• Journal of Microbiology and Biotechnology
• /
• 제27권1호
• /
• pp.112-121
• /
• 2017

Edwardsiella tarda is a gram-negative pathogenic bacterium in aquaculture that can cause hemorrhagic septicemia in fish. Many secreted proteins have already been identified as virulent factors of E. tarda. Moreover, since virulent phenotypes are based on the expression regulation of virulent genes, understanding the expression profile of virulent genes is important. A quantitative RT-PCR is one of the preferred methods for determining different gene expressions. However, this requires the selection of a stable reference gene in E. tarda, which has not yet been systematically studied. Accordingly, this study evaluated nine candidate reference genes (recA, uup, rpoB, rho, topA, gyrA, groEL, rpoD, and 16S rRNA) using the Excel-based programs BestKeeper, GeNorm, and NormFinder under different culture conditions. The results showed that 16S rRNA was more stable than the other genes at different culture growth phases. However, at the same culture time, topA was identified as the reference gene under the conditions of different strains, different culture media, and infection, whereas gyrA was identified under the condition of different temperatures. Thus, in experiments, the expression of gapA and fbaA in E. tarda was analyzed by RT-qPCR using 16S rRNA, recA, and uup as the reference genes. The results showed that 16S rRNA was the most suitable reference gene in this analysis, and that using unsuitable reference genes resulted in inaccurate results.

• Asian-Australasian Journal of Animal Sciences
• /
• 제11권1호
• /
• pp.71-77
• /
• 1998

The experiment was conducted to evaluate Bio-V-Pro as an alternative protein source in broiler diets. Treatments were control, Bio-V-Pro 1% (BP 1), Bio-V-Pro 3% (BP 3), and Bio-V-Pro 5% (BP 5). During the starter period, all treated groups showed beter performance than control group in weight gain and feed intake (p < 0.05). The best FCR was observed in BP 1 group and the worst was found in BP 5 group. For the overall period, chicks fed BP 1 and BP 3 diets gained more than the chicks fed the control and BP 5 diets. All Bio-V-Pro fed groups consumed more feed than the control group (p < 0.05). FCR were similar between the control and BP 1 group, but BP 3 and BP 5 groups showed higher FCR than the control group. During the starter period, all BP groups showed better utilizability of crude protein, crude ash and phosphorus than the control group (p < 0.05). For the finisher period, except for the BP 5 group, the nutrient utilizability was not significantly different in most nutrients. Nutrients utilizability had a tendency (not significant) to decrease as the level of Bio-V-Pro in the diet was increased. Lysine utilizability was not affected by the dietary treatment, however, methionine utilizability was higher in BP 1 and BP 3 group than in the control group. From the results of this experiment, it seems that Bio-V-Pro is a good alternative protein source which can replace fish meal in starter diet up to 3% of the diet effectively.

• 한국수산과학회지
• /
• 제30권1호
• /
• pp.79-87
• /
• 1997

A study on the processing method of anchovy hydrolysate paste (AHP) was carried out to improve the sensory quality of salted and fermented fish. Homogenized whole anchovy was hydrolyzed using commercial pretenses, Complex enzyme-2000 (CE, Pacific Chem. Co.) and Alcalase (AL, Novo), in a cylindrical vessel with 4 baffle plates and 6-bladed turbine impeller. Optimal pH, temperature, and enzyme concentration for the hydrolysis with CE and AL were $7.0,\;52^{\circ}C,\;7\%$, and $8.0,\;60^{\circ}C,\;6\%$, respectively. The rational amount of water for homogenization, agitation speed, and hydrolyzing time were $100\%\;(w/w)$, 100 rpm, and 210 min, respectively. To make the hydrolysate to paste type, it was effective to mix the additives, such as starch, soybean protein, agar, and carrageenan gum to the hydrolysate 5 min before the end of boiling at $100^{\circ}C$ for 30 min. Minimal NaCl concentration for long-term preservation was $15\%$, and this could be reduced to $12\%$ by adding $5\%$ of KCl. yield of the AHP based on the total nitrogen content was $94.6\~97.0\%,\;and\;86.0\~89.2\%$, of the nitrogen was amino nitrogen. Salinity, pH and histamine content of the AHP prepared with $12\%$ NaCl and $5\%$ KCl were $9.3\~9.9\%,\;6.1\~6.2$, and below 13 mg/100 g, respectively. The AHP was stable at $26{\pm}3^{\circ}C$ for 60 days on bacterial growth, and addition of $0.05\%$ of rosemary (Herbalox) extract was effective to inhibit the lipid oxidation of the AHP during storage.

