열처리 방법이 적무 새싹종자(Raphanus sativus)의 미생물 저감화 및 발아율에 미치는 영향

전소윤,이연경 한국식품저장유통학회 2014 한국식품저장유통학회지 Vol.21 No.4

This study was conducted to investigate the effects of various heat treatments on the microbial reduction and germination of red radish seeds for the development of effective and economical sterilization methods of improving microbial safety without reducting the germination rate. Hydrothermal treatment was conducted at 60, 65, 70, 75, 80, and 90℃ for 30 and 60 seconds, and dry heat treatment was performed at 70, 80, 90, and 100℃ for 5 minutes. In the seeds that underwent the hydrothermal treatment, time had little effect on the microbial reduction. There was no significant microbial reduction over time. However, there was significant microbial reduction as temperatures increased (p<0.001). The total plate count (TPC) was reduced by more than 3 logs, and Listeria monocytogenes was not detected at temperatures above 70°C. In the seeds that were subjected to the dry heat treatment, the TPC and the population of the L. monocytogenes were significantly reduced as the temperatures increased (p<0.001). After treatment at 100°C for 5 minutes, the TPC and the L. monocytogenes were reduced by 3 logs. As with the microbial reduction, time had little effect on the germination. There were no significant changes in the germination after the hydrothermal treatment over time; but at the temperatures above 75°C, the germination rate significantly decreased as the temperature increased (p<0.001). When the seeds were soaked after the hydrothermal treatment, their germination was stimulated. The dry heat treatment at temperatures of 80°C and higher significantly decreased the germination rate as the temperature increased (p<0.001). Dry heat treatment before the germination of the seeds soaked in distilled water for three hours significantly decreased the germination at temperatures greater than 90°C (p<0.05). This study showed that appropriate heat treatments can increase the microbiological safety and germination of red radish seeds.

Reduction of Dissolved Fe(III) by As(V)-tolerant Bacteria Isolated from Rhizosphere Soil

Khanal, Anamika,Song, Yoonjin,Cho, Ahyeon,Lee, Ji-Hoon The Korean Society of Environmental Agriculture 2021 한국환경농학회지 Vol.40 No.1

BACKGROUND: Biological iron redox transformation alters iron minerals, which may act as effective adsorbents for arsenate [As(V)] in the environments. In the viewpoint of alleviating arsenate, microbial Fe(III) reduction was sought under high concentration of As(V). In this study, Fe(III)-reducing bacteria were isolated from the wild plant rhizosphere soils collected at abandoned mine areas, which showed tolerance to high concentration of As(V), in pursuit of potential agents for As(V) bioremediation. METHODS AND RESULTS: Bacterial isolation was performed by a series of enrichment, transfer, and dilutions. Among the isolated strains, two strains (JSAR-1 and JSAR-3) with abilities of tolerance to 10 mM As(V) and Fe(III) reduction were selected. Phylogenetic analysis using 16S rRNA genesequences indicated the closest members of Pseudomonas stutzeri DSM 5190 and Paenibacillus selenii W126, respectively for JSAR-1 and JSAR-3. Ferric and ferrous iron concentrations were measured by ferrozine assay, and arsenic concentration was analyzed by ICP-AES, suggesting inability of As(V) reduction whereas ability of Fe(III) reduction. CONCLUSION: Fe(III)-reducing bacteria isolated from the enrichments with arsenate and ferric iron were found to be resistant to a high concentration of As(III) at 10 mM. We suppose that those kinds of microorganisms may suggest good application potentials for As(V) bioremediation, since the bacteria can transform Fe while surviving under As-contaminated environments. The isolated Fe(III)-reducing bacterial strains could contribute to transformations of iron minerals which may act as effective adsorbents for arsenate, and therefore contribute to As(V) immobilization

하수슬러지를 기질로 하는 미생물전기분해전지에서 전극간 거리가 메탄 생산에 미치는 영향

임성원(Seongwon Im),안용태(Yongtae Ahn),정재우(Jae Woo Chung) 大韓環境工學會 2015 대한환경공학회지 Vol.37 No.12

