• Korean Journal of Food Science and Technology
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• v.21 no.1
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• pp.164-172
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• 1989

The formation of galactooligosaccharides by transgalactosidation reactions during hydrolysis of lactose by the ${\beta}-galactosidase$ from Streptococcus thermophilus 510 was investigated. Three oligosaccharides were detected during hydrolysis. It was found that the optimum conditions for the production of oligosaccharides was 40% lactose treated with ${\beta}-galactosidase(50\;ONPG\;units/ml)$ at $37^{\circ}C$ for 4 hours. The oligosaccharides formed accounted for 30% of the total sugars when the lactose had been 94% hydrolysed. 69% of the oligosaccharides were identified as $6-o-{\beta}-D-galactopyranosyl-D-glucose(allolactose)$ and 23% as $6-o-{\beta}-D-galactopyranosyl-D-galactose(isogalactobiose)$. The separation of galactooligosaccharides by the use of Bio-Gel P-2 gel permeation chromatography was also studied.

• Microbiology and Biotechnology Letters
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• v.37 no.1
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• pp.17-23
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• 2009

The gene encoding Thermus thermophilus HJ6 DNA polymerase (Tod) was cloned and sequenced. The open reading frame (ORF) of the Tod gene was composed of 2,505 nucleotides and encoded a protein (843 amino acids) with a predicted molecular weight of 93,795 Da. The deduced amino acid sequence of Tod showed 98% and 86% identities to the Thermus thermophilus HB8 DNA pol and Thermus aquaticus DNA pol, respectively, The Tod gene was expressed under the control of the bacteriophage $\lambda$ promoters PR and PL on the expression vector pJLA503 in Escherichia coli strain BL21 (DE3) codon plus. The expressed enzyme was purified by heat treatment, $HiTrap^{TM}$ Q column, and $HiPrep^{TM}$ Sephacryl S-200 HR 26/60 column chromatographies. The optimal temperature and pH for DNA polymerase activity were found to be $75{\sim}80^{\circ}C$ and 9.0, respectively. The optimal concentrations of $Mg^{2+}$ and $Mn^{2+}$ were 2.5 mM and 1 mM, respectively. The enzyme activity was activated by divalent cations, and was inhibited by monovalent cations. The result of the PCR experiment with Tod DNA polymerase indicates that this enzyme might be useful in DNA amplification and PCR-based applications.

• Journal of Dairy Science and Biotechnology
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• v.33 no.1
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• pp.17-25
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• 2015

The present study was carried out to evaluate the preparation of the fermented milks with rice bran and to prove that the bacteria used are necessary for providing amino acids in this process. The rice bran on fermented milk with Streptococcus thermophilus (ST-body1) and Lactobacillus casei (LC-10). The fermentation limit was set until acidimetry score reaches 1. There are reports of titratable acidity, pH, viable cell count and amounts of organic acids affecting amino acid production about physical and chemical analysis measured using HPLC. Finally, sensory test was surveyed. In this study, the rate of acidification was higher in the fermented milk with rice bran than in the common fermented milk. In case of the number of cells was $1.0{\times}10^8CFU/mL$ in group. The lactic acid and citric acid content in yogurts prepared with rice bran using Streptococcus thermophilus (ST-body1) and Lactobacillus casei (LC-10) was higher than that in the control yogurt. Amino acids derived by rice bran were effected in fermentation for each bacteria's necessary amino acid production, and it made bacteria growth larger. From the physical test of the fermented milk with rice bran, flavor, texture, sweetness, overall taste of the fermented milk of Streptococcus thermophilus (ST-body1) were found to be much better than those of the other groups. The results obtained for the fermented milk prepared with rice bran using Streptococcus thermophilus (ST-body1) are significant.

• Korean Journal of Food Science and Technology
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• v.18 no.6
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• pp.492-496
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• 1986

A compound stimulatory to the growth of S. thermophilus CH-1 was isolated from the cell-free filtrate of L. helveticus YM-1 in milk medium. The stimulant was identified as a peptide with a molecular weight of approximately 5000 and exhibited positive ninhydrin reaction. Some kinds of amino acids confirmed as aspartic acid, alanine, valine, glutamic acid, lysine, proline, leucine were rich in the stimulatory peptide hydrolysate. Among them, glutamic acid was most abundant. Judging from bioautographic results, glutamic acid and phenylalanine were expected to exert an important role for the stimulation.

• Journal of Dairy Science and Biotechnology
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• v.30 no.2
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• pp.69-74
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• 2012

This study was performed to determine by the ability of the mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus to ferment Dioscorea opposita Thunb. (yam) and to evaluate the nutraceutical value of fermented yam. The titratable acidity (TA) value increased from 2 to 6% with increased concentrations in both raw yam and extracted lactic acid bacteria (LAB) fermented yam (LFY). The viable cell counts and the allantoin and diosgenin contents were higher in raw LFY at large concentrations (6%) than in extracted LFY samples at all fermentation periods up to 32 h. Based on these data, it confirmed that raw yam fermented by the combination culture of L. bulgaricus and S. thermophilus for various fermentation periods favors the symbiotic growth of LAB and results in higher nutraceutical content.

