• Journal of Life Science
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• v.30 no.2
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• pp.162-168
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• 2020

Because of a continual reduction in its domestic market share, the quality of the Makgeolli, a Korean traditional liquor, needs to be upgraded. Among the several options for quality improvement, sufficient organoleptic expression of flavor is very important. We analyzed production changes of isoamyl acetate, which has a banana smell, based on fermentation temperature and sugar content through the cultivation of S. cerevisiae 98-5 KCCM 11396P using generally polished rice. The banana flavor of that fermentation mash was organoleptically high at 20℃, but a larger amount of isoamyl acetate was obtained with a higher sugar content at 10℃, based on analysis by GC-MS. Consequently, sufficient production of banana flavor from isoamyl acetate was based on the concentration of isoamyl alcohol as a substrate compound of isoamyl acetate, and the production depended highly on the maintenance of heat stability, since it is unstable in temperature and the minimized inhibition of alcohol acetyl transferase by unsaturated fatty acids. We also found that production of the flavor component required the addition of sugar and a slightly higher temperature of 20~25℃ at the beginning stage of fermentation, with additional mash fermentation and a gradual decrease in temperature to 10~15℃.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.111-116
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• 2012

In this study, we investigated the microbial flora changes in Gugija-Liriope tuber Makgeolli during fermentation and storage periods. We brewed Gugija-Liriope tuber Makgeolli for a week through twostage fermentations and stored the fermentation broth for a month at $4^{\circ}C$ or $20^{\circ}C$. We collected the samples periodically and analyzed microbial flora changes using viable cell counts and PCR-denaturing gradient gel electrophoresis (DGGE). Yeast viable cells were seen to have decreased to 13% of pre-storage levels after storage for 15 days at $20^{\circ}C$; however significant changes were not observed during storage at $4^{\circ}C$. Prolongation of storage time dramatically decreased the availability of viable cells. Yeast viable cell numbers had decreased to 38% of pre-storage levels at $4^{\circ}C$ and 4.8% at $20^{\circ}C$ after storage for 30 days. The results of the DGGE profile for yeast showed that Saccharomyces cerevisiae and Saccharomyces sp. were the predominant strains at the beginning of fermentation and throughout the whole period of storage. Viable cell counts for total bacteria had decreased to 36% of pre-storage levels after storage for 15 days but did not significantly change for the full 30 days of storage at $4^{\circ}C$. Similarly, viable cell counts for bacteria had decreased to 5% while viable cell numbers did not significantly change for the full 30 days at $20^{\circ}C$. Viable cell counts for lactic acid bacteria were performed and the results were similar to those for total bacteria. The results of the DGGE profile for bacteria showed that Weissella cibaria was the predominant strain at the beginning of fermentation. However it had disappeared by the end of fermentation, and Lactobacillus fermentum and Pediococcus acidilactici became the predominant species during storage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.3
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• pp.444-449
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• 2011

Blueberry Makgeolli was made with rice by adding different amounts of blueberries, and the fermentation characteristics of Makgeolli were studied during the fermentation process. The pH was the highest (6.6) at the beginning of the fermentation and decreased when the ratio of blueberries increased. The pH was remarkably reduced until the second day, and remained constant until the seventh day of fermentation. The total acidity was significantly increased until the fourth day of fermentation, and remained constant until the seventh day. Sugar contents ($^{\circ}Brix$) and reducing sugar reached the maximum after 2 days of fermentation, and gradually decreased until the seventh day. Alcohol content of control (0% blueberries) increased continuously until the seventh day of fermentation and was at 13.4%. Alcohol content of 20% blueberry Makgeolli reached the maximum on the 4th day of fermentation and slowly decreased to 10.2% until the seventh day. Total viable bacterial cell counts and yeast cell counts showed the maximum values at the third day of fermentation. In sensory evaluation, the color of the control sample was the most favored by the panelists whereas 20% blueberry sample was the least favored. There were no significant differences in flavor and taste, but overall preference was high in Makgeolli with less than 10% of blueberries.

