[10] Microbial sensors for estimation of biochemical oxygen demand and determination of glutamate

Publisher Summary Various microbial sensors using immobilized microorganisms and electrochemical devices are developed for fermentation processes. Biochemical oxygen demand (BOD) is one of the most widely used and important tests in the measurement of organic pollution. The conventional BOD test requires a 5-day incubation period, and test results tend to depend on the skill of the operator. Therefore rapid and reproducible methods are desirable for the BOD test. A microbial sensor consisting of an immobilized living yeast membrane and an oxygen probe is used for the estimation of the BOD in wastewater from the fermentation process. When the microbial sensor is inserted in a sample solution containing organic compounds, the compounds are assimilated by the yeast in the membrane. The respiration (oxygen uptake) of the yeast is raised, and the dissolved oxygen is, consequently, decreased around the membrane. The BOD of the sample solution could be estimated from the current decrease of the oxygen probe caused by the decrease in dissolved oxygen. The advantages of these sensors are as follows: (1) the sample solution can be measured directly without any pretreatment such as filtration and dialysis, (2) no reagent is required except for a buffer solution, and (3) usually, the microbial sensors are stable for more than 3 weeks.