Dead Bacillus subtilis cells for sensing biochemical oxygen demand of waters and wastewaters

Abstract

Bacillus subtilis, thermally killed by exposing its vacuum-dried cells to 280 °C for 2.5 min, has been used for sensing biochemical oxygen demand (BOD) of waters and wastewaters. The BOD sensor is fabricated by covering a dissolved oxygen probe with a biofilm containing the dead cells. Good BOD sensing characteristics comparable to those shown by microbial BOD sensors are observed. The BOD 5 values of some industrial and synthetic wastewater samples measured by the present sensor compare well with the results obtained by the conventional APHA method. The dead-cell sensor can be stored at room conditions in phosphate buffer solution without BOD or nutrients even for extended periods of time when most microbial BOD sensors would require BOD and nutrient additions to sustain the living microorganisms. This study confirms that Bacillus subtilis killed by a short exposure to high temperature still retains sufficient enzymic viability and activity for biooxidation of organics and BOD sensing.