• Journal of Microbiology and Biotechnology
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• 제30권6호
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• pp.903-911
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• 2020

Addition of probiotics to yogurt with desired health benefits is gaining increasing attention. To further understand the effect of probiotic Lactobacillus plantarum on the quality and function of fermented milk, probiotic fermented milk (PFM) made with probiotic L. plantarum K25 and yogurt starter (L. delbrueckii ssp. bulgaricus and Streptococcus thermophilus) was compared with the control fermented milk (FM) made with only the yogurt starter. The probiotic strain was shown to survive well with a viable count of 7.1 ± 0.1 log CFU/g in the PFM sample after 21 days of storage at 4℃. The strain was shown to promote formation of volatiles such as acetoin and 2,3-butanediol with milk fragrance, and it did not cause post-acidification during refrigerated storage. Metabolomics analysis by GC-MS datasets coupled with multivariate statistical analysis showed that addition of L. plantarum K25 increased formation of over 20 metabolites detected in fermented milk, among which γ-aminobutyric acid was the most prominent. Together with several other metabolites with relatively high levels in fermented milk such as glyceric acid, malic acid, succinic acid, glycine, alanine, ribose, and 1,3-dihydroxyacetone, they might play important roles in the probiotic function of L. plantarum K25. Further assay of the bioactivity of the PFM sample showed significant (p < 0.05) increase of ACE inhibitory activity from 22.3% at day 1 to 49.3% at day 21 of the refrigerated storage. Therefore, probiotic L. plantarum K25 could be explored for potential application in functional dairy products.

• 한국식품과학회지
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• 제23권6호
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• pp.739-744
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• 1991

호화시킨 쌀을 액 당화한 후 젖산발효하고 균질화하여 호상 쌀젖산발효물을 제조하였다. 발효시 ${\alpha}$-아밀라제와 글루코아밀라제를 각각 0.02%수준으로 처리하여 2차 당화와 동시에 발효를 진행함으로써 쌀젖산발효물의 품질을 크게 향상시킬 수 있었다. 이들 효소처리에 의하여 쌀젖산발효물의 신맛과 단맛이 증대되었으며 꺼끌꺼끌한 촉감을 주는 불용성 고형물 입자의 크기가 감소하였다. 쌀젖산 발효물의 관능적 품질은 매우 양호하였으며 기호도가 높았다. 최적화된 공정에 의거하여 제조된 쌀젖산발효물의 이화학적 특성을 조사하였다.

• Journal of Microbiology and Biotechnology
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• 제16권11호
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• pp.1809-1813
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• 2006

A gene corresponding to 4-${\alpha}$-glucanotransferase (${\alpha}GTase$) was cloned from the thermophilic bacterium Thermus brockianus. The nucleotide sequence analysis showed that the ${\alpha}GTase$ gene is composed of 1,503 nucleotides and encodes a polypeptide that is 500 amino acids long with a calculated molecular mass of 57,221 Da. The deduced amino acid sequences of Thermus brockianus ${\alpha}GTase$ (TBGT) exhibited a high level of similarity to the amino acid sequence of ${\alpha}GTase$ of Thermus thermophilus (86%), but low level of homology to that of E. coli (26%). The TBGT gene was overexpressed in E. coli BL21, and the corresponding recombinant enzyme was efficiently purified by Ni-NTA affinity chromatography. The enzymatic characteristics revealed that optimal pH and temperature were pH 6 and $70^{\circ}C$, respectively. Most interestingly, TBGT reacted with small oligosaccharides, especially maltotriose, to form various maltooligosaccharides by using its disproportionation activity.

• 한국미생물·생명공학회지
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• 제37권3호
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• pp.238-242
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• 2009

분자생물학적 방법에 의한 김치유산균 연구의 진행으로 Leuconostoc, Lactobacillus, Weissella 속 유산균의 김치발효 과정 중 생육에 대한 새로운 결과들이 도출되었지만, Pediococcus속의 생육에 대한 새로운 결과는 거의 보고되지 않았다. 본 연구에서는 김치에 존재하는 Pediococcus 속 유산균의 존재에 대한 재조명을 위하여 ampicillin (A)의 첨가로 pediococci의 선발 유효성이 향상된 것으로 보고된 pediococci selective medium(PSM)+A를 이용하여 pediococci 선택적 검출의 유효성을 검토한 결과, 기존에 보고된 결과와는 달리 Pediococcus pentosaceus 외에도 leuconostocs, Lactobacillus casei, Lactobacillus curvatus, Oenococcus oeni, Streptococcus thermophilus에 대한 생육저해가 발생하지 않았다. PSM+A 한천배지를 이용하여 김치에 생육하는 미생물을 검출한 경우, leuconostocs, P. pentosaceus, Weissella koreensis, Lb. curvatus, Lactobacillus brevis, Lactobacillus sakei가 생육하여 김치와 같은 발효침채류의 발효에 관여하는 pediococci의 선택적 선발에는 PSM+A가 유효하지 않은 것으로 확인되었다.

