Xanthan gum: production, recovery, and properties.

The oxygen reduction reaction (ORR) has been studied on polycrystalline Pt3Ni and Pt3Co alloys in acid electrolytes using the rotating ring disk electrode (RRDE) method. Preparation and characterization of alloy surfaces were performed in ultrahigh vacuum (UHV). Clearly defined surface composition was determined via low-energy ion-scattering (LEIS) spectroscopy. Polycrystalline bulk alloys of Pt3Ni and Pt3Co were prepared in UHV having two different surface compositions:  one with 75% Pt and the other with 100% Pt. The latter we call a “Pt-skin” structure and is produced by an exchange of Pt and Co in the first two layers. The base voltammetry in 0.1 M HClO4 solution of the 75% Pt alloy surface indicated a decrease of Hupd pseudocapacitance (ca. 30−40 μC/cm2) consistent with the surface composition determined in UHV. With the exception of the “Pt-skin” surface on Pt3Ni, all the alloy electrodes exhibited stable i−E curves with repeated cycling between 0.05 and 1.0 V at all temperatures. Activities of Pt-a...

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Surface Composition Effects in Electrocatalysis: Kinetics of Oxygen Reduction on Well-Defined Pt3Ni and Pt3Co Alloy Surfaces

Hybridomas are finding increased use for the production of a wide variety of monoclonal antibodies. Understanding the roles of physiological and environmental factors on the growth and metabolism of mammalian cells is a prerequisite for the development of rational scale-up procedures. An SP2/0-derived mouse hybridoma has been employed in the present work as a model system for hybridoma suspension culture. In preliminary shake flask studies to determine the effect of glucose and glutaminE, it was found that the specific growth rate, the glucose and glutamine metabolic quotients, and the cumulative specific antibody production rate were independent of glucose concentration over the range commonly employed in cell cultures. Only the specific rate of glutamine uptake was found to depend on glutamine concentration. The cells were grown in continuous culture at constant pH and oxygen concentration at a variety of dilution rates. Specific substrate consumption rates and product formation rates were determined from the steady state concentrations. The specific glucose uptake rate deviated from the maintenance energy model1 at low specific growth rates, probably due to changes in the metabolic pathways of the cells. Antibody production was not growth-associated; and higher specific antibody production rates were obtained at lower specific growth rates. The effect of pH on the metabolic quotients was also determined. An optimum in viable cell concentration was obtained between pH 7.1 and 7.4. The viable cell number and viability decreased dramatically at pH 6.8. At pH 7.7 the viable cell concentration initially decreased, but then recovered to values typical of pH 7.1–7.4. Higher specific nutrient consumption rates were found at the extreme pH values; however, glucose consumption was inhibited at low pH. The pH history also influenced the behavior at a given pH. Higher antibody metabolic quotients were obtained at the extreme pH values. Together with the effect of specific growth rate, this suggests higher antibody production under environmental or nutritional stress.

A kinetic analysis of hybridoma growth and metabolism in batch and continuous suspension culture: Effect of nutrient concentration, dilution rate, and pH

Oxygen reduction reaction on Pt(111): effects of bromide

Production, recovery and applications of xanthan gum by Xanthomonas campestris

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.260200114

Solubility of oxygen in electrolyte solutions

Differing findings on the volumetric mass transfer coefficients k(L)a in CMC solutions in bubble column bioreactors have been reported in the literature. Therefore, oxygen mass transfer was studied again in CMC solutions in a 14-cm-i.d. x 270-cm-height bubble column using different spargers. The k(L)a values were determined along with the dispersion coefficients by fitting the prediction of the axial dispersed plug model with the experimental oxygen concentration profiles in the liquid phase. Surprisingly, the obtained liquid phase dispersion coefficients for CMC solution are higher than one would expect from correlations. The k(L)a data depend largely on the flow regime. In general, they are lower than those reported in the literature. The data for developing slug and established slug flow are dependent on the gas velocity and the effective viscosity of the solution and can br correlated by a simple correlation. This correlation describes k(L)a values measured on fermentation broth of Penicillium chrysogenum with striking agreement.

Oxygen mass transfer into aerated CMC solutions in a bubble column.

Gas holdups, specific interfacial areas, and mass transfer coefficients of aerated carboxymethyl cellulose solutions in a bubble column

The influence of agitation rate on Xanthan production in a baffled stirred tank reactor is reported. To separate the hydrodynamic effect of agitator speed on any slime layer from the influence on oxygen mass transfer, oxygene-enriched air was used. Furthermore, the influence of agitation speed on the molecular weight distribution was studied

The influence of agitation rate on xanthan production by Xanthomonas campestris

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.260210611

Adrian Schumpe

Papers

Solubility of oxygen in electrolyte solutions

Oxygen mass transfer into aerated CMC solutions in a bubble column.

Gas holdups, specific interfacial areas, and mass transfer coefficients of aerated carboxymethyl cellulose solutions in a bubble column

The influence of agitation rate on xanthan production by Xanthomonas campestris

Estimation of O2 and CO2 solubiliteis in fermentation media