Electroactive biofilm-based sensor for volatile fatty acids monitoring: A review

Quantitative analysis of volatile fatty acids (VFAs) is critical for the monitoring, control and optimization of biological processes. However, commonly used detection techniques such as titration and chromatography are too complex, time-consuming or costly, making them not optimal for industrial applications. Biosensors, which can directly convert chemical energy stored in organics into electrical signals, have emerged as an attractive alternative for VFA measurements. They are simple, sensitive and low-cost, and have shown great potential for online monitoring. Among them, the electroactive biofilm (EAB)-based sensor is the most adopted. Based on a summary of the frontiers in EAB sensor development, direct/indirect contact of biofilm with VFA in tests can largely determine their performance. Various applications can illustrate the feasibility of such biosensors for off- or on-line VFA monitoring in different biological processes. These remarkable progresses have been made in recent years, but they are still facing several challenges that need to be addressed for field applications. Microbial analysis of EAB, introduction of machine learning, and optimization of biosensor design and operation will be interesting for future studies. This review can provide guidelines and references for the research, development and application of EAB sensors for online VFA monitoring.