Abstract: In this article, attention is focused on an online sampling device for bioreactors and its characterization regarding sterility and response time. The integration of this device into analytical systems for biotechnology (FIA with biosensors) resulted in online analysis systems for bioprocess control. The new ESIP version of an in situ sampling system for bioprocess analysis produced by the EPPENDORF-NETHELER-HINZ GmbH, Germany, had a short response time of 8 min (99%), which was determined by means of conductivity measurement after an increase of the medium conductivity due to the gradual addition of KCl. Effectiveness and reliability of the module were tested by bubble point measurement resulting in a bubble point pressure of 2.1 bars. The sampling probe was tested successfully for use in a broad variety of microorganisms and cultivations.

Abstract: The application of an automated flow injection analysis (FIA) system for online determination of microbial activity, during high cell density cultivations of Escherichia coli is reported. Based on a bioelectrochemical principle, the FIA method used a redox mediator (potassium hexacyanoferrate(III)) to facilitate electron transfer from the microorganisms to an electrochemical detector. Assays were carried out using a new sampling device which provided aseptic operation by use of a valve and chemical sterilisation. No sample dilution or pretreatment was necessary for biomass concentrations up to approximately 40 g l-1. The sample volume was 0.5 mL and the overall analysis time was 5 min. FIA signals were found to correlate well with the oxygen uptake rate (OUR). Changes in metabolic activity due to low substrate levels or high inhibitor concentrations in the cultivation medium became obvious from the FIA signals.