A microbial biosensor based on bacterial cells immobilized on chitosan matrix.

Understanding how to detect small molecules in solution is a challenge in analytical chemistry. Traditional methods often require complex instrumentation or reagents. Researchers have explored microbial systems to detect substrates based on cellular metabolism. Prior work has shown that bacterial cells can act as biosensors by measuring changes in oxygen consumption. However, the immobilization of these cells remains a technical hurdle. No prior work had resolved the optimal matrix for immobilizing Gluconobacter oxydans cells. This gap motivated the development of a chitosan-based system. The study aimed to improve biosensor sensitivity by comparing CNT-modified and CNT-free matrices. The approach builds on existing knowledge of microbial respiration and electrochemical detection.

The goal was to create a biosensor using Gluconobacter oxydans cells immobilized on chitosan. The researchers wanted to test whether adding carbon nanotubes would improve performance. They focused on measuring oxygen consumption as a proxy for metabolic activity. The study aimed to determine the optimal conditions for biosensor operation. The team also sought to compare the sensitivity of CNT-modified and CNT-free systems. They were interested in how factors like pH, temperature, and potential affect signal output. The motivation was to develop a reliable method for glucose detection. The approach was to test the system under controlled conditions and analyze its response.

The researchers used Gluconobacter oxydans DSM 2343 as the biological component. They immobilized the cells on two types of chitosan matrices: one with carbon nanotubes and one without. The biosensor was tested by measuring oxygen consumption at -0.7 V using an Ag|AgCl reference electrode. They varied the amount of cells and tested the system under different pH and temperature conditions. The team also examined the effect of working potential on signal output. They calibrated the biosensor by measuring the current response to different glucose concentrations. The system was evaluated for substrate specificity and response time. The data were analyzed to compare the performance of the two matrix types.

The biosensor detected glucose in the range of 0.05 to 1.0 mM. The CNT-modified system had a response time of 40 seconds at 30°C and pH 7.0. The linear relationship between glucose concentration and sensor response was y=1.261x+0.197 for the CNT-modified system. The CNT-free system had a slightly lower sensitivity with y=1.160x+0.151. The R² values were 0.982 and 0.990, respectively, showing strong correlations. The study found that both systems performed well under the tested conditions. The CNT-modified system showed a higher signal amplitude for the same glucose concentration. The results suggest that CNTs may enhance the biosensor’s performance. The data also revealed how pH, temperature, and potential affect the signal output.

The biosensor using Gluconobacter oxydans cells immobilized on chitosan matrices can detect glucose effectively. The CNT-modified system showed a stronger signal than the CNT-free version. The linear response and short response time support the system’s practical use. The study demonstrated that the biosensor works best at 30°C and pH 7.0. The results suggest that CNTs may improve the system’s sensitivity. The authors propose that the immobilization method is key to the biosensor’s stability. They suggest that the system could be adapted for other substrates. The findings support further testing of CNT-modified matrices in biosensor design.