Alternative, Biological Methods in the Flow Profile: Characterization of Bioreactors

In order to determine the flow profile in continuously and batch operated bioreactors, alternative methods were evaluated, using microorganisms (yeasts) as tracer material whose fermentation kinetics were similar to those of the starter cultures. The Modified Raffinose Test thereby proved to be an efficient method when dealing with larger quantitative differences of bottom- and top fermenting yeasts, whereas the IGS2 314 PCR-Capillary Gel Electrophoresis Test delivered trustful results when utilizing mixtures of two strains of top-top, or alternatively two strains of bottom-bottom fermenting yeasts. Both methods are therefore suitable in order to evaluate the flow profile via a step function test, in which the fermentation strain is substituted by a different (tracer) strain..

The presence of tracer yeast in the starter yeast culture could also be clearly detected via RealTime PCR analyses. Yet this test was found to be too sensitive in order to detect larger increments (20 % [w/w]). Hence, this test is rather suitable for the judgment of flowing patterns via the impulse function test, where a small amount of tracer material is being injected into the fermenter, before its presence is being detected subsequently.

BrewingScience - Monatsschrift für Brauwissenschaft, 66 (September/October 2013), pp. 123-134