• Asian-Australasian Journal of Animal Sciences
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• 제11권4호
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• pp.455-461
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• 1998

This study was proposed to investigate effects of inclusion of Chinese milk vetch silage (MVS) and rapeseed meal (RSM) on the growth and rumen fermentation of Hu-sheep. Fifty weanling lambs were randomly divided into five equal groups and offered ammoniated rice straw (ABRS) ad libitum along with 100 g concentrate (Trial 1). The animals in $T_0$, $T_1$, $T_2$, $T_3$ and $T_4$ group were respectively supplemented with MVS at levels of 0, 0, 7, 14 or 21% and with RSM at levels of 0, 15, 10, 5 or 0%. Daily gain of lambs was significantly (p<0.05) higher in $T_1$, $T_2$ and $T_3$ group than that in $T_0$ and $T_4$ group. Feed conversion ratio was greatly reduced in supplemented groups as compared with $T_0$ group. In trial 2, five sheep with rumen cannulae were used in a $5{\times}5$ Latin square design. The experimental treatments were as described in Trial 1, but without concentrate. The intake of AVRS was significantly (p<0.05) lower in $T_4$ group than that in $T_0$ group, and also significantly (p<0.05) lower than those in $T_1$ and $T_2$ group. Little difference among all treatments was found in 48h DM degradability of ABRS, MVS and RSM, and in rumen pH value and microbial protein concentration. Rumen concentrations of individual and total VFA tended to be higher in supplemented groups than those in $T_0$ group.These rusults suggest that supplementation with RSM or RSM plus MVS can effectively improve the performance of lambs, and may fail to influence markedly the rumen digestion of ABRS and rumen environments.

• The Korean Journal of Ecology
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• 제28권4호
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• pp.181-188
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• 2005

Methods used to study carbon sequestration by soil aggregates have often excluded the concentric spatial variability and other dynamic processes that contribute to resource accessibility and solute transport within aggregates. We investigated the spatial gradients of carbon (C) and nitrogen (N) from the exterior to interior layers within macroaggregates, $6.3\sim9.5$ mm, sampled from conventional tillage (CT) and no tillage (NT) sites of a Hoytville silt clay loam. Spatial gradients in C accumulation within macroaggregates were related to the differences in C dynamics by determining the sizes and the turnover rates of fast C and slow C pools in the concentric layers of aggregates. Aggregate exteriors contained more labile C and were characterized by greater C mineralization rates than their interiors in both management systems. In contrast, C in the interior layers of aggregates was more resistant in both systems. These results indicated the spatial differentiation of C dynamics within macroaggregates, i.e., exterior layers as a reactive site and interior layers as a protective site. Greater total C distribution in the exterior layers of NT aggregates indicated more influx of C from the macropores in interaggregate space than C. mineralization (net gain of C), whereas lower C distribution within the exterior layers of CT aggregates indicated net loss of C by greater C mineralization than C influx. We found total C increased approximately 1.6-fold by the conversion of CT soils to NT management systems for a period of 36 years. Differences in total accumulation and the spatial distribution of C within aggregates affected by management were attributed to the differences in aggregate stability and pore networks controlling the spatial heterogeneities of resource availability and microbial activity within aggregates.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.470-473
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• 2000

Indole은 미생물에 강한 독성을 가지고 있으므로 indole의 생물학적 전환이 어려우므로 단지 소수의 미생물들이 Indole이나 그것의 연관물질들로부터 Indigo와 Indirubin을 생산하는데 응용되어 왔다. 본 연구실에서 분리된 Pseudomonas savastanoi BCNU 106은 toluene에 강한 내성을 가졌으며 P. savastanoi BCNU 106의 Indole 내성 정도는 p-xylene이나 toluene이 배지 부피의 20% 로 첨가되었을 때 160 mg/ml로 매우 높은 내성 정도를 나타내었다. Indole (100 mg/ml) 과 p-xylene (0.2 ml/ml)을 포함한 two-phase culture system에서 자란 P. savastanoi BCNU 106은 indole로부터 푸른색 indigo나 보라색 indirubin의 미생물학적 전환을 보여주었다. indigo와 indirubin의 생산은 P. savastanoi BCNU 106가 적절한 농도의 유기용매가 중층된 two-phase system에서 자랐을 경우에만 형성되었다. 그러므로 본 연구는, 분리된 indole 내성 세균이 유기용매하에서 indirubin과 같은 산업적 가치를 가진 유용물질을 생산하는데 응용될 수 있을 것으로 사료된다.

