Plant design concepts for trouble-free biotech

Published: 16-Nov-2012

Biotech applications are particularly susceptible to contamination. When designing a complete plant, it is not the equipment itself that causes the problem; it is the way the whole system is put together that minimises the risk of contamination. Even very small design flaws can lead to product losses.

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The white biotech sector is a relatively new and dynamic manufacturing field that requires hygienic processing. Thorsten Vammen, director of GEA Liquid Processing in Skanderborg, Denmark, looks at what can be done at the design stage to reduce contamination issues.

Biotech applications are particularly susceptible to contamination. Some of the cells used in biotech processing are very sensitive to contamination from the outside; carrying cells from one batch to another can also be disastrous. So designing a plant in the right way to minimise the opportunity for contamination is a primary requirement that can help prevent expensive mistakes.

White biotech is the name given to that particular branch of biotechnology that is concerned with industrial processes. It uses living cells – from yeast, moulds, bacteria and plants – and enzymes to synthesise products that are easily degradable, require less energy and create less waste during their production.

The equipment used for white biotech processing includes fermenters, separators, evaporators, freeze- and spray-dryers, valves and pipework. All of this equipment is designed for efficiency, efficacy and to minimise the opportunities for contamination. When designing a complete plant, it is not the equipment itself that causes the problem; it is the way the whole system is put together and integrated that makes the difference.

Although biotechnology has been practised for decades, it is only relatively recently that the shortage of oil worldwide and environmental concerns relating to fossil fuel emissions have boosted the rise of biotechnology as a means to producing alternatives to oil. It is this driver that has, largely, been at the root of the recent rise in investment. However, the meteoric rise in popularity has also meant that only the newest sites have been designed specifically to handle biotech products. Many existing plants were originally designed as chemical plants where Clean in Place (CIP) technology was not generally employed. Therefore, some plants in use today for manufacturing biotech products are not made for CIP – either because of their original purpose or because people are not used to designing CIP-enabled systems.

The meteoric rise in popularity of biotechnology has meant that only the newest sites have been designed specifically to handle biotech products

One of the problems of not having proper cleaning is that product residues remain in the system. When sterilising, the product that is left over will build up over time and be burned onto the equipment. This makes it difficult for the sterilising steam to reach all the crevices and corners. Even if the material is sterile in itself, it creates a perfect environment for bacteria to grow. In addition, burnt-on product remains will, over time, produce particles that can easily clog and cause a malfunction in components like steam traps and small drain valves.

Dead legs are another challenge. These are areas within pipework that cause air pockets, making it difficult for the steam to reach to the bottom of the dead leg area. These areas typically have seals at the bottom, which can be notoriously difficult to clean.

If the previous batch was based on a bacteria type that is ‘stronger’ than the one being produced, the stronger bacteria will take over the environment and decrease the yield or ‘kill’ the one being produced

In today’s competitive world, plants have to work harder. Many biotech plants are now multi-purpose, producing different products based on different strains of bacteria. In these cases it is very important that there is no cross-contamination from the previous batch especially if the previous batch was based on a bacteria type that is ‘stronger’ than the one being produced. If so, the stronger bacteria will take over the environment and decrease the yield or in the worst-case scenario ‘kill’ the one being produced.

Handling live bacteria

The segment of the industrial biotech sector producing living bacteria frequently requires cleaning and sterilisation systems that achieve a very high efficacy level during product treatment at F0= log109 to log1016.

To obtain this high level it is necessary to have a well-functioning CIP system combined with a well-designed steam sterilisation system (SIP).

To achieve this level of efficacy many factors come into play. The physical system design, selection of most suitable components, care in mechanical manufacturing and a well-designed control system will be of utmost importance. Even very small design flaws can lead to product losses. More importantly, perhaps, if there are faults, finding them can be complicated, difficult and time-consuming, leading to lost production.

If there are faults, finding them can be complicated, difficult and time-consuming, leading to lost production

Frequently it is not the production systems that are the main culprits: utility systems such as water supply, steam generation, ventilation systems and gas and chemical supply systems can harbour bacteria if the cleanliness of these systems does not fall within design parameters. It is often these utilities that do not receive the attention they require and, therefore, can be the starting point for serious problems.

Effective cleaning is important; however, designing systems that are not friendly to bacteria is a vital part of a system. For example, all instruments should be flush mounted to avoid creating dead legs or crevices where bacteria can collect. Every piece of pipework must be designed in such a way as to ensure that the CIP fluid hits all surfaces at the correct velocity and temperature. Utility systems too should be designed to be cleaned and sterilised or if this is not required, a sterile barrier should be created at the point where the utility product meets the sterile process.

Air pockets should be designed out as far as possible. If this is impracticable, the air should be capable of being vented. Air creates an isolation layer between the steam and the metal, preventing the metal surface from reaching the correct temperature for effective sterilisation to take place.

It is also necessary to design out human intervention as far as possible to avoid contamination

It is also necessary to design out human intervention as far as possible to avoid contamination. Instruments need to be placed correctly to ensure that they provide accurate readings of temperature and pressure to validate sterility and, therefore, verify that sterilisation has been performed to the correct level.

Environmental gains

Designing a plant to limit contamination and to make sterilisation easy limits the amount of chemicals, water, and power necessary during the sterilisation process. In turn, this saves money and limits the effect of the process on the environment. The initial investment might be a little higher but the total cost of ownership will be lower, more than compensating for the additional up-front expenditure.

Less use of power reduces fuel bills, avoids penalties for unacceptable emissions and saves resources. Efficient use of chemicals and the clever use of water – including closed circuit systems – minimises disposal costs. Good cleaning means less downtime and can reduce the need to use preservatives.

Save with heat recovery

Heat recovery systems save money and help the environment, so they make good commercial sense and can save up to 20% on heating bills for chemical plants. Modern systems can also contribute significantly to reducing contamination in sanitary operations. Heat recovery systems re-use heat that has already been generated in the plant. One of the main opportunities for heat recovery is after CIP and SIP operations that inherently require high temperatures to be effective. By recovering this energy and using it for pre-heating of the next batch, it is possible for plants to make a significant power saving.

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