The influence of power consumption on the volumetric mass transfer coefficient was studied in a 5 liter stirred tank bioreactor during cultivation of a recombinant Chinese Hamster Ovary (CHO) cell line, which requires low aeration and mixing intensity. Under these conditions and at high cell concentrations, oxygen mass transfer coefficient and consequently volumetric oxygen mass transfer rate w...

In aerobic bioprocesses, oxygen is a key substrate; due to its low solubility in broths (aqueous solutions), a continuous supply is needed. The oxygen transfer rate (OTR) must be known, and if possible predicted to achieve an optimum design operation and scale-up of bioreactors. Many studies have been conducted to enhance the efficiency of oxygen transfer. The dissolved oxygen concentration in ...

A new semiempirical approach is presented for predicting air-to-water oxygen transfer rates in mixed tanks and gravity sewers, using methods adopted from mixing theory. First, a flocculation unit was used to impart selected mean velocity gradients (G) into a completely mixed tank, from which oxygen was first removed, and dissolved oxygen concentrations were measured with time. Regression analys...

background: embryo transfer (et) has traditionally been performed two days after oocyte retrieval. delaying transfer from day two to day three or four would allow for further development of the embryo might therefore optimize the selection of viable and best quality embryos for transfer and may be closer to the physiological time of the entry into the uterus than transfer on day two and might h...

The oxygen uptake rate to suspended cells of Pseudomonas ovalis was measured in two ways using the same cell suspension. Initially the rate was found by measuring the rate of production of gluconic acid by cells suspended in a nitrogenfree, aerated medium. Then, an oxygen electrode was used to measure the rate of transfer of dissolved oxygen to cells suspended in a liquid that was being agitate...

The success of fermentation processes often depends upon the maintenance of an environment sufficient in oxygen concentration so as not to limit or impair normal respiratory activity. Maintenance of such an environment is, in turn, largely dependent on the adequacy of oxygen transfer from air to the liquid medium. Of the possible pathways for oxygen transport, absorption into the medium and sub...