• YAKHAK HOEJI
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• v.51 no.3
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• pp.199-205
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• 2007

Thermostable asparaginase was purified to homogeneity from mesophilic Strepfomyces lincolnensis M-20 by 30${\sim}$70% ammonium sulfate precipitation and asparagine-Sepharose CL 6B affinity column chromatography, The apparent molecular mass of L-asparaginase by SDS-PAGE was found to be 47 kDa, whereas by its mobility on Sephacryl S-300 column was around 180 kDa, indicating that the enzyme at the native stage acts as tetramer, The purified enzyme showed a single band on acrylamide gel electrophoresis. The optimum pH and temperature were pH 9.5 and 55${\circ}$C, respectively. Chemical modification experiments of purified asparagines implied the existence cystein residue located at or near active site. Purified asparaginase retained the 85% of the initial activity after incubation at 90${\circ}$C for 30 min. A correlation between themostability and resistance to proteolysis of commercial asparaginase and purified asparaginase from Strepfomyces lincolnensis M-20 was investigated. Purified thermostable asparaginase was resistant to trypsin and chymotrypsin treatment, while the commercial asparaginase was not themostable and was susceptible to proteolytic treatment with trypsin and chymotrypsin.

• Environmental Engineering Research
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• v.17 no.4
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• pp.211-216
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• 2012

Quantification of the airborne microorganisms (bacteria and fungi) at a swine wastewater treatment plant was performed. Microbial samples were collected at three different phases of the treatment process over a 1-yr period. Cultivation methods based on the viable counts of mesophilic heterotrophic bacteria and fungi were performed. The concentrations of airborne bacteria ranged up to about $5{\times}10^3$ colony-forming unit (CFU)/$m^3$, and those of airborne fungi ranged up to about $9{\times}10^2CFU/m^3$. The primary treatment (e.g., screen, grit removal, and primary sedimentation) was found to be the major source of airborne microorganisms at the site studied, and higher levels of airborne bacteria and fungi were observed in summer. High levels of the respirable bioaerosol (0.65 to $4.7{\mu}m$ in size) were detected in the aeration phase. Among the environmental factors studied, temperature was strongly associated with fungal aerosol generation (with a Spearman correlation coefficient of 0.90 and p-value <0.01). Occupational biorisks are discussed based on the observed field data.

• The Korean Journal of Mycology
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• v.32 no.2
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• pp.105-111
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• 2004

The changes of microflora and chemical characteristics during fermentation process of cotton waste for oyster mushroom cultivation were investigated with 5 l bench-scale reactors placed in an incubator at different temperatures ($40,\;50\;and\;60^{\circ}C$). Cotton waste was wetted to 70% moisture, and air flow rates to the substrate were 50, 100 and 300 cc/min. In processing of composting, the mesophilic bacterial population decreased sharply but thermophilic bacterial population increased. In case of fungi, both mesophilic and thermophilic population decreased. The daily $CO_2$ evolution showed little difference in all treatments, while $NH_3$ dropped sharply after 3 days. The desirable composting temperature and air flow based on the mycelial growth of oyster mushroom were $50^{\circ}C$ and 100 cc/min, respectively.

• Journal of Microbiology and Biotechnology
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• v.23 no.9
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• pp.1221-1228
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• 2013

Two lipase genes (bpl1 and bpl3) from Antarctic Bacillus pumilus strains were expressed in Bacillus subtilis. Both recombinant lipases BPL1 and BPL2 were secreted to the culture medium and their activities reached 3.5 U/ml and 5.0 U/ml, respectively. Their molecular masses apparent using SDS-PAGE were 23 kDa for BPL1 and 19 kDa for BPL3. Both lipases were purified to homogeneity using ammonium sulfate precipitation and HiTrap SP FF column and Superose 12 column chromatographies. The final specific activities were estimated to be 328 U/mg for BPL1 and 310 U/mg for BPL3. Both lipases displayed an optimum temperature of $35^{\circ}C$, similar to other mesophilic enzymes. However, they maintained as much as 70% and 80% of the maximum activities at $10^{\circ}C$. Accordingly, their calculated activation energy at a temperature range of $10-35^{\circ}C$ was 5.32 kcal/mol for BPL1 and 4.26 kcal/mol for BPL3, typical of cold-adapted enzymes. The optimum pH of BPL1 and BPL3 was 8.5 and 8.0, respectively, and they were quite stable at pH 7.0-11.0, showing their strong alkaline tolerance. Both lipases had a preference toward medium chain length ($C_6-C_{10}$) fatty acid substrates. These results indicate the potential for the two Antarctic B. pumilus lipases as catalysts in bioorganic synthesis, food, and detergent industries.

