Nam Su Oh

Bacillus licheniformis Isolated from Traditional Korean Food Resources Enhances the Longevity of Caenorhabditis elegans through Serotonin Signaling

In this study, we investigated potentially probiotic Bacillus licheniformis strains isolated from traditional Korean food sources for ability to enhance longevity using the nematode Caenorhabditis elegans as a simple in vivo animal model. We first investigated whether B. licheniformis strains were capable of modulating the lifespan of C. elegans. Among the tested strains, preconditioning with four B. licheniformis strains significantly enhanced the longevity of C. elegans. Unexpectedly, plate counting and transmission electron microscopy (TEM) results indicated that B. licheniformis strains were not more highly attached to the C. elegans intestine compared with Escherichia coli OP50 or Lactobacillus rhamnosus GG controls. In addition, qRT-PCR and an aging assay with mutant worms showed that the conditioning of B. licheniformis strain 141 directly influenced genes associated with serotonin signaling in nematodes, including tph-1 (tryptophan hydroxylase), bas-1 (serotonin- and dopamine-synthetic aromatic amino acid decarboxylase), mod-1 (serotonin-gated chloride channel), ser-1, and ser-7 (serotonin receptors) during C. elegans aging. Our findings suggest that B. licheniformis strain 141, which is isolated from traditional Korean foods, is a probiotic generally recognized as safe (GRAS) strain that enhances the lifespan of C. elegans via host serotonin signaling.

Dietary Maillard reaction products and their fermented products reduce cardiovascular risk in an animal model

This study examined the effects of Maillard reaction products (MRP) and MRP fermented by lactic acid bacteria on antioxidants and their enhancement of cardiovascular health in ICR mouse and rat models. In previous in vitro studies, the selected lactic acid bacteria were shown to significantly affect the activity of MRP. The expression of genes (e.g., superoxide dismutase, catalase, and glutathione peroxidase) related to antioxidant activity was upregulated by Maillard-reacted sodium caseinate (cMRP), and cMRP fermented by Lactobacillus fermentum H9 (F-cMRP) synergistically increased the expression of catalase and superoxide dismutase when compared with the high-cholesterol-diet group. Bleeding time, the assay for determination of antithrombotic activity, was significantly prolonged by Maillard-reacted whey protein concentration (wMRP) and wMRP fermented by Lactobacillus gasseri H10 (F-wMRP), similar to the bleeding time of the aspirin group (positive control). In addition, the acute pulmonary thromboembolism-induced mice overcame severe body paralysis or death in both the wMRP and the F-wMRP groups. In the serum-level experiment, cMRP and F-cMRP significantly reduced the serum total and low-density lipoprotein cholesterol levels and triglycerides but had only a slight effect on high-density lipoprotein cholesterol. The levels of aspartate transaminase and alanine transaminase also declined in the cMRP and F-cMRP intake groups compared with the high-cholesterol-diet group. In particular, F-cMRP showed the highest reducing effects on triglycerides, aspartate transaminase, and alanine transaminase. Moreover, the expression of cholesterol-related genes in the F-cMRP group demonstrated greater effects than for the cMRP group in the level of cholesterol 7 α-hydroxylase (CYP7A1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), and low-density lipoprotein receptors compared with the high-cholesterol-diet group. The protective role of cMRP and F-cMRP in the high-cholesterol group may have been the result of an antioxidative defense mechanism that regulated cholesterol synthesis and metabolism. Therefore, F-cMRP and cMRP have the potential to play preventive and therapeutic roles in the management of cardiovascular disease.

Improved functionality of fermented milk is mediated by the synbiotic interaction between Cudrania tricuspidata leaf extract and Lactobacillus gasseri strains

This study was designed to investigate the cooperative effect of selected Lactobacillus gasseri strains and Cudrania tricuspidata (CT) leaf extract in enhancing the health-promoting activities of fermented milk. Addition of CT increased total bacterial counts and proteolysis during fermentation of milk with L. gasseri strains. Antioxidant capacities were determined by measuring the ABTS, DPPH, and peroxyl radical scavenging activities and ferric reducing power. The antioxidant capacity of CT-supplemented milk was greater than that of milk without supplementation; moreover, the antioxidant activity of CT-supplemented milk was synergistically improved by fermentation with L. gasseri strains. In particular, CT-supplemented milk fermented by L. gasseri 505 showed the highest antioxidant activity. The phenolic compounds in CT, such as neo-chlorogenic, chlorogenic, and caffeic acid, were metabolized during fermentation with L. gasseri strains, and 3,4-dihydroxy-hydrocinnamic acid was produced as a fermentation metabolite. Moreover, the liberation of bioactive peptides of fermented milk was increased by the proteolytic activity of L. gasseri strains. In particular, six peptides, which were mainly derived from β-casein, were newly identified in this study. These findings suggest that L. gasseri strains metabolize the phenolic acids in the CT and the bioactive peptides released through this interaction improve the antioxidant activity of the fermented milk.

