Mass Flow Controllers Maximize Bioreactor Performance
Protein Design Labs has been able to maximize pilot production control by integrating an automated gas mixing system with Sierra Instruments' microprocessor-based mass flow controllers (MFCs) in their B. Braun Biostat fermenter.
"We had two compelling reasons for specifying mass flow controllers," says Associate Scientist Paul Sauer of Protein Design Labs Cell Culture Development group. "The first was that we needed to minimize the formation of foam in the bioreactor's headspace." To minimize foam, they needed to reduce the net volume of air and oxygen gases that were being bubbled into the culture medium. The rotameter Protein Design Labs had been using was not adequate for measuring the low flow rates needed to prevent excessive foaming.
"We now have a high degree of confidence in our flow rate," says Sauer. "When we were using rotameters to control our flow rate at the lower edge, we experienced a substantial amount of foaming. According to the flow tube, we had been flowing at about 60 ml per minute. But after we installed the Sierra MFCs, we realized that we had been flowing at much more than that--perhaps up to three times as much. At a 60 ml setting, the MFCs reduced the foam significantly.”
Protein Design Labs now uses a B. Braun Biostat® MDC A54 automated fermenter to scale up culture strains to bulk production levels. The six-fermenter Biostat system, configured specifically for Protein Design Labs, includes a digital control unit (DCU) and 12 Sierra mass flow controllers. Working with the B. Braun Biostat fermenter, they have found that Sierra Instruments mass flow controllers permit them to flow a precise low volume of air and reduce foam formation.
Protein Design Lab’s second compelling reason for acquiring a Braun system with mass flow controllers is that it offers a more refined tool that provides more information.
"The mass flow controllers, by monitoring and metering gas mass flow ratios precisely, also provide an elegant and relatively straightforward way of measuring the oxygen uptake rate (OUR) using the static method 1 that was not possible with solenoid valves."
