Isolation and purification of lactic acid bacteria and yeasts based on a multi-channel magnetic flow device and rapid qualitative and quantitative detection

Rapid isolation and identification of lactic acid bacteria and yeasts during fermentation is of great significance for quality control and regulation of fermented foods. In this study, we prepared a multi-channel magnetic flow device for rapid separation and purification of lactic acid bacteria and yeast, and based on SERS spectrum, we made rapid qualitative and quantitative analysis of Lactobacillus plantarum, Lactococcus lactis and Saccharomyces cerevisiae. The results showed that the synthesized Synthesized Fe₃O₄-Van antibiotic magnetic beads are paramagnetic; Fe₃O₄-Van antibiotic magnetic beads achieved capture efficiencies of more than 98.5 % for both L. plantarum and L. lactis at 10²–10⁴ CFU/mL, respectively. Separation and purification efficiency of single S. cerevisiae, L. plantarum and L. lactis by multi-channel magnetic flow device all reached more than 98 % with good isolation and purification results. The SERS spectra of the three microorganisms were classified and analyzed using linear discriminant analysis (LDA), and the accuracy of the established LDA model was 100 %, which completely differentiated the SERS spectra of the three microorganisms,and realized the qualitative identification of L. plantarum, L. lactis, and S. cerevisiae, and finally, quantitative model was established with the logarithmic values (lg C) of different concentrations of L. plantarum, L. lactis, and S. cerevisiae as the horizontal coordinates, and the Raman intensities at their strongest characteristic peaks of 512 cm⁻¹, 1669 cm⁻¹, and 1125 cm⁻¹, respectively, were used as vertical coordinates to establish a quantitative model, with the lowest detection limit of 10 CFU/mL, and the digital quantification of lactic acid bacteria and yeast were achieved. It provided an effective means for real-time monitoring and tracking of the dynamics of lactic acid bacteria and yeast in the fermentation process and the quality control of fermented foods.