May 1, 2011 (Vol. 31, No. 9)
ExcellGene’s Platform Includes No Moving Parts, Low Shear Force, and High Gas Transfer
Molecular biologist Florian Wurm, Ph.D., co-founded ExcellGene in 2001 to improve large-scale mammalian cell manufacturing processes. While working for 10 years at Genentech, Hoechst, and academic institutions, Dr. Wurm, now CSO at ExcellGene, gained insights into how to enhance mammalian cell engineering and bioreactors for scale-up. “Now we drive innovation in the industry to serve our clients.”
ExcellGene’s technology platform reportedly turns DNA constructs into purified recombinant proteins of interest within days or weeks. “Other competitors take months to do that,” Dr. Wurm insists. “Bioreactors are the core of our industry, and I’ve worked with all of them.”
Animal cells grown in suspension cultures face two key problems: suspensions must be stirred gently to avoid damage to the cells from impellers, and oxygen is the key nutrient for animal cell cultures; however, too little or too much can kill cells. The density of cells growing in bioreactors has increased dramatically from 1 to 2 million cells per milliliter to 10 to 15 million cells per milliliter. This raises the demand for oxygen to a new level. To meet the oxygen demand, bioreactors are sparged with pure oxygen at high flow rates, but this also kills cells. Biologists and engineers who work with large-scale bioreactors struggle with these two complex problems.
Orbital Shaker Advantages
Maria de Jesus, Ph.D., co-founder of ExcellGene and COO, came up with the idea to shake cells in cylindrical 50 mL tubes at slow speed. This method produces little damage because cells move in a laminar flow manner with little shear stress and turbulence. The orbital shake method also caused no damage to cells when Drs. de Jesus and Wurm scaled up to 1, 5, 10, and 100 L volumes. Thus was born ExcellGene’s orbital shake platform of bioreactors. The orbital shake bioreactor system makes it easier to scale up production because the fluid hydrodynamics remain similar for all volumes, and no moving parts are needed for stirring. The latest innovation is a 2,500 L orbital shake reactor that is in development.
In addition to reducing cell damage, orbital shakers provide a large surface area for the exchange of gas. This large surface area results in superior oxygen transfer rates, compared to standard stainless steel tanks, and animal cells growing in orbital shakers grow better than in steel tanks. “We developed a system that combines two good things—low shear force and high gas transfer rate,” says Dr. Wurm.
ExcellGene teamed up with Kuhner to develop the orbital shake bioreactor system. Available bioreactors range from 50 mL to 2,000 L. They include the 50 mL (10 mL working volume) Cultiflask/TubeSpin® bioreactors; the 200 L (50–150 L working volume) OrbShake bioreactor fitted with disposable Sartorius Stedim Biotech cell culture bags; and the 2,000 L (500–1,500 L working volume) OrbShake bioreactor with disposable cell culture bags. All OrbShake bioreactors are based on a disposable bag technology that avoids the need for elaborate, costly, and tedious sterilization processes.
Expression and Manufacturing
Before ExcellGene became known for its orbital shake bioreactors, the company pioneered technologies to resolve problems associated with expressing and manufacturing recombinant proteins from mammalian cells. ExcellGene’s technologies cover vectors, gene transfer systems, cell hosts, screening platforms for cells and processes, and scale-up principles.
The company’s protein-expression technology produces high-yielding clonal cell lines in seven weeks, Dr. Wurm reports. Once a cell line is established, gram-per-liter quantities of any recombinant protein can be manufactured within a few weeks, thereby shortening product and process development time lines.
As a service provider, ExcellGene generates upstream cell culture processes for customers. Among the services offered are transfection, selection and isolation of clonal cell populations, evaluation of primary clones for productivity in serum-free suspension culture, and banking of cell populations as prebanks, masterbanks, or working cell banks. The company recently set up a cGMP facility to manufacture proteins and other active pharmaceutical ingredients for clients.
Two cell host systems, CHOExpress and HUGExpress (derived from HEK-293 cells), contribute to speedy protein production. The cell lines are optimized for efficient DNA uptake and high protein expression, grow to high density in suspension cultures, and are easy to scale up. “We are extremely good at taking a client’s DNA and giving them a purified protein in a short time,” explains Dr. Wurm.