• Journal of Microbiology and Biotechnology
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• 제27권2호
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• pp.251-261
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• 2017

Initially, we screened 18 Aspergillus sojae-like strains from Aspergillus spp. isolated from meju (Korean traditional fermented soybean brick) according to their morphological characteristics. Because members of Aspergillus section Flavi are often incorrectly identified because of their phylogenetic similarity, we re-identified these strains at the morphological and molecular genetic levels. Fourteen strains were finally identified as A. sojae. The isolates produced protease and ${\alpha}-amylase$ with ranges of 2.66-10.64 and 21.53-106.73 unit/g-initial dry substrate (U/g-IDS), respectively, which were equivalent to those of the koji (starter mold) strains employed to produce Japanese soy sauce. Among the isolates and Japanese koji strains, strains SMF 127 and SMF 131 had the highest leucine aminopeptidase (LAP) activities at 6.00 and 6.06 U/g-IDS, respectively. LAP plays an important role in flavor development because of the production of low-molecular-weight peptides that affect the taste and decrease bitterness. SMF 127 and SMF 131 appeared to be non-aflatoxigenic because of a termination point mutation in aflR and the lack of the polyketide synthase gene found in other A. sojae strains. In addition, SMF 127 and SMF 131 were not cyclopiazonic acid (CPA) producers because of the deletion of maoA, dmaT, and pks/nrps, which are involved in CPA biosynthesis. Therefore, A. sojae strains such as SMF 127 and SMF 131, which have high protease and LAP activities and are free of safety issues, can be considered good starters for soybean fermentations, such as in the production of the Korean fermented soybean products meju, doenjang, and ganjang.

• Journal of Microbiology and Biotechnology
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• 제27권7호
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• pp.1216-1222
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• 2017

To develop starters for the production of functional foods or materials, lactic acid bacteria producing ${\gamma}-aminobutyric$ acid (GABA) were screened from jeotgals, Korean fermented seafoods. One isolate producing a high amount of GABA from monosodium $\text\tiny{L}$-glutamate (MSG) was identified as Enterococcus avium by 16S rRNA gene sequencing. E. avium M5 produced $18.47{\pm}1.26mg/ml$ GABA when incubated for 48 h at $37^{\circ}C$ in MRS broth with MSG (3% (w/v)). A gadB gene encoding glutamate decarboxylase (GAD) was cloned and overexpressed in E. coli BL21 (DE3) using the pET26b (+) expression vector. Recombinant GAD was purified through a Ni-NTA column and the size was estimated to be 53 kDa by SDS-PAGE. Maximum GAD activity was observed at pH 4.5 and $55^{\circ}C$and the activity was dependent on pyridoxal 5'-phosphate. The $K_m$ and $V_{max}$ values of GAD were $3.26{\pm}0.21mM$ and $0.0120{\pm}0.0001mM/min$, respectively, when MSG was used as a substrate. Enterococcus avium M5 secretes a lot of GABA when grown on MRS with MSG, and the strain is useful for the production of fermented foods containing a high amount of GABA.

• 월간양계
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• 제11권6호통권116호
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• pp.75-83
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• 1979

In order to evaluate the effect of lipids on the utilization of the energy and protein of the diet, the isocaloric and isoprotein diets added with mutton fat, tallow, and lecithin at the levels of two percent and five percent were prepared. The growth of chicken and the feed efficiency were observed on hatched chicken which were fed a commercial diet for the first week, with starters for the next four weeks, and with finisher diets for the last three weeks respectively during the eight weeks of the experiment. Growth rate, feed efficiency, and average body weight gain per day were similar among the chicken fed diets containing various lipids or at the levels of two percent and five percent. The metabolize energy of the diets was found to be from 2.713 kcal to 3.059 kcal per gram, and the metabolizability of the gross energy was from 62 percent to 70 percent. Also the metabolizability of basal diet was higher as compared with the diets containing lipids. And the lower energy utiliztion was found in the broilers fed diets containing five percent lipids than those of two percent, showing not significant difference between them. Daily matabolizable energy of three week old brids ranged from 0.631 gr to 0.738 gr, which showed an increasing tendency on the birds fed five percent mutton fat and tallow in comparison with those of two percent. But the lecithin brought about a reverse tendency. The digestibility of crude fats was found to be from 48 percent to 76 percent, but bot significant difference among diets plus lipids or at the levels of two percent and five percent. The birds fed five percent mutton fat and tallow showed a tendency of lower digestibility as compared with those fed two percent, but the similar results were found between two percent and five percent lecithin fed to the birds. Then, it was tentatively concluded that the effect of the mutton fat on the energy and protein utilization was similar to tallow but resulted different tendency with lecithin.

