• Food Science of Animal Resources
• /
• v.29 no.4
• /
• pp.437-444
• /
• 2009

${\gamma}-Aminobutyric$ acid (GABA) producing lactic acid bacteria, Lactobacillus acidophilus RMK567 was cultivated in 50 L of sterilized MRS broth using a fermenter at $40^{\circ}C$ for 24 h. The cell number was increased to $10.04{\pm}0.13$ Log CFU/mL with a growth rate constant (k) of 0.454 generation/h and a generation time (g) of 2.303 h after a lapse of a lag phase (L) of 5.16 h. A total of 487 g of cell paste with 40.5% moisture was harvested with viable cell number of 12.48 Log CFU/g cell paste. The cell pastes after preparation with glycerol, glucose, and polydextrose as cryo-protectants were lyophilized under a vacuum of 84 m torr. A total of 408 g of freeze dried (FD) cell powders were mixed with a commercial strain of Streptococcus thermophilus to prepare of three types FD starter cultures with the viable cell numbers of 12.42 (FDA-GY), 12.60 (FDBGG) and 12.91 (FDC-GP) Log CFU/g. During preservation the FD cultures at -$18^{\circ}C$, the cell viability of the FD starter cultures were rapidly dropped to below 3.24% of the day of storage. No significant difference was found in the cell viabilities among three types of FD starters cultures, but significant difference (p<0.01) was found in storage periods. Yoghurts fermented through FD starter culture of L. acidophilus RMK567 were determined to contain $155.16{\pm}8.53$ ppm, $243.82{\pm}4.27$ ppm, and $198.64{\pm}23.46$ ppm of GABA, respectively. This study shows that GABA production activity of L. acidophilus RMK567 is not affected during the freeze drying process and would be available for commercial production of yoghurt containing high GABA content.

• Journal of Dairy Science and Biotechnology
• /
• v.33 no.4
• /
• pp.263-269
• /
• 2015

Various carbohydrates (lactose, glucose, and fructose), lactic acid, uric acid, and acetoin were separated on a ZORBAX Carbohydrate Analysis column using the Agilent 1200 HPLC ChemStation$^{TM}$, and were identified according to retention times with 325 Dual Wavelength UV-Vis Detector and Refractive Index Detector with 0.013 N $H_2SO_4$ at a flow rate of 0.8 mL/min. In addition, the lactase activity of four commercial probiotic lactic acid bacteria during 6-hour incubation was determined using a high-performance liquid chromatography (HPLC) method. Among the tested samples, Bifidobacterium animalis subsp. lactis showed the greatest lactase activity, followed by Lactobacillus rhamnosus and Lactobacillus casei, with Streptococcus salivarius subsp. thermophilus showing the lowest activity. Therefore, this HPLC technique shows potential for evaluating the fermentation processes of probiotic lactic acid bacteria and could simultaneously confirm the degree of ripening in various fermented dairy foods within only a half hour.

• Journal of Microbiology and Biotechnology
• /
• v.25 no.10
• /
• pp.1751-1760
• /
• 2015

Mucin2 (MUC2), an important regulatory factor in the immune system, plays an important role in the host defense system against bacterial translocation. Probiotics known to regulate MUC2 gene expression have been widely studied, but the interactions among probiotic, pathogens, and mucin gene are still not fully understood. The aim of this study was to investigate the role of MUC2 in blocking effects of probiotics on meningitic E. coli-induced pathogenicities. In this study, live combined probiotic tablets containing living Bifidobacterium, Lactobacillus bulgaricus, and Streptococcus thermophilus were used. MUC2 expression was knocked down in Caco-2 cells by RNA interference. 5-Aza-2'-deoxycytidine (5-Aza-CdR), which enhances mucin-promoted probiotic effects through inducing production of Sadenosyl-L-methionine (SAMe), was used to up-regulate MUC2 expression in Caco-2 cells. The adhesion to and invasion of meningitic E. coli were detected by competition assays. Our studies showed that probiotic agents could block E. coli-caused intestinal colonization, bacteremia, and meningitis in a neonatal sepsis and meningitis rat model. MUC2 gene expression in the neonatal rats given probiotic agents was obviously higher than that of the infected and uninfected control groups without probiotic treatment. The prohibitive effects of probiotic agents on MUC2-knockdown Caco-2 cells infected with E44 were significantly reduced compared with nontransfected Caco-2 cells. Moreover, the results also showed that 5-Aza-CdR, a drug enhancing the production of SAMe that is a protective agent of probiotics, was able to significantly suppress adhesion and invasion of E44 to Caco-2 cells by upregulation of MUC2 expression. Taken together, our data suggest that probiotic agents can efficiently block meningitic E. coli-induced pathogenicities in a manner dependent on MUC2.