• Applied Biological Chemistry
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• v.10
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• pp.69-100
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• 1968

1. In order to investigate on the microflora and enzyme activity of mold wheat 'Nuruk' , the major source of microorganisms for the brewing of Takju (a Korean Sake), two samples of Nuruk, one prepared at the College of Agriculture, Chung Nam University (S) and the other perchased at a market (T), were taken for the study. The molds, aerobic bacteria, lactic acid bacteria, and yeasts were examined and counted. The yeasts were classified by the treatment with TTC (2, 3, 5 triphenyltetrazolium chloride) agar that yields a varied shade of color. The amylase and protease activities of Nuruk were measured. The results were as the followings. a) In the Nuruk S found were: Aspergillus oryzae group, $204{\times}10^5$; Black Aspergilli, $163{\times}10^5$; Rhizogus, $20{\times}10^5$; Penicillia, $134{\times}10^5$; Areobic bacteria, $9{\times}10^6-2{\times}10^7$; Lactic acid bacteria, $3{\times}10^4$ In the Nuruk T found were: Aspergillus oryzae group, $836{\times}10^5$; Black Aspergilli, $286{\times}10^5$; Rhizopus, $623{\times}10^5$; Penicillia, $264{\times}10^5$; Aerobic bacteria, $5{\times}10^6-9{\times}10^6$; Lactic acid bacteria, $3{\times}10^4$ b) Eighty to ninety percent of the aerobic bacteria in Nuruk S appeared to belong to Bacillus subtilis while about 70% of those in Nuruk T seemed to be spherical bacteria. In both Nuruks about 80% of lactic acid bacteria were observed as spherical ones. c) The population of yeasts in 1g. of Nuruk S was about $6{\times}10^5$, 56.5% of which were TTC pink yeasts, 16% of which were TTC red pink yeasts, 8% of which were TTC red yeasts, 19.5% of which were TTC white yeasts. In Nuruk T(1g) the number of yeasts accounted for $14{\times}10^4$ and constituted of 42% TTC pink. 21% TTC red pink 28% TTC red and 9% TTC white. d) The enzyme activity of 1g Nuruk S was: Liquefying type Amylase, $D^{40}/_{30},=256$ W.V. Saccharifying type Amylase, 43.32 A.U. Acid protease, 181 C.F.U. Alkaline protease, 240C.F.U. The enzyme activity of 1g Nuruk T was: Liquefying type Amylase $D^{40}/_{30},=32$ W.V. Saccharifying type amylase $^{30}34.92$ A.U. Acid protease, 138 C.F.U. Alkaline protease 31 C.F.U. 2. During the fermentation of 'Takju' employing the Nuruks S and T the microflora and enzyme activity throughout the brewing were observed in 12 hour intervals. TTC pink and red yeasts considered to be the major yeasts were isolated and cultured. The strains ($1{\times}10^6/ml$) were added to the mashes S and T in which pH was adjusted to 4.2 and the change of microflora was examined during the fermentation. The results were: a) The molds disappeared from each sample plot since 2 to 3 days after mashing while the population of aerobic bacteria was found to be $10{\times}10^7-35{\times}10^7/ml$ inS plots and $8.2{\times}10^7-12{\times}10^7$ in plots. Among them the coccus propagated substantially until some 30 hours elasped in the S and T plots treated with lactic acid but decreased abruptly thereafter. In the plots of SP. SR. TP. and TR the coccus had not appeared from the beginning while the bacillus showed up and down changes in number and diminished by 1/5-1/10 the original at the end stage. b) The lactic acid bacteria observed in the S plot were about $7.4{\times}10^7$ in number per ml of the mash in 24 hours and increased up to around $2{\times}10^8$ until 3-4 days since. After this period the population decreased rapidly and reached about $4{\times}10^5$ at the end, In the plot T the lactic acid becteria found were about $3{\times}10^8$ at the period of 24 fours, about $3{\times}10$ in 3 days and about $2{\times}10^5$ at the end in number. In the plots SP. SR. TP, and TR the lactic acid bacteria observed were as less as $4{\times}10^5$ at the stage of 24 hours and after this period the organisms either remained unchanged in population or ceased to exist. c) The maiority of lactic acid bacteria found in each mash were spherical and the change in number displayed a tendency in accordance with the amount of lactic acid and alcohol produced in the mash. d) The yeasts had showed a marked propagation since the period of 24 hours when the number was about $2{\times}10^8$ ㎖ mash in the plot S. $4{\times}10^8$ in 48 hours and $5-7{\times}10^8$ in the end period were observed. In the plot T the number was $4{\times}10^8$ in 24 hours and thereafter changed up and down maintaining $2-5{\times}10^8$ in the range. e) Over 90% of the yeasts found in the mashes of S and T plots were TTC pink