Biomedical subjects

Barbara E Wyslouzil

Publications and source records attributed to Barbara E Wyslouzil.

9 recordsLinked to original sources

PubMed2007

Using an aerosol deposition model to increase hairy root growth in a mist reactor.

Gas-phase reactors, including the mist reactor, have distinct advantages over liquid-phase reactors including the ability to manipulate the gas composition, to allow effective gas exchange in a densely growing biomass, and to affect secondary metabolite production. Mathematical modeling suggested that roots in a mist reactor are often too sparsely packed to capture mist particles efficiently and cannot, therefore, meet the nutrient demands required to maintain high growth rates. Indeed, growth rates of Artemisia annua hairy roots increased significantly when the initial packing density increased or when a higher sucrose concentration was used in the medium. Growth kinetics for 2, 4, and 6 days, however, showed a decrease or stationary growth rate after only 4 days for both 3 and 5% sucrose feeds. Residual medium analyses indicated that carbon was not exhausted, nor were any of the other major nutrients including phosphate. Increasing the mist duty cycle at constant carbon flux through the reactor reduced the growth rates slightly. In general, the aerosol deposition model correctly predicted how to optimize hairy root growth in the mist reactor.

Aerosols↗

PubMed2005

Experimental evidence for internal structure in aqueous-organic nanodroplets.

The spatial distribution of species within an aerosol droplet influences how it interacts with its environment. Despite the ubiquity of multicomponent nanodroplets in natural and technological aerosols, there are no published measurements of their internal structure. Here, we report the first experimental results for structure in aqueous organic nanodroplets based on small angle neutron scattering by high number density aerosols. For H(2)O-n-butanol droplets, fitting of the diffraction patterns confirms the picture of an aqueous core containing approximately 3 mol% alcohol covered by a shell of densely packed alcohol molecules.

Aerosols↗

PubMed2005

Aerosol delivery of mammalian cells for tissue engineering.

We developed a two fluid atomizer to spray mammalian cells suspended in phosphate buffered saline (PBS)-Pluronic F-127 polymer solutions. We used the device to spray suspensions of bovine articular chondrocytes and porcine tracheal epithelial cells, in either PBS or the polymer solutions, and studied their viability and growth kinetics. Under the operating conditions examined in this study, the cells had better than 70% viability after spraying, the growth rates were comparable to cells that were not sprayed, and the appearance of the cells at confluence was normal.

Aerosols↗

PubMed2005

Temperature and gas-phase composition measurements in supersonic flows using tunable diode laser absorption spectroscopy: the effect of condensation on the boundary-layer thickness.

We used a tunable diode laser absorption spectrometer and a static-pressure probe to follow changes in temperature, vapor-phase concentration of D2O, and static pressure during condensation in a supersonic nozzle. Using the measured static-pressure ratio p/p0 and the mass fraction of the condensate g as inputs to the diabatic flow equations, we determined the area ratio (A/A*)wet and the corresponding centerline temperature of the flow during condensation. From (A/A*)wet we determined the boundary-layer displacement thickness during condensation (delta#)wet. We found that (delta#)wet first increases relative to the value of delta# in a dry expansion (delta#)Dry before becoming distinctly smaller than (delta#)Dry downstream of the condensation region. After correcting the temperature gradient across the boundary layers, the temperature determined from p/p0 and g agreed with the temperature determined by the laser-absorption measurements within our experimental error (+/-2 K), except when condensation occurred too close to the throat. The agreement between the two temperature measurements let us draw the following two conclusions. First, the differences in the temperature and mole fraction of D2O determined by the two experimental techniques, first observed in our previous study [P. Paci, Y. Zvinevich, S. Tanimura, B. E. Wyslouzil, M. Zahniser, J. Shorter, D. Nelson, and B. McManus, J. Chem. Phys. 121, 9964 (2004)], can be explained sufficiently by changes in delta# caused by the condensation of D2O, except when the phase transition occurs too close to the throat. Second, the extrapolation of the equation, which expresses the temperature dependence of the heat of vaporization of bulk D2O liquid, is a good estimate of the heat of condensation of supercooled D2O down to 210 K.

Journal Article↗

PubMed2005

Homogeneous nucleation of n-propanol, n-butanol, and n-pentanol in a supersonic nozzle.

