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Dong, Dandan,Seo, Dongmin,Seo, Sungkyu,Lee, Jae Woo Techno-Press 2018 Membrane water treatment Vol.9 No.3
This study investigates the role of microbial extracellular polymeric substances (EPSs) as bioflocculants to harvest microalgae (water-microalgae separation). The EPS extracted from waste activated sludge (WAS) by heat extraction were fractionated into soluble EPS (S-EPS), loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS) forms. All the EPSs facilitated the flocculation of microalgal cells from stable growth medium. Of those EPSs, the TB-EPS showed the highest flocculating activity (FA) resulting in the substantial decrease in the amount of EPS added in terms of total organic carbon (TOC) during flocculation. The FA of microalgae was improved with the increase in TB-EPS dose, however, excessive dose of TB-EPS adversely affected it due to destabilization. Both LB- and TB-EPS could be utilized for flocculating microalgae as a sustainable option to the existing chemical-based flocculants. In addition to the conventional assessments, the effectiveness of the two bioflocculants for floc forming was also confirmed using a novel assessment of lens-free shadow imaging technique (LSIT), which was firstly applied for the rapid and quantitative assessment of microalgal flocculation.
Dong, Dandan,Aleta, Prince,Zhao, Xin,Choi, Oh Kyung,Kim, Sungpyo,Lee, Jae Woo Elsevier 2019 Bioresource technology Vol.275 No.-
<P><B>Abstract</B></P> <P>This study presents the effects of nanoscale zero valent iron (nZVI) concentration on the biomethanation of gaseous CO<SUB>2</SUB>. During anaerobic batch experiment with 9 times injection of CO<SUB>2</SUB>, the CO<SUB>2</SUB> concentration in the headspace rapidly decreased by dissolution. Then, when nZVI was added at 6.25 and 12.5 g/L, the dissolved CO<SUB>2</SUB> was biochemically transformed into CH<SUB>4</SUB> at a maximum production rate of 2.38 and 3.93 μmol/hr, respectively. Biomethanation at these two nZVI concentrations continued until the end of experiment. In spite of more H<SUB>2</SUB> evolution by nZVI at 25 g/L, biomethanation did not occur, due to the significant inhibition of methanogenesis by nZVI. As the nZVI concentration increased, relative abundance of the hydrogenotrophic methanogens, especially <I>Methanobacteriales</I>, increased. However, at 25 g/L of nZVI concentration, acetic acid was accumulated and the relative abundance of <I>Clostridium</I> became predominant, indicating that homoacetogenesis was superior over methanogenesis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biomethanation of CO<SUB>2</SUB> coupling with nZVI corrosion was suggested. </LI> <LI> Biomethanation rate was highly affected by the nZVI concentration. </LI> <LI> Excessive nZVI addition promoted homoacetogenesis rather than methanogenesis. </LI> <LI> qPCR supported the biomethanation depending nZVI concentration. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
KRAB family is involved in network shifts in response to osmotic stress in camels
Dandan Cao,Shenyuan Wang,Dong Zhang,Yanru Zhang,Junwei Cao,Yongbin Liu,Huanmin Zhou 한국통합생물학회 2022 Animal cells and systems Vol.26 No.6
A feature of the camel is its tolerance to osmotic stress. However, few studies of osmotic stress in vivo or comparative analyses between different tissues of the camel have been performed. Here, we report the roles of Krüppel-associated box domain containing zinc-finger repressor proteins (KRAB-ZFPs) in transcriptional networks under osmotic stress in camels by analyzing transcriptomes of four different tissues under various osmotic conditions. We found that 273 of 278 KRAB-ZFPs were expressed in our data set, being involved in all of the 65 identified networks and exhibiting their extensive functional diversity. We also found that 110 KRAB-ZFPs were hub genes involved in more than half of the networks. We demonstrated that the osmotic stress response is involved in network shifts and that KRAB-ZFPs mediate this process. Finally, we presented the diverse mechanisms of osmotic stress responses in different tissues. These results revealed the genetic architecture of systematic physiological response in vivo to osmotic stress in camels. Our work will lead to new directions for studying the mechanism of osmotic stress response in anti-arid mammals.
