• 한국미생물·생명공학회지
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• 제18권4호
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• pp.394-400
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• 1990

유전자 조작된 세포 발효공정의 생산수율을 최대화하기 위하여 세포의 성장속도와 제품 생성속도간의 상반관계를 고려하여야 한다. 유전자 조작된 E.coli 발효에 있어, 최적화 이론을 적용하여 두 속도의 가중치를 결정함으로써 생산수율의 최대화를 꾀하였다. 성장저해제의 농도는 비 성장속도를 조절하고 결국 융합된 유전자의 발현 속도를 조절하는 변수로 사용되다. 이런 system의 특성을 위하여 간단한 unstructured model를 사용하였다.

• 신재생에너지
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• 제7권3호
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• pp.6-16
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• 2011

In order to study the utilization of seaweeds as an alternative renewable feedstock for bioethanol production, their properties of hydrolysis and fermentation were investigated. The seaweeds were well hydrolyzed with diluted sulfuric acid. The weight loss of seaweeds reached 75-90%, but only 12-51% of them was converted into reducing sugars after the acid-hydrolysis at $130^{\circ}C$ for 4-6h. The yield of reducing sugars increased with increasing the hydrolysis time up to 4h and then decreased thereafter. In contrast, the ethanol yield from the hydrolysates increased with hydrolysis time except for green seaweeds maximizing at 4h. Optimal fermentation time by Saccharomyces cerevisiae (ATCC 24858) varied with seaweeds; 48h for green seaweeds, 96h for brown and red seaweeds. The ethanol yield from the hydrolysate reached 138${\pm}$37mg/g-dry for green seaweeds, 258${\pm}$29mg/g-dry for brown seaweeds, and 343${\pm}$53mg/g-dry for red seaweeds, which correspond to approximately 1.5-4.0 times more than the theoretical yield from total reducing sugars in the hydrolysates. The results obtained indicate clearly that the non-reducing sugars or oligosaccharides dissolved in the hydrolysate played an important role in producing bioethanol. Considering the productivity and production cost of each seaweed, brown seaweeds such as Laminaria japonica and Undaria pinnatifida seem to be a promissing feedstock for bioethanol production.

• 한국식품과학회지
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• 제30권3호
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• pp.644-649
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• 1998

저온에서 제조한 김치의 저장온도에 따른 발효특성과 내부온도의 변화를 보기 위해 $12{\pm}1^{\circ}C$에서 김치를 제조하여 $17{\pm}1^{\circ}C$와 $4{\pm}1^{\circ}C$ 저장고에 저장하면서 이들의 경시적인 변화를 시험한 결과 $17{\pm}1^{\circ}C$ 저장처리구에서 4일째의 품질이 $4{\pm}1^{\circ}C$ 저장처리구에서는 48일만에 같은 수치를 보였으며 총균수와 젖산균수의 변화는 $17{\pm}1^{\circ}C$ 저장구에서 2일째 $1.5{\times}10^9\;cells/mL$과 $6.3{\times}10^8\;cells/mL$로 최대를, $4{\pm}1^{\circ}C$에서는 저장 9일째 $2.0{\times}10^8\;cells/mL$과 $8.7{\times}10^7\;cells/mL$로 최대를 나타내었다. 김치의 용존 $CO_2$ 함량은 두 처리구 모두에서 9일째 $2,200{\sim}2,400\;ppm$ 정도의 최고치를 보인 후 감소하다가 다시 약간 증가하는 것을 관찰하였다. 내부온도는 초기 $17^{\circ}C$ 및 $4^{\circ}C$에 도달하기 위해 각기 25, 35시간이 소요되었다. 외국인, 특히 일본인들이 우리나라의 전통적 김치에 대한 관능적 기호도를 조사하기 위해 김치를 3가지 염농도별로 제조하여 pH가 $3.9{\sim}4.3$ 되었을 때 약 100 g을 $4{\pm}1^{\circ}C$에서 관능요원에게 제공하고 외관, 조직감, 탄산미, 짠맛, 신맛, 매운맛 및 종합적 기호도를 7점 평점제로하여 평가하게 하였으며 그 결과를 SAS통계프로그램으로 처리하여 유의성을 검사하였다. 염농도가 2.03%인 김치가 1.07%, 2.63%의 김치보다 높은 평가치를 나타내었으며 외관, 조직감, 탄산미, 짠맛 및 신맛은 유의성이 없었으나 매운맛과 종합적 기호도는 P=0.05 수준에서 유의차가 있었다. 일본인의 우리나라 전통적인 김치에 대한 종합적인 기호도는 염농도 2.03%, 2.63%, 1.07%의 김치 순으로 아주 싱거운 김치는 선호하지 않음을 알 수 있었다.

