Cell culture technology is only taught at a handful of universities. However, this interdisciplinary subject is the core of the “Pharmaceutical Biotechnology” programme offered by the Biberach University of Applied Sciences. We talked about the subject with Professor Jürgen Hannemann, founding dean of the “Pharmaceutical Biotechnology” programme, and with Professor Friedemann Hesse, who runs the “cell culture technology” teaching programme.
Hannemann: The term “cell culture” can be defined in many different ways. I believe my personal definition is relatively common. For me, the term “cell culture” refers to the culturing of cells that that goes beyond Petri dishes, and is technically implemented in fermenters.
Hesse: My definition is fairly similar. On the one hand, the term cell culture refers to the technique that is used to culture cells, either in the laboratory or on an industrial scale, in small culture dishes or 15-cubic metre fermenters. On the other hand, the term also refers to the use of cell cultures for the production of products.
Hesse: There are courses in the cultivation of cells in culture flasks at many universities and biological and biochemical institutions. However, people who are interested in actually applying cell culture methods, for example for expressing proteins for research purposes, need to acquire in-depth insights into the technology. They need to be sure that they are using a cell line that does exactly what they expect it to do. And if scientists want to culture cells on a larger scale, they need to have a working knowledge of the entire technical infrastructure, including bioreactor technology and they also need to be able to put in place process management strategies. The application of the technical infrastructure is something that is only taught at a few institutions in Germany. Hannemann: I would go even further. Germany is home to research institutions like the Max Planck and Fraunhofer institutes that are highly proficient in cell culturing methods. However, these institutes are not classical educational establishments, which means that students usually go there to do a doctorate once they have received a degree from a university, but not before. The other university that comes to mind that has bachelor and master courses that offer insights into cell culturing, is the University of Bielefeld (CeBiTec).
Hesse: Or the technology universities in Braunschweig, Stuttgart and Berlin, amongst others. But there are not that many. On the European level, the University of Natural Resources and Life Sciences in Vienna, the Zurich University of Applied Sciences in the Swiss city of Wädenswil, the IMC University of Applied Sciences Krems (Austria) and the IBET in Portugal offer such courses. However, the number of universities that offer cell culture technology courses is somewhat limited.
Hesse: Cell culture technology is not an insignificant area. It is particularly important in the pharmaceutical arena. If you take the statistics relating to the number of drugs that are placed on the market, the majority of these drugs involve monoclonal antibodies, all of which are produced using cell culture methods.
Hannemann: In addition to monoclonal antibodies, a growing number of recombinant proteins are being placed on the market. Eighty per cent of them are produced with animal cells.
Hesse: Cell culturing of course also involves the use of bacterial cells. And the use of bacterial cells requires those who work with them to be proficient in the use of the associated infrastructure.
Hannemann: Yes and no. Our graduates have excellent job prospects. Or to put it another way: why do so few universities offer cell culture courses? The answer is that the technology is relatively costly. The eight fermenters we use, for example, cost around half a million euros. On the other hand, technical work like this does not generate as many publications as other work. Over the last 20 years, it has been far easier for people to build an academic reputation from work involving molecular biology methods. Very few people have been interested in fermentation or even downstream processing. Hesse: In addition, the Helmholtz Centres have now adopted slightly different strategies. I myself spent five years at the GBF (Society for Biotechnological Research, editor's note), which is now known as the Helmholtz Centre for Infection Research. Apart from the Jülich Research Centre, Germany does not have any other biotechnological research centres. I believe that we are undersupplied in this area. However, the fact that our university here in Biberach offers cell culture courses indirectly shows this. It is worth noting that the region’s companies have been working hard to have a cell culture programme established at the Biberach University of Applied Sciences.
Hesse: Yes. Several more “Biberachs” are needed to cover the demand for cell culture specialists.
Hannemann: The bachelor programme is aimed at training students in the production of active pharmaceutical ingredients, to give just one example. And active pharmaceutical ingredients are produced with cell cultures. Of course, this also involves the purification of proteins. I believe that cell culturing and protein purification are the areas that we need to concentrate on.Hesse: This is also reflected in the practical courses we offer. In their third semester, students become acquainted with technical microbiology, in their fourth semester with cell culturing, and in their fifth semester, they undergo comprehensive training in bioprocess engineering where they focus on the entire production process, starting from the thawing of cells to the isolation of the final product under GMP-like conditions. All this is done using the fed-batch strategy, which is typically used to reach high cell densities in bioreactors.
Hannemann: Cell culture technology is not a closed teaching unit. Before students learn about cell culturing, they need to acquire knowledge in cell biology, for example about the cell cycle. This is taught in the “cell biology” lecture offered in the second semester. As our students also need to know how bacteria function in order to be able to ferment them, they are also offered courses in microbiology and technical microbiology, which is taught in the third semester. These courses provide them with insights into the handling of fermenters, how they are disassembled and cleaned. In the second semester, students also attend courses in cell biology, and in the fourth semester, they are given theoretical and practical training related to the cultivation of cells. All the courses build on each other and one semester is not enough to teach students all they need to know about cell culture. In the fifth semester, students are given theoretical and practical insights into protein purification before they attend Professor Hesse’s course where they cover, in practice, virtually everything related to the topic: they thaw the cells, ferment them, purify and analyse the protein product.
