The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Seokhwan Hwang - One of the best experts on this subject based on the ideXlab platform.
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effect of temperature and hydraulic retention time on volatile fatty acid production based on bacterial community structure in anaerobic acidogenesis using swine wastewater
Bioprocess and Biosystems Engineering, 2013Co-Authors: Woong Kim, Seung Gu Shin, Juntaek Lim, Seokhwan HwangAbstract:To investigate the effect of hydraulic retention time (HRT) and temperature (T) on bacterial community structure and volatile fatty acids (VFAs) production of an acidogenic process, and VFA production and changes in the bacterial community in three identical automated anaerobic continuously-stirred tank reactors were analyzed using response surface analysis (RSA) and nonmetric multidimensional scaling (NMDS). For RSA, 11 trials were conducted to find the combination of T and HRT under which VFA production was greatest; VFA production was affected more by HRT than by T. To identify the bacterial community structure in each trial, DNA from each experimental point of the RSA was analyzed using denaturating gradient gel electrophoresis (DGGE), and eight bacteria species were detected. NMDS was conducted on band intensities obtained using DGGE, and bacterial community structure was affected more by T than by HRT. Taken together, these results suggest that VFA production during acidogenesis was more dependent on the physicochemical properties of Acidogens, such as their specific growth rate or contact time with of substrates, than on changes in the microbial community.
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co digestion of lignocellulosics with glucose using thermophilic Acidogens
Biochemical Engineering Journal, 2004Co-Authors: Byungcheol Park, Seokhwan HwangAbstract:Abstract Thermomechanical pulping (TMP) wastewater was tested for the feasibility of augmenting readily biodegradable organics for enhanced microbial hydrolysis by thermophilic Acidogens. A biochemical methane potential test showed approximately 13±1% of the chemical oxygen demand was anaerobically biodegradable. Three glucose concentrations set up in a ratio of 1:3:6, 5, 15, and 30 g/l, were tested to induce the production of short-chain organic acids and ethanol. Compared to the control with no glucose addition, more than six times of the fragmentation of lignocellulosics in the wastewater was achieved.
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biokinetics in acidogenesis of highly suspended organic wastewater by adenosine 5 triphosphate analysis
Biotechnology and Bioengineering, 2002Co-Authors: Conly L. Hansen, Seokhwan HwangAbstract:In this paper, we pointed out the problems of using conventional volatile suspended solids (VSS) and chemical oxygen demand (COD) to evaluate biokinetic coefficients, especially for the treatment of highly suspended organic wastewater. We also introduced a novel approach to evaluate biokinetic coefficients by measurement of adenosine 5'-triphosphate (ATP) of microorganisms. The concept of using ATP analysis in biokinetic evaluations with highly suspended wastewater was shown to be effective. This study also showed that the conventional VSS and COD methods were strongly affected by incoming suspended organics in the wastewater and by biokinetics of microorganisms. A cheese-processing wastewater was used in evaluating the biokinetics of mesophilic Acidogens. The concentration of COD and total suspended solids in the wastewater was 63.3 g/L and 12.4 g/L, respectively. The TSS was 23.6% of total solids concentration. A high ratio of VSS to total suspended solids of 96.7% indicated that most of the suspended particles were organic materials. Lactose and protein were the major organic components contributing COD in the wastewater, and a total of 94.2% of the COD in the wastewater was due to the presence of lactose and protein. Two different physiological conditions where the maximum rates of acetate and butyrate production occurred were tested. These were pH 7 (condition A for acetate production) and pH 7.3 (condition B for butyrate production) at 36.2C, respectively. Based on the molecular structures of the major organic substances and microbial ATP analysis, the residual substrate and microbial concentrations were stoichiometrically converted to substrate COD (SuCOD) and microbial VSS (MVSS), respectively, using correlation coefficients reported previously. These SuCOD and MVSS were simultaneously used to evaluate the biokinetic coefficients using Monod-based mathematical equations. The nonlinear least squares method with 95% confidence interval was used to evaluate biokinetic coefficients. The maximum microbial growth rate, mu(max) and half saturation coefficient, K(s), for conditions A and B were determined to be 9.9 +/- 0.3 and 9.3 +/- 1.0 day(-1) and 134.0 +/- 58.3 and 482.5 +/- 156.5 mg SuCOD/L, respectively. The microbial yield coefficient, Y, and microbial decay rate coefficient, k(d) for conditions A and B were determined to be 0.29 +/- 0.03 and 0.20 +/- 0.05 mg MVSS/mg SuCOD, and 0.14 +/- 0.05 and 0.25 +/- 0.05 day(-1), respectively. Specific substrate utilization rate at condition B was 43.8 +/- 20.6 mg SuCOD/mg MVSS/day, which was 31% higher than that at condition A.
