Updated FTP location. In this study, we have evaluated the differential proteomic responses of a potential novel probiotic Pediococcus pentosaceus M41 under heat, cold, acid, and bile stress conditions. We identified stress response proteins that could provide tolerances against these stresses and could be used as probiotic markers for evaluating stress tolerance. Pediococcus pentosaceus M41 was exposed to 50ºC for 2h (heat stress), 4ºC for 2 h (cold stress), pH 3.0 for 2 h (acid stress) and 0.05% bile for 2 h (bile stress). Proteomic analysis was carried out using 2D-IEF SDS PAGE and LC-MS/MS.