# Plant-Derived Phytobiotics as Emerging Alternatives to Antibiotics Against Foodborne Pathogens
## 4 Impact of Phytobiotics on Microbiota of Food and the Intestine
### Impact on Gut Microbiota
Well-known phytobiotics such as curcumin also inhibit Toll-like receptor 4 (TLR4) and NOD-like receptors (nucleotide-binding oligomerization domain), both of which are involved in initiating innate inflammatory responses [210]. In addition, certain phytobiotics and their synergistic combinations enhance the organism's antioxidant potential, which further supports their anti-inflammatory effects. Phytobiotics indirectly activate antioxidant signaling pathways to reduce oxidative stress, protecting cells from inflammation-associated damage [211; 212; 213; 214; 215]. Moreover, some phytobiotics contribute to maintaining intestinal barrier integrity--a critical factor in preventing chronic inflammation. For example, resveratrol activates the Nrf2/HO-1 signaling pathway, leading to increased expression of tight junction proteins such as ZO-1 and occludin, which reinforce epithelial structure and limit antigen and endotoxin translocation into systemic circulation [216]. Similarly, naringenin exerts protective effects on the intestinal barrier by modulating the MLCK pathway, resulting in reduced production of pro-inflammatory cytokines and improved expression of tight junction proteins [217]. These effects are particularly relevant in the context of intestinal barrier dysfunction observed in inflammatory bowel disease and other chronic conditions. Gut microorganisms are known for their dualistic nature: while they function as essential intestinal symbionts, they also play a key role in the production and preservation of fermented foods. At the same time, effective microbial control during fermentation and storage is necessary to suppress the growth of pathogenic bacteria. In this context, natural phytobiotics--either inherently present in raw materials or added as spices or extracts--can significantly influence the microbiome of fermented foods, improving microbial safety, extending shelf life, and often shaping the sensory profile of the final product. One example is plant-based fermented foods such as vegetable pickles. In addition to the primary vegetable substrate, various herbs and spices--such as dill, garlic, horseradishish, oak leaves, bay leaves, blackcurrent leaves, and chili peppers--are added. These not only contribute to the characteristic flavor of the product but also serve a molecular function by preventing spoilage. For instance, the traditional addition of garlic and horseradish to pickled cucumbers is a well-established method for preventing softening and mold formation. This effect is attributed to phytochemicals such as allicin and mustard oils (from horseradishish), which inhibit the growth of molds and unwanted aerobic bacteria on the surface of the ferment. Bay leaves and allspice, often added to vegetable ferment, release eugenol and other essential oils that enhance microbiological stability--such as reducing surface mold growth in pickled cucumbers. In kimchi, garlic has been shown to linearly increase the initial diversity of fermentative microbiota (mainly _Lactobacillus_ and _Leuconostoc_) in a dose-dependent manner. Higher garlic levels (2-4%) led to earlier and more sustained dominance of LAB, resulting in faster acidification and more effective suppression of undesirable bacteria [218]. Garlic not only accelerated the onset of lactic fermentation but also enhanced metabolite profiles, with increased levels of lactic and acetic acids and elevated production of desirable flavor compounds such as amino acids and esters. Moreover, garlic can serve as a source of autochthonous LAB strains and provides allicin, which selectively eliminates competing microorganisms [161]. Ginger, another common spice in fermented foods, contains phenolic compounds such as gingerol and shogaol with bacteriostatic properties. In kimchi, ginger contributes to the inhibition of _L monocytogenes_ and _Staphylococcus_ spp. [219]. These findings highlight the multifaceted role of phytobiotics in fermented foods--not only as flavoring agents but also as modulators of microbial dynamics.