• 한국균학회지
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• 제26권1호통권84호
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• pp.56-59
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• 1998

목질진흙버섯은 항암활성이 우수한 버섯으로 잘 알려져 있으나 아직까지 자실체 형성 및 발육에 관해 체계화된 연구결과는 보고되지 않고 있으므로 본 연구는 목질진흙버섯균의 인공재배를 위한 기초 자료를 얻고자 수종별 톱밥, 첨가제 및 첨가수준, 배지의 수분함량 등에 따른 균사생장 정도를 비교 분석한 결과이다. 수종별 톱밥에서의 균사생장은 참나무, 뽕나무, 복숭아나무 톱밥에서 양호하였다. 첨가제 및 첨가수준별 균사생장은 쌀겨, 밀기울, 옥수수피를 참나무 톱밥에 $20{\sim}30%$ (V/V) 혼합하였을 때 양호하였다. 참나무 톱밥과 쌀겨를 80:20으로 혼합된 배지의 수분함량은 $60{\sim}70%$에서 균사생장이 양호하였다. 참나무 톱밥과 쌀겨를 80:20으로 혼합하여 polypropylene 850 cc병에 종균 배양기간은 $25^{\circ}C$에서 58일이 소요되었다.

• Preventive Nutrition and Food Science
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• 제8권1호
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• pp.54-60
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• 2003

To develop a functional chungkookjang; the anticancer effects of chungkookjangs prepared with different varieties of soybeans, starters, fermentation periods and seasoning additive ratios; were studied against AGS human gastric adenocarcinoma cells using the MTT assay, at different stages chungkookjang processing. The chungkookjang samples exerted different antiproliferative effects according to the variety of soybeans used. The chungkookjangs manufactured with soybean var. manrikong exhibited the highest cytotoxicity against AGS human cancer cells. The chungkookjangs fermented with rice straw and B. licheniformis strongly inhibited the growth of the AGS human cancer cells. All fermented chungkookjangs had a strong inhibitory effect on the growth of the cancer cells; however, the non-fermented soybean (chungkookjang) showed a low inhibition rate. The fermented chungkookjangs mixed with red pepper powder (RPP) and garlic exhibited strong antiproliferative effect against the cancer cells, and chungkookjang prepaved with 1.1 % RPP and 1.1 % garlic showed the highest cytotoxicity against the cancer cells. The functional chungkookjang fermented with soybean variety of manrikong and B. licheniformis for 3 days at 4$0^{\circ}C$ and then mixed with 7.9% salt, 1.l% RPP and 1.1% garlic, exhibited a higher antiproliferative effect than the chungkookjangs prepared by traditional or modified methods, according to the MTT assay. The functional chungkookjang exhibited a similar anticancer effect to the traditional doenjang. These results indicate that the fermentation period and the ratio of seasoning additives, as well as the variety of soybeans and starter cultures may affect the degree of the anticancer effect of chungkookjang.

• Journal of Microbiology and Biotechnology
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• 제30권9호
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• pp.1404-1411
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• 2020

Lactic acid bacteria (LAB) play an important role in dairy fermentations, notably as cheese starter cultures. During the cheese production and ripening period, various enzymes from milk, rennet, starter cultures, and non-starter LABs are involved in flavor formation pathways, including glycolysis, proteolysis, and lipolysis. Among these three pathways, starter LABs are particularly related to amino acid degradation, presumably as the origins of major flavor compounds. Therefore, we used several enzymes as major criteria for the selection of starter bacteria with flavor-forming ability. Lactococcus lactis subsp. lactis LDTM6802 and Lactococcus lactis subsp. cremoris LDTM6803, isolated from Korean raw milk and cucumber kimchi, were confirmed by using multiplex PCR and characterized as starter bacteria. The combinations of starter bacteria were validated in a miniature Gouda-type cheese model. The flavor compounds of the tested miniature cheeses were analyzed and profiled by using an electronic nose. Compared to commercial industrial cheese starters, selected starter bacteria showed lower pH, and more variety in their flavor profile. These results demonstrated that LDTM6802 and LDTM6803 as starter bacteria have potent starter properties with a characteristic flavor-forming ability in cheese.

