Enhancement of the conventional anaerobic digestion of sludge: comparison of four different strategies

2011 ◽  
Vol 64 (2) ◽  
pp. 375-383 ◽  
Author(s):  
S. I. Pérez-Elvira ◽  
M. Fdz-Polanco ◽  
F. Fdz-Polanco
Keyword(s):  
Anaerobic Digestion ◽  
Thermal Hydrolysis ◽  
General Increase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Key Factor ◽  
Thermophilic Digestion ◽  
Pre Treatment ◽  
Treatment Alternatives ◽  
Rate Limiting

Anaerobic digestion (AD) is the preferred option to stabilize sludge. However, the rate limiting step of solids hydrolysis makes it worth modifing the conventional mesophilic AD in order to increase the performance of the digester. The main strategies are to introduce a hydrolysis pre-treatment, or to modify the digestion temperature. Among the different pre-treatment alternatives, the thermal hydrolysis (TH) at 170 °C for 30 min, and the ultrasounds pre-treatment (US) at 30 kJ/kg TS were selected for the research, while for the non-conventional anaerobic digestion, the thermophilic (TAD) and the two-stage temperature phased AD (TPAD) were considered. Four pilot plants were operated, with the same configuration and size of anaerobic digester (200 L, continuously fed). The biogas results show a general increase compared to the conventional digestion, being the highest production per unit of digester for the process combining the thermal pre-treatment and AD (1.4 Lbiogas/Ldigester·day compared to the value of 0.26 obtained in conventional digesters). The dewaterability of the digestate became enhanced for processes TH + AD and TPAD when compared with the conventional digestate, while it became worse for processes US + AD and TAD. In all the research lines, the viscosity in the digester was smaller compared to the conventional (which is a key factor for process performance and economics), and both thermal pre-treatment and thermophilic digestion (TAD and TPAD) assure a pathogen free digestate.

Characteristics of carbohydrate degradation and the rate-limiting step in anaerobic digestion

1985 ◽  
Vol 27 (10) ◽  
pp. 1482-1489 ◽  
Author(s):  
Tatsuya Noike ◽  
Ginro Endo ◽  
Juu-En Chang ◽  
Jun-Ichi Yaguchi ◽  
Jun-Ichiro Matsumoto
Keyword(s):  
Anaerobic Digestion ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Carbohydrate Degradation ◽  
Rate Limiting

scholarly journals Mutation of Aspartate 238 in FAD Synthase Isoform 6 Increases the Specific Activity by Weakening the FAD Binding

2019 ◽  
Vol 20 (24) ◽  
pp. 6203 ◽  
Author(s):  
Piero Leone ◽  
Michele Galluccio ◽  
Stefano Quarta ◽  
Ernesto Anoz-Carbonell ◽  
Milagros Medina ◽  
...  
Keyword(s):  
Binding Sites ◽  
Specific Activity ◽  
Synthesis Rate ◽  
General Increase ◽  
Respiratory Chain Deficiency ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Acyl Coa Dehydrogenases ◽  
Rate Limiting ◽  
Fad Binding

FAD synthase (FADS, or FMN:ATP adenylyl transferase) coded by the FLAD1 gene is the last enzyme in the pathway of FAD synthesis. The mitochondrial isoform 1 and the cytosolic isoform 2 are characterized by the following two domains: the C-terminal PAPS domain (FADSy) performing FAD synthesis and pyrophosphorolysis; the N-terminal molybdopterin-binding domain (FADHy) performing a Co++/K+-dependent FAD hydrolysis. Mutations in FLAD1 gene are responsible for riboflavin responsive and non-responsive multiple acyl-CoA dehydrogenases and combined respiratory chain deficiency. In patients harboring frameshift mutations, a shorter isoform (hFADS6) containing the sole FADSy domain is produced representing an emergency protein. With the aim to ameliorate its function we planned to obtain an engineered more efficient hFADS6. Thus, the D238A mutant, resembling the D181A FMNAT “supermutant” of C. glabrata, was overproduced and purified. Kinetic analysis of this enzyme highlighted a general increase of Km, while the kcat was two-fold higher than that of WT. The data suggest that the FAD synthesis rate can be increased. Additional modifications could be performed to further improve the synthesis of FAD. These results correlate with previous data produced in our laboratory, and point towards the following proposals (i) FAD release is the rate limiting step of the catalytic cycle and (ii) ATP and FMN binding sites are synergistically connected.

A Kinetic Study on the Methanogenesis Process in Anaerobic Digestion

1989 ◽  
Vol 21 (4-5) ◽  
pp. 175-186 ◽  
Author(s):  
C. Y. Lin ◽  
T. Noike ◽  
H. Furumai ◽  
J. Matsumoto
Keyword(s):  
Anaerobic Digestion ◽  
Substrate Concentration ◽  
Volatile Fatty Acid ◽  
Kinetic Mechanism ◽  
High Concentration ◽  
Two Phase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
The Relationship ◽  
Rate Limiting

Results obtained from experiments on two-phase anaerobic digestion using a high concentration of a volatile fatty acid (VFA) mixture were used to elucidate the kinetic mechanism of the methanogenesis process. The mixture consisted of the major intermediate products of anaerobic digestion, i.e., acetic acid (HAc), propionic acid (HPr) and butyric acid (HBu). The relationship between the rate of substrate utilization and substrate concentration in the digesters was in the form of a Michaelis-Menten equation. The rate-limiting step of the methanogenesis process, i.e., the conversion of HAc to methane, was speeded up in the digesters and this was proved kinetically. A method for determining kinetic constants for substrate-specific microorganisms was suggested. A simulation model for predicting the effluent substrate concentration was demonstrated. The effluent substrate concentration of an anaerobic digester fed by a multisubstrate was found to be simulatively predictable from its influent component substrates.

scholarly journals Impact of physical structure of granular sludge on methanogenesis and methanogenic community structure

RSC Advances ◽  
2019 ◽  
Vol 9 (51) ◽  
pp. 29570-29578
Author(s):  
Xiaofang Pan ◽  
Lina Wang ◽  
Nan Lv ◽  
Jing Ning ◽  
Mingdian Zhou ◽  
...  
Keyword(s):  
Community Structure ◽  
Anaerobic Digestion ◽  
Granular Sludge ◽  
Physical Structure ◽  
Critical Factors ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

Physical structures of sludge are critical factors determining the performance of the anaerobic digestion process, especially for the rate-limiting step, methanogenesis.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
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