• 한국미생물·생명공학회지
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• 제19권4호
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• pp.390-397
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• 1991

효모를 Ca-alginate에 고정화하여 회분발효에서 glucose로부터 에탄올을 생산하여 다음의 결과를 얻었다. 100g wet weight/l($4.3 \times 10^9$ cell/l)의 효모를 pH 7.0, 2% 농도의 Ca-alginate에 고정화하였다. 10 beads volume이 에탄올 생산에 최적이었고 30일 (720 시간) 동안 bead의 수명이 지속되었다. 회분식 발효에서 온도안정성은 고정화 효모의 경우 30~$40^{\circ}C$였으며 free cell의 경우 30~$37^{\circ}C$였다. pH 안정성은 pH 4.0~9.0였으며, 에탄올생산 최적 당농도는 15%였다. 최적조건에서 에탄올수율은 0.45, 생산된 에탄올 농도는 67.6g/l 그리고 에탄올 생산성은 1.99g/l.h로 각각 나타났다.

• Journal of Microbiology and Biotechnology
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• 제23권4호
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• pp.489-498
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• 2013

A new Bacillus strain degrading starch, named Bacillus sp. UEB-S, was isolated from a southern Tunisian area. Amylase production using solid-state fermentation on millet, an inexpensive and available agro-resource, was investigated. Response surface methodology was applied to establish the relationship between enzyme production and four variables: inoculum size, moisture-to-millet ratio, temperature, and fermentation duration. The maximum enzyme activity recovered was 680 U/g of dry substrate when using $1.38{\times}10^9$ CFU/g as inoculation level, 5.6:1 (ml/g) as moisture ratio (86%), for 4 days of cultivation at $37^{\circ}C$, which was in perfect agreement with the predicted model value. Amylase was purified by Q-Sepharose anion-exchange and Sephacryl S-200 gel filtration chromatography with a 14-fold increase in specific activity. Its molecular mass was estimated at 130 kDa. The enzyme showed maximal activity at pH 5 and $70^{\circ}C$, and efficiently hydrolyzed starch to yield glucose and maltose as end products. The enzyme proved its efficiency for digesting raw cereal below gelatinization temperature and, hence, its potentiality to be used in industrial processes.

• Asian-Australasian Journal of Animal Sciences
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• 제25권9호
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• pp.1248-1254
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• 2012

The effect of silage additives on ensiling characteristics and nutritive value of Napier grass (Pennisetum purpureum) silages was studied. Napier grass silages were made with no additive, fermented juice of epiphytic lactic acid bacteria (FJLB), molasses or cassava meal. The ensiling characteristics were determined by ensiling Napier grass silages in airtight plastic pouches for 2, 4, 7, 14, 21 and 45 d. The effect of Napier grass silages treated with these additives on voluntary feed intake, digestibility, rumen fermentation and microbial rumen fermentation was determined in 4 fistulated cows using $4{\times}4$ Latin square design. The pH value of the treated silages rapidly decreased, and reached to the lowest value within 7 d of the start of fermentation, as compared to the control. Lactic acid content of silages treated with FJLB was stable at 14 d of fermentation and constant until 45 d of ensiling. At 45 d of ensiling, neutral detergent fiber (NDF) and acid detergent fiber (ADF) of silage treated with cassava meal were significantly lower (p<0.05) than the others. In the feeding trial, the intake of silage increased (p<0.05) in the cow fed with the treated silage. Among the treatments, dry matter intake was the lowest in the silage treated with cassava meal. The organic matter, crude protein and NDF digestibility of the silage treated with molasses was higher than the silage without additive and the silage treated with FJLB. The rumen parameters: ruminal pH, ammonia-nitrogen ($NH_3$-N), volatile fatty acid (VFA), blood urea nitrogen (BUN) and bacterial populations were not significantly different among the treatments. In conclusion, these studies confirmed that the applying of molasses improved fermentative quality, feed intake and digestibility of Napier grass.

• Food Science and Biotechnology
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• 제15권4호
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• pp.643-646
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• 2006

Cheonggukjang, a popular Korean traditional fermented soyfood, was manufactured by fermenting steamed soybeans in a temperature-controlled room by traditional methods in which steamed soy was exposed to rice straw naturally rich in Bacillus species. B. subtilus and B. licheniformis were found to be the major microorganisms present in cheonggukjang made by the traditional method. We analyzed the composition of 12 kinds of isoflavones and their glycosides present in cheonggukjang collected at various fermentation times. Total isoflavone content in raw soybeans was 2,867 mg/kg and this decreased by about 50% during cooking prior to cheonggukjang preparation. However, total isoflavone content changed slightly during 45 hr of fermentation. Total content of isoflavone glycosides, consisting mainly of daidzin, glycitein, and genistin, decreased by about 40% during 45 hr of fermenting cooked soybeans. The contents of tree isoflavones including daidzein, glycitein, and genistein showed a dramatic increase during fermentation in cheonggukjang preparation, with a 2.9-, 54.0-, and 20.6-fold increase in concentration, respectively, by the end of fermentation (45 hr). In conclusion, short-term fermentation of cooked soybeans with Bacillus species caused conspicuous changes in the composition of isoflavone derivatives, and its implication in terms of health benefits deserves further study.

