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

Abstract

Conventional quantifi cation 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 quantifi ed by species-specifi c qPCR, monitoring the presence of genes encoding for peptidoglycan hydrolases. Quantifi cation of L. helveticus based on qPCR ranged from 2.6×10 6 to 4.1×10 8 CFU·g -1according to the type of the cheese. The microfl ora of cheese consisted of a mixture of starter and non-starter lactic acid bacteria.