Antiproliferative effects of homogenates derived from five strains of candidate probiotic bacteria

Unheated and heat-treated homogenates were separately prepared from candida te probiotic bacteria, including Lactobacillus rhamnosus GG, Bifidobacteriu m lactis, Lactobacillus acidophilus, Lactobacillus delbrueckii subsp. bulga ricus, and Streptococcus thermophilus, We compared the phytohemagglutinin-i nduced proliferation of mononuclear cells in the presence of homogenates an d in the presence of a control containing no homogenate by assessing thymid ine incorporation in cell cultures. All homogenates suppressed proliferatio n, whether the enzymatic activity was inactivated or not inactivated by hea ting, When the proliferation assays were repeated with cytoplasmic and cell wall extracts derived from the homogenate of L. rhamnosus GG, the cytoplas mic extract but not the cell wall extract was suppressive, These findings i ndicate that candidate probiotic bacteria possess a heat-stable antiprolife rative component(s), These bacteria may be used to generate microbiological ly nonviable yet immunologically active probiotic food products that are ea sier to store and have a longer shelf life.