Short communication: In vivo screening platform for bacteriocins using Caenorhabditis elegans to control mastitis-causing pathogens

This study aimed to develop an in vivo screening platform using Caenorhabditis elegans to identify a novel bacteriocin for controlling the mastitis-causing pathogen Staphylococcus aureus strain RF122 in dairy cows. Using Bacillus spp. isolated from traditional Korean foods, we developed a direct in vivo screening platform that uses 96-well plates and fluorescence image analysis. We identified a novel bacteriocin produced by Bacillus licheniformis strain 146 (lichenicin 146) with a high in vivo antimicrobial activity using our liquid C. elegans-Staph. aureus assay. We also determined the characteristics of lichenicin 146 using liquid chromatography-mass spectrometry and confirmed that it shared homologous sequences with bacteriocin family proteins. In addition, RNA-sequencing analysis revealed genes encoding cell surface or membrane proteins (SAB0993c, SAB0150, SAB0994c, and SAB2375c) that are involved in the bactericidal activity of lichenicin 146 against Staph. aureus strain RF122 infection as well as those encoding transcriptional regulators (SAB0844c and SAB0133). Thus, our direct in vivo screening platform facilitates simple, convenient, cost-effective, and reliable screening of potential antimicrobial compounds with applications in the dairy field.

Microbiological characterization and functionality of set-type yogurt fermented with potential prebiotic substrates Cudrania tricuspidata and Morus alba L. leaf extracts.

The objective of this study was to investigate the effect of 2 plant leaf extracts on fermentation mechanisms and health-promoting activities and their potential as a nutraceutical prebiotics ingredient for application in dairy products. The individual active phenolic compounds in the plant extract-supplemented milk and yogurts were also identified. Compared with control fermentation, the plant extracts significantly increased the growth and acidification rate of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. In particular, plant extract components, including monosaccharides, formic acid, and hydroxycinnamic acid, such as neo-chlorogenic, chlorogenic, and caffeic acid, together play a stimulatory role and cause this beneficial effect on the growth of yogurt culture bacteria through fermentation. In addition, supplementation with the plant extracts enhanced antioxidant activities with increased total phenolic contents, especially the highest antioxidant activity was observed in yogurt supplemented with Cudrania tricuspidata leaf extract.

Chemical characteristics and enhanced hepatoprotective activities of Maillard reaction products derived from milk protein-sugar system

The objective of this study was to investigate the characteristics, antioxidative properties, and hepatoprotective effects of Maillard reaction products (MRP) from milk protein reacted with sugars. The MRP were obtained from milk protein, whey protein concentrates and sodium caseinate, using 2 types of sugars, lactose and glucose, by heating the mixture at 55°C for 7d in a sodium phosphate buffer (pH 7.4). Changes in the chemical modification of the milk protein were monitored by measuring the protein-bound carbonyls and PAGE protein profiles. The results showed that the amount of protein-bound carbonyls increased after Maillard reaction (MR). In addition, sodium dodecyl sulfate-PAGE analysis indicated a formation of high-molecular weight complexes through MR. The modification sites induced by MR of milk protein were monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of tryptic-digested gel spots of MRP. As a result, modification and their localization in AA sequence of MRP was identified. Also, the MRP showed higher antioxidant activities than the intact milk protein, and they reduced intracellular reactive oxygen species production and inhibited the depletion of the reduced glutathione concentrations in the HepG2 cells. In particular, glucose-sodium caseinate MRP showed the highest biological activities among all MRP. Therefore, these results suggest that the MRP from milk protein reacting with sugars possess effective antioxidant activity and have a protective ability against oxidative damage.

Probiotic and anti-inflammatory potential of Lactobacillus rhamnosus 4B15 and Lactobacillus gasseri 4M13 isolated from infant feces

A total of 22 Lactobacillus strains, which were isolated from infant feces were evaluated for their probiotic potential along with resistance to low pH and bile salts. Eight isolates (L. reuteri 3M02 and 3M03, L. gasseri 4M13, 4R22, 5R01, 5R02, and 5R13, and L. rhamnosus 4B15) with high tolerance to acid and bile salts, and ability to adhere to the intestine were screened from 22 strains. Further, functional properties of 8 Lactobacillus strains, such as anti-oxidation, inhibition of α-glucosidase activity, cholesterol-lowering, and anti-inflammation were evaluated. The properties were strain-specific. Particularly, two strains of L. rhamnosus, 4B15 (4B15) and L. gasseri 4M13 (4M13) showed considerably higher anti-oxidation, inhibition of α-glucosidase activity, and cholesterol-lowering, and greater inhibition of nitric oxide production than other strains. Moreover, the two selected strains substantially inhibited the release of inflammatory mediators such as TNF-α, IL-6, IL-1β, and IL-10 stimulated the treatment of RAW 264.7 macrophages with LPS. In addition, whole genome sequencing and comparative genomic analysis of 4B15 and 4M13 indicated them as novel genomic strains. These results suggested that 4B15 and 4M13 showed the highest probiotic potential and have an impact on immune health by modulating pro-inflammatory cytokines.

