In the Quality by Design (QbD) and Process Analytical Technology (PAT) era, the generation and validation of a large amount of data have become standard. Parallel bioreactor control systems offer the possibility to test and optimise different process parameters at the same time, thus saving time and resources.
Working with bioprocess control systems that help to develop and optimise processes in terms of time and cost efficiency is crucial. In the Quality by Design (QbD) and Process Analytical Technology (PAT) era, the generation and validation of a large amount of data have become standard. This data is not generated by random trial and error experiments. Experiments are carefully designed with the information gathered from previous experiments. This Design of Experiment (DoE) approach allows profound insights into the process. Parallel bioreactor control systems offer the possibility to test and optimise different process parameters at the same time, thus saving time and resources. This is especially important in the fast-changing biotechnology industry.
We spoke with Dr. Sebastian Kleebank about the DASbox® Mini Bioreactor System, a compact and flexible parallel bioprocess controller for the control of up to 24 bioreactors.
What was one of the most significant experiences in your laboratory life?
Sebastian: Everybody who works in a laboratory running long, work-intensive, and expensive experiments knows the thrilling feeling, and the question in mind: “How does my experiment look like when I will be back In the lab afterthe weekend?”. One of my most prominent incidents for me was, that I stepped into the lab and found my culture everywhere on the floor as a consequence of a foam out.
This was the first time I realised that continuous monitoring of the process is crucial and reliable process control is essential.
What are the major challenges in running a bioreactor control system?
Sebastian: The goal of each scientist is to gain as much process knowledge as possible in a short time. This is especially true for scientists working in industrial laboratories, where the time-to-market is important. To get to know your process, one needs to perform many tests. To save resources, this is mainly done in small working volumes of less than a liter. And here a precise and reliable process control is key to gain high-quality results.
Regarding the foam out mentioned above it is a very comfortable feeling to know that the DASbox system can prevent this. We developed a very sensitive level sensor that can identify even the slightest foam formation and distinguishes precisely between air bubbles and liquid. With a sensitivity in a range between 1 – 20000 µS, foam can be reliably detected and destroyed, especially when you are investigating unknown, new processes.
During fed-batch, perfusion, or continuous cultivations, it can happen that the user underestimates the amount of substrate that the organisms would need. This could lead to exceeding the maximum working volume of the connected bioreactor. With the combination of our very precise pumps in the DASbox system and the powerful DASware software suite, we offer a solution that mitigates the risk of such errors. The software of our DASbox system sums up the added and removed liquid volumes and automatically stops the feeding if the maximum working volume is reached.
How can the DASbox help to optimise all the different steps of a process?
Sebastian: From the inoculation of the bioreactor to harvesting, the DASbox and its control software offer solutions to support you in each individual step.
After inoculation, the oxygen requirement for aerobic cultures increases steadily. With our oxygen cascade (flexible change of stirrer speed, oxygen concentration of the input gas and/or gas flow rate) the oxygen demand of the culture can effectively be covered.
The end of the batch phase can, for example, be reliably identified by the so-called substrate consumption peak of the dissolved oxygen concentration and the substrate pump can be started automatically. When you add an exhaust gas analyser, the substrate can even be added in relation to the metabolic activity of the cells. Our precise pumps ensure that the substrate is added continuously even at very small feed rates of down to 0.3 mL/h. In combination with submerged liquid addition, this results in a very smooth DO (Dissolved Oxygen) signal that enables a reliable process control.
And even the right time for harvesting can be defined for exampleby reaching a certain number of cells (e.g. when using a DASGIP OD sensor) or other measured variables and the harvest pump can be started automatically.
With our scripting functionality, there are virtually no limits to the flexibility of the control strategy. Controller inputs and outputs can be freely configured. Signals from balances, external sensors e.g. for methanol or glucose, as well as internal process values can be selected.
What are the benefits of highly parallel approaches?
Sebastian: The obvious correlation is quite simple: the more experiments are performed in parallel, the more results are collected at the same time. The real advantage of highly parallel approaches is that you can systematically investigate your process and thus increase the knowledge gain. The knowledge about the process is therefore the actual benefit here. The basis for this is that a reliable and reproducible process control can be ensured and that the results can be transferred to large scales. Both can be achieved with the DASbox system.
One way to systematically investigate your process can be to consider the fact that many processes are divided into two parts. The first part being the growth phase and the second part being the production phase. The tricky part is that the optimal growth conditions may not be the optimal conditions for the production phase. When using design of experiments (DoE) you can easily start the growth phase in all setups under the same standard conditions (resulting in the same amount of cells after the end of the growth phase) and then switch the individual conditions to analyse the impact of factors like temperature, pH, and dissolved oxygen concentration on the product concentration and product quality.
But highly parallel setups also own the risk of manual handling errors. For example, a certain setpoint could be assigned to the wrong bioreactor unit. To avoid such programming errors, our DASware design software helps you to import complex experimental designs and automatically assigns the correct setpoints.
How do you keep an overview of all the many process results?
Sebastian: In high parallel experiments, it is crucial to identify which setup worked as expected and which did not. Otherwise, the wrong conclusions are made. DASware control gives a very good overview on every single process using customisable online charts. Thus, you can easily identify the setups which worked as expected. For example, when using a pH setpoint of 7.0 you can easily check if the process value was also 7.0 over the relevant process time. The DASware control software is capable of doing this for all relevant process parameters of up to 24 vessels in parallel.
Additionally, the strength of the software is to compare individual runs, also from past experiments. With DASware control, you can start the inoculation time for each vessel individually. This feature simplifies the comparison of relevant process parameters like pH, DO, temp. profiles between different units and even between different historical runs.
I don't know how much time I spent manually synchronising the time axis of different runs to be able to compare them when I was still actively working in the lab. Now the DASware control software does this with one mouse click.
If I am experienced in bioprocessing, but not in programming, how can I benefit from the scripting possibility of the DASware software?
Sebastian: We have a collection of scripting-templates that can easily be applied by beginners or being modified by expert users with almost no limitation. Just ask our field service and benefit from our long-term experience in the industry.
Where do you see the biggest advantage of the DASbox system?
Sebastian: The biggest advantage of the DASbox system is its compactness combined with the high precision of process control. Together with the powerful DASware control software, the DASbox system is the ideal tool for screening and process development. Up to 24 vessels can be connected to one process computer allowing for highly parallel setups requiring only 1.80 meter/6 feet of bench space and the integrated storage options for accessories ensure that everything is stored where you need it.
Although the DASbox is a very compact system it uses industry-standard ports (PG13.5) that enable the use of standard sensors with an outer diameter of 12 mm.
It offers the ability to use both single-use and glass vessels side-by-side or go completely single-use or glass for certain runs. This is a major advantage as the glass vessels allow users to make impeller changes and accessory adjustments. With the large variety of accessories and modular upgrades, you can easily react to changing process requirements. For example, if there is the need to add further features like exhaust gas analysis, these devices can easily be added to the systems.
The installation is comparatively simple, as only a power supply and the individual gas connections are required on site. There is no cooling water needed for temperature control due to our Peltier technology, which we also use for exhaust gas condensation. With this, we keep the evaporation at a minimum and effectively prevent clogging of the exhaust filters.
With easy workflow guidance on the one hand and options to deeply adjust controller settings, the DASbox system is the optimal tool for beginners and experts alike.
For more information visit:www.eppendorf.com/dasbox