We have measured the nucleation conditions of n-propanol, n-butanol, and n-pentanol in a supersonic Laval nozzle, and estimated that the maximum nucleation rate J is 5 x 10(16) cm(-3) s(-1) with an uncertainty factor of 2. Plotting the vapor pressures p(J(max) ) and temperatures T(J(max) ) corresponding to the maximum nucleation rate as ln(p) versus 1T, produces a series of well separated straight lines. When these values are scaled by their respective critical parameters, p(c) and T(c), the data lie close to a single straight line. Comparing the experimental data to the predictions of classical nucleation theory reveals much higher experimental rates, and the deviation increases with increasing alcohol chain length and decreasing temperature. A scaling analysis in terms of Hale's scaled nucleation model [Phys. Rev. A 33, 4156 (1986); Metall. Trans. A 23, 1863 (1992)], clearly shows that our data are consistent with experimental nucleation rates measured using other devices that have characteristic rates many orders of magnitude lower.

Journal Article↗

PubMed2004

Spatially resolved gas phase composition measurements in supersonic flows using tunable diode laser absorption spectroscopy.

We used a tunable diode laser absorption spectrometer to follow the condensation of D(2)O in a supersonic Laval nozzle. We measured both the concentration of the condensible vapor and the spectroscopic temperature as a function of position and compared the results to those inferred from static pressure measurements. Upstream and in the early stages of condensation, the quantitative agreement between the different experimental techniques is good. Far downstream, the spectroscopic results predict a lower gas phase concentration, a higher condensate mass fraction, and a higher temperature than the pressure measurements. The difference between the two measurement techniques is consistent with a slight compression of the boundary layers along the nozzle walls during condensation.

Journal Article↗

PubMed2003

Scale-up of Artemisia annua L. hairy root cultures produces complex patterns of terpenoid gene expression.

Hairy roots grow quickly, reach high densities, and can produce significant amounts of secondary metabolites, yet their scale-up to bioreactors remains challenging. Artemisia annua produces a rich array of terpenoids, including the sesquiterpene, artemisinin, and transformed roots of this species provide a good model for studying terpenoid production. These cultures were examined in shake flasks and compared with cultures grown in two types of bioreactors, a mist reactor and a bubble column reactor, which provide very different environments for the growing roots. Mist reactors have been shown previously to result in cultures that produce significantly more artemisinin per gram fresh weight of culture, while bubble column reactors have produced greater biomass. We have compared expression levels of four key terpenoid biosynthetic genes: 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), 1-deoxy-D-xylulose-5-phosphate synthase (DXS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), and farnesyl diphosphate synthase (FPS) in the three culture conditions. In shake flasks we found that although all four genes showed temporal regulation, only FPS expression correlated with artemisinin production. Light also affected the transcription of all four genes. Although expression in reactors was equivalent to or greater than that of roots grown in shake flasks, no correlation was found between expression level within six different zones of each reactor and their respective oxygen levels, light, and root-packing density. Surprisingly, transcriptional regulation of HMGR, DXS, DXR, and FPS was greatly affected by the position of the roots in each reactor. Thus, relying on a single reactor sample to characterize the gene activity in a whole reactor can be misleading, especially if the goal is to examine the difference between reactor types or operating parameters, steps essential in scaling up cultures for production.

Aldose-Ketose Isomerases↗

PubMed2003

Growth dynamics of Artemisia annua hairy roots in three culture systems.

The transient growth of Artemisia annua hairy roots was compared for cultures grown in shake flasks and in bubble column and mist reactors. Instantaneous growth rates were obtained by numerically differentiating the transient biomass measurements. Specific sugar consumption rates showed good agreement with literature values. From the growth rate and sugar consumption rate, the specific yield and maintenance coefficient for sugar were determined for all three culture systems. These values were statistically indistinguishable for roots grown in shake flasks and bubble columns. In contrast, the values for roots grown in bubble columns and mist reactors were statistically different, suggesting that sugar utilization by roots grown in these two systems may be different. By measuring respiration rates in the bubble column reactor we also determined the actual biomass yield and maintenance coefficient for O(2) and CO(2). Together with an elemental analysis of the roots, this allowed us to obtain a reasonable carbon balance.

Artemisia annua↗

PubMed2002

Growth of Artemisia annua hairy roots in liquid- and gas-phase reactors.

Artemisia annua hairy roots were grown in liquid-phase bubble column and gas-phase nutrient mist reactors. In most cases the bubble column reactor accumulated more biomass than the mist reactor; the highest final biomass concentrations observed were 15.3 g DW/L in the bubble column reactor and 14.4 g DW/L in the mist reactor. Further analysis showed that the average specific growth rate in the mist reactors was essentially constant and independent of the biomass concentration at the beginning of the mist mode. In contrast, at low packing densities the average growth rate in the bubble column reactors was higher than in the mist reactors, decreasing to comparable rates at high packing densities. Finally, an aerosol deposition model was used to compare the volume of medium captured by the root bed in the mist reactor to the volume of medium required to maintain a specified growth rate. The results suggest that under the current operating conditions, lower growth rates in the mist reactor may be due to insufficient nutrient availability.

Artemisia annua↗