• Journal of Microbiology and Biotechnology
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• v.28 no.10
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• pp.1581-1588
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• 2018

The growth of lactic acid bacteria (LAB) generates a high number of metabolites related to aromas and flavors in fermented dairy foods. These microbial proteases are involved in protein hydrolysis that produces necessary peptides for their growth and releases different molecules of interest, like bioactive peptides, during their activity. Each genus in particular has its own proteolytic system to hydrolyze the necessary proteins to meet its requirements. This review aims to highlight the differences between the proteolytic systems of Streptococcus thermophilus and other lactic acid bacteria (Lactococcus and Lactobacillus) since they are microorganisms that are frequently used in combination with other LAB in the elaboration of fermented dairy products. Based on genetic studies and in vitro and in vivo tests, the proteolytic system of Streptococcus thermophilus has been divided into three parts: 1) a serine proteinase linked to the cellular wall that is activated in the absence of glutamine and methionine; 2) the transport of peptides and oligopeptides, which are integrated in both the Dpp system and the Ami system, respectively; according to this, it is worth mentioning that the Ami system is able to transport peptides with up to 23 amino acids while the Opp system of Lactococcus or Lactobacillus transports chains with less than 13 amino acids; and finally, 3) peptide hydrolysis by intracellular peptidases, including a group of three exclusive of S. thermophilus capable of releasing either aromatic amino acids or peptides with aromatic amino acids.

• Korean Journal of Organic Agriculture
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• v.15 no.1
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• pp.93-108
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• 2007

In order to find a solution to protect pigs from bacterial diarrhea and the nasty smell in stalls which are the most trouble, we composed a bio-formula with Stretococcus thermophilus, Bacillus amyloliquifaciens and Bacillu subtilis. The antagonistic microbe Bacillus amyloliquifaciens can control the growth of Salmonella typhimurium KCTC 1926, Escherichia coli O-157, Listeria and Staphylococcus. S. thermophilus from pig's stomach can live in gastric juice so it also control germs. They worked in its living cell state and its culture fluid. As a result of feeding with piglings, it showed effects of preventing diarrhea and increasing the weight.

• The Korean Journal of Food And Nutrition
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• v.17 no.1
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• pp.8-17
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• 2004

The effect of chlorella extract on the growth and acid production of yoghurt starter was investigated in order to prepare the yoghurt added with chlorella extract. The various levels of chlorella extract powder were added to skim milk medium and the medium was fermented by single or mixed culture of 4 types of lactic acid bacteria such as Streptococcus thermophilus, Lactobacillus acidophilus, Lactobacillus casei, and Lactobacillus bulgaricus. The changes in acid production(pH, titratable acidity) and number of viable cells of the medium during fermentation in skim milk added with chlorella extract powder have determined. When chlorella extract powder was added to skim milk medium at the levels of 0.5%, 1.0%, 2.0%, and 3.0%, the addition of 0.5% chlorella extract powder with the single culture of Str. thermophilus, Lac. casei, and Lac. bulgaricus showed the highest number of viable cell counts after 9 hours incubation. And also all single cultures of the yoghurt starter produced the higher amounts of acid with the addition of 0.5% chlorella extract powder. When chlorella extract powder was added to the medium at the levels of 0.25%, 0.5%, 1.0%, and 2.0%, the addition of lower lever(0.25∼0.5%) of chlorella extract powder with the mixed culture of the lactic acid bacteria showed more the acidity of pH and the number of viable cell counts. Among the treatments tested, the addition of 0.25% chlorella extract powder with the mixed culture of Str. thermophilus and Lac. casei produced the highest number of viable cell counts after 12 hours incubation. Therefore it was suggested to manufacture the yoghurt with the addition of 0.25% chlorella extract powder and the inoculation of mixed culture of Str. thermophilus and Lac. casei for on the stimulation of growth of the yoghurt starter.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.1
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• pp.131-136
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• 2006

During lactic acid bacteria (LAB) transit through the gastrointestinal tract, ingested microorganisms were exposed to successive stress factors, including low pH in the human stomach and in bile acid. These stress factors can be used as criteria for the selection of a viable probiotic strain. Four such strains (Lactobacillus helveticus SGU 0011, Lactobacillus pentosus SGU 0010, Streptococcus thermophilus SGU 0021 and Lactobacillus casei SGU 0020) were isolated from raw milk. When the identified LAB were exposed to synthetic gastric juice, whereas L. casei SGU 0020 and S. thermophilus SGU 0021 exhibited a 0% survival rate, L. helveticus SGU 0011 and L. pentosus SGU 0010 exhibited 60% and 95% survival rates. L. casei SGU 0020 and S. thermophilus SGU 0021 could not be examined with regard to their tolerances to artificial bile juice, as they uniformly died upon exposure. However, L. helveticus SGU 0011 and L. pentosus SGU 0010 individually survived at rates of 39% and 93%. Also, all four of these strains were confirmed to be tolerant of ten different antibiotics.

• Korean Journal of Food Science and Technology
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• v.31 no.3
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• pp.739-745
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• 1999

This study was carried out to investigate the oligosaccharide and amino acid utilization by mixed cultures during soy yogurt fermentation. Three types soy yogurt were prepared by fermenting with Lactobacillus acidophilus and Streptococcus thermophilus, Streptococcus thermophilus and Saccharomyces uvarum, Lactobacillus acidophilus and Saccharomyces uvarum. The utilized amount of oligosaccharide and amino acid was determined by HPLC during the fermentation period. The oligosaccharide and amino acid utilization efficiency of S. thermophilus and Sac. uvarum was greater than the other mixed cultures. It was found that Sac. uvarum produced enzymes which can convert oligosaccharide and common sugars in soy milk into glucose, galactose and fructose which can be fermented by L. acidophilus and S. thermophilus, and in turn stimulated acid production and amino acid utilization of the latter.