The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
Zamin K. Yang - One of the best experts on this subject based on the ideXlab platform.
-
Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times
Biotechnology for Biofuels, 2018Co-Authors: Xiaoyu Liang, Jason M. Whitham, Evert K. Holwerda, Xiongjun Shao, Liang Tian, Yu Wei Wu, Vincent Lombard, Bernard Henrissat, Dawn M. Klingeman, Zamin K. YangAbstract:Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures. Anaerobic microbiomes derived from a digester inoculum were incubated at 55 °C and fed semi-continuously with medium containing 30 g/L mid-season harvested switchgrass to achieve residence times (RT) of 20, 10, 5, and 3.3 days. Stable, time-invariant cellulolytic methanogenic cultures with minimal accumulation of organic acids were achieved for all RTs. Fractional carbohydrate solubilization was 0.711, 0.654, 0.581 and 0.538 at RT = 20, 10, 5 and 3.3 days, respectively, and glucan solubilization was proportional to xylan solubilization at all RTs. The rate of solubilization was described well by the equation r = k(C − C0fr), where C represents the concentration of unutilized carbohydrate, C0 is the concentration of carbohydrate (cellulose and hemicellulose) entering the bioreactor and fr is the extrapolated fraction of entering carbohydrate that is recalcitrant at infinite residence time. The 3.3 day RT is among the shortest RT reported for stable thermophilic, methanogenic digestion of a lignocellulosic feedstock. 16S rDNA phylotyping and metagenomic analyses were conducted to characterize the effect of RT on community dynamics and to infer functional roles in the switchgrass to biogas conversion to the various microbial taxa. Firmicutes were the dominant phylum, increasing in relative abundance from 54 to 96% as RT decreased. A Clostridium clariflavum strain with genetic markers for xylose metabolism was the most abundant lignocellulose-solubilizing bacterium. A Thermotogae (Defluviitoga tunisiensis) was the most abundant bacterium in switchgrass digesters at RT = 20 days but decreased in abundance at lower RTs as did multiple Chloroflexi. Synergistetes and Euryarchaeota were present at roughly constant levels over the range of RTs examined. A system was developed in which stable methanogenic steady-states were readily obtained with a Particulate Biomass feedstock, mid-season switchgrass, at laboratory (1 L) scale. Characterization of the extent and rate of carbohydrate solubilization in combination with 16S rDNA and metagenomic sequencing provides a multi-dimensional view of performance, species composition, glycoside hydrolases, and metabolic function with varying residence time. These results provide a point of reference and guidance for future studies and organism development efforts involving defined cultures.
-
Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times
Biotechnology for Biofuels, 2018Co-Authors: Xiaoyu Liang, Jason M. Whitham, Evert K. Holwerda, Xiongjun Shao, Liang Tian, Yu Wei Wu, Vincent Lombard, Bernard Henrissat, Dawn M. Klingeman, Zamin K. YangAbstract:Background Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Results Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures. Anaerobic microbiomes derived from a digester inoculum were incubated at 55 °C and fed semi-continuously with medium containing 30 g/L mid-season harvested switchgrass to achieve residence times (RT) of 20, 10, 5, and 3.3 days. Stable, time-invariant cellulolytic methanogenic cultures with minimal accumulation of organic acids were achieved for all RTs. Fractional carbohydrate solubilization was 0.711, 0.654, 0.581 and 0.538 at RT = 20, 10, 5 and 3.3 days, respectively, and glucan solubilization was proportional to xylan solubilization at all RTs. The rate of solubilization was described well by the equation r = k ( C − C _0 f _r), where C represents the concentration of unutilized carbohydrate, C _0 is the concentration of carbohydrate (cellulose and hemicellulose) entering the bioreactor and f _r is the extrapolated fraction of entering carbohydrate that is recalcitrant at infinite residence time. The 3.3 day RT is among the shortest RT reported for stable thermophilic, methanogenic digestion of a lignocellulosic feedstock. 16S rDNA phylotyping and metagenomic analyses were conducted to characterize the effect of RT on community dynamics and to infer functional roles in the switchgrass to biogas conversion to the various microbial taxa. Firmicutes were the dominant phylum, increasing in relative abundance from 54 to 96% as RT decreased. A Clostridium clariflavum strain with genetic markers for xylose metabolism was the most abundant lignocellulose-solubilizing bacterium. A Thermotogae ( Defluviitoga tunisiensis ) was the most abundant bacterium in switchgrass digesters at RT = 20 days but decreased in abundance at lower RTs as did multiple Chloroflexi. Synergistetes and Euryarchaeota were present at roughly constant levels over the range of RTs examined. Conclusions A system was developed in which stable methanogenic steady-states were readily obtained with a Particulate Biomass feedstock, mid-season switchgrass, at laboratory (1 L) scale. Characterization of the extent and rate of carbohydrate solubilization in combination with 16S rDNA and metagenomic sequencing provides a multi-dimensional view of performance, species composition, glycoside hydrolases, and metabolic function with varying residence time. These results provide a point of reference and guidance for future studies and organism development efforts involving defined cultures.
