Quantification of Lactobacillus helveticus in a mixture of lactic acid bacteria using qPCR in cheese

Abstract

Conventional quantification of L. helveticus, in presence of other lactobacilli species, using classical plate method employing low selective media is very inaccurate. Determination of L. helveticus using quantitative PCR (qPCR) was performed in six artisanal Kazakh soft cheeses made from cow’s milk or from a mixture of cow’s and goat’s milk. L. helveticus was quantified by species-specific qPCR, monitoring the presence of genes encoding for peptidoglycan hydrolases. Quantification of L. helveticus based on qPCR ranged from 2.6×106 to 4.1×108 CFU·g−1 according to the type of the cheese. The microflora of cheese consisted of a mixture of starter and non-starter lactic acid bacteria.