.90) with significant up-regulation measured at non-inhibitory Cd2+ concentrations. Cd2+ appears to target AMO specifically at lower concentrations and caused oxidative stress at higher concentrations, as indicated by the SOURs (specific oxygen uptake rates) and the up-regulation of trxA. Since Cd2+ inhibition is irreversible and amoA was up-regulated in response to Cd2+ inhibition, it is hypothesized that de novo synthesis of the AMO enzyme occurred and was responsible for the observed recovery in activity. Continuously cultured N. europaea cells were more resistant to Cd2+ inhibition than previously examined batch cultured cells due to the presence of Mg2+ and Ca2+ in the growth media, suggesting that Cd2+ enters the cell through Mg2+ and Ca2+ import channels. The up-regulation of merA during exposure to non-inhibitory Cd2+ levels indicates that merA is an excellent early warning signal for Cd2+ inhibition. Biotechnol. Bioeng. 2009; 104: 1004,1011. © 2009 Wiley Periodicals, Inc. [source] Twenty-four-well plate miniature bioreactor high-throughput system: Assessment for microbial cultivationsBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2007Kevin Isett Abstract High-throughput (HT) miniature bioreactor (MBR) systems are becoming increasingly important to rapidly perform clonal selection, strain improvement screening, and culture media and process optimization. This study documents the initial assessment of a 24-well plate MBR system, Micro (µ)-24, for Saccharomyces cerevisiae, Escherichia coli, and Pichia pastoris cultivations. MBR batch cultivations for S. cerevisiae demonstrated comparable growth to a 20-L stirred tank bioreactor fermentation by off-line metabolite and biomass analyses. High inter-well reproducibility was observed for process parameters such as on-line temperature, pH and dissolved oxygen. E. coli and P. pastoris strains were also tested in this MBR system under conditions of rapidly increasing oxygen uptake rates (OUR) and at high cell densities, thus requiring the utilization of gas blending for dissolved oxygen and pH control. The E. coli batch fermentations challenged the dissolved oxygen and pH control loop as demonstrated by process excursions below the control set-point during the exponential growth phase on dextrose. For P. pastoris fermentations, the µ-24 was capable of controlling dissolved oxygen, pH, and temperature under batch and fed-batch conditions with subsequent substrate shot feeds and supported biomass levels of 278 g/L wet cell weight (wcw). The average oxygen mass transfer coefficient per non-sparged well were measured at 32.6,±,2.4, 46.5,±,4.6, 51.6,±,3.7, and 56.1,±,1.6 h,1 at the operating conditions of 500, 600, 700, and 800 rpm shaking speed, respectively. The mixing times measured for the agitation settings 500 and 800 rpm were below 5 and 1 s, respectively. Biotechnol. Bioeng. 2007;98: 1017,1028. © 2007 Wiley Periodicals, Inc. [source] Bioreactor Production of Human ,1 -Antitrypsin Using Metabolically Regulated Plant Cell CulturesBIOTECHNOLOGY PROGRESS, Issue 3 2002Melody M. Trexler Transgenic rice cell cultures, capable of producing recombinant human ,1 -antitrypsin (rAAT), were scaled up from shake flasks to a 5-L bioreactor. The maximum specific growth rates (,max) observed from two bioreactor runs were 0.40 day,1 (doubling time of 1.7 days) and 0.47 day,1 (doubling time of 1.5 days), and the maximum specific oxygen uptake rates were 0.78 and 0.84 mmol O2/(g dw h). Using a metabolically regulated rice ,-amylase (RAmy3D) promoter, signal peptide, and terminator, sugar deprivation turned on rAAT expression, and rAAT was secreted into the culture medium. After 1 day of culture in sugar-free medium, there was still continued biomass growth, oxygen consumption, and viability. Extracellular concentrations of 51 and 40 mg active rAAT/L were reached 1.7 and 2.5 days, respectively, after induction in a sugar-free medium. Volumetric productivities for two batch cultures were 7.3 and 4.6 mg rAAT/(L day), and specific productivities were 3.2 and 1.6 mg rAAT/(g dw day). Several different molecular weight bands of immunoreactive rAAT were observed on immunoblots. [source] Effect of Elicitation on Growth, Respiration, and Nutrient Uptake of Root and Cell Suspension Cultures of HyoscyamusmuticusBIOTECHNOLOGY PROGRESS, Issue 2 2002Edgard B. Carvalho The elicitation of Hyoscyamus muticus root and cell suspension cultures by fungal elicitor from Rhizoctonia solani causes dramatic changes in respiration, nutrient yields, and growth. Cells and mature root tissues have similar specific oxygen uptake rates (SOUR) before and after the onset of the elicitation process. Cell suspension SOUR were 11 and 18 ,mol O2/g FW·h for non-elicited control and elicited cultures, respectively. Mature root SOUR were 11 and 24 ,mol O2/g FW·h for control and elicited tissue, respectively. Tissue growth is significantly reduced upon the addition of elicitor to these cultures. Inorganic yield remains fairly constant, whereas yield on sugar is reduced from 0.532 to 0.352 g dry biomass per g sugar for roots and 0.614 to 0.440 g dry biomass per g sugar for cells. This reduction in yield results from increased energy requirements for the defense response. Growth reduction is reflected in a reduction in root meristem (tip) SOUR, which decreased from 189 to 70 ,mol O2/g FW·h upon elicitation. Therefore, despite the increase in total respiration, the maximum local oxygen fluxes are reduced as a result of the reduction in metabolic activity at the meristem. This distribution of oxygen uptake throughout the mature tissue could reduce mass transfer requirements during elicited production. However, this was not found to be the case for sesquiterpene elicitation, where production of lubimin and solavetivone were found to increase linearly up to oxygen partial pressures of 40% O2 in air. SOUR is shown to similarly increase in both bubble column and tubular reactors despite severe mass transfer limitations, suggesting the possibility of metabolically induced increases in tissue convective transport during elicitation. [source] | ||||||||||