• Natural Product Sciences
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• 제26권3호
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• pp.183-190
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• 2020

Genome mining has recently emerged as a powerful strategy to discover novel microbial secondary metabolites. However, more than 50% of biosynthetic gene clusters are not transcribed under standardized laboratory culture condition. Several methods have been applied to activate silent biosynthetic gene clusters in the microbes so far. Among the regulatory systems for production of secondary metabolites, global regulators, which affect transcription of genes through regulatory cascades, typically govern the production of small molecules. In this review, global regulators to affect production of microbial secondary metabolites were discussed.

• Journal of Microbiology and Biotechnology
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• 제28권2호
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• pp.305-313
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• 2018

A microbial consortium, TMC7, was enriched for the degradation of natural lignocellulosic materials under high temperature. TMC7 degraded 79.7% of rice straw during 15 days of incubation at $65^{\circ}C$. Extracellular xylanase was effectively secreted and hemicellulose was mainly degraded in the early stage (first 3 days), whereas primary decomposition of cellulose was observed as of day 3. The optimal temperature and initial pH for extracellular xylanase activity and lignocellulose degradation were $65^{\circ}C$ and between 7.0 and 9.0, respectively. Extracellular xylanase activity was maintained above 80% and 85% over a wide range of temperature ($50-75^{\circ}C$) and pH values (6.0-11.0), respectively. Clostridium likely had the largest contribution to lignocellulose conversion in TMC7 initially, and Geobacillus, Aeribacillus, and Thermoanaerobacterium might have also been involved in the later phase. These results demonstrate the potential practical application of TMC7 for lignocellulosic biomass utilization in the biotechnological industry under hot and alkaline conditions.

• Journal of Microbiology and Biotechnology
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• 제20권2호
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• pp.332-339
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• 2010

The lipase from Mucor racemosus NRRL 3631 was partially purified by fractional precipitation using 60% ammonium sulfate, which resulted in a 8.33-fold purification. The partially purified lipase was then immobilized using different immobilization techniques: physical adsorption, ionic binding, and entrapment. Entrapment in a 4% agar proved to be the most suitable technique (82% yield), as the immobilized lipase was more stable at acidic and alkaline pHs than the free enzyme, plus 100% of the original activity was retained owing to the thermal stability of the immobilized enzyme after heat treatment for 60 min at $45^{\circ}C$. The calculated half-lives (472.5, 433.12, and 268.5 min at 50, 55, and $60^{\circ}C$, respectively) and the activation energy (9.85 kcal/mol) for the immobilized enzyme were higher than those for the free enzyme. Under the selected conditions, the immobilized enzyme had a higher $K_m$ (11.11 mM) and lower $V_{max}$ (105.26 U/mg protein) when compared with the free enzyme (8.33 mM and 125.0 U/mg protein, respectively). The operational stability of the biocatalyst was tested for both the hydrolysis of triglycerides and esterification of fatty acids with glycerol. After 4 cycles, the immobilized lipase retained approximately 50% and 80% of its original activity in the hydrolysis and esterification reactions, respectively.

• 한국식물병리학회지
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• 제10권4호
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• pp.297-304
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• 1994

This study was carried out to develop bioassay for detection of pesticide residues in agricultural products by using the soil microbial isolates sensitive to pesticides. One hundred bacterial isolates and eighty five fungal isolates were obtained from soil and their sensitivity to 10 ppm of several pesticides was examined in vitro. Five bacterial isolates and three fungal isolates were found sensitive to organochloride fungicide and two fungal isolates sensitive to organocopper fungicide. Among these isolates, B46, B93 and F67 were tested to find out the difference in sensitivity according to the methods of fungicide treatment. All of the isolates were found sensitive to 10 ppm of organochloride fungicides mixed directly in PDA. But they were found insensitive to the fungicide mixed in PDA after filtering through membrane filter. In case of organocopper fungicide, the isolates were found sensitive only when it was treated in PDA. And their sensitivity showed difference among various kinds of organochloride fungicides. B46 and B93 were employed to check the possibility as the agent for detection of the pesticidal residues in twenty eight agricultural products including rice. It was found that all samples had not residues because the samples did not inhibit the growth of isolates. When organochloride fungicides were applied to the above products, it was possible to detect the residues in fruits and vegetables at the concentration of 10 ppm, but not in starch-rich grains. B46 and B93 were identified as Bacillus sp. according to their bacterial characteristics in culture.

