Preconditioned microbial communities in electrochemical sensing: initial assessment of detection capabilities and durability

Abstract

This study explores the role of pre-colonized microbial cultures in enhancing the long-term effectiveness of microbial electrochemical sensors for water quality monitoring. Microbial electrochemical sensors rely on specific functional microorganisms to detect and signal changes in environmental water quality. Pre-colonization of these cultures on the sensor’s electrode can promote sustained detection sensitivity. This study investigates how specific microbial groups—Geobacter species, sulfate-reducing bacteria (SRB), and acetogen microbes—affect sensor performance when initially enriched and transferred to the biosensor. In the pre-enrichment phase, microbes were incubated in three defined media: Geobacter medium, SRB medium, and acetogen medium. Each culture was cycled through three 48 h incubation periods to establish dominant microbial populations and then introduced to independent biosensors. A control sensor was seeded with natural inoculum from Tasek Kejuruteraan UKM. The results showed that Geobacter-enriched biosensors quickly generated strong electrical signals by oxidizing substrates at the anode, marking them as the most effective at facilitating electron transfer. SRB-enriched sensors produced negative signals, as SRB consumed electrons and thrived at the cathode. Acetogen-enriched biosensors exhibited slower, indirect electron transfer, with lower electrochemical activity. In contrast, the control sensor displayed only minimal increases in signal strength over time. The Geobacter-enriched biosensor, which achieved a significant current drop from 0.478 mA to 0.093 mA (an ~80.5% decrease) upon pollutant exposure, demonstrated the fastest response to rising pollutant levels, followed by SRB, acetogen, and the control. These findings emphasize the importance of starting with targeted microbial populations to optimize biosensor functionality for environmental monitoring applications.