Reliable identification of lactic acid bacteria by targeted and untargeted high-resolution tandem mass spectrometry.

Probiotic lactic acid bacteria (LAB) are generally employed in food industry because they contribute to nutritional value of fermented foods. Although knowledge of LAB composition is of high relevance for various industrial and biotechnological applications, the comprehensive identification of LAB species is sometimes technically challenging. Recently, MALDI-TOF MS-based methodologies for bacteria detection/identification in clinical diagnostics and agri-food proved to be an attractive strategy, complementary to traditional techniques for their sensitivity and specificity. In this study, we propose, for the first time, a novel methodology based on high resolution nano-LC-ESI-MS/MS for LAB identification at genus, species and sub-species level by using the sequence regions 33-52 and 72-82 of the S16 ribosomal protein as proteotypic peptide markers. The developed methodology was then applied to the analyses of buffalo and bovine whey starter cultures, thus assessing the applicability of the approach for the detection of LAB also in complex matrices.