Integrated Chromatographic Systems for On-Line Bioprocess Monitoring Based on Microdialysis or Tangential Flow Filtration

Systems for on-line monitoring of bioprocesses were developed, consisting of a membrane-based sampling unit, a liquid chromatographic (LC) separation step, and a detector. Two sampling units, a tangential flow filtration (TFF) module and a microdialysis probe, were characterised and evaluated for use in different types of bioprocesses. When using the TFF module, an additional sample clean-up step based on solid phase extraction (SPE) was found to be mandatory to protect the chromatographic column. In contrast, the dialysate from the microdialysis probe was less complex and could be directly injected into the LC column, thus omitting the SPE step. Various modes of LC, especially ligand-exchange and anion-exchange chromatography, were utilised for separation of carbohydrates and alcohols in the bioprocess samples. These analytes were then detected by refractive index, electrochemically, or by in-house made enzyme-based amperometric biosensors. The enzymes used in the biosensors were specific for a group of compounds rather than one-substrate specific, and the sensors could therefore be used as selective LC detectors. Data acquisition and presentation of the signals from the detectors were made using chromatographic software. The parts were integrated into several different on-line systems that allowed the unattended monitoring of both substrates and products during fermentations. Three different bioprocesses were studied: the production of fuel ethanol from lignocellulosic materials (the main focus of this work), the enzymatic hydrolysis of biopolymers, and the production of inositol trisphosphate from phytic acid.