Molecular nanoarchitectonic sensing layer for analysis of volatile fatty acids in bioreactor headspaces using a nanomechanical sensor

Anaerobic digestors (ADs) have the potential to become a major green energy source in a future sustainable society. To achieve this, effective operational parameters of the reactors must be established and maintained preferably by automation. In situ monitoring and control of AD systems is currently a challenging matter based on inconsistent feedstuff composition and the complexity of the biological processes involved, so that reactor shutdowns associated with costly downtime are a common problem. Here, a sensing device is developed for the monitoring of volatile fatty acids (VFAs), key intermediates during bioreactor operation, in the headspaces of anaerobic reactors. The device is compact, contains a sensing element based on a self-assembled molecular layer in conjunction with a nanomechanical sensor, and can be used to monitor VFA contents in bioreactors by estimating their relative contents in the reactor headspace in real time. This device allows the close monitoring of VFA concentrations in admixture toward cost-effective operation of bioreactors by reducing or eliminating reactor downtime. It represents a simple solution to the problem of real-time reactor monitoring, making anaerobic digesters a realistic alternative energy source.