D2O metabolic labeling combined with AuNPs@PVP/SA hydrogel SERS platform for rapid quantitative detection of active lactic acid bacteria.

Achieving accurate quantification and counting of active lactic acid bacteria (LAB) is an important technical guarantee for the industrial production and application of LAB and their products. In this study, a gold nanoparticles@polyvinylpyrrolidone/sodium alginate (AuNPs@PVP/SA) hydrogel SERS sensor with outstanding stability and sensitivity was developed. Utilizing this platform as a substrate material to mitigate the "coffee ring" effect, we explored a strategy for the precise quantitative determination of mixed active LAB based on the AuNPs@PVP/SA hydrogel SERS platform and D2O-probed Raman spectroscopy technology. The results indicated that the SERS platform based on AuNPs@PVP/SA hydrogel exhibited excellent spectral reproducibility for LAB as a SERS substrate material, with a significantly reduced "coffee ring" effect. This strategy enabled rapid and quantitative detection of active lactic acid bacteria (LAB), with a limit of detection (LOD) of 10 CFU/mL. Moreover, the strategy had excellent analytical capabilities for the qualitative identification and precise quantification of different species of active LAB in actual samples, achieving an average accuracy of 98.67% with RSD values all less than 5%. It provides a potential technical support for the dynamic monitoring of relative abundance and metabolic phenomena of mixed active LAB in co-culture systems during actual industrial production.