type while both TTC red pink and TTC red types held range of $2{\times}10-3{\times}10^7$ throughout the entire fermentation. f) The population of TTC pink yeasts in the plot SP was as $5{\times}10^8$ much as that is, twice of that of S plot at the period of 24 hours. The predominance in number continued until the middle and later stages but the order of number became about the same at the end. g) Total number of the yeasts observed in the plot SR showed little difference from that of the plot SP. The TTC red yeasts added appeared considerably in the early stage but days after the change in number was about the same as that of the plot S. In the plot TR the population of TTC red yeasts was predominant over the T plot in the early stage which there was no difference between two plots there after. For this reason even in the plot w hers TTC red yeasts were added TTC pink yeasts were predominant. TTC red yeasts observed in the present experiment showed continuing growth until the later stage but the rate was low. h) In the plot TP TTC pink yeasts were found to be about $5{\times}10^8$ in number at the period of 2 days and inclined to decrease thereafter. Compared with the plot T the number of TTC pink yeasts in the plot TP was predominant until the middle stage but became at the later stage. i) The productivity of alcohol in the mash was measured. The plot where TTC pink yeasts were added showed somewhat better yield in the earely stage but at and after the middle stage the difference between the yeast-added and the intact mashes was not recognizable. And the production of alcohol was not proportional to the total number of yeasts present. j) Activity of the liquefying amylase was the highest until 12 hours after mashing, somewhat lowered once after that, and again increased around 36-48 hours after mashing. Then the activity had decreased continuously. Activity of saccharifying amylase also decreased at the period of 24 hours and then increased until 48 hours when it reached the maximum. Since, the activity had gradually decreased until 72 hours and rapidly so did thereafter. k) Activity of alkaline protease during the fermentation of mash showed a tendency to decrease continusously although somewhat irregular. Activity of acid protease increased until hours at the maximum, then decreased rapidly, and again increased, the vigor of acid protease showed better shape than that of alkaline protease throughout. 3. TTC pink yeasts that were predominant in number, two strains of TTC red pink yeasts that appeared throughout the brewing, and TTC red yeasts were identified and the physiological characters examined. The results were as described below. a) TTC pinkyeasts (B-50P) and two strains of TTC red pink yeasts (B-54 RP & B-60 RP) w ere identified as the type of Saccharomyces cerevisiae and TTC pink red yeasts CB-53 R) were as the type of Hansenula subpelliculosa. b) The fermentability of four strains above mentioned were measured as follows. Two strains of TTC red pink yeasts were the highest, TTC pink yeasts were the lowest in the fermantability. The former three strains were active in the early stage of fermentation and found to be suitable for manufacturing 'Takju' TTC red yeasts were found to play an important role in Takju brewing due to its strong ability to produce esters although its fermentability was low. c) The tolerance against nitrous acid of strains of yeast was marked. That against lactic acid was only 3% in Koji extract, and TTC red yeasts showed somewhat stronger resistance. The tolerance against alcohol of TTC pink and red pink yeasts in the Hayduck solution was 7% while that in the malt extract was 13%. However, that of TTC red yeasts was much weaker than others. Liguefying activity of gelatin by those four strains of yeast was not recognized even in 40 days. 4. Fermentability during Takju brewing was shown in the first two days as much as 70-80% of total fermentation and around 90% of fermentation proceeded in 3-4 days. The main fermentation appeared to be completed during :his period. Productivity of alcohol during Takju brewing was found to be apporximately 65% of the total amount of starch put in mashing. 5. The reason that Saccharomyces coreanuss found be Saito in the mash of Takju was not detected in the present experiment is considered due to the facts that Aspergillus oryzae has been inoculated in the mold wheat (Nuruk) since around 1930 and also that Koji has been used in Takju brewing, consequently causing they complete change in microflora in the Takju brewing. This consideration will be supported by the fact that the original flavor and taste have now been remarkably changed.