• Journal of Microbiology and Biotechnology
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• v.20 no.2
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• pp.254-264
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• 2010

To obtain an efficient natural lignocellulolytic complex enzyme, we screened an efficient lignocellulose-degrading composite microbial system (XDC-2) from composted agricultural and animal wastes amended soil following a long-term directed acclimation. Not only could the XDC-2 degrade natural lignocelluloses, but it could also secrete extracellular xylanase efficiently in liquid culture under static conditions at room temperature. The XDC-2 degraded rice straw by 60.3% after fermentation for 15 days. Hemicelluloses were decomposed effectively, whereas the extracellular xylanase activity was dominant with an activity of 8.357 U/ml on day 6 of the fermentation period. The extracellular crude enzyme noticeably hydrolyzed natural lignocelluloses. The optimum temperature and pH for the xylanase activity were $40^{\circ}C$ and 6.0. However, the xylanase was activated in a wide pH range of 3.0-10.0, and retained more than 80% of its activity at $25-35^{\circ}C$ and pH 5.0-8.0 after three days of incubation in liquid culture under static conditions. PCR-DGGE analysis of successive subcultures indicated that the XDC-2 was structurally stable over long-term restricted and directed cultivation. Analysis of the 168 rRNA gene clone library showed that the XDC-2 was mainly composed of mesophilic bacteria related to the genera Clostridium, Bacteroides, Alcaligenes, Pseudomonas, etc. Our results offer a new approach to exploring efficient lignocellulolytic enzymes by constructing a high-performance composite microbial system with synergistic complex enzymes.

• Korean Journal of Food Science and Technology
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• v.49 no.4
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• pp.408-414
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• 2017

Effects of pulsed electric field (PEF) processing on growth inhibition of indigenous aerobic microorganisms and the quality of mandarin and carrot juices were investigated. Mandarin juice was PEF-treated at 15-23 kV/cm for $23-241{\mu}s$, whereas carrot juice was treated at 13-14 kV/cm for 127-198 s. At $25^{\circ}C$ (inlet temperature), PEF treatments at 23 kV/cm for $104{\mu}s$ and 14 kV/cm for $198{\mu}s$ reduced the numbers of total mesophilic aerobes by $6.3{\pm}0.8$ and $5.5{\pm}0.9{\log}\;CFU/mL$ in mandarin juice and carrot juice, respectively. Elevation of inlet temperature to $40^{\circ}C$ increased the reduction rates in both juices. In general, the treatments resulting in the highest microbial inhibition at 25 and $40^{\circ}C$ did not alter the physicochemical and nutritional properties of both juices (p>0.05). PEF is a feasible technology to pasteurize mandarin and carrot juices commercially, with minimal quality deterioration.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1085-1091
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• 2009

A phytase with high activity at low temperatures has great potential for feed applications, especially in aquaculture. Therefore, this study used a degenerate PCR and TAIL PCR to clone a phytase gene from Erwinia carotovora var. carotovota, the cause of soft rot of vegetables in the ground or during cold storage. The full-length 2.5-kb fragment included an open reading frame of 1,302 bp and encoded a putative phytase of 45.3 kDa with a 50% amino acid identity to the Klebsiella pneumoniae phytase. The phytase contained the active site RHGXRXP and HD sequence motifs that are typical of histidine acid phosphatases. The enzyme was expressed in Escherichia coli, purified, and displayed the following characteristics: a high catalytic activity at low temperatures (retaining over 24% activity at $5^{\circ}C$) and remarkably thermal lability (losing >96% activity after incubation at $60^{\circ}C$ for 2 min). The optimal phytase activity occurred at pH 5.5 and ${\sim}49^{\circ}C$, and the enzyme activity rapidly decreased above $40^{\circ}C$. When compared with mesophilic counterparts, the phytase not only exhibited a high activity at a low temperature, but also had a low $K_m$ and high $k_{cat}$. These temperature characteristics and kinetic parameters are consistent with low-temperature-active enzymes. To our knowledge, this would appear to be the first report of a low-temperature-active phytase and its heterogeneous expression.