• Environmental Analysis Health and Toxicology
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• 제22권4호
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• pp.287-297
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• 2007

유산균(Lactic acid bacteria)은 Escherichia coli와 Salmonella typhimurium과 같은 병원균에 항균 활성을 지니며 면역 증강효과를 나타내는 등 건강에 이로운 다양한 역할을 한다. 유산균에 의한 항균 효과는 E. coli와 S. typhiumurium에 대항하는 항균 활성으로 측정되어 졌으며, 면역 증강 효과는 유산균을 처리한 RAW264.7 대식세포의 활성화로 측정하였다. Lactobacillus acidophilus, Streptococcus thermophilus, Bifidobacterium bifidum의 E. coli와 S. typhimurium에 대한 항균활성은 9시간 이상 혼합 배양하였을 때 가장 좋은 항균효과를 나타내었고 E. coli와 S. typhiumurium 두 균주가 9시간 이후에는 모두 콜로니를 형성하지 않았다. RAW264.7 세포는 유산균에 의한 NO와 $TNF-{\alpha}$의 생성과 대식세포의 형태 변화를 알아보기 위한 대식세포로서 이용되었다. NO와 $TNF-{\alpha}$의 생성은 유산균을 처리한 RAW264.7세포의 24,48시간 배양 시 농도 의존적으로 증가하였고 대식세포의 형태 변화 역시 유산균에 의해 영향을 받았음을 확인할 수 있었다. 이를 통하여 (주)쎌바이텍으로부터 분양받은 유산균은 항균활성과 대식세포의 활성을 유도하여 면역을 증강시키는 효과를 지니고 있음을 in vitro 실험을 통해 확인하였다.

• 대한본초학회지
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• 제30권4호
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• pp.29-35
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• 2015

Objectives : The objective of this research was to investigate the antibacterial and antioxidant activities of bio-fermented Sanguisorbae Radix extract.Methods : The Sanguisorbae Radix extract was fermented byStreptococcus thermophilus,and their products was tested for antibacterial activity against pathogenic microorganisms namely,Bacillus cereus,Bacillus subtilis,Staphylococcus aureus,Escherichia coli,Vibrio parahaemolyticusandSalmonella typhimuriumby paper disc diffusion method and the antioxidant activities of extract was evaluated by five different assays as electron donating ability(EDA), superoxide dismutase(SOD)-like activity, polyphenol, flavonoid contents and nitrite scavenging ability.Results : The bio-fermented Sanguisorbae Radix extract was safe from heat. Antibacterial activity of fermented Sanguisorbae Radix extract appeared relatively highly againstBacillus cereusandStaphylococcus aureusand didn't show any difference. EDA in comparison to Vitamin C showed over 90% activity at about the same time of Sanguisorbae Radix extract expressed highly. SOD activity showed 15% in fermentation before and after. The nitrite scavenging ability of Sanguisorbae Radix extract before and after fermentation showed higher numerical value over 70% in pH 2.5 than that of butylated hydroxytoluene(BHT). But SOD activity, EDA and nitrite scavenging ability were not different between the Sanguisorbae Radix extract before and after fermentation. Total polyphenol content expressed over about 20 mg/g, and that of the Sanguisorbae Radix extracts was increased than that of the fermented Sanguisorbae Radix extracts.Conclusions : The results suggest the usefulness of developing functional materials using antioxidant active Sanguisorbae Radix extract was fermented bySalmonella typhimuriumwith high polyphenol contents and nitrite scavenging ability.