• Journal of Microbiology and Biotechnology
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• 제23권1호
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• pp.106-117
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• 2013

Microbial enhanced oil recovery (MEOR) is one of the most economical and efficient methods for extending the life of production wells in a declining reservoir. Microbial consortia from Wafra oil wells and Suwaihat production water, Al-Wusta region, Oman were screened. Microbial consortia in brine samples were identified using denaturing gradient gel electrophoresis and 16S rRNA gene sequences. The detected microbial consortia of Wafra oil wells were completely different from microbial consortia of Suwaihat formation water. A total of 33 genera and 58 species were identified in Wafra oil wells and Suwaihat production water. All of the identified microbial genera were first reported in Oman, with Caminicella sporogenes for the first time reported from oil fields. Most of the identified microorganisms were found to be anaerobic, thermophilic, and halophilic, and produced biogases, biosolvants, and biosurfactants as by-products, which may be good candidates for MEOR.

• Journal of the Korean Wood Science and Technology
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• 제51권5호
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• pp.358-380
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• 2023

The intestinal microbiota plays a crucial role in determining human health, rendering it a major focus of scientific investigation. Rather than eliminating all microbes, promoting the proliferation of beneficial microorganisms within the gut has been recognized as a more effective approach to improving health. Unfavorable conditions potentially alter gut microbial populations, including a reduction in microbial diversity. However, intentionally enhancing the abundance of beneficial gut microbes can restore a state of optimal health. Polysaccharides are widely acknowledged for their potential to improve the gut microbiota. This review emphasizes the findings of recent studies examining the effects of forest product-derived polysaccharides on enhancing the gut microbiota and alleviating inflammation, diabetes symptoms, and obesity. The findings of several studies reviewed in this paper strongly suggest that forest products serve as an excellent dietary source for improving the gut microbiota and potentially offer valuable dietary interventions for chronic health problems, such as inflammation, diabetes, and obesity.

• 미생물학회지
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• 제27권2호
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• pp.139-146
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• 1989

담수상태의 논토양에 처리한 유기인계 살충제 diazinon의분해기작과 그 분해산물에 대하여 조사하였다. 항온조건($30^{\circ}C$)하에서 살균토양에 비하여 비살균토양에서의 diazinon 분해가 보다 빠르게 일어남으로써 담수토양내 diazinon 분해에 미생물의 대사활동이 매우 종요한 것으로 나타났는데, 비살균토양내 diazinon의 반감기는 약 2일이엇고 항온반응 7일만에 95% 이상의 분해가 이루어졌다. 또한 diazinon 분해기간 중 미생물 개체수와 아울러 토양내 monoxygenase 및 esterase 활성의 증가가 이루어졌으며 이는 토양내 diazinon 처리가 이 약제의 분해와 관련된 미생물학적 요인의 생장 또는 활성을 촉진시키고 있음을 보여준다. 이와 관련하여 담수토양내 diazinon 분해산물로서 esterase 작용에 의한 2-isopropyl-6-methyl-4-hydroxy pyrimidine 이외에 monooxygenase에 의한 diazoxon과 hydroxydiazinon, 그리고 sulfotep 등이 mass spectrometry에 의하여 확인되었다.

