By Chris Julien; Reprinted with permission from American Biotechnology Laboratory.
Scaling up from spinners, T-flasks or shakers to a bioreactor system enables the researcher to reap the benefits of saving time. As an example of the typical savings one could expect, a single 5-L bioreactor has been shown to produce the equivalent amount of hybridoma cells as 150 250-mL T-flasks1. Moreover, a bioreactor requires only one laboratory technician and less than 2 ft of bench space for operation. The most significant decision when scaling up rests in selecting the equipment best suited to the users needs. Several factors must be considered, including the amount of product required (milligram or gram quantities); whether the end goal is the biomass itself or the products produced as a result of the culture; and whether the process uses an animal or microbial cell line, since the culture requirements and therefore the reactor design are inherently different for each.
This article focuses on the third factor, providing an overview of the most important differences between microbial culture and mammalian cell culture requirements, as well as describing a single reactor system capable of handling the varied needs of both.
Mammalian vs. Microbial Culture
Six basic areas in which culture requirements differ are growth rate, temperature, pH, dissolved oxygen, shear sensitivity, and foam. The following sections will discuss each of these areas in more detail.
Growth Rate - Growth rate, or the amount of time needed for cells to double, can be counted in minutes for microbes and
upwards of a day for animal cells. A typical microbial culture may run just a few days to a week, and is therefore often run in
batch mode. Because mammalian cultures will likely last several weeks, these systems are of