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Curcumin, the major bioactive constituent of turmeric, has been reported to have a wide range of pharmacological benefits; however, the low solubility in water has restricted its systemic bioavailability and therapeutic potential. Therefore, in the current study, we aimed to investigate the effect of turmeric fermentation on its curcumin content and anti-inflammatory activity by using several lactic acid bacteria. Fermentation with Lactobacillus fermentum significantly increased the curcumin content by 9.76% while showing no cytotoxicity in RAW 246.7 cells, as compared to the unfermented turmeric, regardless of the concentration of L. fermentum-fermented turmeric. The L. fermentum-fermented turmeric also promoted cell survival; a significantly higher number of viable cells in lipopolysaccharide (LPS)-induced RAW 264.7 cells were observed as compared to those treated with unfermented turmeric. It also displayed promising DPPH scavenging (7.88 ± 3.36%) and anti-inflammatory activities by significantly reducing the nitrite level and suppressing the expression of the pro-apoptotic tumor necrosis factor-alpha and Toll-like receptor-4 in LPS-induced RAW 264.7 cells. Western blot analysis further revealed that the anti-inflammatory activity of the fermented turmeric was exerted through suppression of the c-Jun N-terminal kinase signal pathway, but not in unfermented turmeric. Taken together, the results suggested that fermentation with lactic acid bacteria increases the curcumin content of turmeric without increasing its cytotoxicity, while strengthening the specific pharmacological activity, thus, highlighting its potential application as a functional food ingredient.

Lactobacillus rhamnosus GG (LGG) is a probiotic commonly used in fermented dairy products. In this study, RNA-sequencing was performed to unravel the effects of acid stress on LGG. The transcriptomic data revealed that the exposure of LGG to acid at pH 4.5 (resembling the final pH of fermented dairy products) for 1 h or 24 h provoked a stringent-type transcriptomic response wherein stress response-and glycolysis-related genes were upregulated, whereas genes involved in gluconeogenesis, amino acid metabolism, and nucleotide metabolism were suppressed. Notably, the pilus-specific adhesion genes, spaC, and spaF were significantly upregulated upon exposure to acid-stress. The transcriptomic results were further confirmed via quantitative polymerase chain reaction analysis. Moreover, acid-stressed LGG demonstrated an enhanced mucin-binding ability in vitro, with 1 log more LGG cells (p < 0.05) bound to a mucin layer in a 96-well culture plate as compared to the control. The enhanced intestinal binding ability of acid-stressed LGG was confirmed in an animal study, wherein significantly more viable LGG cells (≥ 2 log CFU/g) were observed in the ileum, caecum, and colon of acid-stressed LGG-treated mice as compared with a non-acid-stressed LGG-treated control group. To our knowledge, this is the first report showing that acid stress enhanced the intestine-binding ability of LGG through the induction of pili-related genes.

The use of yeast assist kefir fermentation, but also can cause food spoilage if uncontrolled. Hence, in this study, the microbial composition of an existing commercial kefir starter was modified to produce a functional starter, where Lactobacillus acidophilus KCNU and Lactobacillus brevis Bmb6 were used to replace yeast in the original starter to produce non-yeast kefir-like fermented milk. The functional starter containing L. acidophilus KCNU and L. brevis Bmb6 demonstrated excellent stability with 10 10 CFU/g of total viable cells throughout the 12 weeks low-temperature storage. The newly developed functional starter also displayed a similar fermentation efficacy as the yeast-containing control starter, by completing the milk fermentation within 12 h, with a comparable total number of viable cells (10 8 CFU/mL) in the final products, as in control. Sensory evaluation revealed that the functional starterfermented milk highly resembled the flavor of the control kefir, with enhanced sourness. Furthermore, oral administration of functional starter-fermented milk significantly improved the disease activity index score by preventing drastic weight-loss and further deterioration of disease symptoms in DSS-induced mice. Altogether, L. acidophilus KCNU and L. brevis Bmb6 have successfully replaced yeast in a commercial starter pack to produce a kefir-like fermented milk beverage with additional health benefits. The outcome of this study provides an insight that the specific role of yeast in the fermentation process could be replaced with suitable probiotic candidates.