Development of Binding Ability Assay of Lactococcus lactis Isolated from Cucumber to Mycotoxins by Surface Plasmon Resonance Imaging Assay

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Some microorganisms, including lactic acid bacteria (LAB), can bind to mycotoxins. Its binding ability is useful for mycotoxin mitigation. Conventionally, the binding assay for this ability of microorganisms to mycotoxins has been performed by the so-called in vitro assay. We previously reported that Lactococcus lactis isolated from cucumber had the ability to bind to aflatoxins using the in vitro assay., However, this is an indirect method by which binding ability is estimated from the mycotoxin residue in supernatant after some processes such as mix, incubation, and centrifugation and it takes time. In the present study, we developed a direct and rapid assay to assess their binding ability using a surface plasmon resonance imaging (SPRi) instrument. It could observe the binding ability as a visual image in real time. The efficacy of this SPRi assay was compared with the in vitro assay. Aflatoxin M1-bovine serum albumin conjugate (AFM1-BSA) and deoxynivalenol-BSA conjugate (DON-BSA) were immobilized on the surface of the sensor prism in SPRi assay. The above L. lactis was used to prove the binding ability to the aflatoxin. In vitro assay showed that the binding ratio to AFM1 was higher than that to DON in both live bacterial cells and heated cells. In the SPRi assay, the binding of live cells to AFM1 was confirmed by % of the refractivity change (%ΔR) and visual imaging in real-time. The %ΔR of DON was poor, and no visual image was recognized. On the other hand, the heated cells did not bind to any mycotoxins. The results indicate that the SPRi assay can monitor the binding ability of live cells more rapidly and simpler than in vitro assay. It would be a useful tool for the selection of beneficial mycotoxin-detoxifying LAB.