• KSBB Journal
• /
• v.22 no.5
• /
• pp.297-304
• /
• 2007

For large and rapid screening of high-yielding mutants of lovastatin produced by filamentous fungal cells of Aspergillus terreus, one of the most important stage is to test as large amounts of mutated strains as possible. For this purpose, we intended to develop a miniaturized cultivation method using $7m{\ell}$ culture tube instead of traditional $250m{\ell}$ flask (working volume $50m{\ell}$). For obtaining large amounts of conidiospores to be used as inoculums for miniaturized cultures, 4 components i.e., glucose, sucrose, yeast extract and $KH_2PO_4$ were intensively investigated, which had been observed to show positive effect on enhancement of spore production through Plackett-Burman design experimet. When optimum concentrations of these components that were determined through application of response surface method (RSM) based on central composite design (CCD) were used, maximum spore numbers amounting to $1.9\times10^{10}$ spores/plate were obtained, resulting in approximately 190 fold increase as compared to the commonly used PDA sporulation medium. Using the miniaturized cultures, intensive strain development programs were carried out for screening of lovastatin high-yielding as well as highly reproducible mutants. It was observed that, for maximum production of lovastatin, the producers should be activated through 'PaB' adaptation process during the early solid culture stage. In addition, they should be proliferated in condensed filamentous forms in miniaturized growth cultures, so that optimum amounts of highly active cells could be transferred to the production culture-tube as reproducible inoculums. Under these highly controlled fermentation conditions, compact-pelleted morphology of optimum size (less than 1 mm in diameter) was successfully induced in the miniaturized production cultures, which proved essential for maximal utilization of the producers' physiology leading to significantly enhanced production of lovastatin. As a result of continuous screening in the miniaturized cultures, lovastatin production levels of the 81% of the daughter cells derived from the high-yielding producers turned out to be in the range of 80%$\sim$120% of the lovastatin production level of the parallel flask cultures. These results demonstrate that the miniaturized cultivation method developed in this study is efficient high throughput system for large and rapid screening of highly stable and productive strains.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.35 no.4
• /
• pp.321-326
• /
• 2015

This study was performed to analyze the resident microbial flora and the effects of probiotic inoculation on the fermentation characteristics of whole grain naked barley (Hordeum Vulgare L.) with the goal of evaluating the possibility of utilization as fermented feedstuff. Naked barley grains were harvested 35 days after heading, and the microbial flora was analyzed using MALDI-TOF mass spectrometer. After inoculation of commercial microbes to the naked barley grain (BT), the pH and number of bacteria, such as aerobic bacteria, lactic acid bacteria, yeast and E. coli, were measured and compared with the non-inoculated control (BC). A total of 122 colonies was isolated from the naked barley grain and the most popular bacteria species was Staphylococcus xylosus (n = 30, 24.59%). The pH value decreased more rapidly in BT than in BC, and was significantly lower after 7 days of fermentation at $4.33{\pm}0.02$ and $4.83{\pm}0.01$, respectively. The number of aerobic bacteria, lactic acid bacteria and yeast showed an increasing trend within the first 7 days of fermentation, however, their numbers decreased at 28 and 42 days of fermentation. The population of lactic acid bacteria in BT was higher than in BC, but there was no significant different at 7 days of fermentation, with respective levels of $9.24{\pm}0.20$ and $9.01{\pm}0.10logCFU/g$ (p>0.05). The initial number of E. coli was very high in the naked barley grain but subsequently decreased significantly. After 7 days of fermentation, E. coli was not detected in either BT or BC samples. From these results, it appears that the fermentation of naked barley grain proceeded adequately after 7 days, and that fermentation contributes to the safety of naked barley grain during storage.

• Korean Journal of Food Science and Technology
• /
• v.27 no.2
• /
• pp.156-163
• /
• 1995

The practical shelf-life of pasteurized Korean rice wine ‘Yakju’, aseptically packed in Tetra-pak, was determined. The test sample products were stored at $4^{\circ}C,\;20^{\circ}C,\;30^{\circ}C\;and\;35^{\circ}C$ for 19 weeks, and the quality assessment was made at two weeks interval. The quality parameters evaluated were pH, acidity, reducing sugar, absorbance at 370 nm, total and acid producing bacteria, yeast and mold, and sensory quality. No meaningful changes of pH and reducing sugar were noticed during the storage for 19 weeks at temperatures tested. The absorbance at 370 nm increased slightly during storage. The total numbers of microorganisms in the product decreased during storage and a drastical reduction of acid producing bacteria was observed after 6 weeks of storage. Both yeast and mold were not found in the pasteurized products. The sensory quality of stored rice-wine was evaluated by triangle test and scoring test. The panels could distinguish the product stored at $4^{\circ}C$ from other products stored at the higher temperatures for over 6 weeks. The overall acceptance of the product decreased gradually during storage, and the rate constants for the changes were $7.93{\times}10^{-3},\;at\;20^{\circ}C,\;9.69{\times}10^{-3}\;at\;30^{\circ}C\;and\;13.4{\times}10^{-3}\;at\;35^{\circ}C$, respectively. The activation energy estimated by Arrhenius equation was 24,795 kJ/kmol. The estimated shelf-life of Yakju pasteurized and aseptically packed was 24 months at $10^{\circ}C$, 16 months at $25^{\circ}C$ and 14 months at $25^{\circ}C$. The shelf-life of Yakju in Seoul was calculated to be 20 months, based on the monthly average temperature of the city.

