The biochemical oxygen demand (BOD) test (BOD5) is a crucial environmental index for monitoring organic pollutants in waste water but is limited by the 5-day requirement for completing the test. We have optimised a rapid microbial technique for measuring the BOD of a standard BOD5 substrate (150 mg glucose/l, 150 mg glutamic acid/l) by quantifying an equivalent biochemical mediator demand in the absence of oxygen. Elevated concentrations of Escherichia coli were incubated with an excess of redox mediator, potassium hexacyanoferrate(III), and a known substrate for 1 h at 37 degrees C without oxygen. The addition of substrate increased the respiratory activity of the microorganisms and the accumulation of reduced mediator; the mediator was subsequently re-oxidised at a working electrode generating a current quantifiable by a coulometric transducer. Catabolic conversion efficiencies exceeding 75% were observed for the oxidation of the standard substrate. The inclusion of a mediator allowed a higher co-substrate concentration compared to oxygen and substantially reduced the incubation time from 5 days to 1 h. The technique replicates the traditional BOD5 method, except that a mediator is substituted for oxygen, and we aim to apply the principle to measure the BOD of real waste streams in future work.

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Whole cell biosensors are the focus of considerable and increasing interest worldwide as methods for detecting and quantifying environmental toxicity, including biochemical oxygen demand (BOD), heavy metals, antibiotics, pesticides and herbicides. This review follows the development of whole cell biosensors from attempts to utilise changes in cellular metabolism to determine BOD and general toxicity, through the exploitation of unique metabolic pathways to detect specific toxicants, to the increasingly widespread use of genetic engineering to build new, and modify existing, sensing pathways.

The measured response of rapid biochemical oxygen demand (BOD) biosensors is often not identical to those measured using the conventional 5-day BOD assay. This paper highlights the efficacy of using both glucose-glutamic acid (GGA) and Organisation for Economic Cooperation and Development (OECD) BOD standards as a rapid screen for microorganisms most likely to reliably predict real effluent BODs when used in rapid BOD devices. Using these two synthetic BOD standards, a microorganism was identified that produced comparable BOD response profiles for two assays, the MICREDOX® assay and the conventional 5-day BOD(5) test. A factorial experimental design systematically evaluated the impact of four factors (microbial strain, growth media composition, media strength, and microbial growth phase) on the BOD response profiles using GGA and OECD synthetic standard substrates. An outlier was identified that showed an improved correlation between the MICREDOX® BOD (BOD(sens)) and BOD(5) assays for both the synthetic standards and for real wastewater samples. Microbial strain was the dominant factor influencing BOD(sens) values, with Arthrobacter globiformis single cultures clearly demonstrating superior rapid BOD(sens) response profiles for both synthetic and real waste samples. It was the only microorganism to approach the BOD(5) response for the OECD substrate (171 mg O(2)L(-1)), and also reported BOD values for real waste samples that were comparable to those produced by the BOD(5) test, including discriminating between filtered and unfiltered samples.