Hwang S - One of the best experts on this subject based on the ideXlab platform.
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Co-digestion of lignocellulosics with glucose using thermophilic Acidogens
'Elsevier BV', 2019Co-Authors: Yu Y, Park B, Hwang SAbstract:Thermomechanical pulping (TMP) wastewater was tested for the feasibility of augmenting readily biodegradable organics for enhanced microbial hydrolysis by thermophilic Acidogens. A biochemical methane potential test showed approximately 13 +/- 1% of the chemical oxygen demand was anaerobically biodegradable. Three glucose concentrations set up in a ratio of 1:3:6, 5, 15, and 30 g/l, were tested to induce the production of short-chain organic acids and ethanol. Compared to the control with no glucose addition, more than six times of the fragmentation of lignocellulosics in the wastewater was achieved. (C) 2003 Elsevier Science B.V. All rights reserved.X1118sciescopu
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Augmentation of secondary organics for enhanced pretreatment of thermomechanical pulping wastewater in biological acidogenesis
'Elsevier BV', 2019Co-Authors: Yu Y, Hwang SAbstract:Thermomechanical pulping (TMP) wastewater was used for augmenting readily biodegradable organics in order to enhance microbial hydrolysis by mesophilic and thermophilic Acidogens. A biochemical methane potential test with the TMP wastewater revealed that approximately 12-14% of the total chemical oxygen demand was anaerobically biodegradable. Mesophilic and thermophilic Acidogens at 35 and 55 degreesC in batch mode were tested to investigate the effects of various concentrations of organic acids and ethanol produced from readily biodegradable organics on the hydrolysis of lignocellulosics. The experiment was designed to have initial glucose concentrations of 5, 15 and 30 g/l. The combined effects of the production of organic acids, ethanol, and enriched acidogenic populations by addition of glucose promoted hydrolysis. Compared to the control with no glucose addition, approximately 5.3 and 6.6 times more fragmentation of lignocellulosics in the wastewater occurred in mesophilic and thermophilic acidogenesis, respectively. Higher efficiencies in the thermophilic trials than those in the mesophilic tests were likely due to the elevated temperature. (C) 2003 Elsevier Science Ltd. All rights reserved.X113sciescopu
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Common key acidogen populations in anaerobic reactors treating different wastewaters: Molecular identification and quantitative monitoring
'Elsevier BV', 2018Co-Authors: Kim J, Sg Shin, Han G, Lee C, Hwang SAbstract:Bacterial population dynamics during the start-up of three lab-scale anaerobic reactors treating different wastewaters, i.e., synthetic glucose wastewater, whey permeate, and liquefied sewage sludge, were assessed using a combination of denaturing gradient gel electrophoresis (DGGE) and real-time PCR techniques. The DGGE results showed that bacterial populations related to Aeromonas spp. and Clostridium sticklandii emerged as common and prominent Acidogens in all reactors. Two real-time PCR primer/probe sets targeting Aeromonas or C. sticklandii were developed, and successfully applied to quantitatively investigate their dynamics in relation to changes in reactor performance. Quantitative analysis demonstrated that both Aeromonas- and C. sticklandii-related populations were highly abundant for acidogenic period in all reactors. Aeromonas populations accounted for up to 86.6-95.3% of total bacterial 165 rRNA genes during start-up, suggesting that, given its capability of utilizing carbohydrate, Aeromonas is likely the major acidogen group responsible for the rapid initial fermentation of carbohydrate. C. sticklandii, able to utilize specific amino acids only, occupied up to 8.5-55.2% of total bacterial 16S rRNA genes in the reactors tested. Growth of this population is inferred to be supported, at least in part, by non-substrate amino acid sources like cell debris or