A portable FTIR-ATR process analyzer - online fermentation control

A mid-IR FT spectrometer equipped with a horizontal attenuated total reflection (ATR) unit has been used for fermentation monitoring. The ATR element has been incorporated in a flow cell connected to the fermentation process under investigation via a flexible computer controlled flow system for online monitoring. Measurement of dissolved components is achieved while pumping the sampled fermentation broth through the flow cell. Upon stopping the flow, the microorganisms can be monitored subsequently as they settle on top of the horizontal ATR element. Because of the surface sensitivity of ATR spectroscopy, the cleanness of the ATR surface must be guaranteed throughout a prolonged operating time. For certain bioprocesses, the formation of bio-films on the ATR surface was identified as an important difficulty as they cannot be removed by simple rinsing with distilled water or simple washing solutions such as NaHCO₃. Therefore, different chemical solutions have been tested for efficient bio-film removal. Among the studied solutions, the use of oxidizing agents (e.g. H₂O₂) in concentrations around 2% proved most effective.