Immuno-modulation by heat-killed Lacticaseibacillus paracasei MCC1849 and its application to food products.

Probiotics are microorganisms that confer health benefits to host. Well-known examples include Bifidobacterium and Lactobacillus species. In recent years, interest in promoting our health with probiotics has grown as life expectancy and health awareness has increased. However, some concerns for safety and stability exist for these live organisms. Thus, "postbiotics" and "paraprobiotics," non-viable heat-killed microbial cells or cell fractions that retain health benefits, are increasingly favored. Unfortunately, little information on clinical efficacy and mechanisms of action is available compared with many available probiotics. Lacticaseibacillus (previous name Lactobacillus) paracasei MCC1849 is a commonly used lactic acid bacterial strain in Japan that displays immuno-modulatory effects in humans in non-viable heat-killed form. This review discusses health benefits of heat-killed L. paracasei MCC1849 immune modulation and offers a theoretical basis for its mechanisms of action. We also discuss the feasibility of using heat-killed probiotics for application in food products.