• Microbiology and Biotechnology Letters
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• v.43 no.3
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• pp.259-266
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• 2015

Observed trends in climate change, globalization and an aging population have an effect on public health conditions in Korea, prompting a reevaluation of current environmental regulations. In this study, we evaluated the performance of the total coliform (TC) standard, which is the only microbiological standard in the current regulation regime for hot spring water, by estimating correlation with the presence/absence of Legionella, a non-fecal opportunistic pathogen with heat-tolerance. Microbiological data in 7 studies that surveyed Legionella in hot spring waters were subjected to meta-analyses with the odds ratio (OR) as the effect size. The presence/absence of Legionella was significantly correlated to TC levels [OR = 3.1(1.5–6.4, 95% CI), p = 0.002]. Due to there being no direct explanation as to the reason for the occurrence of TC, mesophilic fecal bacteria, being coupled with Legionella presence, the mechanism of the correlation between the two kinds of bacteria was further investigated. Legionella presence was more prevalent with a high heterotrophic plate count [HPC; 4.0(2.2–7.2); p < 0.001] and water temperature [4.3(1.4–13.6), p = 0.011] when the temperature range was <40℃. However, it was reverse-correlated with water temperature when the temperature was >50℃ [0.2(0.1–0.4), p < 0.001]. Therefore, bacterial standing crops in hot spring waters appear to be determined by water temperature in general, and this forces TC and Legionella levels be correlated. In accordance with this relationship, HPC rather than TC reflect the levels of non-fecal contamination better. Therefore, employing HPC as the sole microbiological standard, or adding HPC into the current standard of hot spring water assessment, is suggested as a proactive measure to prevent health issues arising from contamination.

• Journal of Korea Soil Environment Society
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• v.4 no.3
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• pp.57-65
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• 1999

Generation of gaseous ammonia has been a major problem in composting facilities. Microbial inocula. KMT-199(brand name: CompoBac$^{TM}$). was developed in INBI0NET CORPORATION and tested in the field for its ammonia reducing capability. When KMT-199 was applied. a ten-fold increase of mesophilic and thermophilic microorganisms was observed during the early stage of composting process. Also. the temperature and pH of early stage compost increased at a higher rate when compared to control. KMT-199 treated compost reached highest temperature of $75^{\circ}C$at day 9, indicating treatment could shift the maximum composting temperature to 3 days earlier The highest temperature also reached $3^{\circ}C$ higher than the control. The pH of compost gradually increased during composting. KMT-199 treated compost reached a plateau of pH 9.32 at day 15 after treatment, and then slowly decreased thereafter. On the other hand. pH of the control steadily increased until day 38 of composting. 29% reduction of gaseous ammonia generation during composting was observed compared to that of the control. KMT-199 amended compost resulted in a higher germination rate of radish seeds than the control. These results indicate that application of microbial inocula facilitates degradation of organic materials, including ammonia during the composting process.

• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.338-345
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• 1994

In the course of developing a small composter for dwelling house, we designed two different small bins; one is insullated (type 1) and the other uninsullated (type 2). Several interesting results were abtained from the study using these bins for garbage composting in winter, spring and summer. Changes in microbial number were very similar to those observed in the general composting process. However, microbial flora was relatively simple. The genera Streptomyces and Nocardia of actinomycetes and the genera Aspergillus, Penicillium, Mucor, Absidia, Rhizopus of hypomycetes was observed from the composted materials. Thermophiles secreted most of the ${\alpha}-amylase$ secreted in winter but mesophilic actinomycetes did in summer. The amount of secreted protease was much lower in winter than in summer. Lipases were secreted more by mesophiles than thermophiles. Only Aspergillus of hypomycetes was observed to degrade cellulose. Generally, the appearance of enzyme producing microorganisms increased in summer than in the other seasons. In the point of seasonal increase of temperature and changes in microbial flora, the number of microorganisms was higher in summer or spring than in winter.