Life processes

life processes

The need to monitor cell fermentation put this solenoid valve into the designer genes business.

By Dan Whelahan

Every day the world hears more about the dramatic advances in genome engineering. Cures for the most deadly and debilitating diseases may be on the horizon. Cell culture bioreactors and fermenters manufactured by B. Braun Biotech of Allentown, Pa., have been helping the forerunners in genomic research get there faster.

The company supplies customized process systems, designed for efficient production of the cells that are studied. Part of the system, a multiplexer sold under the name MUX 100, provides the means to monitor and control the cell fermen-tation process.

At its heart, the multiplexer uses solenoid valves supplied by General Valve of Fairfield, N.J., a division of Parker Hannifin.

Fermentation has to be closely watched. A sterilized solution in the fermenter is inoculated with microorganisms; oxygen is added, along with ingredients to control the pH.

Oxygen is the most important gaseous substrate for microbial metabolism, and carbon dioxide is the most important gaseous metabolic product. So one of the most important factors in the operation of a fermenter is adequate gas exchange.

To check on fermentation, the multiplexer directs an exhaust gas sample from the fermenter to a mass spectrometer for analysis. The MUX 100 can sequence up to 12 fermenter samples through one mass spectrometer. An array of solenoid valves manages the flow of the samples.

The valve array in the multiplexer made by B. Braun Biotech of Allentown, Pa.

The analyzer determines the molecular level of each specific gas in the sample and determines the fermentation environment. The analysis will provide information on oxygen transfer and uptake, carbon dioxide evolution, and sugar level. The results may tell the operator or automatic control system to adjust the agitation speed, temperature, flow rates, oxygen percentage, pH level, pressure, or other variables within the bioreactor.

The valves play a critical role in fermentation, but high humidity creates a tough environment for many con-ventional gas valves. B. Braun Biotech's engineers came for technical assistance to the help desk at Parker Hannifin Corp. of Cleveland, which already had supplied them with instrumen-tation fittings and isolation and pilot valves. Help desk representatives put B. Braun Biotech in touch with General Valve, which operates under Parker Hannifin's Pneutronics division.

A Series 66 solenoid valve was selected and mounted onto a four-station Teflon manifold equipped with 1/8-27 quick connect fittings.

The Series 66 solenoid valve has an elastomeric diaphragm and an inert PEEK body, which protect metallic components from fluids. The easy access Parflex fittings, made by a sister company, Partek, are also of PEEK.

The valve offered the added advantage of very low internal and negligibly low unswept volumes. These features allowed B. Braun Biotech's engineers to minimize the sample size, thus reducing any potential interference with fermenation caused by the loss of gas volume.

The valve's low unswept volumes gave B. Braun Biotech the added flexibility of switching lines without concern of carryover from one sample gas stream to the next.

Pneutronics/General Valve's products have found such applications as the piloting of air cylinders, controlling deflation rates in blood pressure cuffs, or introducing solvent gradient mixes into liquid chromatographs. Now the engineers at B. Braun Biotech have put us into genomics research.

Dan Whelahan, a mechanical engineer, works for General Valve in Fairfield, N.J., a division of Parker Hannifin Corp.