Dollars and Sense
Watkins refers to single use as a persistent “buzz”—still topical, still highly desirable, but outside of North America and Europe (and, as noted, with microbial fermentations), stainless steel and glass still rule the world of bioprocessing. Lower labor costs in growing Asian and Pacific markets allow biomanufacturers the luxury of investing in fixed tank processes and cleaning/validating, and to do so economically.
Some other factors also play in determining the relative value of single-use vs. fixed-tank reactors. “Not every company in every market benefits from the traditional advantages of single-use bioreactors,” observes Michelle Mitcho, fermentation product manager at Sartorius Stedim Biotech. “Single use is attractive for companies that need to move quickly and reduce time to market, particularly large biopharmaceutical companies. For them the benefits of reduced cleaning and cleaning validation outweigh the cost of disposables. Not every company is in that category, however.”
Sartorius Stedim Biotech manufactures traditional glass and stainless steel bioreactors, as well as a broad portfolio of single-use upstream processing equipment.
A development-stage cell culture project for a monoclonal antibody therapeutic, for example, might use 50 bench-scale bioreactors. As many single-use vendors have demonstrated, the time, cost, and diversion of human resources toward prepping and cleaning that many bioreactors presents a huge burden. But smaller firms operating in nontherapeutic areas, at a lower level of parallelism, or working with nonmammalian systems, would probably stick to reusable reactors.
“Industries like foods, beverages, additives, even antibiotics, frequently don’t consider the same factors as traditional biopharma when determining costs and time savings,” Mitcho says. “Stainless steel or glass may be more compatible with the process as well, for example when high agitation, pressure, or gas flow rates are required.”
Nonpharmaceutical processes are not regulated as stringently as biopharmaceuticals, for example with respect to cleaning and validation. These factors loom large in any cost justification for single-use systems.
Another consideration is maintaining consistency in materials of construction as processes scale up. The largest single-use cell culture system today runs 2,000 liters, and at least one vendor has introduced 200 liter single-use reactors for microbial fermentations, according to Mitcho. “Larger systems for microbials are coming, but they will have limitations. At very large scale, systems have to be rugged and durable,” she says. Many industrial-scale microbial fermentations, for example, are carried out in tens of thousands of liters.