A team of researchers from Nankai University's College of Environmental Science and Engineering has introduced a new approach for measuring biochemical oxygen demand (BOD) quickly. The method involves using the competitive switching of electrotrophic and heterotrophic pathways of facultative bacteria, and the results of the study were published in Water Research under the title “Switchover of Electrotrophic and Heterotrophic Respirations Enables the Biomonitoring of Low Concentration of BOD in Oxygen-rich Environment.”
After five years, the research team managed to isolate and obtain a strain of Acinetobacter venetianus RAG-1 with both electrotrophic and heterotrophic respiration from microbial electroactive biofilms (EABs). The bacterium was found to be capable of respiration with a polarized graphite electrode even in the absence of a degradable organic carbon source, and the current generated at this point can be used as the baseline of sensors.
When degradable pollutants are present in the water, RAG-1 quickly switches to heterotrophic respiration, resulting in a decrease in current. The decrease in current value is proportional to the concentration of organic pollutants. The research team then developed a new bio-cathode BOD sensor, which has a linear response to common pollutants such as organic acids, sugars, proteins, and humic acids, as well as mixtures such as low-concentration domestic sewage and lake sediments. It can efficiently monitor oxygen-rich and low-BOD water, with a test time of less than three hours.
This study provides a better understanding of the switchover mechanism of facultative electrotrophic bacteria's metabolic pathways and their adaptability and resilience to contaminated environments. Based on this new principle, the research team plans to develop more electrotrophic-heterotrophic microorganisms as sensing elements to support rapid BOD monitoring under complex environmental scenarios. This technique is expected to have numerous applications in water quality regulation for aquaculture, water quality monitoring for reclaimed water, and more.