• Microbiology and Biotechnology Letters
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• v.18 no.5
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• pp.535-540
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• 1990

Bacitlus sphaericus ts-Dl290 was characterized comparatively with the wild type strain 1593 by themeasurements of the biosynthesis of total DNA, RNA and protein on the temperature-shift culturesat permissive temperature of $30^{\circ}C$ and at nonpermissive temperature of $42^{\circ}C$. The growth patterns of the wild type strain and ts-Dl290 were similar at $30^{\circ}C$, but at 4Z C the mutant almost did not grow (temperature-sensitivity). When the growth temperatures of both stains were shifted-up from $30^{\circ}C$ to $42^{\circ}C$ after a 4 hour culture, their growths were normal, but when shifted-down from $42^{\circ}C$ to $30^{\circ}C$ after a 4 h culture, the mutant did not grow. When shifted up from $30^{\circ}C$ to $42^{\circ}C$ after a 4 hculture, the DNA syntheses of the two strains were at a normal rate for 1 h, but after 1 h the biosynthesesdecreased. The rate of DNA synthesis of the wild type strain at the nonpermissive temperature was about 93%, and that of the mutant was about 50% of the ratio of the wild type strain, and the RNA synthesis of the wild type strain was maintained for 3 h, and that of the mutant for 2 h. Thereafter the RNA synthesis decreased, and the synthesis of proteins in the both strains were similarlykept high for 8 h. The reversibility of the DNA synthesis of the mutant at $42^{\circ}C$ was lessened whenthe culture times were increased.re times were increased.

• Journal of Life Science
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• v.27 no.3
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• pp.339-345
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• 2017

Carotenoids are natural lipid-soluble pigments, which are produced primarily by bacteria, algae, and plants. Many studies have focused on the identification, production, and utilization of natural sources of astaxanthin from algae, yeast, and crustacean byproducts as an alternative to the synthetic pigment, which is mostly used today. The aim of the present study was to identify a mutant of Paracoccus haeundaensis by exposure to UV and ethyl methanesulfonate (EMS). The mutant was then exposed to nutrient stress conditions to isolate an astaxanthin-hyperproducing strain, followed by characterization of the mutant. The survival rate decreased in accordance with an increase in the UV exposure time and an increase in the EMS concentration. A mutant of the original P. haeundaensis strain was identified that showed hyperproduction of astaxanthin following exposure to UV irradiation (20 min) and EMS treatment (0.4 M concentration). The optimal culture conditions for the PUE mutant were $25^{\circ}C$, pH 7-8, and 3% NaCl. The effects of various carbon and nitrogen sources on the growth and astaxanthin production of PUE were examined. The addition of 1% raffinose and 3% potassium nitrate influenced cell growth and astaxanthin production. The selected mutant exhibited an increase of 1.58 folds in astaxanthin content compared to initial wild type strain. A genetically stable mutant strain obtained using mutagen (UV irradiation and EMS treatment) may be a suitable candidate for further industrial scale production of astaxanthin.

• Korean Journal of Agricultural Science
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• v.13 no.2
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• pp.279-288
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• 1986

One hundred and fifty one mutant strains were obtained from the parent strain Aspergillus oryzae MF by ultra-violet ray irradiation. Among those mutants a strain, Asp. oryzae UM-36 which hyperprodued protease, was selected and its morphological characteristics and the production of enzymes protease, ${\alpha}$-amylase, and glucoamylase on wheat bran koji and on soy-sauce koji were studied. The results obtained were as follows 1. The selected mutant showed slower growth and weak sporulation on malt agar and on Czapek agar than the parent strain. 2. The conidiophores of the mutant were generally shorter than those of the parent when grown on malt agar. 3. Sectoring in colonies was not found when grown on malt agar and on Czapek agar. 4. The level of protease production by the mutant was increased approximately 1,4-fold higher on wheat bran koji and 2-fold higher on soysauce koji than by the parent. 5. The production of ${\alpha}$-amylase and glucoamylase by the mutant were also increased as compared with the parent on wheat bran koji and on soy sauce koji. 6. In the case of parent strain and mutant strain, the highest activity of protease appeared after three days in wheat bran medium at $30^{\circ}C$ incubation, but the highest activities of ${\alpha}$-amylase and glucoamylase appeared after two days.