하수슬러지를 처리하는 미생물전기분해전지(Microbial electrolysis cell, MEC)의 성능에 미치는 전극간 거리의 영향에관한 실험실 규모 실험을 수행하였다. 각각 다른 전극간 거리(16, 32 mm)를 가진 두 쌍의 전극이 설치된 MEC 반응기가 안정적으로 이루어질 때 전류발생량, 메탄발생량, 메탄수율 등 MEC 성능에 미치는 전극간 거리의 영향을 분석하였다. 전극간거리가 16 mm일 때, 전류밀도와 메탄발생량은 각각 3.74 A/m3과 0.616~0.804 Nm3/m3으로 전극간 거리가 32 mm인 조건에서의 1.50~1.82 A/m3과 0.529~0.664 Nm3/m3보다 높게 나타났다. COD 및 VSS의 제거효율은 각각 34~40%와 32~38%의 범위를 가지는 것으로 나타났다. 전류밀도가 증가함에 따라 MEC의 생물전기화학적 성능이 향상되어 VSS 감소와 메탄생성이 증가하는 것으로 나타났으며 전류밀도는 VSS 제거효율보다 메탄수율에 상대적으로 큰 영향을 미치는 것으로 나타났다. Effect of electrode spacing on the performance of microbial electrolysis cells(MECs) for treating sewage sludge was investigated through lab scale experiment. The reactors were equipped with two pairs of electrodes that have a different electrode spacing (16, 32 mm). Shorter electrode distance improved the overall performance of MEC system. With the 16 mm of electrode distance, the current density was 3.04~3.74 A/m3 and methane production was 0.616~0.804 Nm3/m3, which were higher than those obtained with 32 mm of electrode spacing (1.50~1.82 A/m3, 0.529~0.664 Nm3/m3). The COD removal was in the range of 34~40%, and the VSS reduction ranged 32~38%. As the current production increased, VSS reduction and methane production were increased possibly due to the improved bioelectrochemical performance of the system. Methane production was more affected by current density than VSS reduction. These results imply that the reducing the electrode spacing can enhance the methane production and recovery from sewage sludge with the decreased internal resistance, however, it was not able to improve VSS reduction of sewage sludge.

Continuous Preparation of (S)-3-hydroxy-3-phenylpropionate by Asymmetric Reduction of 3-oxo-3-phenylpropionic Acid Ethyl Ester with Saccharomyces cerevisiae CGMCC No.2266 in a Membrane Reactor

Zhimin Ou,Xiaoyan Chen,Guoqing Ying,Hanbing Shi,Xingyuan Sun 한국생물공학회 2011 Biotechnology and Bioprocess Engineering Vol.16 No.2

In this study, (S)-3-hydroxy-3-phenylpropionate was prepared continuously by coupling microbial transformation and membrane separation. The effect of several factors on membrane flux, reactor capacity, and reaction conversion were investigated. A kinetic model of the continuous reduction process was also developed. The appropriate molecular weight cut-off of the ultrafiltration membrane was 30 kDa. The reactor capacity reached a maximum of 0.136/h at a biomass concentration and membrane flux of 86 g/L (dry weight/reaction volume) and 20 mL/h, respectively. The (S)-3-hydroxy-3-phenylpropionate yield was 3.68 mmol/L/day after continuous reduction over seven days. The enantiometric excess of (S)-3-hydroxy-3-phenylpropionate reached above 99.5%. The kinetic constants of continuous reduction were as follows:r_m = 3.00 × 10^(−3) mol/L/h, k_(cat) = 3.49 × 10^(−4) mol/L/h, k_1 =3.09 × 10^(−2) mol/L, and k_2 = 5.00 × 10^(−7) mol/L. The kinetic model was in good agreement with the experimental data obtained during continuous reduction. Compared with batch reduction, continuous reduction can significantly improve the catalytic efficiency of microbial cells and increase the reactor capacity.

Eco-friendly Indigo Reduction by Using Dietzia sp. KDB1 Strain : Some Variables Required to Develop Process Technology

정찬희,유동일,신윤숙 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11

This study was aimed to develop the reduction process of natural indigo (Indigofera tinctoria) by using bacterialstrain (Dietzia sp. KDB1) separated from Korean traditional fermentation bath. In detail, changes in pH, oxidation reductionpotential (ORP), and color intensity (K/S) of dyed ramie fabric were evaluated by using some of alkaline mediums, pHadjustments, and concentrations of KDB1 and indigo, respectively. In terms of pH control and reducing power, buffersolution of NaHCO3/NaOH was the most effective among the mediums used. In the baths with buffer solution, initial pH 10.7exhibited faster initiation of reduction and higher K/S than other initial pH values. The bath adjusted at pH 10.0 showedhigher K/S and more negative ORP, than the baths adjusted at pH 10.5 and 10.7. Better reducing power was obtained athigher indigo and KDB1 concentrations. With the combination of buffer solution, scale-up, repeat dyeing, and higher KDB1concentration, K/S range of 9.5-16.0 was obtained at days of 4-6. Use of single bacterial strain for indigo reduction attains asimple, reliable and eco-friendly dyeing process which can be applied as an alternative to sodium dithionite reduction.