• Korean Journal of Agricultural Science
• /
• v.23 no.1
• /
• pp.70-79
• /
• 1996

Yogurts were prepared with skim milk powder added with jujube extract of 0%, 1%, 2%, 3%, 4%, 5%, respectively and fermented by mixed culture(Str. thermophilus, and Lac. bulgaricus). The fermented yogurts were evaluated for acid production(pH, titratable acidity), number of viable cell, change of sugars, sensory properties. 1. Addition of jujube extract increased acid production and decreased pH. Acid production was increased in proportion to concentration of jujube extracts added to milk and pH was decreased. 2. In yogurt fermentation, the lactic acid bacteria of yogurt added with jujube extract, increased in proportion to jujube extract concentration added to milk. 3. The viscosity was increased in proportion to concentration of jujube extract during 6 hrs. of fermentation. The viscosity of yogurt added with 4% and 5% jujube extract remarkably decreased for the first 12 hrs. Yogurt added with 5% jujube extract is lowest in its viscosity among the treatments. 4. The concentrations of glucose and fructose were higher in proportion of jujube extract add at 0 hrs. the concentration of lactose was decreased simultaneously, and those of galactose was increased in all the samples at 12 hrs. 5. The taste and odor of yogurt added with the jujube extract of 4% and 5%, respectively, were better than other samples. The color of control was better than other samples. The texture of control yogurt was better than orther samples, but was not clearly difference with the yogurts added with jujube extract of 4% and 5%. In the overall acceptability, the sensory scores of yogurt added with jujube extract of 3% and 4% were higher than other samples.

• Journal of Dairy Science and Biotechnology
• /
• v.31 no.2
• /
• pp.133-141
• /
• 2013

This study was performed to identify the cheese starter potential of antifungal lactic acid bacteria isolated from Kimchi. Eight fungi were isolated from cheese or the cheese ripening room, and identified as Penicillium and Cladosporium by ITS-5.8S rDNA analysis. Twenty-two lactic acid bacteria species with antifungal activity were isolated from Kimchi, and identified as Lactobacillus and Pediococcus by 16S rRNA sequence analysis. Six lactic acid bacteria species were selected (L. sakei subsp. ALJ011, L. sakei subsp. ALI033, L. sakei subsp. ALGy039, P. pentosaceus ALJ015, P. pentosaceus ALJ024, and P. pentosaceus ALJ026) based on higher antifungal activity from the initial 22 species. Out of the six identified species, L. sakei subsp. ALI033 had the highest antifungal activity. For growth of the six lactic acid bacteria, optimal temperature and pH were $30{\sim}37^{\circ}C$ and 7.0, respectively. Proteolytic activities of the six lactic acid bacteria were almost as strong as the commercial strain Str. thermophilus Body-1. Coagulative activities of L. sakei subsp. ALI033, P. pentosaceus ALJ015, and P. pentosaceus ALJ024 were higher than those of L. sakei subsp. ALJ011, L. sakei subsp. ALGy039, and P. pentosaceus ALJ026. The acid resistance of L. sakei subsp. was higher than that of P. pentosaceus. The major organic acid component of the lactic acid bacteria culture medium was lactic acid.