extracellular excretions, particularly in the reactor fed on synthetic glucose wastewater with no amino acid source. The quantitative dynamics of the two acidogen groups of interest, together with their putative functions, suggest that Aeromonas and C. sticklandii populations were numerically as well as functionally important in all reactors tested, regardless of the differences in substrate composition. Particularly, the members of Aeromonas supposedly play vital roles in anaerobic digesters treating various substrates under acidogenic, fermentative start-up conditions. (C) 2011 Elsevier Ltd. All rights reserved.X112222sciescopu
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Anaerobic digestion of cattle offal: protein and lipid-rich substrate degradation and population dynamics of Acidogens and methanogens
'Springer Science and Business Media LLC', 2018Co-Authors: Lee J, Sg Shin, Han G, Koo T, Hwang SAbstract:Anaerobic digestion of cattle offal was investigated in batch reactors at 35 A degrees C to determine the feasibility of using cattle offal as a feedstock. The organic content [i.e., volatile solids (VS)] of the cattle offal was mainly composed of protein (33.9 %) and lipids (46.1 %). Hydrolysis along with acidogenesis was monitored to investigate the substrate degradation and generation of intermediate products (e.g., volatile fatty acids, ammonia). Acetate (2.03 g/L), propionate (0.60 g/L), n-butyrate (0.39 g/L), and iso-valerate (0.37 g/L) were major acidogenesis products (91 % of total volatile fatty acid concentration). Overall protein and lipid degradation were 82.9 and 81.8 %, respectively. Protein degraded first, and four times faster (0.28 day(-1)) than lipid (0.07 day(-1)). Methane yields were 0.52 L CH4/g VSadded and 0.65 L CH4/g VSremoved, indicating that anaerobic digestion of the offal was feasible. A quantitative QPCR assay was conducted to understand the microbial dynamics. The variation patt erns in the gene concentrations successfully indicated the population dynamics of proteolytic and lipolytic Acidogens. A fourth-order Runge-Kutta approximation was used to determine the kinetics of the Acidogens. The molecular biotechnology approach was appropriate for the evaluation of the acidogenic biokinetics. The maximum growth rate, mu (m), halfsaturation coefficients, K (s), microbial yield coefficient, Y, cell mass decay rate coefficient, k (d), of the proteolytic Acidogens were 9.9 day(-1), 37.8 g protein/L, 1.1 x 10(10) copies/g protein, and 3.8 x 10(-1), respectively. Those for the lipolytic Acidogens were 1.2 x 10(-1) day(-1), 8.3 g lipid/L, 1.5 x 10(9) copies/g lipid, and 9.9 x 10(-3) day(-1), respectively.1133sciescopu
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Modeling and biokinetics in anaerobic acidogenesis of starch-processing wastewater to acetic acid
'American Chemical Society (ACS)', 2018Co-Authors: Jh Ahn, Lee S, Hwang SAbstract:Starch-processing wastewater was anaerobically treated to produce acetic acid in laboratory-scale, continuously stirred tank reactors. The optimal conditions, in which the maximum acetic acid production occurred, were 0.56 d hydraulic retention time, pH 5.9, and 36.1 degreesC. Acetic acid production at the optimum conditions was 672 +/- 20 mg total organic carbon(equivalent) L-1, which indicated a 75% conversion efficiency of influent total organic carbon into acetic acid. A fourth order Runge-Kutta approximation was used to determine the Monod kinetics of the Acidogens by using unsteady-state data from continuous unsteady-state experiments at the optimum conditions. The model outputs and experimental data fit together satisfactorily, suggesting that the unsteady-state approach was appropriate for the evaluation of acidogenic biokinetics. These included mu(m), K-s, Y, and k(d), which were evaluated as being 0.13 h(-1), 25 mg total carbohydrate (TC) L-1, 0.38 mg volatile suspended solid mg(-1) TC, and 0.002 h(-1), respectively.X1144sciescopu
Recep Kaan Dereli - One of the best experts on this subject based on the ideXlab platform.