Paul Scherer - One of the best experts on this subject based on the ideXlab platform.
-
The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Biomass to methane: a review
Reviews in Environmental Science and Bio Technology, 2008Co-Authors: B. Demirel, Paul SchererAbstract:Among different conversion processes for Biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various Biomass substrates. In addition to hydrolysis of polymeric substances, the activity and performance of the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Particulate Biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited. Despite, some conclusions can still be drawn. At low concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H_2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a Biomass reactor. However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens. Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature.
-
The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Biomass to methane: A review
Reviews in Environmental Science and Biotechnology, 2008Co-Authors: B. Demirel, Paul SchererAbstract:Among different conversion processes for Biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various Biomass substrates. In addition to hydrolysis of polymeric substances, the activity and perfor- mance of the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogeno- trophic methanogens during anaerobic conversion of Particulate Biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited. Despite, some conclu- sions can still be drawn. At low concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferablyMethanosaetaceae B. Demirel (&) ? P. Scherer Lifetec Process Engineering, Faculty of Life Sciences, Hamburg University of Applied Sciences (HAW Hamburg), Lohbru ¨ggerkirchstrasse 65, 21033 Hamburg, Germany e-mail: Burak.Demirel@rzbd.haw-hamburg.de and and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a Biomass reactor. However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophicmethanogens. Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature.
Xiaoyu Liang - One of the best experts on this subject based on the ideXlab platform.
-
Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times
Biotechnology for Biofuels, 2018Co-Authors: Xiaoyu Liang, Jason M. Whitham, Evert K. Holwerda, Xiongjun Shao, Liang Tian, Yu Wei Wu, Vincent Lombard, Bernard Henrissat, Dawn M. Klingeman, Zamin K. YangAbstract:Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures. Anaerobic microbiomes derived from a digester inoculum were incubated at 55 °C and fed semi-continuously with medium containing 30 g/L mid-season harvested switchgrass to achieve residence times (RT) of 20, 10, 5, and 3.3 days. Stable, time-invariant cellulolytic methanogenic cultures with minimal accumulation of organic acids were achieved for all RTs. Fractional carbohydrate solubilization was 0.711, 0.654, 0.581 and 0.538 at RT = 20, 10, 5 and 3.3 days, respectively, and glucan solubilization was proportional to xylan solubilization at all RTs. The rate of solubilization was described well by the equation r = k(C − C0fr), where C represents the concentration of unutilized carbohydrate, C0 is the concentration of carbohydrate (cellulose and hemicellulose) entering the bioreactor and fr is the extrapolated fraction of entering carbohydrate that is recalcitrant at infinite residence time. The 3.3 day RT is among the shortest RT reported for stable thermophilic, methanogenic digestion of a lignocellulosic feedstock. 16S rDNA phylotyping and metagenomic analyses were conducted to characterize the effect of RT on community dynamics and to infer functional roles in the switchgrass to biogas conversion to the various microbial taxa. Firmicutes were the dominant phylum, increasing in relative abundance from 54 to 96% as RT decreased. A Clostridium clariflavum strain with genetic markers for xylose metabolism was the most abundant lignocellulose-solubilizing bacterium. A Thermotogae (Defluviitoga tunisiensis) was the most abundant bacterium in switchgrass digesters at RT = 20 days but decreased in abundance at lower RTs as did multiple Chloroflexi. Synergistetes and Euryarchaeota were present at roughly constant levels over the range of RTs examined. A system was developed in which stable methanogenic steady-states were readily obtained with a Particulate Biomass feedstock, mid-season switchgrass, at laboratory (1 L) scale. Characterization of the extent and rate of carbohydrate solubilization in combination with 16S rDNA and metagenomic sequencing provides a multi-dimensional view of performance, species composition, glycoside hydrolases, and metabolic function with varying residence time. These results provide a point of reference and guidance for future studies and organism development efforts involving defined cultures.
