Project Description

MICREDOX® is a research platform developed at Lincoln Technology and is a rapid, mediated assay for monitoring cellular respiration. The assay is performed anaerobically and is characterised by high concentrations of microorganisms, comprising the biocomponent, and synthetic redox-active mediator, which acts as the terminal electron acceptor in the cell's respiratory biochemical pathways (Pasco et al. 2000; Webber et al. 2002; Catterall et al. 2003). The technology has been patented in New Zealand (NZ336072), Australia (AUS 717224), USA (6, 379, 914) and Japan (3, 479, 085), with patents under examination in Canada (application no. 2307603) and Europe (application no. 97946176). The MICREDOX® name is registered as a trademark in New Zealand (609120), effective from 24 February 2000. The initial application has been the rapid measurement of biochemical oxgen demand (BOD) in wastewaters.

BOD assays quantify organic pollutants in water and, traditionally, measure the amount of oxygen consumed by microorganisms during the biological oxidation of organic substrates. Substrate oxidation is coupled to oxygen reduction through microbial respiration pathways (Fig 1).

The internationally accepted method for measuring BOD is a 5-day test, BOD₅, but due to the 5-day lag, the results are seldom useful for real time process adjustment or decision making by wastewater treatment operators. It is suggested that the limited solubility of oxygen (9 ppm at 20°C) is rate-limiting in the BOD₅ method and contributes to the 5-day duration of the test.

MICREDOX® parallels the traditional BOD₅ method except that a synthetic mediator replaces the natural co-substrate, oxygen, as the terminal electron acceptor in the microbially catalysed oxidation of substrate (Fig 2). MICREDOX® measures the concurrent accumulation of reduced mediator, rather than monitoring the microbial consumption of O₂ as per other BOD methods. The assay has been optimised to measure the same amount of respiration in one hour as is obtained in five days with the BOD₅ method. Furthermore, the amount of oxidation can be absolutely quantified at any stage of the MICREDOX® assay by measuring the charge required re-oxidise the reduced mediator at the anode of a bulk electrolysis cell. The Biosensor Group has been awarded Government funding from the Pre-Seed Accelerator Fund (PSAF) to develop a pre-commercial prototype of the MICREDOX® biosensor for making rapid BOD measurements.

A further application of the MICREDOX® platform areis being explored, namely rapid toxicity assessment.

The Lincoln Technology Biosensor Group is actively collaborating with Dr Richard John's research group at Griffith University, Gold Coast, Australia and a NZ-based wastewater company, Waste Technology Group (WTG) on the BOD application of MICREDOX®.

Page last updated on 2 February 2005