• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.105-112
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• 2010

Applications of plant residues and green manures generally improve the properties of soil under conventional farming system. Therefore, we investigated the improvement of selected soil physical properties, bulk density, porosity, and water content, soil penetration resistance, and soil microbial biomass carbon (SMBC) content as affected by different management practices: 1) conventional tillage without rice straw or green manure crop treatment (TNT, check plot), 2) no-tillage amended with rice straw (NTRS), 3) no-tillage amended with rye (NTR), 4) no-tillage amended with Chinese milk vetch (NTCMV), 5) no-tillage without rice straw or green manure crop treatment (NTNT), The values of bulk density, porosity, and water content ranged from 1.22 to 1.37 Mg $m^3$, from 48.3 to 54.0%, and from 35.0 to 40.2%, respectively. The management practices might positively influence the changes in the selected soil properties, especially in the second experimental year. The soil penetration resistance and SMBC content were also improved after applying rice straw and green manure crops as comparing with TNT. Therefore, applications of the rice straw and green manure crop management practices under no-tillage system positively influenced soil physical properties and soil microbial activities in paddy field.

• Food Science and Preservation
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• v.30 no.2
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• pp.287-299
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• 2023

In vitro luwak coffee was produced using enzyme­microbial complexes. The coffee quality of non-fermented coffee beans (NFC) and fermented coffee beans (FC) was compared. The total free amino acid content was higher in FC than in NFC. The levels of glutamic acid and γ-amino-n-butyric acid in NFC were higher than those in FC; however, the contents of essential amino acids, such as lysine, leucine, and valine, in FC were higher than in NFC. During fermentation, the sucrose content decreased, whereas the fructose and glucose contents increased (p<0.001). The chromaticity of the coffee extract showed higher lightness (L), redness (a), and yellowness (b) values in FC than those in NFC. The caffeine content was significantly lower in FC (696.94±0.04 ㎍/mL) compared to that in NFC (1,130.22±1.55 ㎍/mL) (p<0.001). Conversely, the polyphenol and chlorogenic acid contents were significantly higher in NFC than in FC (p<0.001). Electronic nose analysis indicated considerable differences between the volatile aromatic components in NFC and FC. Sensory scores were significantly higher for FC than those for NFC. Therefore, the fermentation of coffee beans using enzyme­microbial complexes altered the chemical components, which promoted the Maillard reaction during the coffee bean roasting process. These results suggest the possibility of producing in vitro luwak coffee with better flavor and lower caffeine content.

• Journal of Life Science
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• v.33 no.4
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• pp.325-333
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• 2023

This study compared and analyzed the microbial composition and physicochemical characteristics of kimchi (gimjang kimchi) and mukeunji (aged kimchi). Commercial kimchi and mukeunji products were purchased through an online market. After an analysis of physicochemical characteristics, the pH of the mukeunji samples was found to be lower and the acidity higher than in the kimchi samples. There was no significant difference in salinity between kimchi and mukeunji, but the sugar content was higher in the kimchi samples. The phylogenetic diversity index, which incorporates phylogenetic difference between species, was significantly higher in mukeunji than in the kimchi. The most dominant order in both groups was Lactobacillales, but several lactic acid bacteria, such as the Pediococcus and Lactobacillus species, which may be more acid tolerant or more competitive, are relatively predominant in mukeunji. Beta set-significance analysis based on two different distance metric results revealed that microbial distributions of population were different at the statistical confidence level (p<0.001). We investigated the effect of respective species on total microbial community using the LEfSe (linear discriminant analysis effect size) mechanism. According to the results of LEfSe testing, a relatively higher abundance of Weissella kandleri in kimchi and a higher abundance of Pediococcus inopinatus in mukeunji have the greatest influence on the differences in microbial structure between the two groups.