• 한국식품과학회지
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• 제10권4호
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• pp.380-386
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• 1978

Streptomyces spp. K-14에서 생성되는 포도당 이성화효소의 특성에 대해서 연구하였다. 효소 반응의 최적 pH와 온도는 5 mM $MgSO_4{\cdot}7H_2O$와 2 mM $CoCl_2{\cdot}6H_2O$의 존재 아래에 각각 $7.5{\sim}8.0$ 그리고 $70^{\circ}{\sim}75^{\circ}C$로 나타났다. 이러한 이성화 효소는 $Mg^{++}$과 $Co^{++}$두 양이온에 의하여 활성화 되었는데 $Mg^{++}$는 이성화 반응의 초기 활성화에 소요 되었으며 $Co^{++}$는 효소 단백질을 안정화 하는데 소요 되었다. 포도당 농도 60%까지는 효소 반응속도나 효소의 이성화율에 영향을 끼치지 않았다.

• Toxicological Research
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• 제28권2호
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• pp.103-106
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• 2012

The effect of continuous humidifier use on the bioaerosol concentration in an indoor environment was investigated. An ultrasonic humidifier was operated for 10 hr per day for 15 days in an apartment room. During this time period, viable bioaerosol samples were taken using a single-stage Andersen sampler containing culture media plates for bacteria and fungi. The culture plates were then incubated at room temperature for 2~7 days depending on the media. The counts for the air sample plates were corrected for multiple impactions using the positive hole conversion method and are reported as the colony forming units per cubic meter of air (CFU/$m^3$). While the bacterial concentration measured using the tryptic soy agar (TSA) did not show any significant change during the first 3 days, the concentration increased from the $6^{th}$ day (6979 CFU/$m^3$) and reached a maximum on the $9^{th}$ day (46431 CFU/$m^3$). The concentration then decreased to 2470 CFU/$m^3$ on the $12^{th}$ day, at which point the fungal concentration increased rapidly to 14424~16038 CFU/$m^3$. Also, while the fungal concentration showed a significant change until the $9^{th}$ day of humidifier use, fungal growth was observed on the wallpaper and increased rapidly from the $12^{th}$ day. However, the bacterial concentration increased rapidly after the fungi were removed by remediation. The major fungal species identified in the samples were Penicillium representing 34%, Aspergillus representing 31%, Cladosporium representing 24%, and Alternaria representing 1%. The results also indicated that a relative humidity over 80% was easily achieved with continuous humidifier use. Yet, maintaining a high humidity in a room can cause a rapid outbreak of microbial growth.

• 한국미생물·생명공학회지
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• 제9권1호
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• pp.35-44
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• 1981

대장균이 생산하는 페니실린 아미다제를 젤라틴에 포괄시켜 사출한 후 글루트알데히드로 가교하여 고정화하였다. 이렇게 하여 만들어진 고정화효소는 약 70%의 높은 효소역가를 나타내었고 보관 및 반응조에서 좋은 안정성을 보여주었다. 반응조 내에서의 효소역가 반감기는 약 50일이었으며 최적 PH 및 온도는 각각 8.5와 5$0^{\circ}C$로 나타났다. 효소역가에 미치는 pH 및 온도의 영향은 고정화하기 전과 큰 차이가 없었으나 고온에서의 안정성이 증가되었다. 기질용액으로 완충액을 사용하여 column을 사용하는 관형식 반응조에서의 반응생성률에 기인하는 pH 감소효과를 최소한으로 줄이므로써 효소반응조를 최적화하였다. 반응조 조작상의 중요한 인자 즉 기질농도, 체류시간, 반응 생성물로의 전환율 및 이에 따르는 생산성을 pH 감소효과와 연관시켜 최적반응조건을 논의하였다.