• The Korean Journal of Food And Nutrition
• /
• v.18 no.3
• /
• pp.192-199
• /
• 2005

Quality characteristics of curd yoghurt containing loquat extract were evaluated in terms of sensory properties and quality-keeping properties(number of viable cells, pH, titratable acidity). Curd yoghurts were prepared from $10\%(w/v)$ skim milk added with $10\~20\%(v/v)$ loquat extract and fermented by the mixed culture of Streptococcus thermophilus and Lactobacillus acidophilus(1:1) at $37^{\circ}C$ for 12 hours. The results of sensory evaluation of curd yoghurts indicated that flavor, sweet taste, sour taste, aftertaste and overall acceptability of the curd yoghurts with addition of loquat extract showed higher preference than a curd yoghurt with only skim milk. And the curd yoghurt containing $15\%$ loquat extract added $20\~25\%(w/v)$ oligosaccharide had the higher sensory scores in sweet taste, sour taste, aftertaste and overall acceptability among the treatments. When the curd yoghurts added with $15\%$ loquat extract were kept at $4^{\circ}C\;and\;20^{\circ}C$ for 31 days, the number of viable cell counts of the lactic acid bacteria were slightly higher than those in the curd yoghurt with no addition of loquat extract. And also the pH and titratable acidity of all yoghurts were not significantly changed during the storage at $4^{\circ}C$ for 31 days, while the pH and titratable acidity were remarkedly changed during the yoghurts stored at $20^{\circ}C$ for 31 days. The keeping quality of the curd yoghurts with addition of $15\%$ loquat extract was relatively good at $4^{\circ}C$ and $20^{\circ}C$ for 31 days.

• Journal of Dairy Science and Biotechnology
• /
• v.30 no.1
• /
• pp.23-30
• /
• 2012

This study was carried out to investigate the quality characteristics of yoghurt with varying contents of Sanmeoru (Vitis amurensis Ruprecht) wine (SW). Yoghurts were fermented with 2 kinds of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus; Yo-$MIX^{TM5}505$, Danisco, Denmark). The changes in quality characteristics were investigated during fermentation and storage, and anthocyanin composition was analyzed after fermentation. The pH decreased in all treatments, while titratable acidity and viscosity gradually increased during fermentation. The viscosity of the yoghurt with 5.0% cultured SW added was higher than in other groups. The viable counts of lactic acid bacteria gradually increased during fermentation. The sample of the 5.0% cultured SW-yoghurt was higher than that of the other groups. The pH slowly decreased during the storage period; this was lower in the control yoghurt than in the yoghurts containing SW, and the changes of titratable acidity in the samples containing 5.0% and 30.0% cultured SW were lower than that in the yoghurt containing 1.0% cultured SW and in the control. The change in viscosity and number of viable cells during storage was higher in the yoghurts containing SW than in the control group. The levels of anthocyanin increased with the SW content in the yoghurt. Sensory scores for taste of the yoghurt with 1.0% added SW was significantly higher than for the other groups. Yoghurt with added SW kept at $4^{\circ}C$ for 12 days retained its quality characteristics fairly well.

• Korean Journal of Agricultural Science
• /
• v.25 no.2
• /
• pp.199-215
• /
• 1998

In order to determine the effect of tomato(Lycopersicon escylentnm mill ssp.) on the yogurt quality, skim milk powders were added with tomato juice of 0%, 1%, 3%, 5% and fermented by mixed culture(Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. The results were summarized as follows: 1. Addition of tomato juice in skim milk decreased pH(4.3) and increased acidity(0.93%) more than control did(pH 4.6, titratable acidity 0.85%). By the addition of tomato juice, acid production was increased and pH was decreased in proportion to concentrations of tomato juices added to skim milk. 2. The number of lactic acid bacteria in yogurts added with tomato juice ($4.59{\times}10^{12}cfu/ml$) more increased than those in control yogurt($8.96{\times}10^{11}cfu/ml$). By the addition of tomato juice, the number of lactic acid bacteria counts increased in proportion to concentration of tomato juices added to skim milk. 3. As fermentation time goes by, the Brix degree sugar content in skim milk were decreased more rapidly than control. 4. The pH, titratable acidity, Brix degree and lactic acid bacteria were not significantly changed for all yogurts for the storing at $5^{\circ}C$ for 14 days. 5. In yogurt fermentation, addition of tomato juice with glucose (1% tomato juice + 4% glucose, 3% tomato juice + 2% glucose, 5% tomato juice + 0% glucose) decreased pH and increased acidity than control(5%glucose) did. In addition of tomato juice, acidity was increased and pH was decreased in proportion to concentration of tomato juices added to skim milk. 6. In yogurt fermentation, the number of lactic acid bacteria of yogurt added with tomato juice(1% tomato juice+4% glucose, 3% tomato juice+2% glucose, 5% tomato juice+0% glucose) increased than control(5% glucose). In addition of tomato juice, the number of lactic acid bacteria increased in proportion to concentration of tomato juices added to skim milk. 7. As fermentation time goes by, the Brix degree were decreased more rapidly than control(5% glucose). By the change of pH, titratable acidity, Brix degree and lactic acid bacteria, in yogurt fermentation, we definited that the promotive effect of tomato(Lycopersicon escylentnm mill ssp.) on the yogurt.