• Journal of Environmental Health Sciences
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• v.23 no.2
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• pp.44-56
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• 1997

When sewage sludge is treated by cornposting, higher moisture content and lower C/N ratio on sewage sludge is problems. This paper project to alesolve two problems. The almost trends in run 3 of MC 70% are similar to these in run 1 and 4 of MC 65%. A retention time of the highest temperature (>50$\circ$C) and increase rate of temperature in run 3 are an affinity to these in run 4. Particularly, decrease rate of temperature in run 3 is slower than others and this data shows the more activity of thermal microbial in run 3 than that in others. C/N ratio trends in run 3 shows slow reaction in initial stage but, after 9 days, is similar to that in run 1 and 4. Carbon trends in each run are a similarity to C/N ratio trends. Temperature, MC, carbon and C/N ratio trends in run 5, whose C/N ratio is 15, show less microbial activity than that in run 6, whose C/N ratio is 20. But temperature increase of the beginning stage and pH of the final stage in run 5 are greater than that in run 6. Final MC and carbon content in run 5 and 6 have a similar values. That is, final MC in run 5 and 6 is 49.39% and 48.97% and final carbon content in each run is 25.15% and 22.20%. Expecially, a temperature increase and C/N ratio decrease rate of the beginning stage in run 5 are greater than these in run 6. This shows the shorter lag time in run 5 than lag time in run 6.

• Korean Journal of Ecology and Environment
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• v.46 no.2
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• pp.276-288
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• 2013

The present study investigates the effects of elevated soil nitrogen on growth and decomposition of Oryza sativa shoots. The plants were cultivated in greenhouse until leaf senescence and the total biomass of the plant increased 1.9 times at nitrogen addition plot. Total C and N content in shoot increased; however, lignin, C/N, and lignin/N levels decreased in the N-treated soil. The shoot litters collected from the control and N-treated soil were tested for decay and microbial biomass, $CO_2$ evolution, and enzyme activities during decomposition on the control and N-treated soil at $25^{\circ}C$ microcosm. The remaining mass of the shoot litter was approximately 6% higher in the litter collected from the control soil (53.0%) than the litter collected from high N-treated soil (47.1%). However, the high N-containing litter exhibited faster decay in the control soil than in the N-treated soil. The litter containing high N, low C/N, and low lignin/N showed a higher decomposition rate than that of low quality litter. The N-addition showed decreased microbial biomass C and dehydrogenase activity in soil; however, it exhibited high microbial biomass N and urease activity in soil. When the high N-containing litter decays on the N-treated soil, the microbial biomass C increased rapidly at the initial phase of decomposition and decreased thereafter, and dehydrogenase activity was less that of other treatment; however, there was no effect on the microbial biomass N. The urease in the decomposing litter was highest during the early decomposition stage and dramatically decreased thereafter. The present findings suggested that the N-addition increased N content in litter, but inhibited the decomposition process of above-ground biomass in terrestrial ecosystems.

• Journal of Microbiology and Biotechnology
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• v.19 no.7
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• pp.651-657
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• 2009

Shifts in the activity and diversity of microbes involved in aliphatic and aromatic hydrocarbon degradation in contaminated soil were investigated. Subsurface soil was collected from a gas station that had been abandoned since 1995 owing to ground subsidence. The total petroleum hydrocarbon content of the sample was approximately 2,100 mg/kg, and that of the soil below a gas pump was over 23,000 mg/kg. Enrichment cultures were grown in mineral medium that contained hexadecane (H) or naphthalene (N) at a concentration of 200 mg/l. In the Henrichment culture, a real-time PCR assay revealed that the 16S rRNA gene copy number increased from $1.2{\times}10^5$to $8.6{\times}10^6$with no lag phase, representing an approximately 70-fold increase. In the N-enrichment culture, the 16S rRNA copy number increased about 13-fold after 48 h, from $6.3{\times}10^4$to $8.3{\times}10^5$. Microbial communities in the enrichment cultures were studied by denaturing gradient gel electrophoresis and by analysis of 16S rRNA gene libraries. Before the addition of hydrocarbons, the gas station soil contained primarily Alpha- and Gammaproteobacteria. During growth in the H-enrichment culture, the contribution of Bacteriodetes to the microbial community increased significantly. On the other hand, during N-enrichment, the Betaproteobacteria population increased conspicuously. These results suggest that specific phylotypes of bacteria were associated with the degradation of each hydrocarbon.

