A microfluidic biosensor for microbial quantitative monitoring of air and nutrient solution in the plant factory

Microbial contamination is an inevitable challenge in plant factory, posing substantial risks of economic loss and potential threats to human health if not addressed promptly. However, existing detection methods are characterized by prolonged processing times, high costs, and dependence on skilled technicians, limiting their practicality for routine monitoring. Therefore, there is a critical need for the development of rapid, cost-effective, and reliable device for the quantitative monitoring of microorganisms in both the air and nutrient solutions of the plant factory. We have developed an integrated microfluidic biosensor that can be used to quantitatively monitor microbial levels in air and nutrient solutions by combining ATP bioluminescence. The biosensor was verified and calibrated through a standard ATP solution with Bacillus subtilis bacterial solution, followed by testing of the real air and nutrient solution samples from plant factories. The detection process on the microfluidic chip was automatically controlled to complete within 3 min. The consumption of ATP reaction solution and lysate for one assay was about 10 μL and 16 μL, respectively. The sensitivity of bacterial quantification was up to 6.4 × 10 3 CFU mL −1 with a detection range covering 4 orders of magnitude. This biosensor has been demonstrated to have similar detection accuracy with the culture counting method and enable quantitative monitoring of microorganisms in plant factory, while greatly reducing the detection cycles.