• Food Science of Animal Resources
• /
• v.23 no.3
• /
• pp.250-261
• /
• 2003

This experiment was carried out to examine the fermentation properties of yogurt with Lycii fructus, Lycii folium and Lycii cortex powder, and extract additives at concentrations of 0.5, 1.0, 2.0, 4.0, and 6.0%. Lactic acid bacteria was used in a mixed starter culture of Streptococcus salivarius ssp. thermophilus(ST36) and Lactobacillus delbrueckii ssp. bulgaricus(LB12). When the boxthorn was added with extract types, the changes of pH, acidity and lactic acid bacteria counts of yogurt during the fermenation of 3 hours were pH 5.64, titratable acidity 0.85%, 5.80xl0$\^$6/cfu/ml of viable cell counts for control yogurt, whereas those were pH 4.10∼5.06, titratable acidity 0.98∼1.27%, 1.80∼9.60x10$\^$7/ cfu/ml of viable cell counts for Lycii fructus extract yogurt. The lactose hydrolysis ratio was better for 1.0% Lycii fructus extract yogurt(42.00%) and 1.0% Lycii folium extract yogurt(41.46%) than for control yogurt(28.40%). Also, content of lactic acid of 1.0% Lycii fructus(11.9 times) and 1.0% Lycii folium extract yogurt(10.6 times) produced more than control yogurt(7.3 times). The viscosity of yogurt was better for boxthorn extract yogurt(1,027∼1,382 cps) than for control yogurt(975cps). The sensory scores of color, taste and overall acceptability of yogurt with 0.5, and 1.0% Lycii fructus extract additive were better than other groups. The yogurts made with increased Lycii fructus extract concentration(0.5∼6.0%), showed the increase of lactic acid, titratable acidity, number of lactic acid bacteria, viscosity and lactose hydrolysis rate compared to the treatments of 0.5, 1.0, 2.0, and 4.0% Lycii folium and Lycii cortex extract and powder yogurt. We gained excellent results from the yogurt to which Lycii fructus extract was added with 0.51.0% concentration.

• Food Science of Animal Resources
• /
• v.23 no.3
• /
• pp.269-277
• /
• 2003

This study was carried out to evaluate the safety of Korean human milk. The microorganisms were identified from human milk of 149 healthy mothers by two collection methods, hand and pump expression. The means of total bacterial counts were 2.33x10$^4$ cfu/mL on the samples collected by the pump expression and 7.83xl0$^3$ cfu/mL on those collected by the hand expression. Therefore, the total bacterial counts of pump expression samples was 9.80xl0$^2$∼3.06x10$^4$ cfu/mL more than that of hand expression samples. The coliform counts of pump expression was 9.36xl0$^3$∼8.57xl0$^4$ cfu/mL more than that of hand expression. However, there was any significant differences of the lactic acid bacterial counts between the two samples collected by each methods. 100 strains of 5 patterns of total bacterial counts were isolated based on the morphology of colony in the standard plate count agar. 13 species were identified among the isolated strains. The dominant species in Korean human milk were Staphylococcus which 7 subspecies identified(81% in the rate of total bacteria, 1.07x10$^4$ cfu/mL). Other species identified were Micrococcus, Bacillus, Providencia, Pseudomonas, Yersinia and Acinetobacter. 36 strains of 6 patterns of lactic acid bacterial counts were isolated based on morphology of colony in the BCP agar. 7 species were identified among the isolated strains. The dominant species of lactic acid bacteria in Korean human milk were Lactobacillus brevis(50.9% in the rate of lactic acid bacteria, 4.72xl0$^4$ cfu/mL). Others species identified(49.1% lactic acid bacteria) were Lactobacillus curvatus, Lactobacillus delbrueckii subsp. lactis, Lactobacillus acidophilus, Leuconostic lactis and Streptococcus salivarius subsp. thermophilus.