Bilfinger Industrietechnik Salzburg counts on Arc sensors from Hamilton
Bilfinger Industrietechnik Salzburg GmbH, originally having emerged from the Mannesmann history and later part of MCE, has been independent for more than two years now and is a true knowledge carrier in the biotechnology sector – from a historical perspective to the present day. This also applies when it comes to planning, fabricating and installing pipework, systems and equipment in biotechnology, pharmaceutical and fine chemical industries. The systems engineering business unit, based in Salzburg, Austria, with a team of engineers focus on standardized bioreactors with sizes from 15 to 2,000 liters. Planning and fabricating equipment according to precise customer specifications is a specialty as well. Bilfinger Industrietechnik completes its innovative portfolio of solutions for cell and bacteria cultivation with the market launch of the PROQUBE BRC family of bioreactors. The ongoing further development and deployment of related technologies is based on the fact that microorganisms and animal cells require regulated environment and nutrition in bioreactors. This is the only way controlled cell growth and production can be ensured. As an elementary and essential component of a controlled bioreactor and its sensitive contents, powerful sensors continuously monitor the key process parameters such as the pH value and dissolved oxygen (DO). Especially developed management software, highly user-friendly thanks to the design of the management module and interface, also supports the efficient operation of the bioreactor.
Unsuitable sensors can result in failed product yields
Parameters like the pH value, dissolved oxygen and conductivity are essential to maintain the process in the bioreactor and to achieve the goal of controlled product quality. “We have been working with the sensor specialists from Hamilton Bonaduz AG in this field for many years already,” states Dipl.-Ing. Gerald Berghammer, Head of the Biotechnology, Pharmaceuticals and Fine Chemicals business unit at Bilfinger Industrietechnik Salzburg. In addition to exact measurement, the sensors used have to meet the legal requirements regarding possible contamination. Contrary to customers’ expectations, this is often lacking. “There are enough sensors in the market. But many are unsuitable because sterility cannot be ensured,” says Pablo Pino-Grace, Project Engineer and responsible for the bioreactor product group at Bilfinger Industrietechnik. Pino-Grace adds that, with the decision to favor Hamilton and the Arc product family, sensors have been implemented which, amongst others, withstand the frequent sterilization processes as well.
Clark sensors were yesterday – VisiFerm DO Arc is trend-setting
In the past, electrochemical Clark sensors were commonly used for measuring dissolved oxygen in the biotechnology sector. In their measuring chambers, a platinum cathode and a silver anode are usually connected by an electrolyte solution, with the polarization being set so that electrolysis of the electrolyte solution does not occur. Oxygen diffuses through a permeable membrane in the sensor cap into the measuring chamber. The consequential measuring current allows determining the partial pressure of the dissolved oxygen. Even though Clark sensors have been established for a long time, they have significant disadvantages compared to optical sensors: Next to time-consuming polarization, the membrane is mechanically very sensitive and, along with the electrolyte solution, has to be replaced frequently. Furthermore, deposits of oxidized silver metal occur on the anode as a consequence of the measuring process. The deposits have to be removed to ensure the high conductivity of the electrode. Process control is therefore more difficult because a lot of maintenance is required.
Simple – compact – non invasive
Based on this background, Hamilton developed a truly trend-setting alternative with the Arc sensors. “We are always searching for truly state-of-the art solutions that offer added value for our customers. This is why we have repeatedly involved Hamilton in an ongoing project for China as our cooperation partner and supplier. Here a pH and an optical DO (VisiFerm DO) sensor are used for each reactor. The sensors are mounted laterally and close to the bottom of the bioreactor” Gerald Berghammer says. Positioning close to the bottom ensures that the sensors are in touch with the medium for exact measurement even at minimum volume. For those in charge at Bilfinger Industrietechnik, it has proven advantageous that the sensors with their integrated transmitters and the use of open industry standards provide compensated and backwards-compatible measuring signals, which can be integrated directly into new or existing process control systems. The characteristic Arc micro-transmitter integrated in the head of each sensor stores all relevant data, including calibration and diagnostic information. The sensor technology has already been installed in a 100-liter bioreactor for laboratory use, which was first presented at the Vision Pharma 2014 trade fair in Stuttgart, Germany. In addition to straightforward calibration from a handheld device, the sensors are small, compact and easy to clean.
Luminescence principle in optical O2 measurement
The method for optical DO measurement using VisiFerm DO sensors is based on oxygen-dependent luminescence, occured by excitation with blue light of the luminophore. By absorbing the energy of the blue light, the molecules of the luminophore assert an excited state. This energy will be emitted in an oxygen-free environment as red light. Oxygen measurement as such is performed by measuring the optical phase shift between the pulsating blue excitation and the red luminescence light. The sensors also have a silicone membrane, which was developed by Hamilton especially for oxygen measurement. This optical membrane is far less mechanically susceptible and therefore much more durable than the membrane of the Clark sensor. At the same time, the composition eliminates the need for replacing the electrolyte solution and removing oxidation deposits, significantly, leading to reduced the maintenance effort and enabling trouble-free process control. Tolerance deviations during the process can be corrected using control circuits. Data transmission is sent directly from the control unit to the PC. “Additional benefits in practical knowledge are that our customer can control more than one Arc sensor with just one device, and that there is only one user interface for measuring the process-related parameters” Pablo Pino-Grace sums up, adding in conclusion that it is definitely realistic to use the Hamilton sensors for measuring the cell density in the near future as well.