1950s - Spinner Flasks to Bioreactors

John A. Ryan, Ph.D.


	Figure 1. McLimans' group developed the first "spinner flasks" in 1957.

Biotech companies, such as Genentech and Lonza, now routinely grow CHO and other cell lines as suspension cultures in massive bioreactors as large as 20,000 liters to produce monoclonal antibodies and genetically engineered protein-based drugs worth billions of dollars each year. The technology for producing these products evolved rapidly in the 1950s, the work of those researchers who contributed to this evolution are discussed below (1).

1953

The first successful suspension cultures, lymphoblastic MBIII cells, were grown by Owens, Gey and Gey in 1953 (2). They used rapidly rotating (38 RPM) culture tubes that were attached perpendicular to the axis of rotation of a roller drum so that they tumbled end over end. This “tumble tube” approached allowed the cells to grow in suspension at rates similar to attached cells.

1954

Earle and his group (3) extended these studies to L929 mouse cells growing them in roller tubes (10+ RPM) to prove that normally attached cells could grow in suspension. They then switched to growing them in small Erlenmeyer flasks on rotary shakers (4).

The growth of cells in Erlenmeyer flasks on shaker platforms is still very popular especially for insect cells and other cultures that require higher levels of gas exchange. Both reusable glass and disposable plastic Erlenmeyer flasks, with or without baffles for increased gas exchange, and with a variety of cap and top styles are available.

1956


	Figure 2. By 1960 commercially available magnetically driven spinner flasks with stir bars were available.

Cherry and Hull (5) used a magnetic stir bar suspended from a fishing swivel to keep cells in suspension in a round bottom flask so that they could study the effects of varying the medium, speed and seeding densities on cell growth.

1957

McLimans and his group (6) took the magnetic stir bar and attached it to a sliding wire so that it could be raised a lowered to match the medium volume. They added a side port for sampling and called it a “spinner flask” (Figure 1). This was used to grow suspension cultures for HeLa and L cells in volumes up to 400mL.

Next they adapted this approach to work in commercially available 5L microbial fermentors with baffles and spargers driven by an overhead impeller (7). This showed that suspension cell culture could be successfully scaled up to grow at levels that were commercially useful.

1967

None of the above techniques allowed for the growth of primary or anchorage-dependent cell cultures in suspension since these cells must attach to a substrate to multiply. This bottleneck was solved by van Wezel (8) who used small (200-250µm diameter) solid particles, called microcarriers, as a substrate for cell attachment (Figure 3). These particles were originally made from Sephadex beads but have also been made from a variety of other materials including polystyrene, glass and cross-linked collagen.


	Figure 3. By using microcarrier beads, anchorage dependent cells could be grown in suspension.

The use of these beads in culture required the use of more gentle stirring techniques and by the 1980s spinner vessels were available with a variety of stirring designs including magnetically driven paddles and ball and pendulums. These new designs allowed stirring at much slower speeds reducing the damage from bead-bead collsions and sheer effects. Today several biotherapeutic protein drugs and vaccines are produced on cells grown in suspension on microcarriers.

Today

To meet the today’s demand for cell-based drugs, biotechnology and pharmaceutical companies prefer to use large scale stirred tank bioreactors with capacities from 1 liter to as high as 20,000 liters. In addition, other technologies such as air lift fermentors and large bags placed on rocking platforms are also used.