Employing new single-use technology in bioprocesses

There has been considerable progress in the application of single-use technologies in biopharmaceutical production. CMO Rentschler Biotechnologie discusses recent advances

Cleanroom plant with a 1000L single-use production capacity

Contract manufacturing organisation Rentschler Biotechnologie will add a 2,000-litre single-use bioreactor to be fully operational end of the first quarter of 2015 to its facility in Laupheim, Germany, to match the growing demands for production capacity for all clinical phases.

Single-use technologies have gained broad acceptance in biomanufacturing within the past few years, supporting flexible and cost-effective clinical production. Beyond this, the first manufacturing processes for market products using disposable equipment (Shire, Protalis) have already been approved by European and US authorities. Currently, two thirds of all new bioprocesses are carried out in single-use equipment. Thousand-litre single-use bioreactors (SUBs) represent the common standard, although 2,000L SUBs are on the advance. In general, an optimistic growth market in the double-digit range is predicted.1

Compared with bioreactors made of stainless steel, single-use production plants not only have a low contamination risk, but are also more cost-effective and faster to implement. The initial investment costs are approximately 40% lower, and since systems for cleaning and sterilisation (CIP/SIP) are obsolete and time-consuming pipework is not required, the project lead-time for implementation of single-use production plants is reduced by at least eight months compared with stainless steel reactors, which still have their place in commercial production.

Single-use systems with disposable components made of plastic are also far less damaging to the environment than widely believed

Pharmaceutical customers also benefit from lower energy and maintenance costs. Of particular note, however, is the high degree of flexibility. It is possible to design processes modularly using single-use production systems and so to scale them easily; very rapid product changeovers are possible, and as a result an overall faster time to market can be realised.

Single-use systems with disposable components made of plastic are also far less damaging to the environment than widely believed – particularly when compared with stainless steel reactors. Stainless steel reactors need continual cleaning and sterilisation, which results in a high consumption of chemicals and ultrapure water. Single-use plants have a 46% lower total water consumption and a 35% more favourable CO2 balance than stainless steel reactors.2

Due to the heating of large quantities of water for CIP and SIP, the energy consumption of stainless steel reactors is considerably higher than the production and disposal of plastic bags, the burning of which can also be used to recover energy.3 Rawlings and Pora have calculated that the total energy consumption of single-use systems is about half of that of stainless steel reactors.4 This means that the disadvantages of disposable systems – above all the higher costs for consumables – are more than offset by savings in water, energy and chemicals.

Challenges of single-use bio processes

For demanding processes – particularly in the case of high cell densities and product titers – the classical production process in stainless steel reactors is still superior, especially during product harvesting. During harvesting, all cells and cell fragments are separated from the process liquid normally using centrifugation and subsequent filtration. The centrifugation step in single-use processes, however, must be mapped with a cascade of deep-bed filtration steps, and low filtration capacities have to be accepted.5 Single-use centrifuges have only recently become available, and Rentschler is working on the installation of such a centrifuge to bypass the bottleneck in harvesting.

Virus filtration system for tangential filtration

The capacities of chromatography systems, which are still too low, are another challenge. For example, the titer of the 2,000L single-use bioreactor is limited to 3g/L, because otherwise problems can occur during purification due to the small column sizes. Furthermore suppliers are still working on the development of single-use sensors for measuring pH-value and oxygen. Until these disposable sensors become more robust, optical sensors made of glass or steel will have to be used.

The possible release of so-called leachables and extractables from the plastic bags, which are normally gamma sterilised, represents a major challenge when polymer compounds are used in single-use systems. Leachables and extractables dissolve out of the bags and can migrate into the cell culture medium. Extractables are defined as substances that are washed out from films, bags and tubes under harsh conditions, such as in the presence of antioxidants, plasticisers or their degradation products. In contrast, leachables are washed out in the ongoing process. They not only jeopardise patient safety, but they can also damage the entire manufacturing process.

The possible release of so-called leachables and extractables from the plastic bags, which are normally gamma sterilised, represents a major challenge when polymer compounds are used in single-use systems

Cytotoxic leachables are particularly undesirable under process conditions, because they adversely affect the growth of the cells, their vitality and consequently also the titer. For this reason, a screening with mammalian cell cultures in addition to the extractable studies established by the manufacturer makes sense. Critical films can be identified at an early stage using such screening, the quality control of single-use bags can be improved and their implementation can be simplified. Rentschler and other users of single-use bags therefore regularly carry out appropriate cell culture tests using its own cell lines, culture media and protocols.

A standardised cell culture test was recently published from one Dechema working group.6 The further purification progresses the more risk arises from the leachables in terms of patient safety. For depletion of the leachables, Renschler follows a risk-based approach which incorporates both manufacturer’s data and process data. This guarantees that depletion is carried out within defined limits so that patient safety is ensured at all times.

Advances in single-use technology

By enabling high levels of modularity and flexibility as well as significant energy savings, single-use bioprocesses represent a paradigm shift in the production of clinical material. Some products, however, are better suited to production in stainless steel reactors, and commercial scale production is also usually more cost-effective in reusable stainless steel reactors. But here, too, a rethink is taking place. Rentschler is one of the first toll manufacturers worldwide to establish a complete single-use plant for the upstream and downstream area. The company has a flexible disposable concept consisting of two multi-product single-use bioreactor systems with 2 x 1,000L volume of work and an additional 1 x 2,000L bioreactor coming soon. This allows an easy scale-up as well as the reduction of manufacturing costs and product cycle times.

Single-use bioprocesses represent a paradigm shift in the production of clinical material

The disposable plant involves four independent all-purpose cleanroom suites for operating the 100% mobile one-way production plant for upstream processing and downstream processing as well as an inoculum suite. All the cleanroom suites are connected to a plant-wide data logging system which is preconfigured for ‘plug and play’ of the mobile production equipment. Incidentally, the company supplies all its plastic waste to an incineration plant, thereby contributing to the recovery of a significant amount of heat energy.

What makes single-use facilities attractive is mainly the fact that implementation is cheaper and faster. The initial investment is about 40% lower in comparison with a stainless steel facility at same scale. Furthermore, the project lead time for implementation is reduced by at least eight months. In the near future, the design of single-use production systems will be even more modular to meet increasing and varying demands. Further technological developments of single-use equipment, in particular centrifuges, sensors, chromatography and membrane adsorber, will help to resolve operational limitations.

References

1. E.Langer, R.Rader (2013): Innovation in Stainless-Steel Bioprocessing. Life Science Leader, 31 October 2013

2. Ken Davis (2014). Single-Use Systems – Show Me the Green! ISPE San Francisco/Bay Area Chapter Newsletter Vol 19/2, 18

3. Guldager, N. (2010). Cost Advantages of Single-Use Technologies. Pharmaceutical Technology.

4. Rawlings, B, and Pora, H. (2009). Environmental Impact of Single-Use and Reusable Bioprocess Systems. BioProcess International 7, 18-26.

5. Benjamin Minow et al. (2014). High-Cell-Density Clarification by Single-Use Diatomaceous Earth Filtration. BioProcess International 12(4), 36-47.

6. Regine Eibl et al. (2014). Standardisierter Zellkulturtest zur frühen Identifizierung kritischer Filme für CHO-Zelllinien und chemisch definierte Kulturmedien. Dechema, January 2014

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