• Korean Chemical Engineering Research
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• 제55권2호
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• pp.270-274
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• 2017

본 연구에서는 양자 역학 계산 이론 중 하나인 Density Functional Theory (DFT)를 사용하여 $Pd/Pd_3Fe$ 촉매 표면에서 개미산(HCOOH) 분해 반응으로부터 수소를 생산하는 반응 메커니즘을 분석하였다. 기존 연구에 따르면, 단일 원자 촉매 중에서 개미산 분해 반응에 가장 높은 수소 생산성을 기록하는 원자는 Pd 촉매이지만, 부 반응으로 생산되는 CO가 Pd에 독성을 띄우기 때문에 Pd 촉매의 성능을 저하시킨다. 이러한 단점을 극복하고자, Pd를 기반으로 Pd와 Fe를 3:1로 합금하여 $Pd_3Fe$가 코어(core) 형태로 존재하고 Pd가 표면에 위치한 core-shell $Pd/Pd_3Fe$ 촉매를 설계하여 개미산 분해 반응에 의한 수소 생산 속도를 계산하였다. 순수 Pd촉매 보다 $Pd/Pd_3Fe$ 촉매의 수소 생산 반응의 활성 에너지가 감소하였다. 그 이유는 Pd와 Fe가 합금화 되면서 $Pd_3Fe$의 격자 상수가 $2.76{\AA}$로 줄어 들어 HCOO의 흡착에너지를 0.03 eV 감소시켰고, Fe에서 표면 Pd로 전자가 이동하면서 표면 전자 구조가 변화하여 HCOO의 흡착에너지를 0.29 eV 낮추었기 때문이다. 본 연구에서 제안하는 결과를 바탕으로 추후 개미산으로부터 수소 생산이 더 용이한 새로운 촉매 설계 메커니즘을 제안하고자 한다.

• KSBB Journal
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• 제18권2호
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• pp.149-154
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• 2003

수소를 생산하기 위하여 자연계로부터 분리된 균주는 Enterebacter cloacae로 동정되었으며 이 균주를 YJ-1으로 명명하였다. 수소발생량을 기준하여 이 균주의 최적 성장조건을 살펴본 바, 회분식 배양에서 $35^{\circ}C$, pH 7.5로 나타났다. 따라서 탄소원의 농도를 변화시킨 결과, 최대의 수소생산은 2% glucose, 4% sucrose, 5% fructose에서 각각 950 mL/L, 1000 mL/L, 948 mL/L을 얻어졌으며, 초기에 비해 2.5배 높은 생산량을 얻을 수 있었다. 유기산 축척에 따른 pH 저하를 막기 위해 완충제인 phosphate를 첨가한 결과, 50 mM에서 가장 높은 수소를 생산할 수 있었다. 반회분식 배양으로 50%의 새로운 배지를 8 hr 간격으로 치환하여 48시간동안 수행한 결과 1920 mL/L의 수소를 생산할 수 있었다. Yeast extract는 균체성장에 중요한 성분으로서 0.5%에서 최대의 수소를 생산할 수 있었다. 발효 중 생성된 유기산은 대부분 formic acid, acetic acid이고 적은 양의 propionic acid가 생성되었다.

• Animal Bioscience
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• 제34권6호
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• pp.1038-1048
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• 2021

