Surprisingly for an industry that has historically been recalcitrant to change, disposables dominate current discussions about best practices. On the surface, disposables offer easy solutions. However, what may appear to be a no-brainer on casual inspection belies the need for a complex decision-making process. Many variables must be taken into account, and this means there is no "one size fits all" solution. What makes sense for one process may be completely unsuitable for another because of differences in the product, the production scale, the development phase, or the user's business model.
A TREND IN NEEDThe trend toward disposable manufacturing reflects the pressure on companies to increase capacity without exposure to excessive investment risk. Most biomanufacturing processes are driven by fixed costs and the only way to circumvent this dependence is to shift resources from upfront capital investment into variable costs, i.e., consumables actually used in the production train and not solely as part of the expensive infrastructure. This is, of course, more easily said than done, and the question remains—for what unit operations should disposability be applied?
SHOULD EVERYTHING BE DISPOSABLE?
For every process scenario, there is an optimum level of disposable technology. Some operations should always be disposable, e.g., sterile filtration as well as steps to effectively remove viruses. Here, re-use is inadvisable, to minimize the risk of contamination and carry over. Hence, disposables dominate the final steps of downstream processing and—more recently—front-end purification with encapsulated single-use devices for cell removal and clarification.
But apart from clear-cut cases like those, what is wrong with reusable equipment if there is minimal risk associated with long-term use? It makes little sense to use disposables at any cost. Today's minimum requirements are that process technology should be scalable following clear design principles. In addition, all unit operations should be available in two formats, with either a reusable or a disposable flow path and an identical controlling periphery. The decision about the most appropriate process train assembly must balance economic and technical considerations and can be based on tools for process simulations and cost modeling, which are becoming more readily available.
In conclusion, a rational decision between single-use and repeated-use technology is based on quality, security of supply, investment risk leverage, total cost of ownership, flexibility, and convenience. In addition, recent discussions about the environmental impact of both disposable and reusable process options underline the need for clear assessments to maximize the use of limited resources.
No single manufacturing model can fit all products and processes, and there is no value in dogmatically sticking to either disposable or reusable options. Case-by-case evaluations are the safest bet in an industry whose very success depends on a precarious balance between quality and cost.
Uwe Gottschalk, PhD, is vice president of Purification Technologies at Sartorius Stedim Biotech GmbH, Gottingen, Germany, +49.551.308.2032, firstname.lastname@example.org