• Microbiology and Biotechnology Letters
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• v.12 no.4
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• pp.285-291
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• 1984

In making liquid yoghurt, the influences of proteolytic ability of lactic acid bacteria on acid production and on protein stability were investigated. L. bulgaricus CH-2, L. helviticus IAM 1042 and L. jugurti 3048 showed a comparatively high proteolytic activity in milk, while L. casei YIT 9018 did not show any marked proteolysis. Starter organisms having high proteolytic ability showed more rapid growth and acid production than those having low ability in milk. The most active proteolysis occurred during logarithmic growth phase of yogurt organisms, and most of the proteolysis took place in the first 24-48 hrs of incubation. Highly proteolysed yogurts made by L. bulgaricus CH-2, L. jugurti 3048, L. helviticus IAM 1042, L. acidophilus L-54 and L. casei 3012 had low protein solubility at pH 3.5 and had much protein precipitates during storage of product, but those having little protein hydrolysates made by L. casei YIT 9018 or artificial acidification showed no precipitation during keeping.

• Journal of Microbiology and Biotechnology
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• v.1 no.4
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• pp.246-250
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• 1991

Conditions for the production and regeneration in Lactobacillus bulgaricus protoplasts were investigated. Protoplasts of L bulgaricus strains were obtained by treatment with mutanolysin and lysozyme together in a protoplast forming buffer containing 0.02 M N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) (pH 7.0) and 0.5 M sucrose. High protoplast yield was obtained from cells cultured in the de Man, Rogosa and Sharpe(MRS) medium at the middle to late logarithmic growth phase. Regeneration was efficiently accomplished with a complex medium containing 1% sucrose, 20 mM $MgCl_2$, 5% gelatin, and 0.5% bovine serum albumin. The frequency of regeneration of protoplasts was 10~20% after 5 days of incubation at $30^{\circ}C$.

• Korean Journal of Food Science and Technology
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• v.19 no.2
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• pp.151-156
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• 1987

Four types of soy milk prepared from soybean, defatted soybean, soy protein concentrate (SPC) or soy protein isolate (SPI) were fermented with Lactobacillus acidophilus, L. bulgaricus, L. casei, Leuconostoc mesenteroides or Streptocroccus lactis. Growth and acid production by each organism in soy milks were investigated. Acid production by L. acidophilus was miximum in soy milk while acid production by other organisms was maximum in defatted soy milk. All the organisms produced least amount of acid in SPI-milk. Addition of yeast extract (0.5) to four types of soy milks stimulated acid production by lactic acid bacteria, particularly in case of L. acidophilus. Higher concentration of total solids in soy milks resulted in better growth and more acid production by L. acidophilus and L. bulgaricus.

• Korean Journal of Food Science and Technology
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• v.27 no.1
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• pp.101-104
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• 1995

We isolated sixty lactic acid bacteria(LAB) from lactic fermented products. Among 60 isolates of LAB, 30 isolates were identified as Lactobacillus casei ssp.(5 strains), Lactobacillus acidophilus(2 strains), Lactobacillus delbrueckii ssp. bulgaricus(6 strains), Lactobacillus plantarum(4 strains), Streptococcus salivarius ssp. thermophilus(11 strains), and Streptococcus faecalis(2 strains). The acid tolerance and bile resistance of 30 LAB were determined. Because the acid tolerance was affected by the initial cell concentrations, the analysis of covariance could be used to remove the effect of initial cells on acid tolerance when testing for differences in acid tolerance among six species. Viability of LAB under acidic condition, pH 3 for 2 hours at $37^{\circ}C$, was significantly different among the species. L. casei and L. acidophilus strains showed great viability, but L. bulgaricus and S. thermophilus strains were very weak in acid tolerance.

