• Journal of Microbiology and Biotechnology
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• 제9권5호
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• pp.646-649
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• 1999

A thermophilic bacterium producing D-stereospecific dipeptidase was isolated from Korean soil samples. The enzyme hydrolyzed the peptide bond between D-alanyl-D-alanine (D-Ala-D-Ala). The isolated bacterial strain was rod shaped, gram-positive, motile, and formed an endospore. Morphological and physiological characteristics suggested this microorganism a thermophilic Bacillus species, and was named as Bacillus sp. BCS-l. The production of D-stereospecific dipeptidase was growth-associated and optimal at $55^{\circ}C$. The enzyme was applied for the synthesis of D-amino acid-containing peptide, N-benzyloxycarbonyl-L-aspartyl-D-alanine benzyl ester (Z-L-Asp-D-AlaOBzl), as a model reaction. A thermodynamically controlled synthesis of Z-L-Asp-D-AlaOBzl was achieved in an organic solvent.

• Journal of Microbiology and Biotechnology
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• 제6권2호
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• pp.98-102
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• 1996

A thermostable tyrosine phenol-lyase gene of a thermophilic Symbiobacterium species was cloned and overexpressed in Escherichia coli in order to produce the biocatalyst for the synthesis of 3, 4-dihy-droxyphenyl-L-alanine (L-DOPA). The substrates used for the synthetic reaction were pyrocatechol, so-dium pyruvate, and ammonium chloride. The enzyme was stable up to $60^{\circ}C$, and the optimal temperature for the synthesis of L-DOPA was $37^{\circ}C$ . The optimal pH of the reaction was about 8.3. Enzyme activity was highly dependent on the amount of ammonium chloride and the optimal concentration was estimated to be 0.6 M. In the case of pyrocatechol, an inactivation of enzyme activity was observed at con-centrations higher than 0.1 M. Enzyme activity was increased by the presence of ethanol. Under op-timized conditions, L-DOPA production was carried out adding pyrocatechol and sodium pyruvate to the reaction solution intermittently to avoid substrate depletion during the reaction. The concentration of L-DOPA reached 29.8 g/l after 6 h, but the concentration didn t increase further because of the formation of byproducts by a non-enzymatic reaction between L-DOPA and pyruvate.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권5호
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• pp.383-388
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• 2004

The conversion of a cellulose-producing cell ($Cel^+$) from Gluconacetobacter hansenii PJK (KCTC 10505 BP) to a non-cellulose-producing cell ($Cel^-$) was investigated by measuring the colony forming unit (CFU). This was achieved in a shaking flask with three slanted baffles, which exerted a strong shear stress. The addition of organic acid, such as glutamic acid and acetic acid, induced the conversion of microbial cells from a wild type to $Cel^-$ mutants in a flask culture. The supplementation of $1\%$ ethanol to the medium containing an organic acid depressed the con-version of the microbial cells to $Cel^-$ mutants in a conventional flask without slanted baffles. The addition of ethanol to the medium containing an organic acid; however, accelerated the conversion of microbial cells in the flask with slanted baffles. The $Cel^+$ cells from the agitated culture were not easily converted into $Cel^-$ mutants on the additions of organic acid and ethanol to a flask without Slanted baffles, but some portion of the $Cel^+$ cells were converted to $Cel^-$ mutants in a flask with slanted baffles. The conversion ratio of $Cel^+$ cells to $Cel^-$ mutants was strongly re-lated to the production of bacterial cellulose independently from the cell growth.

• 한국식품위생안전성학회지
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• 제8권4호
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• pp.225-230
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• 1993

This study was conducted to examine the stages showing the antimutagenic effects on the microbial mutation by addition of the juice extracted from small water dropwort. It was not able to find out the signal showing the genic derepression or change of gene repair system by addition of the juice. And it was hardly possible to expect the conversion of 2-AF to inactive form by the juice. however the longer 2-AF and S-9 mix were contacted before addition of the juice, the stronger the microbial mutagenisity of 2-AF was, and after addition of the juice, the mutagenicity was decreased rapidly. It seems that some components in the juice act as inhibitor of a enzyme in S-9 mix, and block the conversion of 2-AF to the ultimate mutagen.

• 신재생에너지
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• 제20권1호
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• pp.175-181
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• 2024

This study analyzed the hydrogen conversion rate and microbial community in conjunction with changes in carbohydrate concentration during hydrogen fermentation using food waste, and presented comprehensive research results for the condition 80 g Carbo COD/L, which showed the highest efficiency with a carbohydrate removal rate of 98.1% and a hydrogen conversion rate of 1.76 mol H₂/mol. The microbial community analysis found that Clostridium sp., widely known as a hydrogen-producing microorganism, was released in 80 g Carbo COD/L and confirmed that it was a dominant species at 98.1%. Conversely, in 100 g Carbo. Under COD/L conditions, Leuconostoc sp. showed the maximun prevalence, which is believed to hinder hydrogen production.