Objective: The study aimed to evaluate the effect of storage time and formic acid (FA) on fermentation characteristics, epiphytic microflora, carbohydrate components and in vitro digestibility of rice straw silage. Methods: Fresh rice straw was ensiled with four levels of FA (0%, 0.2%, 0.4%, and 0.6% of fresh weight) for 3, 6, 9, 15, 30, and 60 d. At each time point, the silos were opened and sampled for chemical and microbial analyses. Meanwhile, the fresh and 60-d ensiled rice straw were further subjected to in vitro analyses. Results: The results showed that 0.2% and 0.6% FA both produced well-preserved silages with low pH value and undetected butyric acid, whereas it was converse for 0.4% FA. The populations of enterobacteria, yeasts, moulds and aerobic bacteria were suppressed by 0.2% and 0.6% FA, resulting in lower dry matter loss, ammonia nitrogen and ethanol content (p<0.05). The increase of FA linearly (p<0.001) decreased neutral detergent fibre and hemicellulose, linearly (p<0.001) increased residual water soluble carbohydrate, glucose, fructose and xylose. The in vitro gas production of rice straw was decreased by ensilage but the initial gas production rate was increased, and further improved by FA application (p<0.05). No obvious difference of FA application on in vitro digestibility of dry matter, neutral detergent fibre, and acid detergent fibre was observed (p>0.05). Conclusion: The 0.2% FA application level promoted lactic acid fermentation while 0.6% FA restricted all microbial fermentation of rice straw silages. Rice straw ensiled with 0.2% FA or 0.6% FA improved its nutrient preservation without affecting digestion, with the 0.6% FA level best.

• Asian-Australasian Journal of Animal Sciences
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• 제24권1호
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• pp.96-102
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• 2011

In this study, we examined the effects of formic acid administration to the drinking water on performance, intestinal microflora and carcass contamination in male broilers. A total of 312 day-old male broiler chicks were allocated to two groups with three replicates. The first group (control) received normal drinking water (pH 7.4) during the experiment. The second group consumed acidified drinking water (pH 4.5) after 5 d of age. At 43 d of age, twelve birds were randomly selected from the control group to determine the effect of acidified drinking water on carcass contamination. These birds were only given normal or acidified (pH 3) drinking water for 8 h prior to slaughter. The reduction of water pH from 7.4 to 4.5 significantly decreased body weights of male broilers at 21 and 42 d of age. However, no differences were observed between male broilers given normal and acidified drinking water in terms of feed intake, feed conversion ratio and mortality. The pH value of the gizzard contents was not significantly affected by acid water treatment. There were no significant differences in the intestinal population of E. coli, total organism and Salmonella between the groups. The total organism and E. coli counts of the carcass slightly decreased in the acidified group. No Salmonella was identified in carcass samples of any of the treatment groups. The results showed that drinking water acidification did not provide beneficial effects on performance, intestinal microflora and carcass contamination in male broilers.

• Journal of Microbiology and Biotechnology
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• 제3권4호
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• pp.266-269
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• 1993

The production of free non-volatile and volatile organic acids in Kimchi during fermentations at 30, 20 and $5^{\circ}C$, were determined by gas chromatography. The order in the amount of non-volatile organic acid, soon after preparation, was malic, citric, tartaric, pyroglutamic, oxalic, lactic, succinic and ${\alpha}-ketoglutaric$ acids. The major non-volatile acids at the optimum ripening time were malic, tartaric, citric and lactic acids, and as the temperature was lowered, the amount of lactic, succinic, oxalic, pyroglutamic and fumaric acids increased, while that of malic and tartaric acids decreased. The order in the amount of volatile acids at the beginning was acetic, butyric, propionic and formic acids. Among these acids, acetic acid was significantly increased in its amount during fermentation and the Kimchi fermented at low temperature produced more acetic acid than that fermented at high temperature.

• Asian-Australasian Journal of Animal Sciences
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• 제16권11호
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• pp.1583-1591
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• 2003

