• Journal of Microbiology and Biotechnology
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• 제27권1호
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• pp.101-111
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• 2017

The task of improving a fungal strain is highly time-consuming due to the requirement of a large number of flasks in order to obtain a library with enough diversity. In addition, fermentations (particularly those for fungal cells) are typically performed in high-volume (100-250 ml) shake-flasks. In this study, for large and rapid screening of itaconic acid (IA) high-yielding mutants of Aspergillus terreus, a miniaturized culture method was developed using 12-well and 24-well microtiter plates (MTPs, working volume = 1-2 ml). These miniaturized MTP fermentations were successful, only when highly filamentous forms were induced in the growth cultures. Under these conditions, loose-pelleted morphologies of optimum sizes (less than 0.5 mm in diameter) were casually induced in the MTP production cultures, which turned out to be the prerequisite for the active IA biosynthesis by the mutated strains in the miniaturized fermentations. Another crucial factor for successful MTP fermentation was to supply an optimal amount of dissolved oxygen into the fermentation broth through increasing the agitation speed (240 rpm) and reducing the working volume (1 ml) of each 24-well microtiter plate. Notably, almost identical fermentation physiologies resulted in the 250 ml shake-flasks, as well as in the 12-well and 24-well MTP cultures conducted under the respective optimum conditions, as expressed in terms of the distribution of IA productivity of each mutant. These results reveal that MTP cultures could be considered as viable alternatives for the labor-intensive shake-flask fermentations even for filamentous fungal cells, leading to the rapid development of IA high-yield mutant strains.

• Journal of Microbiology and Biotechnology
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• 제22권7호
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• pp.889-893
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• 2012

Appressorium is a specialized infection structure of filamentous pathogenic fungi and plays an important role in establishing a pathogenic relationship with the host. The Egh16/Egh16H family members are involved in appressorium formation and pathogenesis in pathogenic filamentous fungi. In this study, a homolog of Egh16H, Magas1, was identified from an entomopathogenic fungus, Metarhizium acridum. The Magas1 protein shared a number of conserved motifs with other Egh16/Egh16H family members and specifically expressed during the appressorium development period. Magas1-EGFP fusion expression showed that Magas1 protein was not localized inside the cell. Deletion of the Magas1 gene had no impact on vegetative growth, conidiation and appressorium formation, but resulted in a decreased mortality of host insect when topically inoculated. However, the mortality was not significant between the Magas1 deletion mutant and wild-type treatment when the cuticle was bypassed by injecting conidia directly into the hemocoel. Our results suggested that Magas1 may influence virulence by affecting the penetration of the insects' cuticle.

• Journal of Microbiology and Biotechnology
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• 제18권3호
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• pp.490-496
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• 2008

Symbiobacterium toebii is a commensal symbiotic thermophile that cannot grow without support from a partner bacterium. We investigated the properties of Symbiobacterium growth-supporting factors (SGSFs) produced by the partner bacterium Geobacillus toebii. SGSFs occurred in both the cell-free extract (CFE) and culture supernatant of G. toebii and might comprise multifarious materials because of their different biological properties. The heavy SGSF contained in the cytosolic component exhibited heat- and proteinase-sensitive proteinaceous properties and had a molecular mass of >50 kDa. In contrast, the light SGSF contained in the extracellular component exhibited heat-stable, proteinase-resistant, nonprotein properties and had a molecular mass of <10 kDa. Under morphological examination using light microscopy, S. toebii cultured with the culture supernatant of G. toebii was filamentous, whereas S. toebii cultured with the CFE of G. toebii was rod-shaped. These results strongly suggest that the SGSFs produced by G. toebii comprise two or more types that differ in their growth-supporting mechanisms, although all support the growth of S. toebii. Upon the examination of the distribution of SGSFs in other bacteria, both cytosolic and extracellular components of Geobacillus kaustophilus, Escherichia coli, and Bacillus subtilis had detectable growth-supporting effects for S. toebii, indicating that common SGSF materials are widely present in various bacterial strains.

• 한국토양비료학회지
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• 제37권3호
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• pp.177-183
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• 2004

최근 시설 재배지에서는 사용된 배양액을 그냥 방출하고 있어서 지표수의 부영양화와 지하수의 오염을 유발시키는 것으로 알려져 있으며, 이와 같은 폐양액 처리 기술이 요구된다. 따라서 본 연구는 국내토양에서 분리된 광합성 독립영양 세균인 cyanobactria 중 우수한 균주를 선발하고 이의 생장에 필요한 다량의 N, P와 미량 필수원소 등 각종영양 물질이 충분히 함유된 폐양액을 이용하여 광합성 세균을 대량배양 하고자 하였다. 4종 (Anabaena HA101, HA701과 Nostoc HN601, HN701)의 미세조류 중 BG-II ($NO_3{^-}$) 액체배지에서 생장과 양분흡수능이 우수한 균체는 Nostoc HN601이었고, 이 균체는 질소 고정능 뿐만 아니라 균체 내 양분 보유능이 우수하여 본 실험을 위하여 최종 선발하였다. 선발된 Nostoc HN601의 최적 배양 조건는 통기처리 시 배양액 부피의 1/2수준의 조건과 초기 폐양액의 pH를 8.0으로만 조절 해주는 non-buffering 시스템이 효과적이었다. 최적 배양 조건하에서 Nostoc HN601을 15 L의 광배양기에 토마토를 수경 재배한 10 L의 폐양액을 이용하여 배양한 결과 균체의 생장은 $16mg\;Chl-a\;L^{-1}$로 실험실조건에서 배양된 균체 ($8.3mg\;Chl-a\;L^{-1}$)보다 약 2배정도 빠르게 증가되었으며, 폐양액 내 인산도 1주일 이내에 100% 제거시킴으로서 인산 제거효율이 매우 우수하였다. 또한 선발된 Nostoc HN601의 질소 고정능은 $22.4nmol\;C_2H_4\;mg^{-1}\;Chl-a\;h^{-1}$로 매우 우수하였고, 균체 내 총 인산과 총 질소함량은 각각 19.1 mg P와 63.3 mg N으로 높게 나타났다. 이러한 결과로 광반응기에서 폐양액을 이용한 cyanobacteria의 대량배양은 부영양화와 지하수 오염을 일으키는 폐양액 내 인산제거에 큰 효과가 있고. 배양된 균체는 높은 질소와 인산을 함유하고 있어서 생물비료로도 이용할 수 있을 것으로 기대된다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.223-227
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• 2003