• BMB Reports
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• 제32권5호
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• pp.480-485
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• 1999

Tyrosine phenol-lyase of thermophilic Symbiobacterium sp. SC-1, which is obligately and symbiotically dependent on thermophilic Bacillus sp. SK-1, was purified and characterized. The enzyme is composed of four identical subunits and contains approximately 1 mol of pyridoxal 5'-phosphate (PLP) per mol subunit as a cofactor. The enzyme showed absorption maxima at 330 and 420 nm, and lost this absorption profile by treatment with phenylhydrazine. The apparent dissociation constsnt, $K'_D$, for PLP was determined with the apoenzyme to be about $1.2\;{\mu}M$. The isoelectric point was 4.9. The optimal temperature and pH for the $\alpha,\beta$-elimination of L-tyrosine were found to be $80^{\circ}C$ and pH 8.0, respectively. The substrate specificity of the enzyme was very broad: L-amino acids including L-tyrosine, 3,4-dihydroxyphenyl-L-alanine (L-DOPA), L-cysteine, L-serine, S-methyl-L-cysteine, $\beta$-chloro-L-alanine, and S-(o-nitrophenyl)-L-cysteine all served as substrates. D-Tyrosine and D-serine were also decomposed into pyruvic acid and ammonia at rates of 7% and 31% relative to their corresponding L-enantiomers, respectively. D-Alanine, which was inert as a substrate in a, $\beta$-elimination, was the only D-amino acid racemized by the enzyme. The $K_m$ values for L-tyrosine, L-DOPA, S-(o-nitrophenyl)-L-cysteine, $\beta$-chloro-L-alanine, and S-methyl-L-cysteine were 0.19, 9.9, 0.36, 12, and 5.5 mM, respectively.

• 한국환경과학회지
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• 제28권1호
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• pp.159-162
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• 2019

This study aimed to evaluate the effects of dietary microbial-fermented molasses on egg production and egg quality in laying hens.In total, 90 Hy-line Brown laying hens were divided into two treatment groups (control and 1% microbial-fermented molasses)with three replicates of 15 birds each. During the experimental period, supplementation of hen diets with 1% microbial-fermented molassesdid not influence egg weight, hen-day egg production, egg mass, and feed conversion ratio (p > 0.05), except for feed intake. Regarding egg quality, diets containing 1% microbial-fermented molasses significantly affected eggshell thickness, Haugh unit, and albumen height (p < 0.05). However, there were no remarkable differences between control and 1% microbial-fermented molasses in eggshell color and egg yolk color (p > 0.05). These results indicate that supplementing 1% microbial-fermented molasses to the diet of laying hens improved egg quality parameters such as eggshell thickness, Haugh unit, and albumen height rather than egg production.

• Journal of Microbiology and Biotechnology
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• 제14권6호
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• pp.1275-1279
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• 2004

Citron peel oil was extracted from citron (Citrus funas) fruit by steam distillation, and was used as starting material for microbial conversion to synthesize attractive flavor compounds by using Enterobacter agglomerans 6L. E. agglomerans was isolated from citron peel and was able to metabolize the citron peel oil and grew well ($A_{600}:\;3.0$) on the citron peel oil as the sole carbon source. Multiple terpene metabolites were produced by E. agglomerans 6L on M9 salt media with citron oil vapor. The identified bioconversion products from the citron peel oil included trans-2-decenal, octanol, $\delta$­valerolactone, $\gamma$-valerolactone, cryptone, hydroxycitronellol, cuminol, and $\gamma$-dodecalactone.

• Archives of Pharmacal Research
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• 제15권1호
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• pp.41-47
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• 1992

In order to obtain acetaminophen, a popular analgesic-antipyretic, though microbial p-hydroxylation and N-acetylation of aniline, various Streptomyces strains were screened. Aniline N-acetylation activity was rather ubiquitous but-hydroxylation activity was selective. Microbial conversion pathway of aniline to acetaminophen was considered to be through N-acetylation and p-hydroxylation or vice versa. However, depending on species used, o-hydroxylation and its degradation activity (S. fradiae) and acetaminophen degradation activity (S. coelicolar) were also detected. Among the screened Streptomyces strains, S fradiae NRRL 2702 showed the highest acetanilide p-hydroxylation activity (203% conversion rate). Furthermore, in S. fradiae carbon source and its concentration, phosphate ion concentration and pH of growth medium were found to play the crucial roles in p-hydroxylation activity. Through the proper combination of factors mentioned above, the ten times more activity (26-30% conversion rate) was attained.

• Journal of Microbiology and Biotechnology
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• 제2권4호
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• pp.278-283
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• 1992

Aldehyde production by cells of a methanol utilizing yeast, Hansenula nonfermentans KYP-1 was improved when they were grown in a methanol-limited continuous culture, in comparison with cells grown in a batch culture. A higher cell yield was also obtained in continuous culture than in batch culture. This could be due to the fact that a lower methanol concentration was maintained in the jar fermentor to minimize growth inhibition by methanol. A maximum cell productivity of 0.219 g.$liter^{-1}.hr^{-l}$ and a cell yield of 47% were obtained at dilution rates of 0.1 $hr{-1}$ and 0.06 hr{-1}, respectively. The greatest amount of aldehyde was measured at a dilution rate of 0.08 $hr{-1}$. Under optimum reaction conditions, 915.7 mM of acetaldehyde was produced from 1.5 M ethanol after 21 hours reaction, with a conversion rate of 61%. Propionaldehyde and acrolein were produced with conversion rates of 32.7% and 44%, respectively.