• 한국식품과학회지
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• 제34권6호
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• pp.1085-1090
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• 2002

Dextransucrase의 수용체반응(acceptor reaction)을 이용하여 판노스(panose)를 포함한 다양한 당전이화합물을 발효식품에서 생성하기 위하여 고활성 dextransucrase를 저온에서 생성하는 Leuconostoc속 균주를 동치미김치로부터 분리 및 선발하였다. 동치미를 제조하여 $8^{\circ}C$에서 발효시키면서 분리한 Leuconostoc속 균주중에서 균체의 증식유도기간(lag phase), 최대균체량(g/L), 균체의 비성장속도$(\mu)$ 및 dextransucrase 활성을 종합적으로 비교하여 우수균주를 선발하였고, 최종적으로 MIDI를 이용하여 Leuc. mesenteroides로 동정하였다. 본 균주는 김치를 포함한 저온성 발효식품에서 당전이화합물을 생성하여 기능성을 부여하는 스타터로 사용될 수 있을 것으로 판단된다.

• 한국식품영양과학회지
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• 제26권6호
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• pp.1068-1076
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• 1997

This study was carried out to elucidate the utility of fusant for shortening the ripening time of imitation processed cheese. L. bulgaricus exhibited the highest protease and lactase activity and L. helveticus revealed the highest lipase activity. Fusant was shown to be high in the activity of protease and lactase. The total volatile free fatty acid produced by the cheese treated with L. helveticus was markedly increased after four ripening days and was gently increased after nine ripening days. However, L. bulgaricus significantly increased the total volatile free fatty acid between four and nine ripening days. In the case of fusant, the amount of total volatile free fatty acid was observed to increase at a constant rate relative to the ripening time. In free fatty acid production at different ripening times, L. bulfaricus generated caproic acid and caprilic acid abundantly while it produced a poor quantity of capric acid, lauric acid, and myristic acid. In the cheese sample treated with L. helveticus, the amount of caproic acid and capylic acid was on increase as the ripening time increased. The amount of caproic acid and caprylic acid produced by fusant was less than that produced by the other two starters. In the panel sensory evaluation, the flavor intensity and preference increased as the ripening time increased. The cheese sample treated with fusant showed the highest flavor intensity at 7 days, whereas cheese treated with L. helveticus exhibited the highest flavor intensity at 15 or 30 days. The cheese treated with L. helveticus showed the highest preference at 7 days, but cheese treated with fusant exhibited the highest preference at 30 days.

• Journal of Microbiology and Biotechnology
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• 제29권2호
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• pp.209-221
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• 2019

Gamma-aminobutyric acid (GABA) is a neurotransmitter that exerts several physiological functions and positive effects on human health. The aim of this study was to isolate and characterize the strains that had GABA-producing abilities from various fermented fish products. A total of 91 acid-producing strains were isolated from 41 samples of fermented fish products, and 27 strains showing GABA-producing abilities were identified by the 16S rDNA sequences. Among the strains, 31% strains tolerated at high-salt environment of 10-20% throughout the fermentation of fish sauces. The 27 isolates that produced GABA at various concentrations did so in the range of 5 to 454 mM. These GABA-producing isolates were identified as lactic acid bacteria of 14 strains, which included twelve Lactococcus lactis, one Enterococcus faecium, and one Lactococcus pentosus; eight Bacillus cereus group, which included seven B. thuringiensis and one B. cereus; and five Staphylococcus spp. Interestingly, with Vietnamese fish sauces, we mostly identified species of B. thuringiensis and Staphylococcus spp., while with Korean fermented fish products, the majority of the strains identified belonged to L. lactis. Among the strains, B. thuringiensis LH2134 produced the highest levels of GABA at 366 mM among the strains identified from Vietnamese fish sauces, whereas L. lactis LA43, a new strain isolated from Korean jeotgal (salted shrimp paste), produced the highest amount of GABA at 454 mM and the glutamate concentration in the medium was essential for GABA accumulation. Therefore, such the isolates might serve as good starters for development of more GABA-reinforced foods among fermented fish products.

• 한국미생물·생명공학회지
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• 제49권4호
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• pp.501-509
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• 2021

The increasing demand for baked products has given a boost to research on isolation and selection of novel yeast strains with improved leavening activity. Twelve sourdough samples were collected from several localities of the Fez region in Morocco. The pH and total titratable acidity (TTA) values of these samples varied from 3.03-4.63 and 14-17.5 ml of 0.1 N NaOH/10 g of sourdough, respectively, while yeast counts ranged from 5.3 6.77 Log CFU/g. Thirty-two yeast isolates were obtained and evaluated for their leavening ability. Out of all isolates, four yeasts molecularly identified as Saccharomyces cerevisiae (three strains) and Kluyveromyces marxianus (one strain) showed highest specific volumes of 4.69, 4.55, 4.35 and 4.1 cm³/g, respectively. These strains were further assessed for their tolerance to high concentrations of salt, sugar, elevated temperatures, and low pH conditions. K. marxianus showed higher resistance than the S. cerevisiae. Thus, Moroccan sourdoughs harbor technologically relevant yeasts that could be used as potential starters for bread preparation.