Application of stimulating agents on the immobilized bioluminescence strain Pseudomonas putida mt-2 KG1206, preserved by deep-freezing, for the convenient biomonitoring

This study was conducted to develop methods for the application of an immobilized bioluminescence strain (KG1206), preserved by deep-freezing (DF), for the monitoring of contaminated environments. The immobilized cells, preserved by DF, required approximately 2 hr for reconstitution of their activity. A large reduction in bioluminescence was observed due to the DF process; 0.07-0.58 times that of the non deep-frozen (NDF) immobilized strain. The decreased bioluminescence activity induced by the DF process was enhanced by the stimulants, sodium lactate (SL) and KNO3. However, regardless of the inducer chemical tested, the immobilized strain modified with KNO3 consistently produced greater bioluminescence than that treated with SL, in the range of 3.0-10.7 (avg. 6.7 ± 3.69) and 1.2-4.2 (avg. 2.4 ± 1.47) times that of control, respectively. All KNO3 treatments of contaminated groundwater samples also resulted in an increase in bioluminescence activity, but the rate of stimulation varied for each sample. Also, no strong linear correlation was observed between the bioluminescence and the total concentration of an inducer, which may related to the complex characteristics of the environmental samples. Overall, the results demonstrated the ability of immobilized genetically engineered bacteria, preserved by DF, to measure a specific group of environmental contaminants using a stimulating agent (KNO3), suggesting the potential for its preliminary application in a field-ready bioassay.