• Journal of Life Science
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• v.28 no.8
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• pp.923-930
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• 2018

In this study, Tenebrio molitor (T. molitor) was fermented with Lactobacillus plantarum JBMI F3 (F3), Lactobacillus plantarum JBMI F5 (F5), Lactobacillus gasseri Ba9 (Ba9), Aspergillus kawachii KCCM 32819 (Ak), Saccharomyces cerevisiae KACC 93023 (Sc), and Bacillus subtilis KACC 91157 (Bs). After fermentation, the fermented products were extracted by water, ethanol, and methanol, and their physicochemical and biological properties were investigated. In a DPPH assay, the water extracts of the fermented products of T. molitor showed high antioxidant ability. Among the water extracts, the fermented product by Bs showed the highest DPPH radical scavenging activity. The total contents of phenolic compounds and flavonoids were highest in the fermented products by Ak and Bs, respectively. Reducing activity was detected the most high activity on ethanol extract of fermented product by Bs. The water extract of the fermented product by Bs exhibited strong enzymatic activity for fibrinogen and starch hydrolysis. Based on the observed physicochemical and biological properties, the fermented products of T. molitor by microorgansims can likely be applied as functional materials in various industries.

• Microbiology and Biotechnology Letters
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• v.6 no.1
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• pp.17-22
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• 1978

The microbial and chemical changes, and characterization of the predominant acid-producing bacteria in the fermenting pig feces blended with corn meal at a ratio of 50：50 were studied. The fermentation was dominated by lactobacilli, which multiplied rapidly for the first 24 hours. The acid produced during the fermentation caused rapid pH drop to pH 4.5 and halted the growth of E. coli and yeast. The initial acid producing bacteria in the mixture was predominantly Streptococcus species, which were reduced in number rapidly. After 7 days of fermentation, three lactobacilli species were appeared L. acidophilus, L. fermenti, L. delbrueckii. Chemical changes during the fermentation were also studied. The lactic acid fermentation imparted a good tangy acid flavor to the corn-feces mixture by removing or covering the .fecal ordour and made the corn-feces mixture palatable for the animal as well as halted the unwanted microbial flora. We hope the lactic acid fermentation will replace the heat processing in the utilization of animal feces.

• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.489-493
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• 1988

To obtain a new yeast strain that is able to efficiently produce ethanol from starch, the glucoamylase gene of Saccharomyces diastaticus was transformed into S. cerevisiae without a cloning vector. The competent cells of S. cerevisiae, induced by the treatment of Li$_2$SO$_4$, were transformed with the partial BamHI-digests of chromosomal DNA of S. diastaticus, and the transformants were selected by their abilities to utilize and ferment starch. The transformants, which appeared at a frequency of 8.5$\times$10$^{-7}$, were able to withstand up to 800 ppm of copper sulfate like the recipient and retained the phenotypic expression of the recipient with the exception of the acquisition of STA gene and MAL gene, as regards fermentation of carbohydrates. The enzymatic properties of glucoamylases produced by transformants were very similar to those produced by S. diastaticus as based on optimium pH and temperature.

