Characterization of Chitinolytic and Antifungal Activities in Marine-Derived Trichoderma bissettii Strains

Dawoon Chung,Yong Min Kwon,Ji Yeon Lim,Seung Sub Bae,Grace Choi,이대성 한국균학회 2022 Mycobiology Vol.50 No.4

Trichoderma fungi have been intensively studied for mycoparasitism, and the latter is closely related to their cell-wall degrading enzymes including chitinase. Here, we studied marine- derived Trichoderma spp., isolated from distinct sources and locations, for chitinolytic and antifungal activity. Based on morphological and phylogenetic analyses, two strains desig- nated GJ-Sp1 and TOP-Co8 (isolated from a marine sponge and a marine alga, respectively) were identified as Trichoderma bissettii. This species has recently been identified as a closely related species to Trichoderma longibrachiatum. The extracellular crude enzymes of GJ-Sp1 and TOP-Co8 showed activities of chitobiosidase and b-N-acetylglucosaminidase (exochiti- nase) and chitotriosidase (endochitinase). The optimum chitinolytic activity of the crude enzymes was observed at 50 C, pH 5.0, 0–0.5% NaCl concentrations, and the activities were stable at temperatures ranging from 10 to 40 C for 2 h. Moreover, the crude enzymes showed inhibitory activity against hyphal growth of two filamentous fungi Aspergillus flavus and Aspergillus niger. To the best of our knowledge, this is the first report of the chitinolytic and antifungal activity of T. bissettii.

Fungi in salterns

Dawoon Chung,김하련,Hyun Seok Choi 한국미생물학회 2019 The journal of microbiology Vol.57 No.9

Salterns are hypersaline extreme environments with unique physicochemical properties such as a salinity gradient. Although the investigation of microbiota in salterns has focused on archaea and bacteria, diverse fungi also thrive in the brine and soil of salterns. Fungi isolated from salterns are represented by black yeasts (Hortaea werneckii, Phaeotheca triangularis, Aureobasidium pullulans, and Trimmatostroma salinum), Cladosporium, Aspergillus, and Penicillium species. Most studies on saltern-derived fungi gave attention to black yeasts and their physiological characteristics, including growth under various culture conditions. Since then, biochemical and molecular tools have been employed to explore adaptation of these fungi to salt stress. Genome databases of several fungi in salterns are now publicly available and being used to elucidate salt tolerance mechanisms and discover the target genes for agricultural and industrial applications. Notably, the number of enzymes and novel metabolites known to be produced by diverse saltern-derived fungi has increased significantly. Therefore, fungi in salterns are not only interesting and important subjects to study fungal biodiversity and adaptive mechanisms in extreme environments, but also valuable bioresources with potential for biotechnological applications.

Identification and characterization of a marine-derived chitinolytic fungus, Acremonium sp. YS2-2

Dawoon Chung,Kyunghwa Baek,Seung Seob Bae,정재준 한국미생물학회 2019 The journal of microbiology Vol.57 No.5

Chitin is the most abundant biopolymer in marine environments. To facilitate its utilization, our laboratory screened marine-derived fungal strains for chitinolytic activity. One chitinolytic strain isolated from seawater, designated YS2-2, was identified as Acremonium species based on morphological and phylogenetic analyses. Acremonium species are cosmopolitan fungi commonly isolated from both terrestrial and marine environments, but their chitinolytic activity is largely unknown. The extracellular crude enzyme of YS2-2 exhibited optimum chitinolytic activity at pH 6.0–7.6, 23–45°C, and 1.5% (w/v) NaCl. Degenerate PCR revealed the partial cDNA sequence of a putative chitinase gene, chiA, in YS2-2. The expression of chiA was dramatically induced in response to 1% (w/v) colloidal chitin compared to levels under starvation, chitin powder, and glucose conditions. Moreover, the chiA transcript levels were positively correlated with chitinolytic activities under various colloidal chitin concentrations, suggesting that ChiA mediates chitinolytic activity in this strain. Our results provide a basis for additional studies of marinederived chitinolytic fungi aimed at improving industrial applications.

