Whole-cell biosensors that utilize bacterial stress responses to toxic substances can be powerful tools in environmental monitoring. An oxidative stress response found in many Gram-negative bacteria called the glutathione-gated potassium efflux (GGKE) response has been identified as
a good biological indicator to be used in a biosensor designed to detect the presence of oxidative chemicals in water. The authors of this study propose the development of a GGKE biosensor using an environmental strain of PSEUDOMONAS AERUGINOSA. The immobilization of cells is an important
factor in the design of a whole-cell biosensor, and must yield viable and active cells over time. In this study, the use of an octanol-based emulsification method for the immobilization of P. aeruginosa in calcium alginate microbeads was evaluated on the long-term mechanical stability,
viability, and GGKE response of the immobilized cells. The alginate microbeads were mechanically stable in solutions containing up to 20 mg/L K+ for 15 days. LIVE/DEAD® and specific oxygen uptake rate (SOUR) analyses showed that the microbeadimmobilized cells recovered
in membrane integrity within 5 days but not in cellular respiration. The immobilized cells had no GGKE potential in response to 50 mg/L N-ethylmaleimide after 14 days. Further analyses suggested that octanol impeded cellular activities of the immobilized cells. Overall, the octanol-based
emulsification method is not suitable for the immobilization of P. aeruginosa for use in the GGKE biosensor and other microscale immobilization methods should be studied.
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