• Microbiology and Biotechnology Letters
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• v.23 no.2
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• pp.214-219
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• 1995

In fermentation of dairy products, bifidobacteria is used in conjunction with other lactic acid bacteria, such as L. acidophilus, L. bulgaricus and S. thermophilus, rendering the enumeration of bifidobacteria difficult. In order to develop optimum conditions for selective enumeration of bifidobacteria, we examined MIC of several antibiotics against various bifidobacteria and other lactic acid bacteria. The growth of L. acidophilus, L. bulgaricus and S. thermophilus were inhibited by lithium chloride at the concentration of less than 4 mg/ml, whereas growth inhibition of bifidobacteria occurred at concentrations over 6-10 mg/ml. Tetracycline and chloramphenicol were also found to selectively inhibit growth of other lactic acid bacteria at the concentration of 1-3 $\mu$g/ml. Addition of 6 mg/ml lithium chloride, 1 $\mu$g/ml, tetracycline or 3 $\mu$g/ml chloramphenicol to medium was found to be optimal for selective enumeration of bifidobacteria. By using these three inhibitory chemicals in the TPY medium, higher number of bifidobacteria were selectively isolated than with NPNL agar and LP agar.

• Microbiology and Biotechnology Letters
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• v.7 no.4
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• pp.205-209
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• 1979

Lactobacillus acidophilus exhibited more growth and produced greater amounts of acid in the soy milk than Streptococcus thermophilus, Lactobacillus bulgaricus, and Lactobacillu helveticus examined. The supplementation of the soy milk with glucose accelerated the growth of L. acidophilus, and enhanced acid production by L. acidophilus whereas sucrose addition was without effect. The supplementation of the soy milk containing five percent glucose with a methionine accelerated the growth of L. acidophilus, and enhannced acid production by L. acidophilus. L. acidophilus showed greater population in the soy milk containing five percent glucose which was treated with 0.0008％ protease (9.40$\times$10$^{8}$ /m/) than the soy milk containing five percent glucose (2.02$\times$10$^{9}$ /ml) moreover L. acidophilus produced greater amounts of acid in the soy milk containing five percent glucose which was treated with 0.0008％ protease (1.47 ％) than in the soy milk containing five percent glucose (0.56％)

• Food Science of Animal Resources
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• v.35 no.4
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• pp.541-550
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• 2015

The purpose of this study was to investigate the effect of lactic acid bacteria (LAB) cell wall extract on the proliferation and cytokine production of immune cells to select suitable probiotics for space food. Ten strains of LAB (Lactobacillus bulgaricus, L. paracasei, L. casei, L. acidophilus, L. plantarum, L. delbruekii, Lactococcus lactis, Streptococcus thermophilus, Bifidobacterium breve, and Pedicoccus pentosaceus) were sub-cultured and further cultured for 3 d to reach 7-10 Log colony-forming units (CFU)/mL prior to cell wall extractions. All LAB cell wall extracts failed to inhibit the proliferation of BALB/c mouse splenocytes or mesenteric lymphocytes. Most LAB cell wall extracts except those of L. plantarum and L. delbrueckii induced the proliferation of both immune cells at tested concentrations. In addition, the production of T_H1 cytokine (IFN-γ) rather than that of T_H2 cytokine (IL-4) was enhanced by LAB cell wall extracts. Of ten LAB extracts, four (from L. acidophilus, L. bulgaricus, L. casei, and S. thermophiles) promoted both cell proliferating and T_H1 cytokine production. These results suggested that these LAB could be used as probiotics to maintain immunity and homeostasis for astronauts in extreme space environment and for general people in normal life.

