The LEX Bubbling System for Highly Parallel Protein Expression

To produce hundreds of novel protein structures requires expressing protein in cell cultures ranging from a few hundred millilitres to a few litres. The SGC's LEX system addresses this problem by means of parallel bubbling, which has the following advantages over the more common use of shakers:

- Oxygenation - While vigorous shaking can improve oxygenation, bubbling makes it possible to directly control the rate of oxygen input. In fact, even moderate bubbling provides more than necessary oxygen. At the SGC, we often induce at OD600 4 or higher to provide a great yield of recombinant protein. The importance proper aeration increases with OD.
- Space efficiency - Shakers are bulky and can only accommodate a handful of multi-litre flasks at a time. Moreover, to ensure sufficient aeration, it is necessary to use shaker flasks much larger than culture volume. With bubbling, it is possible to match bottle size with culture volume and stack them side by size, requiring a much smaller footprint for a given number of proteins to be expressed, or enabling a larger number of proteins to be expressed in a given footprint.

While bubbling and even parallel bubbling are not novel, our approach is notedly efficient, in terms of size, cost and operations.

The LEX design comprises (i) standard media bottles with modified caps, (ii) a manifold for roughly even distribution of air flow and (iii) an air filter system.

Air may be supplied from a central building compressor or a portable unit. The plastic caps of standard glass media bottles are modified to add to each an in-line flow regulator (for individual air flow control) and a quick disconnect (for ease of set up and harvest). Typically, the flow rate for each bottle is set at roughly 4-6 L/min. Flow adjustment and anti-foam are necessary to prevent over-foaming,

As seen below, our current design accomodates 24 x 1L bottles (or 12 x 2 L bottles), twice the capacity of a typical shaker in half the footprint.




The air filter atop the LEX system pulls air through a carbon filter before releasing it into the laboratory atmosphere.

Contact Harbinger Biotechnology & Engineering if you are interested in the Lex system.