• Biotechnology and Bioprocess Engineering:BBE
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• 제11권3호
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• pp.240-244
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• 2006

To develop a health-aid preparation of Chinese yam (Dioscorea batatas Decne), lactic acid fermentation was attempted using a mixed starter comprising of Lactobacillus acidophilus, Streptococcus thermophilus, and Bifidobacterium bifidus. The anaerobic fermentation of a 5% Chinese yam flour suspension gave a uniform suspension of pH 4.35, containing $7.76{\times}10^6 CFU/mL$ lactic acid bacteria (LAB), and which was found to be acceptable to the panel from a sensory assessment. During the administration of the lactic acid fermented (LAF) Chinese yam to Sprague Dawley rats for 6 weeks, a smaller body weight gain, but greater excretion of feces were observed, implying the creation of a healthy gastrointestine on the administration of LAF Chinese yam, which was also confirmed by the gastrointestinal motility of the feed in rats fed on LAF Chinese yam. The constipation induced by loperamide was further suppressed in a rat group fed on a LAF Chinese yam diet, which was qualified from healthy gastrointestinal flora established by LAB. A serochemical analysis revealed a slight improvement in the blood glucose, neutral lipid and total cholesterol concentrations on administration of LAF Chinese yam, suggesting LAF Chinese yam could be served as a healthy-aid preparation, even for hyperglycemia or hyperlipidemia patients.

• Molecules and Cells
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• 제43권4호
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• pp.350-359
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• 2020

Pathogenic aminoacyl-tRNA synthetases (ARSs) are attractive targets for anti-infective agents because their catalytic active sites are different from those of human ARSs. Mupirocin is a topical antibiotic that specifically inhibits bacterial isoleucyl-tRNA synthetase (IleRS), resulting in a block to protein synthesis. Previous studies on Thermus thermophilus IleRS indicated that mupirocin-resistance of eukaryotic IleRS is primarily due to differences in two amino acids, His581 and Leu583, in the active site. However, without a eukaryotic IleRS structure, the structural basis for mupirocin-resistance of eukaryotic IleRS remains elusive. Herein, we determined the crystal structure of Candida albicans IleRS complexed with Ile-AMP at 2.9 A resolution. The largest difference between eukaryotic and prokaryotic IleRS enzymes is closure of the active site pocket by Phe55 in the HIGH loop; Arg410 in the CP core loop; and the second Lys in the KMSKR loop. The Ile-AMP product is lodged in a closed active site, which may restrict its release and thereby enhance catalytic efficiency. The compact active site also prevents the optimal positioning of the 9-hydroxynonanoic acid of mupirocin and plays a critical role in resistance of eukaryotic IleRS to anti-infective agents.

• 한국축산식품학회지
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• 제36권4호
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• pp.558-565
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• 2016

The aim of this study was to investigate the influence of proteolytic pork hydrolysate (PPH) on yoghurt production by Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. Fresh lean pork was cut into pieces and mixed with deionized water and dealt with protease, then the resulting PPH was added to milk to investigate the effects of PPH on yoghurt production. The fermentation time, the viable cell counts, the flavor, free amino acids compounds, and sensory evaluation of yoghurt were evaluated. These results showed that PPH significantly stimulated the growth and acidification of the both bacterial strains. When the content of PPH reached 5% (w/w), the increased acidifying rate occurred, which the fermentation time was one hour less than that of the control, a time saving of up to 20% compared with the control. The viable cell counts, the total free amino acids, and the scores of taste, flavor and overall acceptability in PPH-supplemented yoghurt were higher than the control. Furthermore, the contents of some characteristic flavor compounds including acids, alcohols, aldehydes, ketones and esters were richer than the control. We concluded that the constituents of PPH such as small peptide, vitamins, and minerals together to play the stimulatory roles and result in beneficial effect for the yoghurt starter cultures growth.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2017년도 9th Asian Crop Science Association conference
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• pp.365-365
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• 2017

Yogurt is a food produced by bacterial fermentation of milk and the bacteria used to make it are known as "yogurt cultures". Most of them belong to probiotics such as Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus bacteria. Domestic fermented milk market is increasing and about 30 companies are producing yogurt. The purpose of this study was to analyze the quality characteristics of domestic commercial semisolid type yogurt. We collected 20 types of commercial yogurt at local markets. Physicochemical properties including pH, sugar content, acidity, viscosity and microbial characteristics of lactic acid bacteria counts were measured. The yogurt showed pH 4.5, 7.4~18.1% of sugar contents, 0.6~1.3% of total acids and 282~748 cP of viscosities. In the microorganism populations, lactic acid bacteria count were 6.5~11.5 Log CFU/mL and anaerobic lactic acid bacteria count were 7.2 ~ 11.1 Log CFU/mL. The quality characteristics were different depending on the constituents of the sample and the microorganisms used. These results are related to the quality characteristics of yogurts which are useful information about identifying new trends in domestic fermented milk industry.