Novel and simple qPCR system for the detection and quantification of the probiotic bacteria in food supplements

Abstract

The food supplements gain an attractivity among consumers due to their pronounced health benefits. There is no legal frame for probiotic food supplements and the only controllable aspect is the agreement of the declaration with the real composition. The culture methods and subsequent identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) suffer from many inconsistencies like a different growing rate of each microorganism to their close DNA relatedness and similar profile undistinguishable by MALDI-TOF MS. Despite their inability to assess viability, qPCR methods have become more popular due to their sensitivity, specificity and speed. This paper reports about 29 originally designed qPCR assays for the detection of the probiotic species present in food supplements. Moreover, an innovative procedure for the quantification of components in supplements without necessity to run calibration curve was introduced and validated. The whole process was tested on 35 commercially available food supplements. More than half of them did not meet the declaration of the manufacturer. It was also found out that the qPCR was too sensitive as it detected low numbers of non-declared species in all analyzed samples. Therefore, a cut-off value of Cq > 30 had to be applied. The quantification of the individual probiotic species by qPCR showed a good agreement with the declaration of the manufacturers. The same was true for the total number of microorganisms with two exceptions. The developed qPCR assays provide a very simple and inexpensive tool for the detection and quantification of probiotic species in food supplements.