A MICROSCALE BIOSENSOR FOR METHANE CONTAINING METHANOTROPHIC BACTERIAAND AN INTERNAL OXYGEN RESERVOIR

A microscale biosensor for continuous measurement of methane partial p ressure based on a novel counterdiffusion principle is presented. Meth ane-oxidizing bacteria placed in the microsensor utilize oxygen from a n internal oxygen reservoir when methane from the exterior diffuses th rough the tip membrane. The transducer is an internal oxygen microsens or with its tip positioned between the oxygen reservoir and the sensor tip membrane. The external partial pressure of methane determines the rate of bacterial oxygen consumption within the sensor, which in turn is reflected by the signal from the transducer. Tip diameters were do wn to 20 mu m, enabling us to study methane distribution on a microsca le. The microscale construction also results in a low stirring sensiti vity and a 95% response time down to 20 s. By tailoring the geometry, sensors can be made to exhibit a linear response in the full range of 0-1 atm partial pressure of methane or, alternatively, to exhibit a li near response only at lower concentrations, improving the sensitivity to below 0.1 kPa, corresponding to similar to 1 mu M in aqueous soluti on. Temperature, oxygen, and H2S interfere with the signal; no interfe rences were detected from H-2, NH3, CO2, or acetate.