Investigation of Enzymatic Activities in Marine Algae-Derived Fungi

Chung Dawoon,Yu Woon-Jong,Jang Hyeong Seok,Kwon Yong-Min,Bae Seung Seob,Choi Grace (사)한국해양생명과학회 2023 한국해양생명과학회지 Vol.8 No.1

Marine macroalgae are important in coastal ecosystems and interact with marine microorganisms. In this study, we isolated fungi from seven types of marine macroalgae including Cladophora sp., Gloiopeltis furcate, Gracilariopsis chorda, Hydroclathrus clathratus, Prionitis crispata, Sargassum micracanthum, and Ulva lactuca collected in Korea. Morphological and phylogenetic analyses identified the isolates as four Aspergillus spp. (A. fumigatus, A. sydowii, A. tamarii, and A. terreus), three Penicillium spp. (P. crustosum, P. jejuense, and P. rubens), and Cladosporium tenuissimum. Among them, A. fumigatus TOP- U2, A. tamarii SH-Sw5, and A. terreus GJ-Gf2 strains showed the activities of all enzymes examined (amylase, chitinase, lipase, and protease). Based on the enzymatic index (EI) values in solid media, A. terreus GJ-Gf2 and C. tenuissimum UL-Pr1 exhibited the highest amylase and lipase activities, respectively. Chitinolytic activity was only observed in A. terreus GJ-Gf2, A. tamarii SH-Sw5, and A. fumigatus TOP-U2. Penicillium crustosum UL- Cl2 and C. tenuissimum UL-Pr1 showed the highest protease activities. To the best of our knowledge, this is the first report of lipolytic and proteolytic activities in a marine-derived C. tenuissimum strain. Overall, the fungal strains isolated from the marine macroalgae in this study actively produced industrially important enzymes.

확장된 도구로서의 일렉트로닉스: 서울국제컴퓨터음악제 2022 참관기

정다운(Chung,Dawoon) 한국전자음악협회 2022 에밀레 Vol.20 No.-

동적 소스 라우팅에서의 효율적인 파워 세이빙 알고리즘

정다운(Dawoon Chung),노원종(Wonjong Noh),한규호(Kyuho Han),임경수(KyungSoo Lim),안순신(Sunshin Ahn) 한국정보과학회 2004 한국정보과학회 학술발표논문집 Vol.31 No.1A

배터리 파워는 모바일 애드 혹 네트워크(Mobile Ad hoc Network)에서 중요한 리소스이다. 기존의 라우팅 알고리즘에서는 노드의 파워를 on-off 시키는 방법으로 파워를 관리해왔다. 본 논문에서는 DSR (dynamic source routing)에서 route discovery, route maintenance를 할 때 각 노드의 배터리 파워 레벨을 고려하여 파워 레벨이 낮은 노드들은 RREP packet을 보내지 않음으로써 소스에서 데스티네이션까지의 경로를 오래 유지시킬 수 있고, 또한 파워 레벨이 높은 하나의 노드에 트래픽이 집중되지 않도록 하기 위해 큐(queue)에 담겨있는 트랜스미션 패킷과 리시브 패킷의 수까지 고려하여 경로를 설정한다. 이 알고리즘을 이용함으로써 각 노드의 파워를 효율적으로 관리함은 물론, 전체 네트워크의 load 균형을 맞춤으로 네트워크의 수명을 길게 할 수 있다.