-
Development and characterization of stable anaerobic thermophilic methanogenic microbiomes fermenting switchgrass at decreasing residence times
Biotechnology for Biofuels, 2018Co-Authors: Xiaoyu Liang, Jason M. Whitham, Evert K. Holwerda, Xiongjun Shao, Liang Tian, Yu Wei Wu, Vincent Lombard, Bernard Henrissat, Dawn M. Klingeman, Zamin K. YangAbstract:Background Anaerobic fermentation of lignocellulose occurs in both natural and managed environments, and is an essential part of the carbon cycle as well as a promising route to sustainable production of fuels and chemicals. Lignocellulose solubilization by mixed microbiomes is important in these contexts. Results Here, we report the development of stable switchgrass-fermenting enrichment cultures maintained at various residence times and moderately high (55 °C) temperatures. Anaerobic microbiomes derived from a digester inoculum were incubated at 55 °C and fed semi-continuously with medium containing 30 g/L mid-season harvested switchgrass to achieve residence times (RT) of 20, 10, 5, and 3.3 days. Stable, time-invariant cellulolytic methanogenic cultures with minimal accumulation of organic acids were achieved for all RTs. Fractional carbohydrate solubilization was 0.711, 0.654, 0.581 and 0.538 at RT = 20, 10, 5 and 3.3 days, respectively, and glucan solubilization was proportional to xylan solubilization at all RTs. The rate of solubilization was described well by the equation r = k ( C − C _0 f _r), where C represents the concentration of unutilized carbohydrate, C _0 is the concentration of carbohydrate (cellulose and hemicellulose) entering the bioreactor and f _r is the extrapolated fraction of entering carbohydrate that is recalcitrant at infinite residence time. The 3.3 day RT is among the shortest RT reported for stable thermophilic, methanogenic digestion of a lignocellulosic feedstock. 16S rDNA phylotyping and metagenomic analyses were conducted to characterize the effect of RT on community dynamics and to infer functional roles in the switchgrass to biogas conversion to the various microbial taxa. Firmicutes were the dominant phylum, increasing in relative abundance from 54 to 96% as RT decreased. A Clostridium clariflavum strain with genetic markers for xylose metabolism was the most abundant lignocellulose-solubilizing bacterium. A Thermotogae ( Defluviitoga tunisiensis ) was the most abundant bacterium in switchgrass digesters at RT = 20 days but decreased in abundance at lower RTs as did multiple Chloroflexi. Synergistetes and Euryarchaeota were present at roughly constant levels over the range of RTs examined. Conclusions A system was developed in which stable methanogenic steady-states were readily obtained with a Particulate Biomass feedstock, mid-season switchgrass, at laboratory (1 L) scale. Characterization of the extent and rate of carbohydrate solubilization in combination with 16S rDNA and metagenomic sequencing provides a multi-dimensional view of performance, species composition, glycoside hydrolases, and metabolic function with varying residence time. These results provide a point of reference and guidance for future studies and organism development efforts involving defined cultures.
B. Demirel - One of the best experts on this subject based on the ideXlab platform.
-
The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Biomass to methane: a review
Reviews in Environmental Science and Bio Technology, 2008Co-Authors: B. Demirel, Paul SchererAbstract:Among different conversion processes for Biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various Biomass substrates. In addition to hydrolysis of polymeric substances, the activity and performance of the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Particulate Biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited. Despite, some conclusions can still be drawn. At low concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H_2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a Biomass reactor. However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens. Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature.
-
The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of Biomass to methane: A review
Reviews in Environmental Science and Biotechnology, 2008Co-Authors: B. Demirel, Paul SchererAbstract:Among different conversion processes for Biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various Biomass substrates. In addition to hydrolysis of polymeric substances, the activity and perfor- mance of the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogeno- trophic methanogens during anaerobic conversion of Particulate Biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited. Despite, some conclu- sions can still be drawn. At low concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferablyMethanosaetaceae B. Demirel (&) ? P. Scherer Lifetec Process Engineering, Faculty of Life Sciences, Hamburg University of Applied Sciences (HAW Hamburg), Lohbru ¨ggerkirchstrasse 65, 21033 Hamburg, Germany e-mail: Burak.Demirel@rzbd.haw-hamburg.de and and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a Biomass reactor. However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophicmethanogens. Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature.
Bengt Carlsson - One of the best experts on this subject based on the ideXlab platform.
-
A simplified model of an activated sludge process with a plug-flow reactor
Proceedings of The 9th EUROSIM Congress on Modelling and Simulation EUROSIM 2016 The 57th SIMS Conference on Simulation and Modelling SIMS 2016, 2018Co-Authors: Jesús Zambrano, Bengt Carlsson, Stefan Diehl, Emma NehrenheimAbstract:The analysis of a simplified activated sludge process (ASP) with one main dissolved substrate and one main Particulate Biomass component has been conducted with respect to its steady-state. The ASP ...
-
Steady-State Analyses of Activated Sludge Processes with Plug-Flow Reactor
Journal of environmental chemical engineering, 2017Co-Authors: Stefan Diehl, Jesús Zambrano, Bengt CarlssonAbstract:Activated sludge processes (ASPs) consisting of a plug-flow reactor (PFR) and a settler are analyzed in steady-state operation using a reduced model consisting of one soluble substrate and one Particulate Biomass component modelling the dominating biological process. Monod Biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steady-state settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steady-state concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steady-state behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steady-state solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steady-state equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.
-
Steady-state analysis of activated sludge processes with a settler model including sludge compression
Water Research, 2015Co-Authors: Stefan Diehl, Jesús Zambrano, Bengt CarlssonAbstract:A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant Particulate Biomass and one soluble substrate component are modelled. While the Biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and Biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Burger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of Biomass decay rate, influent volumetric flow, and substrate concentration.
-
Analyses of Activated Sludge Processes Consisting of a Plug-Flow Reactor and a Non-ideal Settler
2015Co-Authors: Bengt Carlsson, Stefan Diehl, Jesús ZambranoAbstract:An activated sludge process (ASP) consisting of a plug-flow reactor (PFR) and a non-ideal settler is modelled and analysed. One soluble substrate component and one Particulate Biomass are assumed. ...