Identification of novel probiotic strains is of great interest in the field of functional foods. Specific strains of heat-killed bacteria have been reported to exert immunomodulatory effects. Herein, we investigated the immune-stimulatory function of heat-killed Lactobacillus plantarum KCTC 13314BP (LBP). Treatment with LBP significantly increased the production of TNF-α and IL-6 by macrophages. More importantly, LBP was able to enhance the phagocytic activity of macrophages against bacterial particles. Activation of p38, JNK, ERK, NF-κB, and STAT3 was involved in the immunomodulatory function of LBP. LBP treatment significantly increased production of TNF-α by bone marrow-derived macrophages and splenocytes, further confirming the immunostimulatory effect of LBP in primary immune cells. Interestingly, the immunomodulatory effects of LBP were much stronger than those of Lactobacillus rhamnosus GG, a well-known probiotic strain. These results indicate that LBP can be a promising immune-enhancing functional food agent.

Enzyme technology has many potential applications in the baking industry because carbohydrate-active enzymes specifically react with carbohydrate components, such as starch, in complex food systems. Amylolytic enzymes are added to starch-based foods, such as baking products, to retain moisture more efficiently and to increase softness, freshness, and shelf life. The major reactions used to modify the structure of food starch include: (1) hydrolysis of α-1, 4 or α-1, 6 glycosidic linkages, (2) disproportionation by the transfer of glucan moieties, and (3) branching by formation of α-1, 6 glycosidic linkage. The catalytic reaction of a single enzyme or a mixture of more than two enzymes has been applied, generating novel starches, with chemical changes in the starch structure, in which the changes of molecular mass, branch chain length distribution, and the ratio of amylose to amylopectin may occur. These developments of enzyme technology highlight the potential to create various structured-starches for the food and baking industry.

There is an increasing interest in using inactivated probiotics to modulate the host immune system and protect against pathogens. As the immunomodulatory function of heat-killed Lactobacillus brevis KCTC 12777BP (LBB) and its mechanism is unclear, we investigated the effect of LBB on immune response based on the hypothesis that LBB might exert stimulatory effects on immunity. In the current study, we demonstrate that administration of LBB can exert immune-stimulatory effects and promote clearance of foreign matters through enhancing phagocytosis. Treatment with LBB induced the production of TNF-α, IL-6, and nitric oxide in macrophages. Importantly, LBB directly increased the phagocytic activity of macrophages against bacterial particles. LBB was able to promote the production of TNF-α in bone marrow-derived macrophages and splenocytes and also increase the proliferation rate of splenocytes, suggesting that the immune-stimulating activity of LBB can be observed in primary immune cells. Investigation into the molecular mechanism responsible revealed that LBB upregulates TAK1 activity and its downstream ERK, p38, and JNK signaling pathways. To further confirm the immunomodulatory capability of LBB in vivo, we orally administered LBB to mice and assessed the effect on primary splenocytes. Splenocytes isolated from LBB-treated mice exhibited higher TNF-α expression and proliferative capacity. These results show that heat-killed L. brevis, a wildly consumed probiotic, may provide protection against pathogens through enhancing host immunity.

In sourdough fermentation, lactic acid bacteria perform important roles in the production of volatile and antimicrobial compounds, and exerting health-promoting effects. In this study, we report the probiotic properties and baking characteristics of Lactobacillus plantarum SPC-SNU 72-2 isolated from kimchi. This strain is safe to use in food fermentation as it does not carry genes for biogenic amine production (i.e., hdc, tdc, and ldc) and shows no β-hemolytic activity against red blood cells. The strain is also stable under simulated human gastrointestinal conditions, showing tolerance to gastric acid and bile salt, and adheres well to colonic epithelial cells. Additionally, this strain prevents pathogen growth and activates mouse peritoneal macrophages by inducing cytokines such as tumor necrosis factor-α, interleukin (IL)-6, and IL-12. Furthermore, the strain possesses good baking properties, providing rich aroma during dough fermentation and contributing to the enhancement of bread texture. Taken together, L. plantarum SPC-SNU 72-2 has the properties of a good starter strain based on the observation that it improves bread flavor and texture while also providing probiotic effects comparable with commercial strains.

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