재외동포 아동 대상 한국어 문식성 향상 방안 - 학습 한국어 교육을 중심으로

정다운(Chung, Dawoon) 중앙어문학회 2020 語文論集 Vol.84 No.-

본고에서는 재외동포 아동들이 균형 잡힌 이중 언어 화자가 되기 위해서는 무엇보다 문식성 능력이 향상되어야 한다고 보았다. 즉, 균형 잡힌 이중 언어 화자가 되기 위해서는 한국어를 단순히 읽고 쓸 줄 아는 수준을 넘어서서 고급 수준의 문식성을 갖추어야 한다는 것이다. 이러한 고급 수준의 문식성은 결국 학업 상황에서의 읽고 쓰는 능력과 관련이 된다. 따라서 문식성 능력을 향상시키기 위해 학습 한국어 교육이 효과가 있으리라 판단하고 이를 위한 학습 한국어 교육 방안과 교육 내용에 대해 논하였다. 특히 본고에서는 재외동포 아동을 위한 학습 한국어 교육을 위해 모국어 화자를 위해 개발된 교과서를 활용하는 방안에 초점을 두고 교과서에 제시된 내용 중 학습 한국어 교육 내용으로 어떤 내용을 선정할 수 있는지를 살펴보았다. 그 결과 수업 구성 원리와 수업 목적을 고려하여 학습 목표, 학습 어휘, 수업 이해를 위한 표현, 읽기 텍스트, 수업 활동의 항목으로 교육 내용을 선정하였으며 초등학교 과학 교과와 사회 교과의 한 단원을 대상으로 하여 학습 한국어 교육 내용이 어떻게 구성될 수 있는지를 보여주었다. 본 연구는 재외동포 아동들의 문식성 능력 향상을 위해 그동안 거의 논의되지 않았던 학습 한국어를 활용하는 방안을 제시했다는 점에서 의미를 가질 수 있다. For overseas Korean children to become balanced bilingual speakers, their Korean language literacy skills must be improved. In other words, beyond simply being able to read and write Korean, they must have a high level of literacy. This high level of literacy is ultimately related to academic literacy. Therefore, I decided that cognitive academic Korean education would be effective in improving literacy skills and discussed cognitive academic Korean education methods and content. In particular, this study focused on how to use textbooks developed for native speakers in cognitive academic Korean education for overseas Korean children and looked at what content could be selected as cognitive academic Korean content among the content presented in the textbooks. The content of the cognitive academic Korean class was selected using five categories: the aims of the lesson, learning vocabulary, expressions for understanding the class, reading texts, and class activities. Lastly, I looked at how the content of science and social studies subjects in elementary school could be organized for cognitive academic Korean class for overseas Korean children.

The Molecular Gas Kinematics of HI Monsters

Dawoon E. Kim,Aeree Chung,Min S. Yun,Daisuke Iono 한국천문학회 2020 天文學會報 Vol.45 No.1

Analysis of underwater coherence transmission loss by finite difference method based on wave equation

Dawoon Lee,Ho Seuk Bae,Woo-Shik Kim,Wookeen Chung 한국마린엔지니어링학회 2020 한국마린엔지니어링학회지 Vol.44 No.3

Relationship between metformin use and mortality in tuberculosis patients with diabetes: a nationwide cohort study

( Eunki Chung ),( Dawoon Jeong ),( Jeongha Mok ),( Doosoo Jeon ),( Hee-yeon Kang ),( Heejin Kim ),( Heesun Kim ),( Hongjo Choi ),( Young Ae Kang ) 대한내과학회 2024 The Korean Journal of Internal Medicine Vol.39 No.2

Background/Aims: To determine whether metformin, which is considered a host-directed therapy for tuberculosis (TB), is effective in improving the prognosis of patients with TB and diabetes mellitus (DM), who have higher mortality than those without DM. Methods: This cohort study included patients who were registered as having TB in the National Tuberculosis Surveillance System. The medical and death records of matched patients were obtained from the National Health Information Database and Statistics Korea, respectively, and data from 2011 to 2017 were collected retrospectively. We classified patients according to metformin use among participants who used diabetes drugs for more than 28 days. The primary outcome was all-cause mortality during TB treatment. Double propensity score adjustment was applied to reduce the effects of confounding and multivariable Cox proportional hazard models were used to estimate adjusted hazard ratio (aHR) with 95% confidence interval (CI). Results: The all-cause mortality rate during TB treatment was lower (9.5% vs. 12.4%, p < 0.01) in the metformin user group. The hazard of death due to all causes after double propensity score adjustment was also lower in the metformin user group (aHR 0.76, 95% CI 0.67-0.86, p < 0.01). There was no significant difference in mortality between metformin users and non-users for TB-related deaths (p = 0.22); however, there was a significant difference in the non-TB-related deaths (p < 0.01). Conclusions: Metformin use in patients with TB-DM co-prevalence is associated with reduced all-cause mortality, suggesting the potential for metformin adjuvant therapy in these patients.