Enhanced Microbial, Functional and Sensory Properties of Herbal Yogurt Fermented with Korean Traditional Plant Extracts

This study evaluated the effects of two Korean traditional plant extracts (Diospyros kaki THUNB. leaf; DK, and Nelumbo nucifera leaf; NN) on the fermentation, functional and sensory properties of herbal yogurts. Compared to control fermentation, all plant extracts increased acidification rate and reduced the time to complete fermentation (pH 4.5). Supplementation of plant extracts and storage time were found to influence the characteristics of the yogurts, contributing to increased viability of starter culture and phenolic compounds. In particular, the increase in the counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus was highest (2.95 and 1.14 Log CFU/mL respectively) in DK yogurt. Furthermore, supplementation of the plant extracts significantly influenced to increase the antioxidant activity and water holding capacity and to produce volatile compounds. The higher antioxidant activity and water holding capacity were observed in NN yogurt than DK yogurt. Moreover, all of the sensory characteristics were altered by the addition of plant extracts. Addition of plant extracts increased the scores related to flavor, taste, and texture from plain yogurt without a plant extract, as a result of volatile compounds analysis. Thus, the overall preference was increased by plant extracts. Consequently, supplementation of DK and NN extracts in yogurt enhanced the antioxidant activity and physical property, moreover increased the acceptability of yogurt. These findings demonstrate the possibility of using plant extracts as a functional ingredient in the manufacture of herbal yogurt.

Probiotic Lactobacillus fermentum strain JDFM216 stimulates the longevity and immune response of Caenorhabditis elegans through a nuclear hormone receptor

Here, we examined the functionality of Lactobacillus fermentum strain JDFM216, a newly isolated probiotic bacterium, using a Caenorhabditis elegans model. We determined bacterial colonization in the intestinal tract of C. elegans by plate counting and transmission electron microscopy and examined the survival of C. elegans using a solid killing assay. In addition, we employed DNA microarray analysis, quantitative real time-polymerase chain reaction, and immunoblotting assays to explore health-promoting pathways induced by probiotic bacteria in C. elegans. Initially, we found that the probiotic bacterium L. fermentum strain JDFM216 was not harmful to the C. elegans host. Conditioning with JDFM216 led to its colonization in the nematode intestine and enhanced resistance in nematodes exposed to food-borne pathogens, including Staphylococcus aureus and Escherichia coli O157:H7. Interestingly, this probiotic strain significantly prolonged the life span of C. elegans. Whole-transcriptome analysis and transgenic worm assays revealed that the health-promoting effects of JDFM216 were mediated by a nuclear hormone receptor (NHR) family and PMK-1 signaling. Taken together, we described a new C. elegans-based system to screen novel probiotic activity and demonstrated that preconditioning with the probiotic L. fermentum strain JDFM216 may positively stimulate the longevity of the C. elegans host via specific pathway.

The growth kinetics and metabolic and antioxidant activities of the functional synbiotic combination of Lactobacillus gasseri 505 and Cudrania tricuspidata leaf extract

In a previous study, the synbiotic combination of selected Lactobacillus gasseri strains and Cudrania tricuspidata leaf extract (CT) was shown to significantly improve the functionality of fermented milk, and the greatest synbiotic effect was exhibited with L. gasseri 505. The aim of the present study was to investigate the growth kinetics and fermentation metabolism of this specific synbiotic combination. Fermentation was carried out in synthetic media and milk with or without CT supplementation using L. gasseri 505. Whole genome sequencing and comparative genomics analyses were conducted to verify the novelty of strain. Titratable acidity, pH, microbial population, and organic acid production were measured during the fermentation period. The addition of CT accelerated the acidification rate, supporting the growth of L. gasseri 505, and the production of fermentation metabolites such as lactic acid and pyruvic acid also significantly increased during fermentation of both of CT-supplemented synthetic media and milk. In particular, the formic acid and propionic acid in CT were significantly utilized during fermentation of milk by L. gasseri 505. Moreover, the antioxidant capacity of CT-supplemented fermented milk increased due to the release of bioactive compounds until the exponential growth phase, after which the antioxidant activity declined due to degradation and loss of potency. Therefore, this study established that L. gasseri 505 efficiently utilized the CT-related nutrients during fermentation producing resulting metabolites with health-promoting effects, although it is necessary to control the fermentation time to obtain dairy products with optimum functionality.