Effect of Washing Treatments on Pesticide Residues and Antioxidant Compounds in Yuja (Citrus junos Sieb ex Tanaka)

성정민,권기현,김종훈,정진웅 한국식품과학회 2011 Food Science and Biotechnology Vol.20 No.3

This study investigated the removal efficiency of pesticide residues and microorganisms, and changes of the amount of antioxidant compounds on yuja (Citrus junos Sieb ex Tanaka) by various washing methods. The washing methods were mechanical washing (MW),mechanical washing after soaking in SAcEW, strong acidic electrolyzed water (SAcEW+MW), and soaking detergent solution (DW), with a tap water washing (TW) as the control. After treatment of MW and SAcEW+MW, the microbial count were 3.71 and 2.66 log CFU/g, respectively. Compared with the TW treatment (5.77 log CFU /g), MW and SAcEW+MW treatments showed a higher reduction. As a result of pesticide residue, the SAcEW+MW removed 70.5-98.1% and was the most effective, regardless of the pesticides. Antioxdant activities, as measured by DPPH radical, ranged from 20.36 to 21.27% and there was no significant difference from the washing methods. The results of this study demonstrated that the SAcEW+MW was the most effective method for removing residual pesticides without affecting the quality of the yuja.

Phosphate enhanced abiotic and biotic arsenic mobilization in the wetland rhizosphere

Zhang, Zheyun,Moon, Hee Sun,Myneni, Satish C.B.,Jaffé,, Peter R. Elsevier 2017 CHEMOSPHERE - Vol.187 No.-

<P><B>Abstract</B></P> <P>Although abiotic process of competitive sorption between phosphate (P) and arsenate (As(V)), especially onto iron oxides, are well understood, P-mediated biotic processes of Fe and As redox transformation contributing to As mobilization and speciation in wetlands remain poorly defined. To gain new insights into the effects of P on As mobility, speciation, and bioavailability in wetlands, well-controlled greenhouse experiments were conducted. As expected, increased P levels contributed to more As desorption, but more interestingly the interactions between P and wetland plants played a synergistic role in the microbially-mediated As mobilization and enhanced As uptake by plants. High levels of P promoted plant growth and the exudation of labile organic carbon from roots, enhancing the growth of heterotrophic bacteria, including As and Fe reducers. This in turn resulted in both, more As desorption into solution due to reductive iron dissolution, and a higher fraction of the dissolved As in the form of As(III) due to the higher number of As(V) reducers. Consistent with the dissolved As results, arsenic-XANES spectra from solid medium samples demonstrated that more As was sequestered in the rhizosphere as As(III) in the presence of high P levels than for low P levels. Hence, increased P loading to wetlands stimulates both abiotic and biotic processes in the wetland rhizosphere, resulting in more As mobilization, more As reduction, as well as more As uptake by plants. These interactions are important to be taken into account in As fate and transport models in wetlands and management of wetlands containing As.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Increased PO<SUB>4</SUB> <SUP>3−</SUP> loading to wetlands stimulates abiotic and biotic As mobilization. </LI> <LI> Increased PO<SUB>4</SUB> <SUP>3−</SUP> loading results in more As-reducing bacteria in wetland sediments. </LI> <LI> Increased PO<SUB>4</SUB> <SUP>3−</SUP> loading results in more As reduction in wetland sediments. </LI> <LI> Increased PO<SUB>4</SUB> <SUP>3−</SUP> loading results in more As uptake by wetland plants. </LI> <LI> Increased PO<SUB>4</SUB> <SUP>3−</SUP> loading to wetlands results in lower ORP and less Fe reduction. </LI> </UL> </P>

Influence of calcium on microbial reduction of solid phase uranium(VI)

Liu, Chongxuan,Jeon, Byong-Hun,Zachara, John M.,Wang, Zheming John Wiley & Sons 2007 Biotechnology and bioengineering Vol.97 No.6

<P>The effect of calcium on the dissolution and microbial reduction of a representative solid phase uranyl [U(VI)], sodium boltwoodite (NaUO<SUB>2</SUB>SiO<SUB>3</SUB>OH · 1.5H<SUB>2</SUB>O), was investigated to evaluate the rate-limiting step of microbial reduction of the solid phase U(VI). Microbial reduction experiments were performed in a culture of a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1, in a bicarbonate medium with lactate as electron donor at pH 6.8 buffered with PIPES. Calcium increased the rate of Na-boltwoodite dissolution and U(VI) bioavailability by increasing its solubility through the formation of a ternary aqueous calcium-uranyl-carbonate species. The ternary species, however, decreased the rates of microbial reduction of aqueous U(VI). Laser-induced fluorescence spectroscopy (LIFS) and transmission electron microscopy (TEM) collectively revealed that microbial reduction of solid phase U(VI) was a sequentially coupled process of Na-boltwoodite dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) to U(IV) that accumulated on bacterial surfaces/periplasm. Under studied experimental conditions, the overall rate of microbial reduction of solid phase U(VI) was limited by U(VI) dissolution reactions in solutions without calcium and limited by microbial reduction in solutions with calcium. Generally, the overall rate of microbial reduction of solid phase U(VI) was determined by the coupling of solid phase U(VI) dissolution, U(VI) aqueous speciation, and microbial reduction of dissolved U(VI) that were all affected by calcium. Biotechnol. Bioneg. 2007;97: 1415–1422. © 2007 Wiley Periodicals, Inc.</P>

