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The possibility of sensing seawater BOD (biochemical oxygen demand) by microbial sensors using tamed Bacillus licheniformis is test. Microbial biosensors of BOD are fabricated based on the Clark oxygen electrode and the biological sensing material is immobilized Bacillus licheniformis isolated from starch wastewater and tamed in saline water. Results show sensors has a linear response of 0 to 40 mg/L BOD and the linearity is perfect (r=0.999). The response-time is 8 minutes and the recovery time less than 10 minutes. The sensor shows stability within 60 days without any decrease in signal. The standard deviation of continuous measurements (n=7) is within 5%. Storage capacity of sensors is more than 4 months by present experiments. The sensor can gives stable signals in a range of pH from 6.5 to 10.5 and the best working temperature is 35degC. The salt concentration does not affect measure signals obviously until NaCl is 80 g/L in samples. Sensors show to be capable for monitoring low concentration BOD in seawater.