Optimizing cell culture involves numerous strategies, undertaken from the earliest stages of cell-line engineering or selection, through development, and even during full-scale manufacturing.
In addition to higher yield, cell-culture optimization confers the benefit of improving downstream operations. For example, the fewer cells that die, the cleaner the purification stream. “Upstream drives downstream,” comments Scott Deeter, CEO of Invitria, which specializes in media and feed supplements. “If you don’t start with the right material at the front end, it’s difficult to produce high-quality product on the back end.”
Cell death causes the release of proteases, and glycosidases degrade therapeutic protein backbones and glycans, respectively. Deeter notes that the protein A capture step can be made more efficient by improving cell viability and thus reducing nonspecific binding to the column.
Invitria manufactures an array of feeds based on recombinant albumin (the principal serum protein), lactoferrin (a growth factor with anti-apoptosis activity), lysozyme (a cell lysis-inducing agent), and transferrin (iron transport). In addition, the company offers ZapCho, a multicomponent additive for CHO cultures, and Zap-Hybridoma, for hybridoma cells.
An aggressive media development and feed/supplementation program is the best way to ensure optimal productivity during production. Increasingly, bioprocessors are employing these methods at the earliest stages to assist in clone selection under best-case conditions and to assist cells in adapting to the desired culture medium. “Using supplements can shave many weeks off development time,” Deeter explains.
Speed and Versatility
Bioprocesses have historically been tightly controlled whether they occurred in glass, stainless steel, or single-use equipment. Scaling up introduces variables, however, as bench, development, pilot, and production scales differ not only in size, but in the operation of engineering phenomena such as mass transfer and oxygenation levels, and shear stress.
Roman Rodriguez, global product manager for bioreactors at ATMI, makes a good case for retaining the same bioreactor platform or geometry throughout development to minimize the effects of these differences.
ATMI specializes in single-use bioreactors and mixing systems, which, according to Rodriguez, enable customers to retain the bioreactor’s critical physical characteristics at successively larger scales. The process-contact components of mixing systems, acquired through the NewMix® and LevTech® brands, are fully disposable and scalable. The bioreactors provide the usual benefits of reduced cleaning and cleaning validation, as well as rapid changeover.
“Pressures on cell-culture developers are increasing from regulators and due to time-to-market considerations. The disposables approach permits less down-time and saves on cleaning and validation. This is what makes disposables so attractive during development.”
He argues that, unburdened with cleaning and limitations on appropriate cell-culture capacity, process developers can test more process scenarios in parallel than ever before during development and begin a new run immediately after the old run ends, with no worries about cross-contamination. And they can achieve optimized lab-, bench-, pilot-, and production-scale cell cultures—up to 1,000 L—in a familiar, fully characterized system without re-validation.
Disposables can also come to the rescue for processes scaled down in volume to accommodate rising productivity, Rodriguez says. “Everybody wants to do more in smaller volume,” but to achieve that smoothly, processors must fully understand the mixing characteristics of the vessel.
ATMI products are designed for mammalian cell culture, but Rodriguez says they should be compatible with fermentation as well. “That’s our next step. It will require more validation, testing, and perhaps some upgrades.”