Environmental Microbiology and Engineering : Effects of Microbial Iron Reduction and Oxidation on the Immobilization and Mobilization of Copper in Synthesized Fe(III) Minerals and Fe-Rich Soils

( Chaohua Hu ),( Youchi Zhang ),( Lei Zhang ),( Wensui Luo ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.4

The effects of microbial iron reduction and oxidation on the immobilization and mobilization of copper were investigated in a high concentration of sulfate with synthesized Fe(III) minerals and red earth soils rich in amorphous Fe (hydr)oxides. Batch microcosm experiments showed that red earth soil inoculated with subsurface sediments had a faster Fe(III) bioreduction rate than pure amorphous Fe(III) minerals and resulted in quicker immobilization of Cu in the aqueous fraction. Coinciding with the decrease of aqueous Cu, SO4 2- in the inoculated red earth soil decreased acutely after incubation. The shift in the microbial community composite in the inoculated soil was analyzed through denaturing gradient gel electrophoresis. Results revealed the potential cooperative effect of microbial Fe(III) reduction and sulfate reduction on copper immobilization. After exposure to air for 144 h, more than 50% of the immobilized Cu was remobilized from the anaerobic matrices; aqueous sulfate increased significantly. Sequential extraction analysis demonstrated that the organic matter/sulfide-bound Cu increased by 52% after anaerobic incubation relative to the abiotic treatment but decreased by 32% after oxidation, indicating the generation and oxidation of Cu-sulfide coprecipitates in the inoculated red earth soil. These findings suggest that the immobilization of copper could be enhanced by mediating microbial Fe(III) reduction with sulfate reduction under anaerobic conditions. The findings have an important implication for bioremediation in Cucontaminated and Fe-rich soils, especially in acid-mine-drainage-affected sites.

미생물 촉매제를 이용한 슬러지 감량화에 관한 연구

신동철,양은지,이연구,박철휘 대한환경공학회 2018 대한환경공학회지 Vol.40 No.2

In this study, evaluation of sludge reduction and advanced treatment were performed using the batch test. Sludge reduction rate was checked by batch experiment on excess sludge and aerobic sludge. The maximum sludge reduction rate was 37% for excess sludge and 34% for aerobic sludge. As a result of the batch process, the SCODCr 26%, S-N 62% and S-P 82% were removed. Therefore, it is possible to reduce the amount of sludge during the microbial catalyst injection and to remove the organic matter and nutrients simultaneously. In particular, the removal efficiency of S-P is higher than that of the conventional treatment. Especially, the removal efficiency of S-P was higher than that of conventional A2O treatment. In order to evaluate sludge reduction ability after microbial catalytic agent injection, the yield of heterotrophic biomass (YH), decay coefficient of heterotrophic biomass (bH) and observed or net biomass yield (Yobs) were estimated. The yield of YH was 0.32 and 0.25, which was less than 50% of the YH (BOD based) value of general heterotrophic microorganisms. On the other hand, bH was 0.232 day-1, which is a general value. Therefore, it is considered that the main factor of sludge reduction using microbial agent is due to the decrease of biomass build-up rather than the death of sludge microorganisms. 본 연구는 batch-test를 통해 미생물 촉매제의 적정 주입량을 산정하고 슬러지 감량화에 대하여 검토하였다. 잉여슬러지와 호기조 슬러지를 대상으로 batch 실험을 통해 슬러지 감량화율을 확인하였으며 잉여슬러지는 최대 37%, 호기조 슬러지최대 34%의 슬러지 감량화율을 나타내었다. Batch test를 통하여 고도처리 효율을 산정한 결과 SCODCr 26%, S-N 62%, S-P 82% 제거되었다. 따라서 미생물 촉매제 주입 시 슬러지 감량화가 가능하고 유기물 및 영양염류의 동시제거가 가능한 것으로나타났으며 특히 S-P의 경우 기존 처리공정의 인 제거효율보다 높은 제거효율을 보였다. 미생물 촉매제 주입 이후 슬러지감량능을 평가하기 위하여 종속영양미생물 생산계수(YH), 종속영양미생물 사멸계수(bH), 미생물 생산계수(Yobs)의 산정을 통해 분석하였다. YH 산정결과 0.32, 0.25으로 나타났으며 일반적인 종속영양미생물의 YH (BOD based) 값의 50% 이하의 값을보였다. 반면에 bH는 0.232 day-1로 일반적인 수치를 보여 미생물 촉매제를 이용한 슬러지 감량의 주 요인은 슬러지 미생물의사멸이 아닌 증식 저하에 따른 것이라 판단된다.