Nonalcoholic fatty liver disease (NAFLD) is recognized one of the leading metabolic diseases globally, and the younger age population with the disease is rapidly growing, especially in developed countries. Since there has been no approved medicine, losing weight is known to be the only best remedy to control or reverse the disease. Recently, the field of microbiome has attracted much attention to offer more practical choices for patients. Here, we provide experimental evidence that Streptococcus thermophilus LM1012 (LM1012), a safe probiotic strain, is effective for improving NAFLD indexes. In the methionine-choline deficient (MCD) diet induced C57BL/6 mouse model, administration of LM1012 promoted marked reductions of aspartate transaminase (23.8%), total bilirubin (27.8%), hydroxycholesterol (64.2%), triglyceride (29.7%) and IL-1β (68.3%) compared to the MCD diet alone group. Also, the histopathological data imply that LM1012 inhibited fat accumulation and inflammation in the liver, which are the key biomarkers for progression of the disease. Together, these findings suggest that human consumption of LM1012 as a healthy nutritional supplement, may be helpful in reducing the risk of liver damages in NAFLD patients.

Probiotic strain is known to regulate the immune system by colonizing in the intestine and interact with intestinal cell receptors of lymphoid tissue. In this study, safety of Streptococcus thermophilus KCTC14471BP and silk fibroin coating effects was evaluated with respect to mucin binding abilities and immune system modulation. S. thermophilus KCTC14471BP was coated with silk fibroin by adding 1% water-soluble calcium and 0.1% silk fibroin. S. thermophilus KCTC14471BP showed the high activities of leucine arylamidase and β-galactosidase. Regarding the antibiotic resistance tests, S. thermophilus KCTC14471BP was susceptible to ampicillin, vancomycin, gentamicin, kanamycin, streptomycin, erythromycin, clindamycin, tetracycline, and chloramphenicol. S. thermophilus KCTC14471BP coated with silk fibroin showed the improved mucin binding ability from 16.1% to 71.3% and was confirmed to have no cytotoxicity against RAW 264.7 macrophage. S. thermophilus KCTC14471BP coated with silk fibroin showed dose-dependently significant increases in pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. These results suggested that S. thermophilus KCTC14471BP can be expected as a promising probiotic bacteria for applications to food industries such as fermentation or functional foods.

자연적으로 일어나는 형질전환은 세균에서 유전 요소의 수평적 전달 메커니즘의 하나로서 세균 생리학에서 빠질 수 없을 만큼 중요한 현상이다. S. thermophilus는 자연적으로 형질전환이 가능한 상태로 변환하기 위해서 Rgg-타입의 response regulator인 ComR과 소수성 펩타이드 페르몬인 ComS를 포함하는 새로운 quorum sencing 시스템을 이용한다. S. thermophilus를 화학적 제한배지에서 배양하면 대수기 초기에 신호서열이 분리된 ComS는 세포외부로 배출된다. 배출된 ComS는 올리고 펩타이드 전달 시스템인 Ami를 통하여 세포내로 유입되어 ComR과 결합하게 된다. ComS와 결합된 활성화된 ComR은 후기 형질전환 관련 유전자들의 전사를 조절하는 대체형 시그마펙터(σ^x)를 암호화하는 comX 유전자의 발현을 유도함으로써 형질전환이 일어나도록 만든다. 신호서열이 제거된 ComS를 합성하여 화학적 합성배지에 첨가하게 되면, S. thermophilus의 형질전환을 인공적으로 유도할 수 있다. Leuconostoc 속 유산균들 은 그들이 후기 형질전환 관련 유전자들과 서열이 유사한 단백질 유전자들을 보유하고 있음에도 불구하고 자연적 형질전환 메커니즘은 아직 밝혀지지 않았다. Leuconostoc 속의 자연적 형질전환의 메커니즘을 규명하는 연구는 김치산업에서 사용될 수 있는 개량된 균주 개발을 가능하게 할 것이다.

This study was conducted to evaluate the influence of Lactobacillus bulgaricus and/or Sterptococcus thermophilus on the fermentation of yoghurt containing 5% (w/v) buckwheat sprouts. The results revealed that after 12 hours of fermentation the appropriate pH, titratable acidity and number of viable cells were attained. At that time, the rutin content of the buckwheat sprout-added yoghurt prepared by the mixed culture method was not changed, but the quercetin content increased greatly. Conversely, the rutin content of yoghurt that only contained Streptococcus thermophilus was decreased while the quercetin content was increased. The total phenol contents as well as the DPPH radical scavenging activities of both the mixed culture and Streptococcus thermophilus yoghurt did not differ significantly. Taken together, the results revealed that the use of a mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus during the preparation of buchwheat sprout-added yoghurt was desirable due to the decrease in pH and increase in titratable acidity and viable cells that occurred after 12 hr of fermentation. Moreover, phytochemicals in buckwheat sprouts such as rutin, quercetin and phenol compounds were comparatively increased during fermentation and influenced the antioxidant activity in buckwheat sprout-added yoghurt.

This study aimed to provide basic evidence regarding the development of materials by analyzing the physicochemical properties and antioxidant activities of Streptococcus thermophilus KCCM 3782 strain-fermented Cordyceps militaris grown on Tenebrio molitor. Among the solvents tested, DPPH radical scavenging activity was the highest in the hot water-extracted sample after 30 min of extraction. Moisture content decreased, whereas crude protein and fat content increased, after lactic acid bacteria-mediated fermentation. Sodium, magnesium, calcium, and zinc contents increased, with potassium levels attaining the maximum value, whereas free amino acid content decreased after the fermentation. Among Hunter's color values, a value increased to 66.7→149.92 after fermentation, whereas the L and b values decreased to 15.79→-15.75 and 54.45→0.01, respectively. Cordycepin content assay increased from 7.02 mg% to 8.66 mg%. The DPPH free radical scavenging activity of the fermented product was 91.92 EDA%, which was higher than that of the extract (84.69 EDA%). The ABTS free radical scavenging and superoxide dismutase (SOD) activities were also higher in the fermented products.

새로운 항염증 및 미백 소재를 찾기 위해서, 본 연구에서는 6가지 한약재 추출물(유자, 상백피, 오미자, 율무, 당귀, 고삼)을 Streptococcus thermophilus에 의해 발효한 발효분말의 미백 및 항염증 효과를 피부섬유아세포에 대한 피부독성, 산화질소 생성, tyrosinase 활성, 멜라닌 형성의 저해 효과를 측정함으로써 평가하였다. 발효물은 37 ℃에서 2일 동안 Streptococcus thermophilus에 의해 발효한 후, 동결건조에 의해 발효분말을 제조하였다. 발효분말은 피부섬유아세포에 대해 500 μg/mL의 농도에서 cytopathic effect reduction 방법을 사용하면서 측정하였을 때 세포독성을 나타내지 않았다. 또한 발효분말은 Griess reagent system을 사용하면서 산화질소 생성에 대한 저해 효과를 나타내었다. 더욱이 발효분말은 tyrosinase 활성에 대한 저해 효과가 농도의존적으로 나타났다. 발효분말은 배양액으로부터 멜라닌 생성에 대해 유의적인 저해를 나타내었다(p < 0.05). 그러므로 이러한 자료로부터 발효분말은 항염증 및 미백 효과를 갖는 것으로 나타났으며, 화장품을 위한 효과적인 성분으로써 사용가능할 것으로 사료된다.