• Journal of Microbiology and Biotechnology
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• v.5 no.4
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• pp.241-243
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• 1995

A lipopolysaccharide (LPS) defective mutant of Bradyrhizobium japonicum was characterized in terms of its cell surface hydrophobicity (CSH). By monitoring the kinetics of adhesion to hexadecane the LPS mutant was found to be far more hydrophobic than the wild type strain; the removal coefficients were 4.65 $min^{-1}$ for the mutant, as compared with only 2.40 $min^{-1}$ for the wild type. The possible role of cell surface hydrophobicity of B. japonicum in nodulation process is discussed.

• Journal of Microbiology and Biotechnology
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• v.2 no.3
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• pp.226-229
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• 1992

An ethanol tolerant mutant was selected by successive transfers of Clostridium thermohydrosulfuricum ATCC 33223 into the media with progressively higher ethanol concentrations. The growth kinetics of the mutant were characterized under various growth conditions. Physiological differences such as enhanced growth, tolerance to various solvents, alteration of the optimum temperature and the ratio of end products during fermentation were noticed in the mutant.

• Journal of Microbiology and Biotechnology
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• v.26 no.9
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• pp.1570-1578
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• 2016

Commercial application of laccase is often hampered by insufficient enzyme stocks, with very low yields obtained from natural sources. This study aimed to improve laccase production by mutation of a Coriolopsis gallica strain and to determine the biological properties of the mutant. The high-yield laccase strain C. gallica TCK was treated with N-methyl-N-nitro-N-nitrosoguanidine and ultraviolet light. Among the mutants isolated, T906 was found to be a high-production strain of laccases. The mutant strain T906 was stabilized via dozens of passages, and the selected ones were further processed for optimization of metallic ion, inducers, and nutritional requirements, which resulted in the optimized liquid fermentation medium MF9. The incubation temperature and pH were optimized to be 30℃ and 4.5, respectively. The mutant strain T906 showed 3-times higher laccase activity than the original strain TCK under optimized conditions, and the maximum laccase production (303 U/ml) was accomplished after 13 days. The extracellular laccase isoenzyme 1 was purified and characterized from the two strains, respectively, and their cDNA sequence was determined. Of note, the laccase isoenzyme 1 transcription levels were overtly increased in T906 mycelia compared with values obtained for strain TCK. These findings provide a basis for C. gallica modification for the production of high laccase amounts.

• Journal of Microbiology and Biotechnology
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• v.26 no.3
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• pp.452-460
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• 2016

Acid stress can affect the viability of probiotics, especially Bifidobacterium. This study aimed to improve the acid tolerance of Bifidobacterium longum BBMN68 using adaptive evolution. The stress response, and genomic differences of the parental strain and the variant strain were compared by acid stress. The highest acid-resistant mutant strain (BBMN68m) was isolated from more than 100 asexual lines, which were adaptive to the acid stress for 10^th, 20^th, 30^th, 40^th, and 50^th repeats, respectively. The variant strain showed a significant increase in acid tolerance under conditions of pH 2.5 for 2 h (from 7.92 to 4.44 log CFU/ml) compared with the wild-type strain (WT, from 7.87 to 0 log CFU/ml). The surface of the variant strain was also smoother. Comparative whole-genome analysis showed that the galactosyl transferase D gene (cpsD, bbmn68_1012), a key gene involved in exopolysaccharide (EPS) synthesis, was altered by two nucleotides in the mutant, causing alteration in amino acids, pI (from 8.94 to 9.19), and predicted protein structure. Meanwhile, cpsD expression and EPS production were also reduced in the variant strain (p < 0.05) compared with WT, and the exogenous WT-EPS in the variant strain reduced its acid-resistant ability. These results suggested EPS was related to acid responses of BBMN68.

• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1093-1100
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• 2015

Acetate and lactate in growth media are detrimental to the production of Thermus maltogenic amylase (ThMA), a heterologous protein, as well as to the growth of recombinant Escherichia coli. Only 50 mM of acetate or 10 mM of lactate reduced 90% of specific ThMA activity. In this study, mutant E. coli strains blocked in the ackA-pta or ackA-pta and ldh pathways were created, characterized, and assessed for their culture performace in 300 L-scale fermentation. The ackApta and ldh double-mutant strain formed significantly less lactate and acetate, and produced a concomitant increase in the excretion of pyruvate (17.8 mM) under anaerobic conditions. The ackA-pta mutant strain accumulated significant acetate but had an approximately 2-fold increase in the formation of lactate. The ackA-pta and ldh double-mutant strain had superior overall performance in large-scale culture under suboptimal conditions, giving 67% higher cell density and 66% higher ThMA activity compared with those of the control strain. The doublemutant strain also achieved a 179% improvement in volumetric ThMA production.

• Journal of Microbiology and Biotechnology
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• v.29 no.11
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• pp.1806-1816
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• 2019

Candida albicans is an opportunistic fungus possessing multiple virulence factors controlling pathogenicity. Cell wall proteins are the most important among these factors, being the first elements contacting the host. Ddr48 is a cell wall protein consisting of 212 amino acids. A DDR48 haploinsufficient mutant strain was previously found necessary for proper oxidative stress response and drug resistance. In this study, we aimed to further elucidate the role of Ddr48 by performing additional phenotypic characterization assays. A combinatory proteomic and bioinformatics approach was also undertaken to determine differentially expressed cell wall proteins. Results showed that the mutant strain exhibited a 10% decrease in adhesion mirrored by a 20% decrease in biofilm formation, and slight sensitivity to menadione, diamide, and SDS. Both strains showed similar hyphae formation, virulence, temperature tolerance, and calcofluor white and Congo red sensitivities. Furthermore, a total of 8 and 10 proteins were identified exclusively in the wild-type strain grown under filamentous and non-filamentous conditions respectively. Results included proteins responsible for superoxide stress resistance (Sod4 and Sod6), adhesion (Als3, Hyr4, Pmt1, and Utr2), biofilm formation (Hsp90, Ece1, Rim9, Ipp1, and Pra1) and cell wall integrity (Utr2 and Pga4). The lack of detection of these proteins in the mutant strain correlates with the observed phenotypes.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.3
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• pp.173-178
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• 2003

To improve the erythritol productivity of Penicillium sp. KJ81, mutants were obtained using UV irradiation and NTG treatment Among these mutants, Penicillium sp. KJ-UV29 revealed no morphological changes, yet was superior to the wild strain in the following three points: (1) Penicillium sp. KJ-UV29 produced more erythritol than the wild strain under the same conditions, (2) no foam was produced during cultivation, unlike the wild strain, and (3) the mutant produced a Significantly lower amount of glycerol. Penirillium sp. KJ-UV29 produced as much as 15.1 g/L of erythritol, whereas the wild-type Penirillium sp. KJ81 only produced 11.7 g/L. Penicillium sp. KJ-UV29 only generated 6.1 g/L of glycerol, compared to 19.4 g/L produced by the wild strain. When investigating the optimal culture conditions for erythritol production by the mutant strain Penicillium sp. KJ-UV89, sucrose was identified as the most effective carbon source, and the mutant was even able to produce erythritol in a 70% sucrose-containing medium, although a 30% sucrose medium exhibited the highest productivity. The production of erythritol by Penirillium sp. KJ-UV29 was also significantly increased by the addition of ammonium carbonate, potassium nitrate, and sodium nitrate. Accordingly, under optimal conditions, Penicillium sp. KJ-UV29 produced 45.2 g/L of erythritol in a medium containing 30% sucrose, 0.5% yeast extract, 0.5% (NH$_4$)$_2$C$_2$O$_4$, 0.1% KNO$_3$, 0.1% NaNO$_3$, and 0.01% FeSO$_4$ with 1 vvm aeration and 200 rpm agitation at 37$^{\circ}C$ for 7 days in a 5-L jar fermentor.