Improvement in enzyme productivities from mold cultivations using the liquid-phase oxygen supply strategy.

Cultivations of Aspergillus niger cells in which oxygen was provided through the liquid-phase oxygen supply strategy (which involves the need-based decomposition of H2O2 pulses to yield the necessary oxygen) were studied. Concentrations of H2O2 in the range of 1 to 5 mM were found to be suitable for use in cultivations. The growth rate constant of 0.

Improvement in bioreactor productivities using free radicals: HOCl-induced overproduction of xanthan gum from Xanthomonas campestris and its mechanism.

Free-radical induction has been employed as a novel strategy to improve bioreactor productivity and, more specifically, the quality and productivity of xanthan gum from Xanthomonas campestris cultures. A 210% increase in xanthan yield and a 20% increase in viscosity (quality) resulted from HOCl (oxidant) treatment. The acetate mass fraction in xanthan gum decreased by 42% and its pyruvate mass fraction increased by 63% as a result of HOCl treatment.

Mechanism of oxygen availability from hydrogen peroxide to aerobic cultures of Xanthomonas campestris.

Fundamental studies on the availability of oxygen from the decomposition of H(2)O(2), in vivo, by Xanthomonas campestris, when H(2)O(2) is used as an oxygen source are presented. It was found that the H(2)O(2) added extracellularly (0.1-6 mM) was decomposed intracellularly.

Oxygen supply without gas-liquid film resistance to xanthomonas campestris cultivation.

Alternative methods of oxygen supply are of crucial importance, especially in viscous fermentations and shear-sensitive fermentations. A method of oxygen supply that completely eliminates the gas-liquid transport resistance has been presented. The method involves a need-based liquid-phase decomposition of hydrogen peroxide to provide the necessary oxygen.

Intracellular pH responses of hybridoma and yeast to substrate addition and acid challenge.

The pHi responses of hybridoma and yeast cells to substrate and external acid additions were measured using the fluorescent pHi indicator, 9-aminoacridine. The pHi change, following CCCP addition, indicated by 9AA, compared very well with that indicated by BCECF. No change in pHi was observed following glucose or glutamine additions to hybridoma cells under glucose- and glutamine-absent conditions.

Intracellular pH-based controlled cultivation of yeast cells: II. cultivation methodology.

Intracellular pH (pH(i)) was measured on-line in a bioreactor using a fluorescent pH(i) indicator, 9-aminoacridine, and controlled fed-batch cultivations of yeast cells based on pH(i) (FB-pH(i)) were performed. In FB-pH(i) cultivations, automated glucose additions were made to the culture in response to culture pH(i). The average ethanol (an-aerobic product) yield was significantly lower [0.

Intracellular pH based controlled cultivation of yeast cells: I. Measurement methodology.

A method has been developed to continuously measure the intracellular pH (pH(i)) of cells cultivated in a bioreactor in an on-line fashion over extend time periods. The methods is attractive in its simplicity and involves the use of a fluorescent pH(i) indicator 9-aminoacridine (9A A) which is a week base. An expression has been derived to calculate changes in pH(i) from measured 9AA-fluorescence changes.

Bovine colostrum or milk as a serum substitute for the cultivation of a mouse hybridoma.

A mouse-mouse hybridoma was grown in serum-free medium supplemented with bovine milk or colostrum. Bovine colostrum supported growth of the hybridoma whereas bovine milk alone did not support cellular proliferation. For growth in medium supplemented with colostrum, the maximum cell concentration achieved was 1.