The influence of varying levels of urea and additives on nitrogen (N) retention and chemical composition of wheat straw was studied. The wheat straw was treated with 4, 6 and 8% urea and ensiled with 1.5, 2 and 2.5% of acetic or formic acid and 2, 4 and 6% of corn steep liquor (CSL) or acidified molasses for 15 days. The N content of wheat straw was significantly different across all treatments. The N content of urea treated wheat straw was increased with the increasing level of urea. The N content was higher in urea treated wheat straw ensiled with acetic or formic acid as compared to urea treated wheat straw ensiled without these organic acids. The N content of urea treated wheat straw was further enhanced when it was ensiled with CSL or acidified molasses. This effect was significant across all levels of urea used to treat the wheat straw. Nitrogen retention in urea treated wheat straw was decreased linearly as the urea level was increased to treat the wheat straw. The N content was increased linearly when higher levels of CSL or acidified molasses were used to ensile the urea treated wheat straw. Most of the N in urea treated wheat straw was held as neutral detergent insoluble N (NDIN). The NDIN content was increased linearly with the increasing levels of urea and additives. The neutral detergent fiber (NDF) contents were higher in urea treated wheat straw ensiled with acetic or formic acid as compared to urea treated wheat straw ensiled without additive. The NDF content further increased in urea treated wheat straw ensiled with CSL and acidified molasses. The entire increase in NDF content was because of fiber bound N. The hemicellulose content of urea treated wheat straw ensiled with CSL or acidified molasses was higher as compared to urea treated wheat straw ensiled with acetic or formic acid. The acid detergent fiber content of urea treated wheat straw ensiled with or without additives remained statistically non-significant. The cellulose contents of wheat straw was linearly reduced when urea level was increased from 4 to 6 and 8% to treat the wheat straw. This effect was further enhanced when urea treated wheat straw was ensiled with different additives. The results of the present study indicated that fermentable carbohydrates might improve the Nitrogen retention and bring the favorable changes in physiochemical nature of wheat straw. However, biological evaluation of urea treated wheat straw ensiled with fermentable carbohydrates is required.

• Applied Biological Chemistry
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• 제34권4호
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• pp.386-392
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• 1991

Propene으로부터 propylene oxide를 생산하기 위하여, methane 자화성 세균인 Methylosinus trichosporium OB3b를 이용하였다. 이 균주는 methane을 methanol로 전환시키는 methane monooxygenase를 가지고 있는데, 이 효소는 또한 propene을 propylene oxide로 전환시킬 수 있다. 이 균주의 휴지세포를 이용하여 propene으로부터 propylene oxide 생산의 최적조건을 검토하였다. 최적 pH는 7.0이었으며, 최적온도는 $35^{\circ}C$이었다. 최종산물인 propylene oxide는 propylene oxide의 생산반응을 저해하지 않았으며, 더 이상 대사되지도 않았다. Methane 대사중간물질들(methanol, formaldehyde, formic acid)의 첨가는 propylene oxide의 생산을 $3{\sim}4$배 증가시켰으며, 특히 methanol 첨가의 경우에 가장 좋은 효과를 보였다. 상기의 최적조건하에서, 1시간 반응시 propylene oxide의 최대 생산량은 14.2 mM이었으며, 이 때 공급한 propene으로부터 propylene oxide로의 전환율은 약 8.0%이었다.

• KSBB Journal
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• 제30권4호
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• pp.191-196
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• 2015

Blueberry juice possesses rich-procyanidins and - anthocyanidin, comprised a group of with numerous health benefits such as protection against coronary heart disease, detoxification, and obesity. Blueberry (Vaccinium virgatum) juice extracts were analyzed and separated by an HPLC method for the purpose of the separation and quantification in polyphenolic groups. In specific HPLC conditions, a binary mobile phase consisting of formic acid: water (10:90, v/v, solvent A) and formic acid: water: acetonitrile (10:60:30, v/v/v, solvent B) was utilized and it is detected at 546 nm wavelength. The phenolic contents of the extracts are determined using Folin-Ciocalteu phenol reagent. In order to test anti-inflammation activity assay, after producing nitric oxide (NO) in lipopolysaccharide activated RAW 264.7 cells, at concentration of $20-500{\mu}g/mL$ it reduced to NO production at a dose-dependent manner. Importantly, cytotoxicity assay with up to $500{\mu}g/mL$ of the extract from blueberry juice showed ~100% cell viability for RAW264.7 cell line. Therefore, Korean blueberry juice might have potential as anti-oxidant and antiinflammation agents.

