Setup for in situ monitoring of biofermentation processes based on chemoresistive gas sensors

The paper presents a study on the anaerobic digestion of three substrates, based on expired dairy products (milk, yoghurt, and cream – with increasing fat content), in a bench-scale reactor with surplus activated sludge inoculate. Data on the biofermentation processes were obtained for a duration of 24 days using a chemoresistive gas sensor and used to estimate the differences along the three substrates. In all cases, the kinetic profiles were associated with a higher level of volatile species, present in the biogas, during the first 5-12 days, followed by a shift to products with lower reactivity and sensor response. In the case of the cream-based substrate the biofermentation kinetics were slowest, possibly due to its higher fat content. The study can be used as a proof-of-concept demonstration for the possibility to use inexpensive chemoresistive gas sensors for real-time monitoring of biofermentation processes.