• 한국수산과학회지
• /
• 제46권4호
• /
• pp.445-453
• /
• 2013

Walleye pollock Theragra chalcogramma fisheries in Korean waters have changed dramatically during the last three decades: the highest catches occurred in 1981, followed by continuous decreases through the 1990s, ending with a complete collapse of the population in the 2000s. The major spawning ground of walleye pollock is located in North Korean waters, and some juveniles (called nogari in Korean, <300 mm) migrate to the south for feeding and growth. Since the 1960s, Korean fishermen have often caught juveniles, and the weight (metric tons) of juvenile catch was recorded from 1975-1997. However, because the walleye pollock were not aged, the population age structure was not delineated. We developed a model to estimate the number of walleye pollock of each size class based on catch statistics of adults and juveniles, the catch proportion of each size class, and length and weight information on specimens collected by Danish-seine and drift-gill-net fisheries. The model results demonstrated that the recruitment size of walleye pollock was consistently within the 200-250mm size class, and the highest number of this size class occurred in 1981, although values greatly fluctuated interannually. The number of juvenile pollock was 10.4 times higher than that of adult pollock during 1975-1997. The total yield of juvenile pollock was 0.95 million tons, which was equivalent to about 68.2% of total pollock production. The number of juvenile pollock caught during the same period, however, was 16 billion, comprising about 91.2% of the total number caught. Such high fishing pressure on juvenile pollock is considered one of the main factors causing the collapse of the pollock population.

• 한국미생물·생명공학회지
• /
• 제30권4호
• /
• pp.415-419
• /
• 2002

본 연구는 배추김치 제조시 김치의 단백질원인 젓갈 대신 치즈를 첨가하였을 때 김치의 발효적, 이화학적 및 관능적 품질 특성을 조사하였다. 젓갈이 첨가된 대조구와 치즈가 첨가된 김치 모두 담근 후 2일까지 빠른 속도로 미생물이 증식되었으나, 담근 후 3일부터는 치즈 첨가 김치가 대조군 김치에 비하여 높은 생균수를 보였으며, 치즈 첨가량이 많을수록 더욱 더 높았다 pH는 대조구와 치즈 첨가 김치 모두 담근 후 하루동안 일시적으로 약간 상승하다가 2일째부터 급격히 저하되어 3일째에는 pH4.33-4.18로 가장 맛있다고 일반적으로 평가되는 김치의 pH 범위를 보였으며, 치즈 첨가량이 많을수록 pH가 다소 낮은 경향이었다. 발효속도는 대체로 치즈 첨가량이 많을수록 빨랐으며 특히 발효 3일 이후에는 7% 치즈 첨가군이 발효속도가 가장 빨랐다. 일반성분을 분석한 결과 치즈를 첨가한 시험구에서는 수분이 대조구보다 다소 낮게 나타났고 조단백질과 조지방이 다소 높은 경향을 보였다. 담근 후 3일 된 김치의 관능검사를 실시한 결과 젓갈을 넣은 대조구 김치보다 치즈를 3%, 5% 첨가한 김치가 외관, 향미, 질감, 맛 등 관능에서 대체적으로 좋은 점수를 받았다

• 한국물환경학회지
• /
• 제23권5호
• /
• pp.676-682
• /
• 2007

The bacterial number, extracellular enzyme activities and structure of bacterial community which are major constituent of aquatic ecosystem within the artificial vegetation island (AVI) were compared to those of the nearby pelagic lake waters in order to evaluate the possibility of the AVI as a eco-technological measure for water quality improvement and restoration of littoral zone in man-made reservoirs. There was not a significant difference in the total number of bacteria, but the number of active (viable) bacteria within the AVI was about 0.7 to 4.1 times higher than nearby pelagic lake water. The ratio of the number of active bacteria versus the total number of bacteria was also higher in the AVI than nearby pelagic lake water. The activities of ${\beta}$-glucosidase and phosphatase were 1.0 to 13.1 and 0.8 to 7.3 times higher respectively in the AVI than nearby pelagic lake water, showing that microorganisms were more active within the AVI. The bacterial communities of the two waters, examined by FISH method, did not indicate a clear difference in the springtime when the growth of macrophytes was immature, but during summer and fall it showed a clear difference indicating the formation of distinct bacterial community within the AVI compared to nearby lake water. From the results of this study, we conclude that AVI can contribute to make up the littoral ecosystem which show rapid cycling of matters through active detritus food chain in the dam reservoirs which have unstable aquatic ecosystem due to short hydraulic residence time and to strengthen the self-purification capacity of the lake.

• 한국어류학회지
• /
• 제30권1호
• /
• pp.46-54
• /
• 2018

멸종위기어류인 미호종개 Cobitis choii의 서식지 특성과 연령 등의 생태적 특징을 밝혀 보전학적으로 활용하기 위하여 2011년 금강 지류인 지천에서 조사를 실시하였다. 미호종개의 서식지는 하류부의 모래톱이 형성된 지역으로, 모래 입자 크기는 대부분 0.21~1.18 mm (88.7%)로 작은 편이었다. 치어는 수심이 5~20 cm로 낮고 유속은 0~15 cm/sec로 느린 곳에 주로 서식하고 있었지만, 1년생과 2년생, 3년생 이상의 개체들은 공통적으로 수심 20~50 cm, 유속 10~25 cm/sec의 느린 여울부에 서식하고 있었다. 성장은 활동기인 4월부터 10월까지 급격한 성장을 보였으나 월동기인 11월부터 3월까지는 성장을 멈추었다. 연령(암컷)은 6월을 기준으로 만 1년생은 전장 40~61 mm, 만 2년생은 64~79 mm, 만 3년생은 80~91 mm, 만 4년생 이상은 92~106 mm로 추정되었다.

