Performances of aseptic sampling devices for on‐line monitoring of fermentation processes

Two liquid sampling systems, which are set in the bioreactor and can be sterilized in place, are described. They are composed primarily of an inorganic membrane filter which is either stationary or is set in a rotating motion. These systems have been tested during three types of fermentation processes (ethanol, lactic acid, and polysaccharide productions). The rotating system gave better filtration performances than the stationary sampler which can be used only in alcoholic fermentation. The rotating sampler was coupled with a high-pressure liquid chromatograph for the on-line quantitation of the major compounds present in the filtrate. The results are in good agreement with those obtained from off-line analysis on samples taken manually.