Traditionally, the comparison of single-use versus stainless-steel processes is made on the basis of consumable cost versus
capital cost, but other costs must also be taken into account to make an accurate comparison, including labour, validation
and quality. Selection of the cost minimum option depends on the specifics of the application and accurate accounting of the
associated costs of each technology. Labour rates and process costing assumptions are taken from Biosolve cost modelling software
(Biopharm Software Solutions). Tables I and II summarise the results of the cost analysis for a typical redundant filtration process using two 10 in. cartridges. The costs
assumed here are representative of industry costs; it is assumed that difference in cost for utilities and materials (e.g.,
CIP solution, water for injection) does not significantly affect the cost comparison. The costs of pump and extractables–leachables
validation are similar for both stainless steel and singleuse setup, so these costs were excluded from the analysis.
Table I: Capital and validation cost. Capital and validation costs are taken over 10-year expected lifetime of the facility.
SURF assemblies offer further benefits over stainless-steel setups. Equipment turnover for new products is quicker with single
use assembly. For example, additional testing and cleaning time associated with equipment release and documentation is reduced
or eliminated if singleuse technologies are used. It also provides more production flexibility because single-use assemblies
can be made to order in the size and configuration required with the need for additional equipment or validation. It also
eliminates the need to have multiple setups in place to meet the production demands of different products.
Table II: Cost per batch. The cost calculations in this table are based on 12.5 h batch time for stainless steel setup and
6.5 h batch time for single-use assembly. The batch time is lower for single-use assembly due to elimination of preparation
steps, cleaning procedure and ease of handling.
This study identified a suitable design for redundant filtration operations by utilising single-use technology. An optimised
utilisation sequence for preparatory steps was designed and tested. Conducting a pre-use integrity test on a pre-sterilised
redundant filtration setup can be challenging, but an effective filter wetting step is important to avoid false negative integrity
test results. For highvalue products, the drying step after integrity testing is crucial to minimise product dilution. All
preparatory steps and filtration operations can be successfully performed on a single-use assembly. SURF assemblies are robust
and efficient disposable solutions for bulk and final fill processes.
Ranjeet Patil process engineer II
Michael Felo applications engineer consultant
George Oulundsen process engineer III EMD Millipore
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3. European Commission, "Guidelines to Good Manufacturing Practice—Manufacture of Sterile Medicinal Products," Annex 1, Nov. 25, 2008 (Brussels, Belgium).
4. Lentine et al, Bioprocess International,
4 (6), 44-47 (2006).