• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.568-572
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• 2005

Saccharomyces yeast spores are more resistant to drying and storage than vegetative cells. For the mass production of yeast spores, compressed yeast was directly inoculated into a sporulation medium (SM). The effects of inoculum size and the addition of rice wine cake (RWC) into SM on the sporulation were examined using flasks. With $1\%$ inoculum of compressed yeast, $1.45{\times}10^8/ml$ of asci was obtained. The addition of $0.5\%$ RWC into SM improved the cell growth and spore yield, and the number of asci formed was $2.31{\times}10^8/ml$. The effects of culture temperature, temperature-shift, and concentrations of inoculum, potassium acetate, and RWC on the sporulation were also evaluated using a jar fermentor. The optimum temperature for spore formation was $22^{\circ}C$ where the number of asci formed was $2.46{\times}10^8/ml$. The shift of culture temperature from initial $30^{\circ}C$ for 1 day to $22^{\circ}C$ for 3 days increased the number of asci formed to $2.96{\times}10^8/ml$. The use of $2\%$ (w/v) inoculum of compressed yeast, $2\%$ potassium acetate, and $1\%$ (w/v) RWC in SM with the shift of culture temperature of initial $30^{\circ}C\;to\;22^{\circ}C$ resulted in $90\%$ sporulation ratio and formation of $6.18{\times}10^8\;asci/ml$.

• Journal of Microbiology
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• v.44 no.3
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• pp.269-275
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• 2006

Atmospheric-pressure cold plasma (APCP) using helium/oxygen was developed and tested as a suitable sterilization method in a clinical environment. The sterilizing effect of this method is not due to UV light, which is known to be the major sterilization factor of APCP, but instead results from the action of reactive oxygen radicals. Escherichia coli, Staphylococcus aureus, and Saccharomyces cerevisiae deposited on a nitrocellulose filter membrane or Bacillus subtilis spores deposited on polypropylene plates were exposed to helium/oxygen plasma generated with AC input power at 10 kHz, 6 kV. After Plasma treatment, nitrocellulose filter membranes were overlaid on fresh solid media and CFUs were counted after incubation overnight. D-values were 18 sec for E. coli, 19 sec for S. aureus, 1 min 55 sec for S. cerevisiae, and 14 min for B. subtilis spores. D-values of bacteria and yeast were dependent on the initial inoculation concentration, while the D-value of B. subtilis spores showed no correlation. When treated cells were observed with a scanning electron microscope, E. coli was more heavily damaged than S. aureus, S. cevevisiae exhibited peeling, and B. subtilis spores exhibited shrunken morphology. Results showed that APCP using helium/oxygen has many advantages as a sterilization method, especially in a clinical environment with conditions such as stable temperature, unlimited sample size, and no harmful gas production.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.184-189
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• 2004

Rice wine cake (RWC) is the solid waste obtained after rice wine fermentation. For the mass production of the spores of yeast Saccharomyces from RWC, the optimum pretreatment condition of RWC, the optimum composition of culture medium, and the optimum culture condition were examined. For sporulation, yeast cells were grown in the pre sporulation medium (PSM), transferred into sporulation medium (SM) containing 1 % potassium acetate, and incubated in a rotary shaking incubator at $25^{\circ}C$ for 4 days. The supernatant of the mixture of RWC and water was used as the presporulation medium (PSM). The optimum temperature and time for the pre-incubation of the mixture of RWC and water (1:2) to obtain maximum sporulation yield were $V^{\circ}C$ and 24 hr, respectively, and optimum culture time in PSM was 48 hr. Using these optimum conditions, the asci number obtained was 0.72$ 1.06${\times}$10^{8}$$m\ell$. The addition of wheat coat koji into SM increased the final number of asci to beTEX>$10^{8}$ $m\ell$. Spores were formed in the SM with the initial pH of 7-11, but no spores were formed in the SM with the initial pH of 5. To save the time and effort to pretreat the RWC, 2% and 0.5% RWC without any pretreatment were directly added into PSM containing 1 % brown sugar and SM, respectively, and the maximum asci number of $1.27${\times}$10^{8}$ /$m\ell$ was obtained.

• Korean Journal of Microbiology
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• v.33 no.3
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• pp.199-202
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• 1997

The effect of electric shock (AC 38 Vll.3 cm) on the lethal effect and induction rate of mutation of chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) was examined by using the spores of Streptomyces and the cells of haploid and polyploid yeast strains of Saccharomyccrs. Spores of Sireptomyces were all alive after 180 min of electric shock, hut all dead after 960 min-treatment. When the spores of Streptomyces or the cells of haploid and polyploid yeast were treated with electric shock and NTG, the electric shock increased the lethal effect of NTG; the survival rate of Streptomyces dropped from 72 to 48% after 180 min-treatment and those of haploidand polyploid-yeast decreased from 8 to 3% and 25 to lo%, respectively, after 40 min-treatment. The electric shock also increased mutation rates of Streptomyces and haploid yeast. from 1.8 to 13.6%' after 120 min-treatment and from 2.4 to 4.8% after 40 min-treatment, respectively.