• Korean Journal of Food Science and Technology
• /
• v.53 no.5
• /
• pp.648-656
• /
• 2021

This study analyzed the physicochemical properties of Danyangju and Iyangju fermented using uncooked germinated brown rice. Total bacteria and yeast from Danyangju and Iyangju showed the maximal value on day 1 of fermentation, but their numbers decreased by the seventh day. On the seventh day, the total bacteria were higher in Iyangju than in Danyangju, but yeast was the lowest in Iyangju. Both Danyangju and Iyangju showed decreased whiteness in color, whereas redness and yellowness increased with fermentation. Sugar contents, reducing sugar, acidity, alcohol, and polyphenol contents increased during fermentation in both Danyangju and Iyangju; this increase was higher in Iyangju than in Danyangju. Iyangju and Danyangju showed gradual increases in α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity until day 5. The γ-aminobutyric acid (GABA) content increased with fermentation in Iyangju and Danyangju, and Iyangju showed over 10-fold increase after fermentation.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.10 no.1
• /
• pp.115-125
• /
• 2000

Three major hospitals with over 500 beds located in and near Seoul were surveyed for airbone microorganisms from February 1, 1998 to February 18, 1998. The purpose of the study was to identify and quantify microbiological organisms circulating in the air of three different areas in the hospitals. For the study, a RCS air sampler was utilized equipped with two different collection media, the agar strip GK-A for bacteria and the agar strip HS for fungi. The areas investigated were the intensive care unit (ICU) in the Department of internal medicine, the Newborns room in the Department of Obstetrics, and the microbiology laboratory. The results were as follows; 1. The average numbers of general microbiological particles collected on the agar strip GK-A media were $205CFU/m^3$, $232CFU/m^3$, and $128CFU/m^3$ in each hospitals. The highest concentration of $387CFU/m^3$ was found in the ICU of A hospital at 15:00 during the day. Further analysis of the collected bioaerosols by gram staining, revealed that there were gram positive cocci (89.5%), gram positive bacilli (7.2%), gram negative bacilli (2.8%), and fungi (0.5%), in descending order of frequency. 2. Ten different genes were identified from the agar strip GK-A. The most frequently identified organisms were: the Coagulase negative staphylococcus (55.0%), Micrococcus (21.4%), Enterococcus species(10.4%), and Bacillus species (7.2%). A series of antibiotics susceptibility test were conducted against the aforementioned four(4) organisms. Ninety percent of coagulase negative stapylococcus were sensitive to Penicillins. Pathogenic microbes isolated include: Staphylococcus aureus, Acinetobacter species, Klebsiella pneumonia, Klebsiella oxytoca, and Pseudomonas aeroginosa. 3 Although 56.8% of the microorganisms grown on the strip HS media for fungi could not be identified, some of them were successfully identified. The most frequently found fungi were Aspergillus (35.3%), Yeast or Molds (6.2%), and Penicillium (0.7%). Based on the results obtained from the study, it was concluded that some areas in the hospitals had abnormally high bioaerosol concentrations which could be attributed to human activity. Therefore, it is recommended that periodic assessments of indoor bioaerosols aiming to identify the possible sources should be conducted in order to maintain clean indoor environment in the hospitals.

• Korean Journal of Food Science and Technology
• /
• v.49 no.2
• /
• pp.132-140
• /
• 2017

Nuruk, a traditional Korean alcoholic beverage starter, was evaluated as an additional saccharifying agent comprising up to 1.5% (w/w) of malt weight in ale-type beer processing. Sample characteristics were monitored during fermentation, ripening, and storage. Beer containing nuruk showed higher numbers of total viable bacteria and yeast cell counts. Additionally, ethanol (6.19-6.35%), color (Standard Reference Method), foam stability ($228.49-368.24{Sigma}$), saccharogenic power (307-417), and reducing sugar (3.83-5.25%) increased as the amount of nuruk was increased, while viscosity (3.13-2.07 cP) and bitterness unit (19.68-13.13) were lower than in samples without nuruk. Overall acceptance and aftertaste of the beer were significantly higher in a preference test. These results demonstrate that nuruk can be used to produce a new type of ale.

