As the need to understand bioprocesses grows, continuous online measurement using accurate and reliable analytical techniques is essential. As Richard Ahearne explains, innovative multiple task equipment is now bringing advanced process control nearer.
The pharmaceutical and biotechnology sectors of industry are currently engaged in major change as process developments benefit from the latest technology and innovation is accepted as a key element of a modern economy.
Production of pharmaceuticals is increasingly moving away from processes based on chemical synthesis to biotech methods, particularly methods using genetically modified micro-organisms.
The speed at which new production methods are being introduced has created a significant information gap. There is a real need for a wider understanding of processes if the drive for the increased efficiency that is available from integrated process development is to be attained.
Real-time monitoring
Real time monitoring is essential for the control of bioreactors and downstream processes. Continuous online measurement, using analytical techniques that are both accurate and reliable, is essential.
Innovative multiple task equipment that delivers real-time process data is now being used to establish process models, achieve process optimisation and develop advanced process control (APC).
APC is a control method based on intelligent process models that manages production processes whilst deriving additional process knowledge through an understanding of interactions between process variables.
Relationships between non-linear variables are explained and systems established that will handle multi-parameter systems and apply economic constrains. This high quality output delivers capacity, yield and quality increases with less process variations and interventions resulting in savings of both energy and raw materials.
In-situ automated testing equipment offers great potential for process optimisation and quality control for basic biochemical and biomedical applications, one of the most important being the monitoring and control of the fermentation processes used in the manufacture of primary additives.
The measurement of component concentrations and the monitoring of the purity, results in increases of throughput and a reduction in batches that are below-specification.
Automatic and continuous control of the fermentation variables is needed for performance studies and successful process optimisation.
Efficient biotech process monitoring requires detailed information on a variety of physical and chemical parameters. The biotech data needed extends beyond the parameters currently in use, such as dissolved oxygen, pH and temperature, which give no direct information about the chemical state of the process.
Up to now, the measurement of substrate and nutrient levels, metabolite formation, and biomass concentration has been obtained by discrete sampling.
The off-line laboratory methods used yield results in 0.5 to 8 hours and these are then fed into the process computer. The time delay markedly limits the control options available and an operator's ability to optimise any fermentation process.
Siemens initiatives in the field of on-line sampling are now changing the biotechnology horizon.
By using near infrared (NIR) and mass spectroscopy (MS), the company has made it possible to create a continuous, on-line picture of the state of the fermentation broth.
Information is obtained about the physical state of the fermentation and, more importantly, on the biological state of the fermentation process. The reaction can be monitored through each intermediate phase and, when the required degree purity is reached, the reaction can proceed without interruption.
Manufacturers are interested in trends as part of the statistical element of process control in order to maintain the balance of the fermentation liquid before discrete laboratory results are to hand.
Fourier transform (FT) and acoustic optical tuneable filtration (AOTF), together with NIR and MS, permits in-situ measurements to be made of glucose, lactic acid, ammonia concentrations together with cell density and viability.
The ability to characterise the cell status quantity, quality, and morphology enables a distinction to be made between viable producer cells and cells that have entered apoptosis or necrosis. This creates the possibility of on-line monitoring of the production cells that can be used for both on-line optimisation and process control.
Process characteristics
In addition to this quantitative method, the company has developed a qualitative approach that is based on monitoring the shift in the NIR spectrum during fermentation. This allows information to be obtained on the fermentation path and the behaviour of different process characteristics.
This method opens the gateway to real-time monitoring for the complete whole process pathway and waste is reduced as the method allows an immediate response to be made when process variations, caused by all kinds of interference, take place.
As a result of drastically improved resolution, ion cyclotron resonance Fourier transform (ICR-FT), coupled with mass spectroscopy for off-gas analysis, now enables separate measurements to be made of two extremely important components for fermentation control, namely carbon monoxide and nitrogen, which respectively inhibit or enhance microbial growth.
The application of these new methods of analysis to bioprocess modelling, control and optimisation applications is already a reality. A broad range, basic model has been established based on process theory and the metabolic pathways of micro-organisms. Application specific hybrid models are then developed using the real-time data from new in-line analytical systems.
Hybrid building blocks
Precise information on the identity and concentration of fermentation bulk products, such as the concentration of various nutrients, off-gas composition, the state of the fermentation broth and the synergy and interaction of each between are the hybrid building blocks.
This hybrid model is a combination of the parameters identified by the base model refined by real-time data to produce forward operating objectives to progress the production cycle to the target purity or host cell count.
Siemens intelligent process model combines with actual process information to deliver a solution that is now known as an APC.
Such models permit the early prediction of undesirable process, the avoidance of waste and optimisation of quality and yield, attributes that are combined with minimum energy and raw materials consumption.
The on-line control of fermentation processes also facilitates detailed research into biotechnology transformations and the optimisation of genetically modified organisms for the production of the active components of modern pharmaceuticals.
The APC solutions developed for bioreactor control are part of the integrated Life Sciences Suite that consists of APC Tools such as INCA, Pathfinder and Presto. All are available for use on the global PCS7 platform. These tools are usually interfaced, via an OPC client channel, with a PCS7 historical database and data obtained by state-of-the-art in-line analytical systems such as SINIS and QUANTRA. PCS7 and APC expand the process optimisation functions available to customers.
The link that is created between the planning and scheduling functions and the process control functions has delivered a powerful bio-fermentation tool, which is complemented by a comprehensive range of options from advice through validation and quality measurement to full scheme implementation including commissioning from start-up to full process optimisation.
Richard Ahearne is marketing manager of Siemens Process Automation, contact Richard.Ahearne@spa.siemens.co.uk
