Qualitative and quantitative detection of the quorum sensing signalling molecule autoinducer-2 in fermented milk based on 2,3-diaminonaphthalene derivatization

Abstract

Autoinducer-2 (AI-2) serves as a signaling molecule in the luxS/AI-2 quorum sensing (QS) system of lactic acid bacteria (LAB). However, there is currently a lack of rapid and accurate method for the quantitative and qualitative detection of AI-2 in LAB. In this study, a cost-effective, rapid, and accurate method was developed, involving the derivatization of AI-2 using 2,3-diaminonaphthalene (DAN), followed by detection via high-performance liquid chromatography (HPLC) without the need for external detectors. The results demonstrated that the derivatization process required 40 min, while the HPLC analysis took 24 min. The method exhibited a linear detection range of 250–8000 ng/mL, with a fitting equation of Y = 0.2437X + 26.8111 (R² = 0.9991), and the limit of detection (LOD) is 26.10 ng/mL, indicating high accuracy and precision. Furthermore, the method was successfully applied to five different Lactobacillus broth medium and fermented milk systems, demonstrating its ability to resist interference from complex components in these matrices and to reproducibly and accurately detect AI-2. This study provides an excellent technology for rapid quantification of AI-2 in LAB and fermented milk.