**2.5 Paraprobiotics**

Paraprobiotics are represented by dead probiotic bacteria cells and cell constituents. The idea of treating with inactivated bacterial strains or fragments or even bacterial metabolite products instead of probiotics is reasonable taking into consideration the risk of administrating probiotics in sepsis, immunosuppressed subjects, and premature babies [74, 75]. They are manufactured by cultivating selected strains of bacteria and their subsequent inactivation [76, 77].

The advantages of paraprobiotic administration are the following [78–80]:


Several highly efficient bacterial strains for the health have been selected to be used as paraprobiotics: Bifidobacterium lactis Bb12, Bifidobacterium longum, Lactobacillus gasseri OLL2716, Lactobacillus brevis SBC8803, and Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 and Saccharomyces cerevisiae. Moreover, proteins and peptides, polysaccharides (glucans), and fragments of genetic material in the form of AT DNA obtained from Lactobacillus spp. have similar effects [81].

At the moment, there are several *in vitro* studies demonstrating the beneficial immunomodulatory effect of paraprobiotics in IBD patients. Also, some of the paraprobiotic proteins can improve the regeneration of the intestinal mucosa, and yeast cell wall components may improve digestion.

*In vitro* studies demonstrated immunomodulatory, anti-inflammatory, antiproliferative, and antioxidant effects of paraproteins, which seem to be able to prevent and improve the clinical symptoms of IBD patients [82–84].