• 한국식품위생안전성학회지
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• 제37권4호
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• pp.277-284
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• 2022

시판 유통 중인 건조 인삼류(백삼 24점, 홍삼 26점) 포장 제품을 수집하여 곰팡이 발생 조사를 수행하였다. 백삼과 홍삼은 각각 50%와 46%의 시료에서 곰팡이가 검출되었고 검출 시료의 평균 곰팡이 오염도는 각각 0.5와 0.2 log₁₀ CFU/g이었다. 백삼에서는 Penicillium polonicum, P. chrysogenum, Rhizopus microsporus가 각각 18.2%로 우점하였으나 홍삼은 Aspergillus spp.이 87.6%로 우점하였으며 이 중 A. chevalieri가 50.0%로 가장 높았다. 이 중 독성 종으로 알려진 P. polonicum, P. chrysogenum, P. melanoconidium, A. chevalieri 균주의 citrinin 독소 생성 가능성을 분석한 결과, 13 균주 모두 독소 유전자가 검출되지 않았다. 이 결과는 조사한 시료의 곰팡이독소 오염 위험은 매우 낮지만, 건조 인삼류에 곰팡이 오염이 가능함을 보여준다.

• 생명과학회지
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• 제33권4호
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• pp.325-333
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• 2023

본 연구에서는 김치와 묵은지의 미생물 군집 구조와 이화학적 특성을 비교 분석하였다. 김치와 묵은지의 이화학적 특성 분석 결과 묵은지 시료들의 pH가 김치보다 더 낮았으며, 산도는 더 높은 것으로 나타났다. 김치와 묵은지 간의 염도에는 차이가 없는 것으로 나타났으며, 김치에서 당도가 묵은지보다 높은 것으로 나타났다. α-diversity 분석 결과 김치와 묵은지 사이에 종 추정치와 종 풍부도 지수는 차이가 없는 것으로 나타났으나, 계통발생학적 차이를 반영한 phylogenetic diversity 지수는 묵은지에서 김치보다 유의한 수준으로 높은 것으로 나타났다. 김치와 묵은지의 미생물 군집을 생물학적 분류수준에 따라 분석한 결과 두 그룹 모두 공통적으로 과(family) 수준에서 Lactobacillaceae가 가장 우점하였으나, 높은 내산성을 갖거나 김치 내에서 높은 성장 경쟁력을 갖는 것으로 알려진 Pediococcus 속과 Lactobacillus 속 유산균의 상대적인 분포가 묵은지에서 높은 것으로 나타났다. 김치와 묵은지의 전체 미생물 군집 구조에 통계학적으로 차이가 있는지 분석하기 위해 beta set-significance 분석을 수행한 결과 김치와 묵은지 두 그룹의 전체 미생물 군집구조가 통계학적으로 신뢰수준에서 매우 다른 것으로 나타났으며, 김치에서 상대적으로 높은 Weissella kandleri의 분포와 묵은지에서 상대적으로 높은 Pediococcus inopinatus의 높은 분포가 김치와 묵은지의 전체 미생물 군집 구조 차이에 가장 큰 영향을 미치는 것으로 나타났다.

• 한국식품저장유통학회:학술대회논문집
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• 한국식품저장유통학회 2003년도 제23차 추계총회 및 국제학술심포지움
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• pp.188.1-188
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• 2003

To examine the effect of vacuum packaging on the quality of chicken during storage, microbial (total bacterial counts, mold and yeast, E. coli, and Pseudomonas) changes and drip loss were determined. fresh chicken breasts were prepared and packaged using polyethylene film under vacuum and normal atmosphere, respectively. Samples were then stored at 4$^{\circ}C$ for two weeks. At various time intervals during storage, sample was taken homogenized, and diluted with 0.1% sterile peptone water, and followed by microbial counts. Microbial changes of total bacterial counts, mold and yeast, E. coli, and Pseudomonas during storage of chicken were significantly decreased by vacuum packaging. Drip loss was also significantly decreased. These results indicate that vacuum packaging of chicken should be recommended as a suitable storage method in terms of microbial safety as well as quality of chicken.