• Asian-Australasian Journal of Animal Sciences
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• 제16권1호
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• pp.77-82
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• 2003

This investigation was conducted to study the effect of dietary formic acid (FA) and propionic acid (PA) mixture on inhibitory effect of Salmonella pullorum in layer chicks. Nine groups of one day-old layer chicks in addition to positive and negative controls, were fed with acids treated feed containing mixture of different acids concentrations, from 0.5% and 0.5% up to 1.5% and 1.5% FA and PA, respectively. Positive and negative controls were fed untreated feed. Groups except the negative control were challenged orally on day three with $10^4$ cfu/ml S. pullorum. Cloacal swabs were taken at three successive days and at 7, 14 and 21 days of challenge. After 1, 2 and 3 weeks after challenge, 4 chicks from each group were sacrificed and crop and cecal contents were examined for S. pullorum and pH. The numbers of S. pullorum positive culture from the excretion of all treated groups except groups treated with mixture of 0.5% and 0.5%, 1% and 0.5%, 0.5% and 1% FA and PA decreased significantly (p<0.05) as compared with the positive control. The mortality rates of all treated groups except the group treated with 0.5% FA and 0.5% PA were decreased significantly (p<0.05) as compared with the positive control. The treatment significantly (p<0.05) lowered the pH of the crop and cecal contents in all groups except the group treated with 0.5% FA and 0.5% PA as compared with the control. Also, the treatment significantly (p<0.05) lowered the pH of the crop and cecal contents in all groups after three weeks of treatment compared to the first and second weeks. The treatments significantly (p<0.05) lowered the frequency of S. pullorum recovery from crop and cecal contents in six groups treated with 1.5 and 0.5, 1 and 1, 1.5 and 1, 0.5 and 1.5, 1 and 1.5, 1.5% and 1.5% FA and PA respectively. These results indicate that addition of FA and PA mixture in a total concentration of 2 % or more to the diet of newly hatched infected layer chicks significantly decreases the crop and cecal colonization by S. pullorum and significantly decreases S. pullorum fecal excretion and reduced the chick mortality rate.

• 한국미생물·생명공학회지
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• 제26권2호
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• pp.89-95
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• 1998

R. sphaereides K7 및 E15-1은 혐기적 광합성조건에서 glucose를 탄소원으로 하여 배양초기 24시간 동안은 수소가스를 계속 생산하였으나, 그 이후에는 배양액에 축적된 acetic acid및 formic acid가 배양액의 pH를 4.2-4.8로 저하시켜 수소를 거의 생산하지 못하였다. 또한 배양 6일 후에도 R. sphaeroides K7 및 E15-1의 glucose의 이용율은 각각 43% 및 74%에 불과하였다. 그러나 배양액의 pH를 6.8-7.0으로 유지하면서 배양한 결과 R. sphaeroides K7및 E15-1 두 균주 모두의 수소생산율과 glucose의 이용율이 증가되어, 수소생산은 배양 10일까지도 계속 증가되었으며, glucose도 두 균주 각각 배양후 2.5일 및 4.5일 후에 완전 소비하였다. 뿐만 아니라 균체 배양액의 pH를 중성으로 유지하면서 R. sphaeroides K7 및 E15-1을 배양할 경우 균체의 표백현상이 제거되어 배양 7일 후에는 각각 균체의 bacteriochlorophyll 함량이 약 44배 및 9배 증가되었으며, 이때 균체의 농도는 각각 약 10배 및 2.4배 증가되었다. R. sphaeroides K7 및 E15-1은 혐기적 광합성조건에서 acetic, lactic, butyric 및 malic acid로 부터도, 비록 그 양이 glucose로 부터보다는 적으나, 수소를 생산하였다. 본 실험 결과로 미루어 혐기적 광합성 조건에서 R. sphaeroides K7 및 E15-1은 glucose로부터 수소를 생성할 때 NADH 산화 및 hydrogenase가 관여한 대사가 우선적으로 일어나고, 2차적으로는 이때 생성된 유기산을 전자 공여체로 광합성 작용에 의해 질소원이 존재하지 않을 때 nirogenase에 의해서 양성자(H$^{+}$)가 환원되어 수소(H$_2$)가 생성되는 것으로 생각된다.