• The Korean Journal of Ecology
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• v.18 no.4
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• pp.503-512
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• 1995

The present paper describes partial results of the study on the activities of microbes in the soil of Quercus mongolica forest from July, 1994 to April, 1995. To determine the relationship between structure and function of soil microbial ecosystem, the author investigated the seasonal change of physical environmental factors, microbial population and soil enzyme activities. The changes of pH was not significant and the temperature of surface soil was 2℃ higher than lower soil through out the year. Moisture contents (％) of soil samples ranged from 7.64％ to 42.11％. However, soils of site 3 at Mt. Komdan in which vegetation is successional have higher moisture content than the others. The bacterial population increased in summer, but continuously decreased in autumn and winter, and then reincreased again in spring. Bacterial population of surface soil was higher than those of 30 cm depth all the year round. Dehydrogenase activity (DHA) was about two-fold higher throughout in surface soil compared to those of lower soil. And the correlation coefficient between DHA and bacterial population size was 0,713, It was suggested that DHA could be used as a primary index of soil microbial population and activity in soil ecosystem.

• Journal of Korean Society on Water Environment
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• v.28 no.5
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• pp.717-722
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• 2012

Fluoride can be easily found in semiconductor and display industry. However, there is a lack of research for its effects on the related wastewater treatment. The objective of this study is to evaluate the microbial inhibitory effect by fluoride injection. The research entailed the assessment of removal efficiency of $TCOD_{Cr}$ according to the fluoride concentration and also the Specific Oxygen Uptake Rate (SOUR) was measured. The laboratory scale reactor was prepared and operated with the fluoride concentrations of 0, 10, 50, 100, and 200 mg/L based on concentrations frequently occurring in the wastewater. The results from this study showed that, as the fluoride concentration increase, the Specific Substrate Utilization Rate (SSUR) tend to decrease as expected. Also, the increase in fluoride concentrations resulted in the decrease in SOUR. It is determined that fluoride injection affects the microbial activity. Especially, The addition of above 200 mg/L fluoride into reactor caused rapidly decreased SSUR and SOUR due to the inhibitory effects of fluoride.

• The Korean Journal of Ecology
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• v.15 no.3
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• pp.267-279
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• 1992

The relationship between pb, zn, cd, and the microbial biomass and activity were investigated in three public park soils of central and outer london. Variability with distance from the roadside and profile were studied. The heavey metal concentrations were the highest in hampstead heath and hyde park with high trafic density and the lowest in hainault. The highest concentrations of heavy metals were found adjacent to the roadside in the upper parts of the soil profile. Dehydrogenase activity, adenosine tri-phosphate and ergosterol contents used as indices of micrbial biomass and activity, were generally higher in hainadult, and also higher in the upper pats of the soil profile. Simple regression analysis indicated that the microbial biomass and activity were affected significantly by moisture content, water holding capacity, total organic carbon, total nitrogen, and organic mater rather than heavy metal concentration. Highest inputs of nitrogen and carbon were associated with high inputs of heavey metals, all three being derived from vehicle emissions adjacent to the road. The hyde park and hampstead heath microbial populations were able to respond to the c and n input positively by increase in biomass and activity, whereas the hainault populations could not. This rsult suggrsts adaptation in he former to heavy matals, but not in the latter.

• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.19.1-19.12
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• 2021

Objectives: The purpose of this study was to conduct a systematic review and meta-analysis of in vitro studies regarding the effectiveness of reciprocating and rotary instrumentation on microbial reduction in root canals. Materials and Methods: PubMed, Scopus, Web of Science, the Cochrane Library, and the gray literature were searched through December 2019. Studies comparing the influence of reciprocating and rotary instrumentation on the removal of microorganisms from root canals that quantified the antimicrobial effect were included. Data extraction was completed using a systematic form for data collection. The risk of bias of the studies was evaluated. Standardized mean differences (SMDs) and confidence intervals (CIs) were calculated using a random effects meta-analysis. Results: Seventeen in vitro studies were included in this systematic review, of which 7 provided adequate data for inclusion in the meta-analysis. Both reciprocating and rotary systems were similarly effective in reducing the microbial load in infected root canals (SMD [95% CI], 0.0481 [-0.271, 0.367]). Three studies showed a low risk of bias, whereas most of the studies (82%) presented a medium risk. Conclusions: Although both techniques decrease the microbial content (with reductions of 23.32%-88.47% and 23.33%-89.86% for reciprocating and rotary instrumentation, respectively), they are not able to provide complete disinfection of root canals.