Even as contract manufacturers were investing in new, larger-scale production facilities over the past few years to address a projected capacity crunch, the realization was emerging that at some point it would be more efficient and cost-effective to invest in research aimed at making more from lessproducing more product with the existing capacity.
This sparked a renewed focus on increasing fermentation and cell culture yields by improving recombinant strains, optimizing expression systems, and maximizing process output.
As a result, whereas expression levels of 1 g/L were the norm for monoclonal antibody production a few years ago, 5 g/L is now the expectation, and, according to Julien, "some believe expression levels of 10 g/L will be achievable in the next decade."
The emphasis in bioreactor/fermentor design has taken a 180 shift away from scale-up to large 10,00020,000 L systems, and is now focused on "scale-down," according to Julien. He describes scale-down as the desire to mimic eventual manufacturing-scale processes on benchtop units, doing process design and validation and optimizing process parameters at a smaller, 210 L scale, saving time, resources, and labor.
Customers have demonstrated that a well-defined small-scale system can make scale-up sufficiently predictable that, for example, it is possible to optimize a 12 L process and scale it directly to 600 L, without devoting the time and effort to take the process through a series of intermediate scale-up volumes.
"The segregation of duties has been challenged," says Julien, explaining that the lines between R&D, process development, and production are blurring. The goal is to modify processes in their infancy so they can run at manufacturing scale without significant changes and redesign.
The staff responsible for production is now reaching down into the process-development venue to share their expertise and collaborate on the selection of first-tier bioreactors and fermentors and on early-stage process design.
One result of this trend is increased demand for online sensing and more sophisticated monitoring and control strategies, requiring instrumentation and methods that have typically been limited to larger systems.
Julien cites frequent requests by customers for greater functionality on benchtop units, and, in particular, more advanced approaches to controlling dissolved oxygen.
Sartorius has responded to these market demands by integrating its controllers and bench-top systems with an increasing number of auxiliary sensors that enable online monitoring and control, to support the Process Analytical Technology (PAT) initiative, and generate the data needed to validate a system at small scale, simplifying validation and regulatory compliance at manufacturing scale.
Increasing adoption of PAT and demand by customers for greater integration of system components led Sartorius to introduce an OPC driver that enables its systems to communicate with any OPC-based instrument.
The needs of the research community are driving the trend toward downsizing, concurs Stephen Mitchell of ATR (www.atrbiotech.com). With few real differences in the design of the various bioreactor and fermentor units on the market today, innovation centers on the control components. Mitchell identifies one of the key challenges in bioprocess scale-down as the need to develop smaller-scale sensing devices, with the emphasis being on fiber optic sensing technology.
In late summer, ATR will launch the Twinfors benchtop reactor, a modified version of the company's Sixfors product. Whereas the Sixfors has six individual bioreactors in a single chassis, with each reactor vessel available in either a 300 mL or 500 mL maximum working volume, Twinfors offers the same small working volumes in a dual-vessel configuration.
Users can link up to three Twinfors using a single electronics package. ATR has also added a larger vessel option with a maximum working volume of 1 liter, widening the working volume range per reactor to 80 mL up to 1 L.
Depicting the current market as a battleground between traditional stainless steel tanks and disposables, with the latter being considered a replacement for the former, is a misrepresentation of the true market landscape, in the view of Julien. "Neither technology has all the answers," he states. "The true power is in the integration of the two."
Sartorius recently signed a worldwide distribution agreement with TC Tech (www.tc-tech.com), giving it access to the company's disposable mixing technology.
About six months ago Sartorius introduced its SuperSpinner incubator-based cell culture device with disposable membrane aeration.
The FibraStage cell culture device is New Brunswick Scientific's (NBS; www.nbsc.com) newest entry into the disposables market. This small-scale system can accommodate four 500-mL bottles, each containing 10 g of FibraCel support matrix. At the base of each bottle are collapsible bellows that "push media up through the packed bed of the FibraCel disk," as it is compressed, explains Mike Sattan, director of marketing at NBS.
The inoculate becomes entrapped in the support matrix as essential nutrients are forced through the culture and waste products are pushed out. When the bellows expand, air is pulled through the cell bed, facilitating oxygen transfer and gas exchange.
A controller allows for variable speed settings to control the up-and-down movement of the bellows and can be programmed to incorporate "hold times" for exposure of the cells to the media or gases.
A single, disposable FibraStage reactor bottle can produce the equivalent amount of product as 2040 roller bottles, according to Sattan. The cells remain in the disk bed, media replacement and product recovery can be achieved by decanting the media from the bottle. On the horizon, Sattan sees a need for perfusion-type disposable devices.
NBS has expanded its line of modular BioFlo Pro sterilizable-in-place systems to include fermentation vessels up to 3,000 L and has increased the maximum volume of its bioreactor vessels from 150 to 500 L.
Commenting on the increasing penetration of disposables into the bioprocess market, Mitchell points to ATR's ongoing pilot program in which the company is evaluating various forms of disposable reactors. "Bags are huge," he says. "They have working volume limitations, but are perfect for the research/small-scale side." The use of disposables can eliminate about "50% of the up-front and post-product clean-up," he adds.
Optical detection to monitor parameters such as dissolved oxygen, pH, and biomass will rely on fiber optics, predicts Mitchell, "because it is so inexpensive." Technological advances in sensing will enable optimization of processes in smaller-scale vessels.