Mevinolic acid (MA), a secondary metabolite produced by a filamentous fungus Aspergillus terreus, is acidic form of lovastatin which has been identified as a powerful cholesterol-lowering agent in humans. When immobilized cell culture was performed, MA production was about 5.3-fold higher than the parallel suspended cell culture. Although the immobilized cells proliferated slowly during exponential in comparison with the suspended cells, oxygen uptake rate and oxygen mass transfer coefficient of the immobilized cell culture were about 1.3- and 2.5- fold higher respectively than those of the parallel suspended cell culture. From these results, it was concluded that MA biosynthesis was closely dependent on the cell growth rate, morphology and oxygen availability.

• 미생물학회지
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• 제30권6호
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• pp.514-518
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• 1992

The present study has been perromed to investigate the optimal conditions for protoplast formation and regeneration of oleandomycin-producing Streptomyces antibioticus (S. antibioticus) KCTC 1081. Mycelia were grown in YME medium containing 0.2% (w/v) glycine and converted into the protoplast by incubating at 35.deg.C for 60 minutes in protoplast buffer (P buffer) containing 4 mg/ml lysozyme. The reversion of protoplasts to the normal filamentous state was examined by the growth on various synthetic agar media. A high reversion rate was obtained by incubating the protoplasts on a hypertonic agar medium containing 20 mM $Mg^{++}$, 5 mM $Ca^{++}$ and 0.3 M sucrose at 28.deg.C for 5 days. From these experiments, we established the improved regeneration medium and a protocol which supports higher and more consistent levels of regeneration of S. antibioticus protoplasts. The regenerant showed an increased antimicrobial activity compared with that of the initial strain.n.n.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권6호
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• pp.571-575
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• 2005

A simple, but effective on-line method for estimating the mycelial cell mass concentration from agitation speed data, a most readily-available process variable, has been developed for DO-stat cultures of Agaricus blazei. The dynamic change of dissolved oxygen concentration (DOC) in the initial transient period and the change in yield were considered in the development of the estimation algorithm or estimator. Parameters in the estimation algorithm were calculated from the agitation speed data at 20% of DOC. The proposed estimator could accurately predict the cell mass concentration regardless of DOC levels in the tested range of $10{\sim}40%$, showing a good extrapolation capability.

• KSBB Journal
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• 제30권3호
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• pp.119-124
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• 2015

Arthrospira platensis (A. platensis) is a microscopic and filamentous cyanobacterium that derives its name from the spiral or helical nature of its filaments. In this study, we induced mutants of A. platensis through NMU treatment and selected two strains by level of ipid contents. We named mutant '1-9', '2-5', and they were cultivated in the same way with the wild type. During 12 days cultivation, cell growth, dry cell weight, pigment content, and lipid content were measured for characteristics of mutants. As a result, pigment and lipid content of mutants were increased about 3.6, 1.8 times compared with wild type, respectively. It was shown that total flavonoid and polyphenol contents of mutants were increased about 1.5 times compared with wild type. And radical scavenging effect of mutants were increased about 10% compared with wild type.

• 한국막학회:학술대회논문집
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• 한국막학회 1993년도 춘계 총회 및 학술발표회
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• pp.41-41
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• 1993

Recently, the advanced membrane separation technology has even been applied to the post treatment to biological process of wastewater treatment, since the efficiency of biological treatment significantly depends on maintaining a high biomass concentration in the bioreator. Particularly, anaerobic microbes in the biological system have slower growth rates than aerobic microbes and thus it takes a long hydaulic retention time(HRT) to prevent biomass washout in the completely mixed anaerobic digester. The anaerobic sludge also has poor settleability owing to its diffusible and somewhat filamentous nature. Moreover, the residual gasification and consequent sludge rise in the clarifier compartment become a considerable problem, which proves that complete separation of biological solids is difficult.

• Mycobiology
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• 제47권3호
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• pp.273-279
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• 2019

A new species, Pythium subutonaiense, isolated from aquatic environments (lake) in China is being described based on morphological characters and molecular evidence. The isolates grew at temperatures between $5^{\circ}C$ and $38^{\circ}C$, and the optimum temperature was $30^{\circ}C$, with a radial growth rate of 17.6 mm at $25^{\circ}C$ per day. It is homothallic and characterized by globose to sub-globose shaped and mostly terminal or sometimes catenulate hyphal swellings, filamentous non-inflated sporangia, and smooth oogonia with hypogynous and monoclinous antheridia that contained one plerotic oospore. In phylogenetic analysis, inferred based on the internal transcribed spacer region of the ribosomal RNA gene and mitochondrial cytochrome c oxidase subunit 1 gene, the new species formed a distinct lineage in Pythium clade B. Differences between the new species and phylogenetically related and morphologically similar species are discussed.