• Korean Journal of Food Science and Technology
• /
• v.52 no.5
• /
• pp.538-545
• /
• 2020

Kimchi is a widely consumed traditional Korean food, and its probiotic properties have received great attention. In this study, changes in the quality characteristics of fermentation broths obtained from two types of Chinese cabbage kimchi (red with red pepper and white without red pepper) were assessed after the administration of blue light emitting diode (BLED) irradiation at 4℃; characteristics assessed included acidity, chromaticity, antioxidant activity, and growth modulation of isolated microorganisms. The pH of the white kimchi (WK) broth decreased with time; the decrease was delayed significantly under BLED irradiation (p<0.05). BLED irradiation decreased the L (lightness) and b (yellowness) values and increased a (redness) in WK, whereas the a and b values of the red kimchi (RK) broth increased with BLED irradiation. Growth stimulation of lactic acid bacteria by BLED irradiation was observed in both WK and RK. The numbers of yeast and mold were also increased in RK (p<0.05), but not in WK. There was no change observed in the scavenging activities against ABTS (2,2'-azido-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals in both kimchi broths after BLED treatment. The results of this study indicated that BLED irradiation could modulate the fermentation process and the quality characteristics of kimchi during storage.

• Korean Journal of Food Science and Technology
• /
• v.39 no.3
• /
• pp.304-308
• /
• 2007

This research was conducted to investigate the changes in quality characteristics of meju made with 24-hour germinated soybeans according to fermentation time. The study confirmed that the amino nitrogen content immediately after soaking was 15.5 mg%, and the content rapidly increased in the beginning of the germination process and continued to increase to 312.9 mg% by 48 hours of fermentation. The number of fungi in the whole soybean meju made with 24-hour germinated soybeans was higher than the numbers of bacteria and yeast since the Aspergillus oryzae was inoculated artificially. The content of organic acids, in which the amount of citric acid was highest followed by tartaric acid and malic acid, increased with the fermentation process. The level of free amino acids in the whole soybean meju made from the 24-hour germinated soybeans increased rapidly with fermentation. The free amino acid content after 48 hours of fermentation (2,513.5 mg%) was 5.7 times higher than the content of the soaked germinated soybeans. The content of glutamic acid was highest followed by aspartic acid, lysine, leucine, and proline. The ratio of glutamic acid to the total free amino acids at 48 hours fermentation was 21.2% for the whole soybean meju. It was confirmed that the total isoflavone content, in which the content of genistein was highest followed by daidzein and glycitein, increased at the beginning of the fermentation process, but did not change thereafter.

• Food Science and Preservation
• /
• v.19 no.1
• /
• pp.144-152
• /
• 2012

The temperature changes and quality characteristics of $Makgeolli$ produced using rice treated with $Gaeryang-Nuruk$ (commercial improved $Nuruk$) extract were investigated. During fermentation, the treated rice maintained a lower temperature than the control and then rose after the fifth mashing day. For all the treatments, the numbers of yeast, LAB and AAB colonies increased on the second mashing day, and then gradually decreased. As the fermentation proceeded, the pH gradually increased from the third mashing day, and eventually became higher than that on the initial mashing day. The total acid contents increased on the first mashing day, but as the fermentation progressed, they showed little change. The amino acidity and soluble solid contents during overall fermentation and reducing-sugar contents was reduced until the first mashing day, and increased from the day after. As for the alcohol content, that of the control was 6.87% on the first mashing day, and then gradually increased, nuruk-extract-treated rice began with 9~10% alcohol content and then increased as the fermentation proceeded. Among the organic acid contents, lactate was the main material. In the sensory evaluation, the 24 h-, 48 h- and 72 h- treated rice samples showed somewhat good response.

• Korean Journal of Microbiology
• /
• v.51 no.4
• /
• pp.407-418
• /
• 2015

This study is focused on establishing the optimal conditions to enhance the production of antilisterial substances by Lactobacillus paracasei BK57 isolated from Baikkimchi. In addition, the growth and in situ lactic acid and bacteriocin production of this strain were investigated during the manufacture of fresh cheese. And then the efficacy of using Lactobacillus starter as a protective culture to improve the safety of fresh cheese against Listeria monocytogenes KCTC 3569 was estimated. Maximum growth rate and activity of antibacterial substances were obtained in Lactobacilli MRS broth at $37^{\circ}C$ with controlled pH 6.0 after 30 h of incubation under aerobic condition. However, the growth rate and antimicrobial activity of bacteriocin produced in whole milk supplemented with yeast extract (2.0%) as a substrate were lower than those obtained in MRS broth. Live cells and cell-free culture supernatant of BK57 strain were effective in the suppression of L. monocytogenes in milk, whereas the inhibitory of the bacteriocin obtained from BK57 strain was higher in BHI broth than in milk. During storage at $4^{\circ}C$ and $15^{\circ}C$ for 6 days, no significant difference was found in the cell viability and antimicrobial activity of BK 57 strain in fresh cheese. In samples held at two temperatures, there was at least a 15% reduction in the numbers of the pathogen in fresh cheese artificially contaminated with approximately $10^5CFU/ml$ of L. monocytogenes within 6 days. Our results demonstrated the usefulness of L. paracasei BK57 having antilisterial activity as a biopreservative in the cheese making process.