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a systematic study on the effect of substrate acidification degree and acidogenic biomass on sludge filterability
Water Research, 2015Co-Authors: Recep Kaan Dereli, Frank P Van Der Zee, Lefki Loverdou, Jules B. Van LierAbstract:The influence of substrate acidification on sludge filtration characteristics was systematically investigated by using short term filtration tests. Four reactors were operated with raw and acidified whey permeate in order to evaluate the effect of Acidogens on sludge filterability. The results showed that feeding non-acidified substrate promoted the growth of Acidogens which in return decreased the median particle size of the sludge and adversely influenced specific resistance to filtration (SRF). In addition to the presence of Acidogens, the food to mass (F:M) ratio was found as an important operation parameter on sludge filterability. Various filterability indicators, such as capillary suction time (CST), SRF and supernatant filterability, tended to became worse at increased F:M ratios. The decreased filterability at high F:M ratio was attributed to the accumulation of soluble microbial products (SMP) in the reactors. Interestingly, impact of Acidogens on short term critical flux tests was not significant, but this may be a consequence of the experimental set-up.
Willy Verstraete - One of the best experts on this subject based on the ideXlab platform.
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contact angle measurement and cell hydrophobicity of granular sludge from upflow anaerobic sludge bed reactors
Applied and Environmental Microbiology, 1995Co-Authors: Daniele Daffonchio, Jullapong Thaveesri, Willy VerstraeteAbstract:The contact angle, which is generally used to evaluate the hydrophobicities of pure bacterial strains and solid surfaces, was used to study mixed cell cultures of bacteria involved in anaerobic digestion. Previously published data and data from this study showed that most Acidogens are hydrophilic (contact angle, 45(deg)). The hydrophobicities of mixtures of hydrophilic and hydrophobic cells were found to be linearly correlated with the cell mixing ratio. The hydrophobicities of cells present in effluents from upflow anaerobic sludge bed reactors which were treating different types of substrates were different depending on the reactor conditions. When the reactor liquid had a high surface tension, cells sloughing off from sludge granules, as well as cells present on the outer surfaces of the granules, were hydrophobic. Short-term batch enrichment cultures revealed that proteins selected for highly hydrophilic cells. Long-term in-reactor enrichment cultures revealed that sugars selected for hydrophilic Acidogens on the surfaces of the granules, while fatty acids tended to enrich for hydrophobic methanogens. When linear alkylbenzenesulfonate was added, the cells on the surfaces of granules became more hydrophilic. Control tests performed with pure cultures revealed that there was no change in the surface properties due to linear alkylbenzenesulfonate; hence, the changes in the wash-out observed probably reflect changes in the species composition of the microbial association. A surface layer with moderate hydrophobicity, a middle layer with extremely high hydrophobicity, and a core with high hydrophobicity could be distinguished in the grey granules which we studied.
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Granulation and Sludge Bed Stability in Upflow Anaerobic Sludge Bed Reactors in Relation to Surface Thermodynamics
'American Society for Microbiology', 1995Co-Authors: Jullapong Thaveesri, Daniele Daffonchio, B. Liessens, P. Vandermeren, Willy VerstraeteAbstract:Adhesion of bacteria involved in anaerobic consortia was investigated in upflow anaerobic sludge bed reactors and was related to surface thermodynamics. The adhesion of hydrophilic cells appeared to be enhanced at a low liquid surface tension ((gamma)(infLV)), while the adhesion of hydrophobic cells was favored at a high (gamma)(infLV). Growth in protein-rich growth media resulted in low granular biomass yields; addition of polycations, such as poly-l-lysine and chitosan, increased the (gamma)(infLV) and the granular biomass yield. On the basis of the results of activity tests and microbial counts with wash-out cells, we identified two types of structured granules that were related to the influence of (gamma)(infLV). In one type of granules, hydrophilic Acidogens surrounded a more hydrophobic methanogenic association. These granules were selected at a low (gamma)(infLV) provided that carbohydrates were available as substrates. The other type of granules was selected at a high (gamma)(infLV); hydrophobic cells (i.e., methanogens) were predominant throughout these granules. The granules which had Acidogens as solid-phase emulsifiers around a methanogenic association appeared to allow more stable reactor performance. Decreasing the (gamma)(infLV) in the reactor by adding trace amounts of a surfactant also increased reactor stability
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acidogenesis in relation to in reactor granule yield
Water Science and Technology, 1992Co-Authors: B Vanderhaegen, E Ysebaert, K Favere, M Van Wambeke, T Peeters, V Panic, V Vandenlangenbergh, Willy VerstraeteAbstract:A systematic study of in-reactor granule yield data was set up in the laboratory. Methanogenic granular sludge growth in fed batch shake flasks for different substrates appeared to decrease with the energy content of the substrate and required the presence of a mixing force. In UASB reactors, granular cell yields were found to be quite variable suggesting the involvement of complex microbiological interactions. The factor foremost in influencing the build-up in the reactor of granular sludge was the presence of high-energy carbohydrates; pre-acidified influents affected in-reactor granular sludge yield very negatively. The influence of sulphate reduction and sulphide concentrations was found not to be of primary importance. The ionic strength of the medium also had no strong influence. Granule formation proceeded somewhat better at low than at nigh strength buffer capacity. High levels of protein, however, reduced the in-reactor granular sludge build-up strongly. Measurement of the acid production by granular and fluffy sludges revealed that the former rapidly produce volatile acids, particularly propionate, while the latter do not. Measurement of the pH in the granule indicated that the outside layer of the granule is rich in Acidogens. Calculations of proton and hydrogen fluxes in the granule support the concept that Acidogens, able to ferment high energy carbohydrates efficiently to cells and exo-cellular binding materials, might be of primary importance for in-reactor granular growth.
