In the field of probiotic industry, the conventional method for the bacterial counting is the time-consuming plate culture (24–72 hrs). A rapid and accurate technique for quantifying bacteria is much important to achieve the real-time monitoring during fermentation process. We apply the electrokinetic theory to successfully design a ring-shaped interdigitated electrode (RIDE) chip under the microlithographic technique. The main function of RIDE chip is to rapidly concentrate the bacterial particles in a certain detection zone. Then, the total bacterial number could be automatically counted by image capture and processing. Also, the fluorescent dye has been used to label the live and dead bacterial, respectively. The RIDE platform is cost-effective and easy-to-use to provide an innovative solution for concentrating and quantifying bacteria without a time-consuming culture process, which could be completed within 30 mins.

For quantifying the bacterial number, the traditional plate count is a time-consuming process (1-3 days). The disadvantages of PCR-based technique involve a complicated procedure and 4-h detection time. The flow cytometry is a huge and expensive equipment. This innovative technique integrating the electrokinetics, microfluidic system, and application of semi-conductive materials is able to concentrate the bacterial microparticles in a small-volume sample. The image-processing software is successfully developed to automatically count the bacterial number. It realizes the culture-free bacterial counting to eliminate the manpower burden and  the user-by-user variability.

Automatic bacterial counting platform is a powerful tool for the real-time monitoring of probiotics during fermentation. We have finished 5 pilot runs to fabricate 918 chips with over 90% of defect-free rate in electrical performance. Under the simple protocol of labeling viable and dead bacteria with fluorescent dye, the rapid bacterial count using the desktop reader could be accomplished within 30 min. Blind tests show the 100% accuracy for different strains based on the error of ≤ ±1 log between the results of conventional plate count versus this designed platform. The platform carrying out rapid quantification of bacterial number without a time-consuming culture enables probiotic companies to rapidly monitor the manufactures and adjust the parameters to enhance the production yield.