Powdered media

The simpler forms of Eagle s media (and some other media) are available commercially in powdered form from for example Flow Laboratories or Gibco (see Appendix 3). This is the cheapest way of buying media if large quantities are used the powder occupies little space and may be stored in the cold room in sealed containers for 6-12 months. 

Powdered medium should be reconstituted at room temperature as per maufacturers instructions, which leads to 1 X medium. It is important not to leave traces of powder undissolved. Bicarbonate is added separately and the pH adjusted to about 7.1 before sterilisation by filtration. Before use, glutamine should be added, if not already present, together with serum (usually to 10%, as described in Appendix 1). 

Each batch should be checked for bacterial contamination in 

Although not generally recommended by the maufacturer, if care is taken to ensure that all the powder is dissolved we have found that Glasgow MEM powder can be reconstituted to give a 10 X stock 

The advantages of reconstituting to 10 X are 1) there is a smaller volume to filter sterilise 2) the 10 X stock occupies less cold room space 3) it is more economical to buy bottles which reconstitute to 5 1 of 10 X stock (50 1 of 1 X medium) than smaller amounts. 

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Ray K. Validation of a Novel Process for Large-scale Production of Powdered Media Evaluation of Blend Uniformity. Presented at the Raw Materials and Contract Services Conference (Williamsburg Bioprocessing Eoundation), St. Louis, MO, May 19-21, 1999. 

The ubiquitous problem encountered in all positronium decay rate measurements to date is isolating the positronium from the formation medium in order to determine the vacuum decay rate. In both gas and powder experiments the interactions (Ps quenching and Ps polarization) with these media need to be accounted for. This can involve extrapolations of A to zero density in the formation medium, as in the Michigan experiment, and/or spectroscopic corrections for 2q decays as in the Tokyo experiment. At Michigan we decided a decade ago to abandon powder media in future precision experiments because we could... 

Media are composed of a mixture of essential salts, nutrients, and buffering agents. Sterile media are usually purchased in solution. Alternatively, packaged premixed powders are available. Powdered media and concentrated formulations usually do not contain sodium bicarbonate... 

The reaction operation provides sinks for tPA-CHO cells, from cold storage at -70°C, and HyQ PF-CHO media in water, air, and carbon dioxide. Its effluent is a source of tPA, at 112 kg/yr, endotoxin, cell debris, water, nitrogen, and carbon dioxide. When separated, these species are the sources for the product sinks from the flowsheet. Note that the combined cell growth and tPA production operation takes place at 37°C, 1 atm, and pH = 7.3. The latter is achieved by the NaHC03 in the powder media, with fine tuning by manipulation of the flow rate of CO2. 

In this case, only one mixing operation is introduced, in which the HyQ PF-CHO powder media is mixed with water, as shown in Figure 3.13. Otherwise the sources and sinks are matched directly. However, the effluent from the cell growth, tPA production reactor must be separated before its species are matched with the product sinks. 

Health and safety aspects Handling powdered media (e.g. filter aids) can pose health and safety problems, and disposal of contaminated media may require special considerations. 

Table 2.19 Example characteristics of PSS sintered metal (316L stainless steel) powder media for liquid filtration (Pall).

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