• Food Science of Animal Resources
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• v.27 no.4
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• pp.522-530
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• 2007

This experiment was carried out to measure the content of lactoferrin, IgA, $IgG_1,\;IgG_2$, in Holstein colostrum, and to test the effect of it's colostrum on the antibacterial activity to pathogenic bacteria and the growth stimulation of lactic acid bacteria. Colostrum was collected at the first, second, and third day after parturition in summer and winter season. The levels of lactoferrin, IgA, $IgG_1,\;and\;IgG_2$ in Holstein cow colostrum were 0.30 mg/mL, 0.37 mg/mL, 4.00 mg/mL, 0.37 mg/mL, respectively, on the first day of the summer season whereas they were 1.16 mg/mL, 2.60 mg/mL, 13.35 mg/mL, 1.30 mg/mL on the first day of the winter season, postpartum. Heat treated ($65^{\circ}C$ for 30 min) or non-treated colostrum showed antibacterial activity toward Escherichia coli. The growth of commercial mixed strains (Bifidobacterium longum, Lactobacillus acidophilus, Streptococcus themophilus), L. acidophilus, L. casei, L. bulgaricus, and L. lactis subsp. cremoris were improved in first, second and third day colostrum compared to normal milk. Commercial miked strains (B. longum, L. acidophilus S. themophilus) lowered the pH to 4.97-5.22 and 4.89 while increasing the titratable acidity to 0.75-0.88% and 0.70% in colostrum and normal milk, respectively. However, L. casei, L. bulgaricus, L. lactis subsp. cremoris lowered the pH to 5.96-6.47 and 6.5-6.8 while increasing the titratable acidity to 0.29-0.48% and 0.20-0.25% in colostrum and normal milk, respectively.

• Korean Journal of Agricultural Science
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• v.21 no.2
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• pp.111-121
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• 1994

In order to investigate the effects of ginseng extract on the acid production and bacterial growth in the skim milk medium, ginseng extract was added to skim milk medium for 0.3 to 2.4% and the medium was fermented by Str. thermophilus, L. bulgaricus and mixed strain with both bacteria. The acidity and bacterial number were examined by incubation time. The results were summarized as follows: 1. The acidity of medium without ginseng extract after 12 hours incubation by Str. thermophilus was 11.1% and that by L. bulgaricus was 1.01%, whereas that of medium with ginseng extract was 1.08~0.61% for Str. thermophilus and 0.99~0.49% for L. bulgaricus. Therefore, acid production was inhibited by ginseng extract. 2. The number of bacteria in the medium without ginseng extract after 12 hours incubation was $5.2{\times}10^8/m{\ell}$ for Str. thermophilus and $3.2{\times}10^8/m{\ell}$ for L. bulgancus, whereas that in the medium with ginseng extract was $3.6{\times}10^8/m{\ell}{\sim}1.3{\times}10^8/m{\ell}$ for Str. thermophilus and $2.9{\times}10^8/m{\ell}$ and $1.4{\times}10^8/m{\ell}$ for L bulgancus. Therefore, the number of bacteria was decreased by the amount of ginseng extract increased. 3. However, when skim milk medium was fermented by mixed strains, ginseng extract was not affected on the acid production and bacterial number. On the contrary, in some case, the number of bacteria was increased by addition of ginseng extract.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.740-744
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• 2003

The antimicrobial substance produced by Lactobacillus bulgaricus was inactivated by pretense, which confirmed it as a bacteriocin and referred to 'bulgaricin HJ'. The bulgaricin HJ showed the inhibitory activity against mastitis pathogens, gram-positive and gram-negative bacteria. The optimal conditions for the production of bulgaricin HJ were at the temperature of $30^{\circ}C$ and 10 h after cultivation of L. bulgaricus. Staph. and Strep. agalactiae, common bovine mastitis pathogens, were treated with bulgaricin HJ by the agar well diffusion method and showed antimirobial activities to the bovine mastitis pathogens. The activity of the bulgaricin HJ was maintained at pH 6-7 and $100^{\circ}C$ for 60 min against the mastitis pathogens. The bulgaricin HJ was determined as class IV bacteriocin by various enzyme treatments. Colony forming units analysis with indicator strains by the treatments of bulgaricin HJ indicates that the mode of bacteriocin action was bactericidal rather than bacteriostatic.