Hesse: Cell culture technology integrates several different disciplines. We also focus on physiology because we need to know how cells function. We need biochemistry in order to learn about cellular processes. And we also focus on process engineering; some aspects are already being touched on by the second semester. And all this is building up to a practical course that is offered to fifth-semester students.
Hesse: Yes. Our graduates go into careers in many different areas, including research focusing on tissue engineering. We receive very positive feedback from many research institutions and companies, for example from the Fraunhofer Society in Stuttgart or from small spin-off companies that are active in this field.
Hannemann: There are three people (Gaisser, Hesse and Hannemann, editor’s note) in our faculty who deal with the fermentation of bacteria and animal cells, as well as with cell culture technology. There are many outstanding researchers in Germany, but the University of Applied Sciences here in Biberach has an excellent profile in terms of teaching the culturing of cells. Our bachelor courses provide excellent training in cell culture and fermentation. There are only a handful of technical universities in Germany that offer similar courses.
Hesse: We also work with microorganisms. When students first come into contact with fermentation technologies, they work with microorganisms. At a later stage, they will use what they have learnt with bacterial cells in work involving animal cells. We mainly use cell types that are used in the pharmaceutical industry, for example CHO cells and hybridoma cells.
Hannemann: We work with HeLa and HEK (human embryonic kidney) cells in the master’s course. But we do not use plant cells. In addition, we work with E. coli and two antibiotics-producing bacterial strains.
Hesse: We also work with insect cells in the master’s course because these cells are particularly useful for some areas in the field of biopharmaceutical research and development.
Hannemann: The production of active pharmaceutical ingredients not only involves therapeutic proteins. Some of these proteins need to be modified, which is done with enzymes that are produced with insect cells, for example. Insect cells are used because they are able to generate high protein yields in a relatively short time.
Hesse: We also use insect cell culture systems to express enzymes or receptors that are used as drug targets.
Hesse: Specific methods are required for the cultivation of cells. One must ensure that only the cell line that one wants to culture is present in the culture. Specific methods are required from the very first second in order to exclude contaminating pathogens. People working with cell cultures need to establish sterile work techniques from the word go.
Hannemann: Technology can mean both technical equipment such as fermenters and methods. The question is, when is a bioreactor required and when is process engineering required?
Hesse: Not all laboratories are equally suitable for working with cell cultures. A lot of technological equipment is needed before cells can be cultured.
Hannemann: First of all, acquainting students with cell culturing means that a lot of supervision is required. The sterile handling of the cultures is very complicated and mistakes can be made at any one of the steps involved. Contaminations can occur at any time. Our cell culture laboratories are equipped with six so-called laminar air flow cabinets and the students’ work is overseen by three supervisors. This means that we have one supervisor standing behind any two lamina air flow cabinets at any given time in order to ensure that students only use one of these systems at a time. This type of supervision requires high staffing levels and is also very arduous because not all students have the same fine motor skills required for such work.
Hesse: The practical bioprocess engineering course is divided into three areas. When students start the course, they first learn to set up work instructions according to GMP (good manufacturing practice) standards. These work instructions are then checked and revised by our staff before students start their practical work. This work involves the culture of cells in flasks of 10 ml to 500 ml. Once this is in place, the cells are transferred into 2-l bioreactors and cultured using fed-batch strategies. This means that the culture volume in the fermenter is gradually increased by adding nutrition media and the supernatant is harvested after a period of two weeks, processed and analysed. Students carry out these steps by closely following previously established work instructions.
Hesse: The current trend is moving towards smaller bioreactors and single-use systems. I believe that the 15-cubic metre reactors that are currently used in industrial production will not be so important in the future. The reason for this is that they are expensive to run and the production capacity has been improved to a degree that smaller bioreactors are sufficient for producing the product quantities required. We’re moving towards using single-use bioreactors as this contributes to saving costs and increasing flexibility. Of course, the use of single-use bioreactors might also lead to problems, for example, with regard to their availability over longer periods of time. This might prove to be a problem in our fast-moving company landscape. Who knows, maybe stainless steel reactors will experience a revival in about ten years’ time. For me, the purification of the final product is the biggest bottleneck in the production of biopharmaceuticals. Around 80 per cent of all costs involved in biopharmaceutical production are associated with the purification of the proteins. This is why I believe further improvements will be necessary in this area.
Hesse: Yes. Before the human cell line Per.C6 came into use a few years ago, very few new cell lines were being developed. Today, several cell lines are being developed, including bird cell lines and human cell lines. I imagine a lot more will occur in this field in the not-too-distant future. The advantage of human cell lines is that they are able to equip recombinant proteins with the carbohydrate structures that are typical for humans. Such carbohydrate structures make drugs more efficient and they are also better tolerated by patients.
Hannemann: Yes, we will of course adapt the new programme to state-of-the-art knowledge. However, this is the first time that this course will be taught and we have not yet finalised all the subjects on the programme. I imagine that we will also include yeast cells in this course.
Hesse: White biotechnology, for example, provides products to the chemical industry, especially for the low-budget sector. The use of animal cells is rather expensive, which is why such compounds are not produced with animal cells. Fungi such as Aspergillus are used instead. We will of course also focus on biocatalysis, i.e. the application of microbial enzymes in chemical production. The interview was conducted by Walter Pytlik, BioRegionUlm.