• Food Science and Biotechnology
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• 제16권6호
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• pp.994-998
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• 2007

Changes in microflora, pH, reducing sugar content, lactic acid content, and ethanol content during Korean rice wine fermentation were investigated. Typical quality characteristics of Korean rice wine fermentation including pH, reducing sugar content, lactic acid content, and ethanol content were evaluated. While a fungus was not detected in our Korean rice wine mash, yeast was found to be present at fairly high quantities (1.44-4.76\;{$\times}\;10^8\;CFU/mL$) throughout the fermentation period. It is assumed that lactic acid bacteria (LAB) had effects on the variations of fragrance and flavor for traditional Korean rice wine. The main LAB during the Korean rice wine fermentation was determined and identified as a Gram-positive, straight rod-shaped cell. Genotypic identification of the isolated strain by amplification of its 16S rRNA sequence revealed that the isolated strain was most closely related to Lactobacillus plantarum (99%) strains without any other comparable Lactobacillus strains. Therefore, we designated the major LAB identified from traditional Korean rice wine fermentation as L. plantarum RW.

• 한국식품영양과학회지
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• 제29권1호
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• pp.68-75
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• 2000

Optimum processing conditions for vinegar fermentation using fig, pear and persimmon were determined. Alcohol contents in the fermentatio broth of crushed fruits of fig, pear and persimmon were 7.5%, 5.1% and 6.8%, respectively. Alcohol contents increased up to 14.3~15.1% by adding 24% of sugar to the fruit juices. The total acidity of 7.04%, 3.30% and 3.66% were obtained for fig, pear and persimmon, respectively, through acetic acid fermentation of fruit juices containing 8% ethanol. Acetic acid yield increased by shaking during fermentation for pear and persimmon broth. Acetic acid yield increased 1.80~1.92 times by adding 0.5% of yeast extract to the fermentation broth of pear and persimmon. After fermentation, each fruit vinegar was clarified up to 93.1~97.4 of light transmittance by using 0.6% of kaki shibu for 4 days at 1$0^{\circ}C$. After aging for 60 days at 1$0^{\circ}C$, the acidity of fruit vinegar decreased slightly. Tannin content of persimmon vineger was remarkably higher than the other, while light absorbance of pear vinegar was higher than the other vinegars. Acetic acid was identified as the main volatile organic acid in the fruit vinegars, while propionic, isobutyric and isovaleric acids were identified as the minors. The content of non-volatile organic acids in the pear vinegar was higher than that in the persimmon vinegar. Sensory evaluation results indicate that the fig vinegar was preferred to the pear vinegar in the aspects of color, flavor and overall acceptability, but the fig vinegar had a strong background taste. Sensory scores of the persimmon vinegar increased significantly by pasteurization, but those of the fig and pear vinegars did not by pasteurization.

• 한국축산식품학회지
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• 제36권6호
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• pp.787-790
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• 2016

Kefir is a unique fermented dairy product produced by a mixture of lactic acid bacteria, acetic acid bacteria, and yeast. Here, we compared the antimicrobial spectra of four types of kefirs (A, L, M, and S) fermented for 24, 36, 48, or 72 h against eight food-borne pathogens. Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, and Cronobacter sakazakii were used as test strains, and antibacterial activity was investigated by the spot on lawn method. The spectra, potencies, and onsets of activity varied according to the type of kefir and the fermentation time. The broadest and strongest antimicrobial spectrum was obtained after at least 36-48 h of fermentation for all kefirs, although the traditional fermentation method of kefir is for 18-24 h at $25^{\circ}C$. For kefir A, B. cereus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited, while B. cereus, S. aureus, E. coli, S. Enteritidis, P. aeruginosa, and C. sakazakii were inhibited to different extents by kefirs L, M, and S. Remarkably, S. aureus, S. Enteritidis, and C. sakazakii were only inhibited by kefirs L, M, and S, and L. monocytogenes by kefir M after fermentation for specific times, suggesting that the antimicrobial activity is attributable not only to a low pH but also to antimicrobial substances secreted during the fermentation.