Static optics FTIR spectroscopy for the measuring and control of fermentation

Abstract

Fermentation is one of the most promising development areas in modern manufacturing and processing sectors. Offline analysis of the fermentation vessel to monitor levels of feedstock molecules, nitrogen and nutrient levels and contaminant signalling molecules (such as organic acids) is a powerful technique, but is slow and prone to errors through sample preparation. Online analysis using pH and temperature probes is possible, but more advanced analysis online can be very difficult to do high solids loading and the filamentous nature of the biomass.Here we present the development of a novel static optics FTIR instrument specifically designed for online monitoring of industrial scale processes. The extremely stable optical design allows for long term online monitoring of both batch and continuous fermentation processes. We present the design of the static optics and explain how this allows the removal of fragile and unreliable mid infrared fiber optics from the instrument, and replacement with a solid light pipe.We then proceed to present the results from various online fermentation installations, both in terms of batch and continuous processes. We will discuss how the data generated (such as concentration profiles over time for various different sugars, organic acids and alcohols) can be used for closed loop control to optimise the process and maximise biomass growth rate.We will lastly compare static optics FTIR with other technologies such as Raman and near-infrared spectroscopy. We discuss the different challenges present for seemingly similar technologies, and explain how FTIR coupled with attenuated total reflectance probes are naturally well-suited for fermentation and biomass growth processes.