• Journal of Ecology and Environment
• /
• 제32권4호
• /
• pp.257-265
• /
• 2009

We estimated monthly and annual secondary productivity of pelagic zooplankton in Lake Paldang and Lake Cheongpyong. Secondary productivity was calculated by combining estimated zooplankton biomass and biomass-specific productivity for each site and depth from March to November 2008. In addition to somatic production, we measured production of eggs and exuviae for three dominant species: Daphnia galeata, Bosmina longirostris, Cyclops sp. In terms of biomass, B. longirostris was dominant in Lake Paldang in April and May, B. longirostris showed explosive biomass growth, especially in May. In June and July, B. longirostris and D. galeata were both dominant. Lake Cheongpyeong showed much lower zooplankton biomass than Lake Paldang. In August, there was little or no biomass in both lakes probably due to heavy rain. The Gyeongan River contributed most of the secondary productivity and B. longirostris contributed the most secondary productivity in Lake Paldang. D. galeata also contributed in the Gyeongan River, the South Han River and at the Paldang Dam in spring and fall. Overall, Lake Cheongpyeong showed lower secondary productivity than Lake Paldang. B. longirostris made the largest contribution to secondary productivity in the Cheongpyeong Dam area while D. galeata contributed the most near Nami Island. Somatic production constituted ~80% of the total secondary productivity (the sum of somatic, egg and exuvia production) for D. galeata and B. longirostris. Although production-to-biomass (P/B) ratios were usually <<1 B. longirostris sometimes showed very high P/B ratios, probably due to fish predation. D. galeata showed much lower P/B ratios than B. longirostris after the summer at most sites.

• 한국양식학회지
• /
• 제11권2호
• /
• pp.159-166
• /
• 1998

참전복용으로 경제적인 배합사료를 개발하기 위해 이미 수행된 실험 결과를 바탕으로, 배합되는 원료의 조성비(7 종류)와 단가(사료원료의 단가:kg당 5,000원에서 800원대)를 달리하여 외국산 수입사료 및 천연먹이 (건조미역)와 그 효능을 비교하였다. 평균체중 120 mg의 참전복 치패를 선별하여 각 실험수조에 70마리씩 완전임의 배치하여 각 실험사료마다 3반복으로 4개월간 사육실험하였다. 사육 결과, 생존률은 71~90% 범위였으며, 미역 공급구가 71%로 가장 낮은 값을 보였다. 최종 평균체중, 증체율 가식부 중량, 체중에 대한 가식부 중량비, 평균 각장 및 각폭은 사료 단가가 5,000원대로 가장 비싼 사료와 건조 미역 공급구가 가장 낮은 값을 보여 타 실험구와 차이를 보였으며(P<0.05), 그 외 실험사료들은 서로 유의차가 인정되지 않았다.(P>0.05). 실험 종료시 가식부의 일반성분 중에서 수분과 회분은 실험구간에 서로 유의차가 없었으나(P>0.05), 단백질 함량은 사료 단가가 5,000원대인 사료가 가장 낮았으며, 지질함량은 건조 미역구가 0.73%로 가장 낮았다(P<0.05). 위와 같이 단가가 가장 비싼 사료구 외의 실험 배합사료는 외국 수입사료와 비교하였을 때 그 효능이 전혀 뒤지지 않은 것으로 보아, 사료의 단가는 kg당 1,000원 전후로 낮아질 수 있을 것으로 기대된다.

• 한국양식학회지
• /
• 제9권4호
• /
• pp.429-435
• /
• 1996

사육 수온이 넙치의 성비에 미치는 영향을 조사하기 위해 일반 넙치 및 자성발생성 2배체 넘치 자어를 대상으로 부화 후 35일(전장 1.2 cm)부터 100일(전장 12 cm)까지 사육 수온 18, 21, 24 및 $27^{\circ}C$로 나누어 2회 반복하여 실험하였다. 사육 수온이 높을수록 암컷의 비율은 낮게 나타나 사육 수온과 암컷 비율에 있어 역상관관계를 보였다. 자성발생성 2배체 실험군의 경우 $18^{\circ}C$에서 $94.4\%$의 암컷을 보인 반면 $27^{\circ}C$에서는 $57.6\%$로 나타나 암수비가 1 : 1이었다(P<0.01). 사육 수온에 따른 생존율은 일반 넙치 및 자성발생성 2배체 넙치 모두 18, 21, 24 및 $27^{\circ}C$ 순으로 높았으나 $27^{\circ}C$를 제외한 나머지 실험군은 유의차가 없었으며 $18^{\circ}C$를 제외한 나머지 실험군의 체중 성장은 유의차가 없었다(P>0.05).