• Applied Biological Chemistry
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• v.46 no.3
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• pp.201-206
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• 2003

An apple wine was prepared by fermentation at $25^{\circ}C$ for 2 weeks using Saccha개myces cerevisiae KCCM 12224, followed by aging at $15^{\circ}C$ for 14 weeks, and its physicochemical and microbiological changes were investigated. The viable bacterial cell numbers, increased from $1.4{\times}10^3\;CFU/ml$ at the beginning of fermentation, to $2.8{\times}10^6\;CFU/ml$ after 2 weeks, but decreased to $1.0{\times}10^5\;CFU/ml$ after aging. The viable yeast cell numbers changed from $4.3{\times}10^4\;CFU/ml$ to $1.2{\times}10^7\;CFU/ml$ during the fermentation, and decreased to $1.2{\times}10^4\;CFU/ml$ after aging. Sugar content changed from $20.0^{\circ}Brix$ to $8.5{\circ}Brix$, and reducing sugar content was changed from 9.66% to 6.44%. Alcohol content and acidity increased to 7.0% and from 0.19% to 0.24%, respectively. No changes in acidity, pH, and sugar content were observed during the aging, but reducing sugar and solid contents decreased. When apple wine was fultered through $0.45\;{\mu}m$ nitrocellulose membrane followed by various ultrafiltration membranes with different molecular weight cut-off values, the initial flux $(121.2\;liter/m^2/h)$ and the average flux of Biomax 100k membrane were the highest among the membranes used. These membrane filtration treatments resulted in complete removal of microorganisms as well as decrease in turbidity and solid content without changes in other chemical properties. No changes in the physicochemical properties of the apple wine and no microorganisms were detected during the storage at $156{\circ}C$ for 6 weeks.

• Journal of Life Science
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• v.28 no.7
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• pp.827-834
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• 2018

In this study, the biological activities of aqueous, ethanol, and methanol extracts of larvae of the edible insect Protaetia brevitarsis seulensis, fermented using several kinds of microorganisms, were tested in in vitro experimental models. Six effective microorganisms were used for fermentation, namely Lactobacillus plantarum JBMI F3, Lactobacillus plantarum JBMI F5, Lactobacillus gasseri Ba9, Aspergillus kawachii KCCM 32819, Saccharomyces cerevisiae KACC 93023, and Bacillus subtilis KACC 91157. Biological activities (${\alpha},{\alpha}^{\prime}-diphenyl-{\beta}-picrylhydrazyl$ [DPPH] free radical scavenging activity, reducing power, and fibrinolytic activity), and biochemical properties (phenolic compounds and flavonoids) were examined in aqueous, ethanol, and methanol extracts from P. brevitarsis seulensis powder and fermented P. brevitarsis seulensis powder. The total phenolic compounds and flavonoid contents were highest in the aqueous extract of B. subtilis-fermented P. brevitarsis seulensis powder. DPPH radical scavenging activity and reducing power were stronger in the fermented group than the nonfermented group. Fibrinolytic activity were highest in the extract from B. subtilis-fermented P. brevitarsis seulensis powder. The ${\alpha}-amylase$ activity in starch was higher in the fermented group than the nonfermented group, but there was no significant difference. These results provide basic data to understand the biological activities of bioactive materials derived from fermented P. brevitarsis seulensis larvae for the development of functional foods.

• KSBB Journal
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• v.4 no.2
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• pp.172-176
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• 1989

The alcohol fermentation was carried out to study the effect of aeration and unsaturated fatty acids added on the ethanol tolerance of Saccharomyces cerevisiae STV89 and Kluyveromyces fragilis CBS397. The cell growth rate and ethanol production rate was stimulated by aeration and the cell mass production and ethanol production were also substantially improved. With respect to strains, the maximum specific growth rate and overall ethanol productivity of K. fragilis under aerated condition were 6.4 fold and 4.4 fold higher than those of strictly anaerobic condition, although those of S. cerevisiae were increased 1.7 times and 2.3 times by aeration. The addition of ergosterol, linoleic acid and oleic acid also improved the cell growth and ethanol production of S. cerevisiae and K. fragilis. Thus it was found that oxygen and unsaturated fatty acids added played a decisive role on the increase of ethanol tolerance of yeast strains.