Seung Gu Shin - One of the best experts on this subject based on the ideXlab platform.
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Common key acidogen populations in anaerobic reactors treating different wastewaters: Molecular identification and quantitative monitoring
'Elsevier BV', 2014Co-Authors: Kim Jaai, Seung Gu Shin, Han Gyuseong, O'flaherty Vincent, Lee Changsoo, Hwang SeokhwanAbstract:Bacterial population dynamics during the start-up of three lab-scale anaerobic reactors treating different wastewaters, i.e., synthetic glucose wastewater, whey permeate, and liquefied sewage sludge, were assessed using a combination of denaturing gradient gel electrophoresis (DGGE) and real-time PCR techniques. The DGGE results showed that bacterial populations related to Aeromonas spp. and Clostridium sticklandii emerged as common and prominent Acidogens in all reactors. Two real-time PCR primer/probe sets targeting Aeromonas or C. sticklandii were developed, and successfully applied to quantitatively investigate their dynamics in relation to changes in reactor performance. Quantitative analysis demonstrated that both Aeromonas- and C. sticklandii-related populations were highly abundant for acidogenic period in all reactors. Aeromonas populations accounted for up to 86.6-95.3% of total bacterial 16S rRNA genes during start-up, suggesting that, given its capability of utilizing carbohydrate, Aeromonas is likely the major acidogen group responsible for the rapid initial fermentation of carbohydrate. C. sticklandii, able to utilize specific amino acids only, occupied up to 8.5-55.2% of total bacterial 16S rRNA genes in the reactors tested. Growth of this population is inferred to be supported, at least in part, by non-substrate amino acid sources like cell debris or extracellular excretions, particularly in the reactor fed on synthetic glucose wastewater with no amino acid source. The quantitative dynamics of the two acidogen groups of interest, together with their putative functions, suggest that Aeromonas and C. sticklandii populations were numerically as well as functionally important in all reactors tested, regardless of the differences in substrate composition. Particularly, the members of Aeromonas supposedly play vital roles in anaerobic digesters treating various substrates under acidogenic, fermentative start-up conditions.close11
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effect of temperature and hydraulic retention time on volatile fatty acid production based on bacterial community structure in anaerobic acidogenesis using swine wastewater
Bioprocess and Biosystems Engineering, 2013Co-Authors: Woong Kim, Seung Gu Shin, Juntaek Lim, Seokhwan HwangAbstract:To investigate the effect of hydraulic retention time (HRT) and temperature (T) on bacterial community structure and volatile fatty acids (VFAs) production of an acidogenic process, and VFA production and changes in the bacterial community in three identical automated anaerobic continuously-stirred tank reactors were analyzed using response surface analysis (RSA) and nonmetric multidimensional scaling (NMDS). For RSA, 11 trials were conducted to find the combination of T and HRT under which VFA production was greatest; VFA production was affected more by HRT than by T. To identify the bacterial community structure in each trial, DNA from each experimental point of the RSA was analyzed using denaturating gradient gel electrophoresis (DGGE), and eight bacteria species were detected. NMDS was conducted on band intensities obtained using DGGE, and bacterial community structure was affected more by T than by HRT. Taken together, these results suggest that VFA production during acidogenesis was more dependent on the physicochemical properties of Acidogens, such as their specific growth rate or contact time with of substrates, than on changes in the microbial community.
