Whether evaluating conventional stainless steel or single-use bioreactors, every system must accomplish the same thing: control a bioprocess for an intended result. The result may be biomass, product titer, substrate conversion, or any number of complex, process-specific productivity measures.
Each system shares the same basic elements, including a bioreactor vessel and a gas addition subsystem. The vessel uses an agitation subassembly, gas sparger, and in some cases, gas overlay elements. These must be properly engineered to work in concert to deliver acceptable process performance. However, the presence of these features does not in itself ensure the growth of a culture, nor does it indicate the level of effort required to achieve the desired productivity.
Other factors — such as sound process engineering, a solid understanding of the bioprocess, and an understanding of critical system responses — play an equally important role. This paper examines a combination of unique capabilities designed into the XDR single-use bioreactor from Xcellerex. Together, these features represent a “process productivity” tool kit that enables the process scientist or engineer to achieve exceptional control and superior bioprocess performance — with the greatest confidence and convenience.
Tool #1: System Characterization
Successful operation of a bioreactor requires an understanding of the relationship between physical system features:
- impeller diameter
- impeller type
- tank height: diameter ratio
- sparger type
- sparger location
… and critical performance parameters determined by those features:
- power number (Np),
- mass transfer coefficient (KLa)
- blend or mixing time
For conventional stainless steel systems, these relationships are typically well understood. Once a system is characterized, these relationships are fixed or set as long as the underlying system features are not changed. In many single-use systems, the process engineering required to characterize a new system is left to the operator. That characterization effort may require hundreds of man-hours of unplanned engineering time and considerable expense.
With its XDR single-use bioreactor systems, Xcellerex has conducted detailed characterization on all critical operating parameters, from the 50-L scale to the 2,000-L scale. The precise understanding of system performance that is accomplished through careful characterization enables the process scientist and engineer to carefully control interrelated system responses to create and maintain the desired operating environment. With the fully characterized XDR bioreactors, the scientist or engineer can focus on his/her process, not on the functioning of her/his hardware.
Tool #3: Predictive Process Modeling
The third tool Xcellerex makes available with its XDR system is an extensive predictive modeling database that encompasses all the most typical, conventional stainless steel bioreactor types and processes. The modeling database also reflects the XDR bioreactor’s Six degrees of Freedom and system characterization.
Starting with the known operating preferences, the planned scale-up strategies and process sensitivities, the database model provides the process scientist or engineer with a clear, well-defined roadmap to achieve high performance — from the first-run in the XDR system.
The Xcellerex XDR “Process Toolkit” enables the process scientist and engineer to focus on the process, not the equipment. In most cases, new cell culture bioprocesses run on the XDR bioreactor platform achieve 80% or better of the target performance on the very first run. In many cases, the expanded control provided by the XDR bioreactor system and these tools enable the process scientist or engineer to surpass prior productivity goals.
Kenneth Clapp is senior director of product management and global marketing at Xcellerex, Inc., 170 Locke Drive, Marlborough, MA 01752- 7217; 1-508-683-2221, fax 1-508-480-9238; firstname.lastname@example.org; www.xcellerex.com;www.xcellerex.com.