Lactobacillus *Use for Plant Fermentation: New Ways for Plant-Based Product Valorization DOI: http://dx.doi.org/10.5772/intechopen.104958*

It also reduced the inflammatory state by limiting the production of proinflammatory cytokines IL-8 [57]. Another study showed that the fermentation of turmeric by *L. fermentum* has increased the curcumin yield by 9.76%. The AI activity was demonstrated in RAW 264.7 cells by modifying the nitrite level, the expression of TNF-alpha and TLR-4, and the activation of the JNK pathway. These phenolic compounds also showed a protective effect against the activation of TLR-4 receptor cascade, TNF-alpha, and nitric oxide production. In addition, the extract limited the proinflammatory response and low-grade oxidative stress induced by LPS [58].

### **2.3 Antimicrobial activity**

The molecules produced during the fermentation of plant biomasses by *Lactobacillus* can also exhibit antimicrobial activities. The production of antimicrobial molecules by *Lactobacillus* has already been described, including lactobrevin and lactobacillin [59]. For example, in [60], an interesting concept of valorization of okara by solid-state fermentation was presented with a coculture of the yeast *Yarrowia lipolytica* and *Lactobacullis casei*. Okara is an oleaginous by-product of plant milk production. The authors used fermentation to generate molecules with antimicrobial activity (up to 33% reduction of *Bacillus subtilis* development and a modest effect on *Aspergillus niger* one)[60].

In reference [61], a metabolic study on *Allium tuberosum* to produce a food additive with antimicrobial activity against poultry pathogens was conducted. Endophytic *Lactobacillus* have been isolated from Chinese chives. Among those *Lactobacillus* strains, *L. plantarum* can produce flavonols with antimicrobial activity [61]. In [62], fermentation of quinoa by the strain *L. plantarum* CDL 778 leads to a higher production of antifungal compounds. It was also observed that during the fermentation of sweet lemon juice (*Citrus limetta*), the antimicrobial activity against *Escherichia coli* and *Salmonella Typhimurium* was increased. These activities were correlated with the increase in lactic acid content and the decrease of citric acid, total phenolic compounds, and sugar content [63]. Moreover, fermentation of the red sorghum cereal allows the conversion of flavanones into eriodyctiol and naringenin, which have shown an interesting antimicrobial activity [22].

### **2.4 Prebiotic activity**

Several studies have shown that fermented fruits and vegetables have prebiotic effects. The compounds produced by the fermentation of plants induce a modification of the intestinal microbiota. These fermented extracts offer great prospects. Studies highlighted their health potential for humans but also animals. Indeed, two fermented extracts obtained from algae and chicory, plantain, alfalfa, and broad leaf dock presented prebiotic and AO effects. This study was conducted on weaned lambs, and the results showed improved resistance to infection and survival for both extracts. Similar studies have shown the same effects for thyme and rosemary [64]. In reference [65], the prebiotic potential was determined, and the AI effect of chicory root and pulp compared with inulin, as a positive control, on the intestinal barrier on IPEC-J2 cells. These tests were performed with five fermented by-products (chicory roots, chicory and citrus pulp, rye bran, and soybean bark) by different *Lactobacillus spp.* An increase of *Lactobacillus* spp. was observed for all substrates except for chicory roots. The latter was very fermentable and produced a butyrate ratio similar to that of inulin, while chicory pulp had a higher ratio than inulin. For acetate, chicory and citrus pulp and soybean bark had a higher ratio than inulin. These short-chain fatty acids (SCFAs) derived from dietary

Lactobacillus *Use for Plant Fermentation: New Ways for Plant-Based Product Valorization DOI: http://dx.doi.org/10.5772/intechopen.104958*

fiber fermentation contribute to maintain intestinal health. Rye bran caused a significant stimulation of the growth of *Bifidobacterium spp.* Rye bran and soybean bark have a positive effect on the gut microbiota. Fermented chicory roots and pulp promote the upregulation of tiny junction genes and maintain the integrity of the gut barrier. Finally, fermented chicory pulp inhibits proinflammatory cytokines such as TNF-alpha and triggers the metabolic pathway that inhibits inflammatory cytokine production [65].

#### **2.5 Other bioactivities related to medicine**

Many bioactivities could result from the lactic fermentation of plant by-products. In reference [66], they associated the AO activity with potential hypoglycemic effects of *Diospyros lotus* fruit fermented by *L. plantarum* and *Microbacterium flavum*. They observed an inhibition of the α-glucosidase activity *in vitro*. In addition, the authors showed that catechinic, tannic, and ellagic acid levels were enhanced during fermentation [66]. Similarly, several studies were interested in the capacity of *Lactobacillus* fermented products to exert a positive effect in the prevention of obesity and associated metabolic diseases. In [67], cabbage-apple juice fermented by *L. plantarum* exerted antiobesity and hypolipidemic effects *in vivo* in high-fat diet–fed rats was highlighted [67].

Moreover, soy products fermented with *Lactobacillus spp.* have interesting biomolecular contents and present antitumoral effects. Indeed, these fermented soybean extracts could inhibit, *in vitro,* the growth of several cancerous cell models: fibrosarcoma and adenocarcinoma of the breast. It also reduces the risk of breast cancer, significantly influencing survival, apoptosis, and tumor inhibition rates in mice. Clinical studies were also conducted to investigate the effects of fermented soybean extract on chemotherapyinduced immunosuppression. The results showed that the populations of immune cells with activity against tumor cells, the natural killer cells, are significantly increased [23]. Using cell-based experiments, other work has investigated putative health effects associated with AO activity. Indeed, the authors showed promising antiproliferative and apoptotic effects of the extracts on the HeLa cancer cell line. In another study, the authors showed that blueberries fermented by *L. plantarum* exhibited anticancer activities. Their results suggest that polyphenols, in high concentrations in blueberries, were metabolized during fermentation into active phenols such as catechol [68].