• 유기물자원화
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• 제7권1호
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• pp.67-77
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• 1999

공기유입속도가 $217l{\cdot}m^{-3}{\cdot}min^{-1}$이었을 경우, 고온 호기조를 이용하여 PAC로 응집, 탈수된 조류의 분해 특성을 관찰한 결과 다음과 같이 요약할 수 있다. 10% 폐 식용유의 혼합조건이 본 연구에서 최적 조건으로 온도는 $55^{\circ}C$ 이상을 나타내었고, 수분은 55%를 일정하게 유지하였으며, $CO_2$의 농도는 최고 3.7%, 투입 탄소량의 92%가 $CO_2$-C로 변환하였다. 적정한 폐식용유의 혼합은 미생물의 활동을 활발하게 하였지만 과도한 혼합은 수분 증발로 건조상태로 되었으며 오히려 분해 활성에 저해 영향을 주었다. 처리가 종료된 담체는 고농도의 알루미늄이 축적되어 있으므로 별도의 처리가 요구된다.

• Journal of Microbiology and Biotechnology
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• 제30권8호
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• pp.1244-1251
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• 2020

Phospholipase A₂ (PLA₂) from Streptomyces violaceoruber is a lipolytic enzyme used in a wide range of industrial applications including production of lysolecithins and enzymatic degumming of edible oils. We have therefore investigated expression and secretion of PLA₂ in two workhorse microbes, Pichia pastoris and Escherichia coli. The PLA₂ was produced to an activity of 0.517 ± 0.012 U/ml in the culture broth of the recombinant P. pastoris. On the other hand, recombinant E. coli BL21 star (DE3), overexpressing the authentic PLA₂ (P-PLA₂), showed activity of 17.0 ± 1.3 U/ml in the intracellular fraction and 21.7 ± 0.7 U/ml in the culture broth. The extracellular PLA2 activity obtained with the recombinant E. coli system was 3.2-fold higher than the corresponding value reached in a previous study, which employed recombinant E. coli BL21 (DE3) overexpressing codon-optimized PLA₂. Finally, we observed that the extracellular PLA₂ from the recombinant E. coli P-PLA₂ culture was able to hydrolyze 31.1 g/l of crude soybean lecithin, an industrial substrate, to a conversion yield of approximately 95%. The newly developed E. coli-based PLA₂ expression system led to extracellular production of PLA₂ to a productivity of 678 U/l·h, corresponding to 157-fold higher than that obtained with the P. pastoris-based system. This study will contribute to the extracellular production of a catalytically active PLA₂.

• Asian-Australasian Journal of Animal Sciences
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• 제33권3호
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• pp.373-381
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• 2020

There is a need for newer feed additives due to legal prohibition on inclusion of growth promoting antibiotics in livestock diets in several countries due to antimicrobial resistance. In this context, rare earth elements (REE) have gained attention among animal nutritionists as potential growth promoters. Currently, several studies have reported better weight gain, milk production, egg laying capacity and feed conversion efficiency among different breeds of farm animals following supplementation with REE, with however largely inconsistent results. Furthermore, REE supplementation has also shown to improve ruminal fibrolytic and proteolytic activities as well as flavor of meat with negligible residues in edible tissue, however the mechanism behind this action is still unclear. According to existing research, due to their poor absorption and similarity with calcium REE might exert their action locally on gut microbial populations within the gastrointestinal tract (GIT). Moreover, REE have also shown anti-inflammatory, anti-oxidative as well as immune stimulating effects. The present review aims to broaden the knowledge about use of REE as feed additives for livestock and sum up efficacy of REE supplementation on performance and health of animals by comparing the findings. Till date, researches with REE have shown properties that make them a promising, new and safe alternative feed additive but further exploration is recommended to optimize effects and clarify discrepancy of various results before practical proposals can be drafted.

• Applied Biological Chemistry
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• 제48권1호
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• pp.16-22
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• 2005

키토산분해효소(Chitosanases, EC 3.2.1.132)는 당질가수분해효소군의 하나로, 아미노당인 D-glucosamine polymer인 chitosan의 ${\beta}-1,4-glycoside$ 결합을 가수분해하는 효소이며, 세균, 곰팡이, 식물 등에 널리 분포한다. 본 논문에서는 chitosanase의 N-말단 아미노산의 서열과 입체구조에 근거한 family 및 clan 분류, 작용모형, 절단 유형, subclass 분류, 및 family-subclass 상관성을 검토하였다. 아미노산 서열과 입체구조와 기질의 분해패턴 사이에는 깊은 상관이 있음을 확인 제시하였다. 다양한 종 유래 chitosanase의 1차구조의 해명과 진화적 상관 규명, 나아가 보다 정교한 chitosanase의 정의와 다양한 산업적 응용에의 가능성도 검토하였다.