Granulation of Activated Sludge in a Continuous Flow Airlift Reactor by Strong Drag Force
Dandan Zhou,Mengyuan Liu,Jun Wang,Shuangshi Dong,Ning Cui,Linlin Gao 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.2
Most aerobic granule cultivation has been based on the sequencing batch reactor (SBR) and then the factors that affect aerobic granulations were developed in the SBR. However, little work has been done to cultivate aerobic granules in a continuous-flow bioreactor with simple structure that is realistic for engineering. This work is the first to cultivate aerobic granules in a continuous flow airlift fluidized bed reactor (CAFB) possesses a very simple structure and without settling time and starvation time controlling. The configuration of CAFB was the simplest continuous-flow aerobic granular bioreactor reported by now. The majority of granules could be formatted in the CAFB after 12 days cultivation. The effluent COD concentration maintained at 50 ± 10 mg/L for the variable COD loading rate of 3.5 g COD/L/d and 4.8 g COD/L/d, which confirmed that the CAFB performed good anti-shock abilities. CAFB performed good nitrification ability, however, little denitrification was found under the operating conditions of this study. The shear stress acting on the solid phase were hundreds of times stronger in the CAFB than in the SBR at the same aeration strength. It seems CAFB is very efficient for granulation due to the strong shear-force exertion,which is promising for continuous-flow aerobic granular bioreactor. Protein, positive to the hydrophobicity, was predominant in extracellular polymeric substances in the granules, and favored the granules formation in the CAFB combined with the polysaccharides. However, filamentous bulking always happened in 35 days operation of the CAFB, thus further study on the stability of this bioreactor is urgently necessary.
Dandan Han,Dong Wha Park,최대기,Minglei Tian,노경호 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.5
Ionic liquids (ILs) have gained wide recognition as novel solvents in chemistry. Their application in analytical chemistry, especially in separating analytes, is warranted due to their unique properties such as negligible vapor pressure, good thermal stability, tunable viscosity and miscibility with water and organic solvents, as well as good extractability for various organic compounds and metal ions. Recently, some new chromatographic separation media, formed by combining ILs on silica and polymer surface using covalently or non-covalently interaction, have been developed and applied to biological separation and environment analysis. This review will focus on some of the properties of ILs and their potential application as mobile phase modifier and surface-bonded stationary phase in high-performance liquid chromatography (HPLC) separation.
미세조류 분리/회수를 위한 세포외 고분자물질 생물 응집제 활용
최오경,Dong Dandan,김종락,맹승규,김극태,이재우 대한상하수도학회 2021 상하수도학회지 Vol.35 No.1
Microalgae are primary producers of aquatic ecosystems, securing biodiversity and health of the ecosystem and contributing to reducing the impact of climate change through carbon dioxide fixation. Also, they are useful biomass that can be used as biological resources for producing valuable industrial products. However, harvesting process, which is the separation of microalgal biomass from mixed liquor, is an important bottleneck in use of valorization of microalgae as a bioresource accounting for 20 to 30% of the total production cost. This study investigates the applicability of sewage sludge-derived extracellular polymeric substance (EPS) as bioflucculant for harvesting microalgae. We compared the flocculation characteristics of microalgae using EPSs extracted from sewage sludge by three methods. The flocculation efficiency of microalgae is closely related to the carbohydrate and protein concentrations of EPS. Heat-extracted EPS contains the highest carbohydrate and protein concentrations and can be a best-suited bioflocculant for microalgae recovery with 87.2% flocculation efficiency. Injection of bioflocculant improved the flocculation efficiency of all three different algal strains, Chlorella Vulgaris, Chlamydomonas Asymmetrica, Scenedesmus sp., however the improvement was more significant when it was used for flocculation of Chlamydomonas Asymmetrica with flagella.
Han, Dandan,Tian, Minglei,Park, Dong Wha,Row, Kyung Ho Natural Product Communications 2013 Natural product communications Vol.8 No.2
<P>A solid-phase extraction (SPE) method for the determination of procatechuic acid, ferulic acid and caffeic acid in Salicornia herbacea L. (Hamcho) has been developed. The optimal conditions were obtained by using a C18 SPE cartridge. By using ethanol and acetonitrile /water/ trifluoracetic acid as washing and eluting solvents, most interfering compounds originating from the hamcho matrix were eliminated. The extracts were sufficiently clean to be directly injected into the HPLC for further chromatographic analysis. Good linearity was obtained from 0.1 to 200 microg/mL (r > 0.999) for procatechuic acid, 0.2 to 400 microg/mL (r > 0.999) for caffeic acid and 0.3 to 600 microg/mL (r > 0.999) for ferulic acid, with the relative standard deviations being less than 3.6%. The mean recoveries of procatechuic acid, ferulic acid and caffeic acid from hamcho were more than 79.2% and the detection limit (S/N = 3:1) was 0.02 microg/mL for procatechuic acid, 0.01 microg/mL for caffeic acid and 0.04 microg/mL for ferulic acid. This method is a viable alternative to the existing HPLC methods for analyzing the content of procatechuic acid, ferulic acid and caffeic acid in hamcho.</P>