New Magnetic Flow Device Speeds Up Detection of Lactic Acid Bacteria and Yeast in Fermentation

In many grocery stores around the world, supermarkets have unfettered access to many fermented foods. These foods include yogurt and cheese, among other products (1). Unlike other food products, yogurt and cheese achieve their flavor and quality from microbial activity from Lactobacillus plantarum, Lactococcus lactis, and Saccharomyces cerevisiae (1). To ensure the quality of these type of foods, rapid and accurate detection of these microorganisms during fermentation is essential.

Techniques such as high-performance liquid chromatography (HPLC) have been used in the past to identify and analyze anaerobic bacteria, which is present in several fermented food products (2). In this recent study published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, researchers led by Lijun Zhao from Henan Agricultural University, have developed a multi-channel magnetic flow device that enabled the rapid isolation and identification of lactic acid bacteria and yeast (1). This advancement holds great potential for improving quality control processes in the production of fermented foods.

Homemade Greek Yogurt, cream cheese | Image Credit: © mizina - stock.adobe.com

The research team designed a multi-channel magnetic flow device capable of efficiently isolating and purifying lactic acid bacteria and yeast. This device works in tandem with synthesized Fe₃O₄-vancomycin (Fe₃O₄-Van) magnetic beads, which were shown to possess strong paramagnetic properties (1). The magnetic beads were able to capture L. plantarum and L. lactis with efficiencies exceeding 98.5% at concentrations between 10²–10⁴ CFU/mL (1). This indicates a high level of precision in microorganism separation, which is critical for analyzing complex fermentation environments.

Next, the researchers looked at analyzing these microorganisms. The research team used surface-enhanced Raman spectroscopy (SERS). SERS is renowned for its sensitivity in detecting biomolecules at low concentrations (1). In the study, the researchers took the SERS spectra of L. plantarum, L. lactis, and S. cerevisiae, using linear discriminant analysis (LDA) to analyze the spectra (1). Using their model to conduct this study, the researchers demonstrate the utility of it, as it was able to differentiate the SERS spectra with 100% accuracy (1).

Their model correlated the logarithmic values (lg C) of varying concentrations of the microorganisms with their Raman intensities at characteristic peaks: 512 cm⁻¹ for L. plantarum; 1669 cm⁻¹ for L. lactis; and 1125 cm⁻¹ for S. cerevisiae (1). The lowest detection limit was established at 10 CFU/mL. Because the detection limit was that low, it proved that minimal levels of microorganisms could be detected.

The researchers showed that their model can quickly isolate and accurately identify specific microorganisms allows producers to detect any deviations in the fermentation process before they affect the final product (1). The result is that significant production efficiencies can be improved by reducing waste, saving costs, and eliminating batch failures (1).

Using SERS with the magnetic flow device demonstrated in this study shows how technological advancements can result in practical solutions. The food industry is dependent on technology to improve efficiencies, and the high capture efficiency and precision of the LDA model support reliable and swift differentiation of microorganisms, making this approach especially valuable for dynamic and real-time applications (1).

Although the study focused on the primary strains involved in common fermentation processes, it opens the door for further exploration into other microorganisms. The researchers suggested that future research could extend the use of this technology to monitor additional strains or investigate its application in other industries, such as pharmaceuticals and biotechnology (1).

References

1. Wu, H.; Liu, S.; Li, M.; et al. Isolation and Purification of Lactic Acid Bacteria and Yeasts based on a Multi-channel Magnetic Flow Device and Rapid Qualitative and Quantitative Detection. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2025, 327, 125296. DOI: 10.1016/j.saa.2024.125296
2. Ehrlich, G. G.; Goerlitz, D. F.; Bourell, J. H.; et al. Liquid Chromatographic Procedure for Fermentation Product Analysis in the Identification of Anaerobic Bacteria. Appl. Environ. Microbiol. 1981, 42 (5), 878–885. DOI: 10.1128/aem.42.5.878-885.1981