• Preventive Nutrition and Food Science
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• v.12 no.4
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• pp.251-258
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• 2007

Thermal resistance and heat activation characteristics of Clostridium botulinum ATCC 25763 spores were evaluated. The effects of nisin and pH on the activation and subsequent germination were also investigated. Spores of C. botulinum were not inactivated by heat treatments up to $92^{\circ}C$ for 2 hr. Heat treatment at $85^{\circ}C$ for 90 min was selected as the optimal activation condition based on monitoring subsequent germination. L-alanine alone or in combination with L-cysteine was not sufficient to germinate the spores of this strain. Tryptone-Peptone- Glucose-Yeast extract (TPGY) broth supplemented with L-alanine was used as a suitable germination medium. Decreasing pH of activation suspension increased the degree of phase darkening, i.e., germination. In addition, the presence of nisin during activation increased the degree of phase darkening. The majority of spore populations were dormant at a pH of less than 2.8, and these populations required heat activation to increase the culturability on TPGY agar medium. However, extended heating in the presence of nisin at pH 2.8 decreased the spore count; however, heat activation was less necessary at pH 3.4, compared at pH 2.8.

• Mycobiology
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• v.33 no.2
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• pp.69-76
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• 2005

Conidial development of Cordyceps militaris was observed from germinating ascospores and vegetative hyphae through light and scanning electron microscopy (SEM). Ascospores were discharged from fresh specimens of C. militaris in sterile water as well as Sabouraud Dextrose agar plus Yeast Extract (SDAY) plates. We observed ascospore germination and conidial formation periodically. Under submerged condition in sterile water, most part-spores germinated unidirectionally and conidia were developed directly from the tips of germinating hyphae of part-spores within 36 h after ascospore discharge, showing microcyclic conidiation. First-formed conidia were cylindrical or clavate followed by globose and ellipsoidal ones. Germination of ascospores and conidial development were observed on SDAY agar by SEM. Slimy heads of conidia on variously arranged phialides, from solitary to whorl, developed 5 days after ascospore discharge. Besides, two distinct types of conidia, elongated pyriform or cylindrical and globose, were observed in the same slimy heads by SEM. Conidia were shown to be uninucleate with 4,6-diamidino-2-phenylindole staining. Conidiogenous cells were more slender than vegetative hyphae, having attenuated tips. Microcyclic conidiation, undifferentiated conidiogenous hyphae (phialides), polymorphic conidia and solitary, opposite to whorled type of phialidic arrangement are reported here as the characteristic features of asexual stage of C. militaris, which can be distinguished from other Cordyceps species.

• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1982-1992
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• 2019

The alkaliphilic, calcium carbonate precipitating Bacillus sp. strain AK13 can be utilized in concrete for self-repairing. A statistical experimental design was used to develop an economical medium for its mass cultivation and sporulation. Two types of screening experiment were first conducted to identify substrates that promote the growth of the AK13 strain: the first followed a one-factor-at-a-time factorial design and the second a two-level full factorial design. Based on these screening experiments, barley malt powder and mixed grain powder were identified as the substrates that most effectively promoted the growth of the AK13 strain from a range of 21 agricultural products and by-products. A quadratic statistical model was then constructed using a central composite design and the concentration of the two substrates was optimized. The estimated growth and sporulation of Bacillus sp. strain AK13 in the proposed medium were 3.08 ± 0.38 × 10⁸ and 1.25 ± 0.12 × 10⁸ CFU/ml, respectively, which meant that the proposed low-cost medium was approximately 45 times more effective than the commercial medium in terms of the number of cultivatable bacteria per unit price. The spores were then powdered via a spray-drying process to produce a spore powder with a spore count of 2.0 ± 0.7 × 10⁹ CFU/g. The AK13 spore powder was mixed with cement paste, yeast extract, calcium lactate, and water. The yeast extract and calcium lactate generated the highest CFU/ml for AK13 at a 0.4:0.4 ratio compared to 0.4:0.25 (the original ratio of the B4 medium) and 0.4:0.8. Twenty-eight days after the spores were mixed into the mortar, the number of vegetative cells and spores of the AK13 strain had reached 10⁶ CFU/g within the mortar. Cracks in the mortar under 0.29 mm were healed in 14 days. Calcium carbonate precipitation was observed on the crack surface. The mortar containing the spore powder was thus concluded to be effective in terms of healing micro-cracks.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.776-783
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• 2000

