Expression and Production
How to Balance High-Titer
Processes with Consistent Quality?
XD® Technology Gives the Answer to This Challenge
Figure 1: Comparing cell growth and product concentration of a CHO
clone cultivated using the 2-L XD and 5-L fed-batch bioreactors.
Figures 2: Comparing the scale-up effect of XD on product titer using
the CHO cell line and the same medium
BioProcess International
XD titer boost
Product Titer (g/L)
The original CHO-based 12-day fed-batch process yielded 1 g/L
of a fusion protein. Early trials applying XD® technology
combined with DSM’s active experience in biologics
manufacturing resulted in eightfold improvement in titer using
the same medium. Further process development included
optimization of the feeding strategy, media component, and
process parameters. Such developments resulted in extremely
high cell density of 175 × 106 cells/mL on day 12 (Figure 1).
Product concentration was improved eightfold over a fed-batch
run at the same duration (12 days, Figure 2).
Scale-Up: The process was further scaled up to a 50-L
bioreactor. Continuous optimization and scale-up of the
process resulted in consistent high titers at the 50-L scale
(Figure 2). In addition, the culture maintained a high viability
(>95%) right up to the point of harvest. This can potentially
facilitate downstream clarification and purification. The use of
XD® technology to achieve an eightfold titer increase compared
with the original 400-L fed-batch decreases the plant footprint
and extends related equipment and facility capabilities. Finally,
because the product is collected inside the bioreactor within
the same time frame of a standard fed-batch process, only a
small and concentrated batch is harvested. Therefore, the need
50L XD
5L Fed batch
Case Study
8× higher
he high cell culture process (XD®) is a continuous
process in which both cells and product are retained
in a stirred-tank bioreactor using suspension
mammalian culture. This is accomplished using a
retention system: Fresh medium is continuously supplied, and
metabolic byproducts are withdrawn and discarded through
the retention system. XD® provides a controlled environment
that leads to consistent product quality in terms of bioactivity,
glycosylation pattern, and other product characteristics.
Moreover, XD® technology is independent of the cell line (e.g.,
CHO, PER.C6®, hybridoma, myeloma). Developments have led to
very high viable cell densities of >150 × 106 cells/mL and IgG
concentrations of 10–27 g/L in a period of 10–14 days. In the
case of CHO cells, XD® delivered 8–13 times higher titer than
comparable fed-batch runs. With the XD® technology the
volumetric productivity of the bioreactor is boosted to very
high levels and can ideally produce large amounts of product
with minimum development and investment. It is also suited
for manufacturing nonantibody proteins, which can be difficult
to produce at high titers in traditional fed-batch systems due to
limited cell specific productivity. XD® delivers consistent
product quality and titer during scale-up, and its application in
cGMP manufacturing opens new avenues for biologic
therapeutics production.
Same duration
Time (days)
to collect and purify large, multiple-volume harvest batches is
eliminated. A similar process was transferred for the cGMP area
for further manufacturing and scale up. •
Rolf Douwenga is vice president of global R&D; Gerben Zijlstra, PhD
is a senior scientist in R&D; and Alberto D’Avino, PhD, and
corresponding author Amir Goudarzi, PDEng, are associated
scientists in USP R&D, DSM Biologics, Zuiderweg 72/2, 9744 AP
Groningen, The Netherlands, 31-505-222-389; [email protected]
com, www.dsmbiologics.com.
Industry Yearbook 2010 - 2011