Various alcohol yeast strains have been isolated from main mashes of Korean traditional liquors, and their genetic diversities were previously reported [23]. In this study, the strain SHY111, showing the highest alcohol production, was tested for its fermentation and sporulation characteristics. Additionally, its haploid cells were isolated and tested for their growth and fermentation patterns. The strain was identified as Saccharomyces cerevisiae based on its morphological and physiological characteristics. The sequences of the ITS(internal transcribed spacer) and 5.8S rDNA regions of S. cerevisiae SHY111 were found to be identical to those of S. cerevisiae that was obtained from through the yeast genome project. The maximum fermentation ratio obtained by the strain SHY111 (96.7%) was almost the same as that by S. cerevisiae Balyun No. 1 (96.5%) that was a little higher than that by S. cerevisiae KCCM11215(95.8%). The strain was induced for sporulation in a sporulation liquid medium using log phase cells grown in different types of pre-sporulation media, and its haploid cells were obtained by spore dissection using a micromanipulator. The majority of the spores formed a small colony on a YPD agar plate, and the haploid yeast cells derived from the strain SHY111 showed a variety of growth and alcohol fermentation patterns. It was proposed that the fermentation patterns were related to their growth phenotypes in the most haploid strains, but possible not in some strains.

• Korean Journal of Microbiology
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• v.21 no.4
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• pp.229-237
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• 1983

Total tRNA genes from Aspergillus nidulans were cloned for the further investigation of the structure and expression of Aspergillus tRNA genes. Aspergillus DNA was isolated from spores and cloned into pBR322 plasmid DNA using BamHI and $T_4$ ligase. The recombinant hybrid DNA was transformed into E. coli HB101 and some 30,000 transformants were initially selected. Of these, about 5,300 E. coli clones containing Aspergillus DNA inserted into plasmid pBR322 at BamHl site have been isolated. The hybridization data obtained from the labeled Aspergillus $^{32}P-tRNA$ indicated that 105 colonies carried the total tRNA genes. From the data above and cohybridization experiment, tRNA genes of Aspergillus nidulans seem to be twice more clustered than those of yeast.

• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.369-372
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• 1998

Microbial insecticide formulations were prepared by liquid and semi-solid fermentations using Bacillus thuringiensis subsp. kurstaki, HL-106 (BTK-HL106), B. thuringiensis subsp. israelensis HL-63 (BTI-HL63) and B. sphaericus 1593 (BS-1593) strains. The liquid fermentation medium contained molasses 2%, dextrose 1.5%, peptone 2%, D-xylose 0.025%, CaCl$_2$ 0.1%, K$_2$HPO$_4$ 0.1%, KH$_2$PO$_4$ 0.1%, MgSO$_4$$.$7H$_2$O 0.03%, FeSO$_4$$.$7H$_2$O 0.002%, ZnSO$_4$$.$7H$_2$O 0.02%. The composition of the semi-solid fermentation medium was rice bran 45.2%, zeolite 31%, yeast powder 0.02%, corn powder 5%, dextrose 3%, lime 0.3%, NaCl 0.06%, CaCl$_2$ 0.02%, and H$_2$O 15.42%. Insecticide formulations produced in the liquid fermentation named BTK-HL106, BTI-HL63 and BS-1593 pesticides and those in the semi-solid fermentation were designated as BTK-HL106-1, BTI-HL63-1 and BS-1593-1 pesticides, respectively. The number of spore (endotoxin crystals) was 2.65${\times}$10$\^$9/ spores per $m\ell$ in the BTK-HL106 and 3.5${\times}$10$\^$10/ in the BTK-HL106-1 3.8${\times}$10$\^$9/ spores in the BTI-HL63 and 7.0${\times}$10$\^$10/ in the BTI-HL63-1, and 7.5${\times}$10$\^$9/ in the BS-1593 and 1.4${\times}$10$\^$10/ in the BS-1593-1. The spores in the BS-1593 formulation was produced two times more than the other formulations. The spores in the BTI-HL63-1 were contained twice than those in the BTK-HL106-1, and five times than those in the BS-1593-1. The results indicated that spore (endotoxin crystals) productions in the semi-solid fermentation increased about ten times than those in the liquid fermentations. $LC_{50}$s of the BTI-HL63 and BS-1593 were 4.5 $\mu\textrm{g}$, and those of the BTI-HL63-1 and BS-1593-1 were 1.5 $\mu\textrm{g}$. $LC_{50}$ of the BTK-HL106 was 1.5 mg and that of the BTK-HL106-1 was 0.9 mg. The $LC_{50}$s of the formulations in the semi-solid fermentations showed about two to three times higher than those in the liquid fermentations.