Browsing by Subject "Digestion"

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Demand-driven biogas production in anaerobic filters
(2017) Krümpel, Johannes; Jungbluth, Thomas
Fluctuating energy sources, namely wind turbines and photovoltaic, will be the mayor contributors to the increase in share of renewable energies. The intermittent energy supply by these sources poses challenges for the power grid and need to be counter balanced. A demand-driven energy supply by weather independent biomass conversion can offer these grid services. Flexible energy production from biogas has been identified as a vital approach to provide the grid with positive and negative balancing power. The two-staged anaerobic digestion may be especially suitable for demand orientated gas production due to the advantages of the anaerobic FIlters to withstand high organic loading rates and shock loading. Two staged anaerobic digestion is characterized by a spatio-temporal separation of acidification and methane production. A liquid rich in soluble products, such as volatile fatty acids, alcohols and sugars is produced in the first stage and and is subsequently converted to biogas in the second stage. The methanation stage as the main gas producing unit in such a system is in the focus of this research.The ability to react to sudden changes in demand might be influenced by substrate composition and controlled hydrolysis towards certain intermediates could improve the reaction times towards increased demand. It is therefore one focus of this research work to examine intrinsic methane production kinetics of common intermediates of anaerobic digestion. Other major questions are how fast the methane production can be adapted to sudden changes in demand and to what extent these adaptions are reproducible. It was therefore of interest to demonstrate the feasibility, reproducibility and the possible extent of demand-driven biogas production in anaerobic filters, with respect to changing substrate composition. Furthermore the evaluation of the process effciency based on carbon fluxes should be examined to unfold effects resulting from changing operational conditions. With a newly developed methodology, introduced in the publication "Kinetics of Biogas Production in Anaerobic Filters" kinetic parameters of methane production for individual volatile fatty acids (VFA) could be determined. The bandwidth of tested intermediates was broadened in the second research paper "Intrinsic Gas Production Kinetics of Selected Intermediates in Anaerobic Filters for Demand Orientated Energy Supply". It has been found that intermediates could be ordered according to their half-lives of methane production. The apparent order, beginning with the fastest was acetic acid >ethanol >butyric acid >iso-butyric acid> valeric acid> propionic acid> propanediol> lactic acid. However the mixture of these individual components administered as a naturally produced hydrolysate revealed the fastest methane production kinetics. Differences in the absolute values of determined kinetic parameters between the two experiments can be attributed to variations in organic loading rate (OLR), since degradation rates of a specific substrate are determined by substrate concentration. But also other parameters influence the absolute rate at which methane is produced, such as the concentration of products or unionized substrate itself, pH, nutrient availability, bioenergetics, temperature, inhibition, mass transfer and microbial population. In the third research paper "Demand-Driven Biogas Production in Anaerobic Filters "the previous findings have been put to the test by applying changes in OLR throughout the day and examining different substrate compositions with respect to the methane production rates. As demonstrated, the gas production followed the applied OLR with a distinctive expression of each change in the OLR. That marks the process as highly predictable and defined boundaries within safe operation of AD, in terms of VFA accumulation,can possibly be satisfied by process control. The inclusion of three reactors in the analysis emphasizes the repeatability and therefore the predictability of such an approach of operation. Feasibility and reproducibility of demand-driven biogas production by anaerobic filters could thus be demonstrated. It has been found that the hydrolysate composition has no significant influence on methane production kinetics for demand orientated gas production, since the maximum rate is limited by acetoclastic methanogenesis. The control of the hydrolysis should focus on high overall degradation, rather than towards the production of specific intermediates. A key factor in order to prevent large fluctuation in gas composition is alkalinity, specifically the provision of nitrogenous compounds is vital to maintain stable conditions. Anaerobic filters or attached biomass reactors in general seem to exhibit superior performance towards shock loading and are therefore especially suited for demand orientated gas production as they recover quickly from overloading.Formation of soluble microbial products (SMP) and extracellular polymeric substances (EPS) may be influenced or exaggerated by constantly changing HRT and OLR. Further research in order to evaluate the limits of safe operation is recommended as more extreme scenarios than the ones examined in this work are imaginable in practice.
Demethoxycurcumin and Bisdemethoxycurcumin are more bioavailable than Curcumin: A meta-analysis of randomized cross-over trials in healthy umans and an In Vitro mechanistic exploration
(2023) Desmarchelier, Charles; Sus, Nadine; Marconot, Grégory; Gillet, Guillian; Resseguier, Noémie; Frank, Jan
Background: Curcuminoids are secondary plant metabolites found in turmeric and many dietary supplements. They usually consist of a mixture of curcumin (CUR), demethoxycurcumin (dCUR) and bisdemethoxycurcumin (bdCUR). CUR, the main curcuminoid, has been intensely investigated for its putative effects against, e.g., inflammation, oxidative stress and cancer. However, CUR displays very poor bioavailability. We have previously shown that, when brought by turmeric, dCUR and bdCUR, which can also exert health effects, display greater in vitro bioaccessibility than CUR (PMID: 37073511). However, their bioavailability relative to that of CUR has not been thoroughly investigated. Objective: We aimed to compare the bioavailability of dCUR and bdCUR to that of CUR in a meta-analysis of clinical trials in healthy humans and to compare their in vitro bioaccessibility and enterocyte uptake efficiency. Methods and Results: Studies published until 2022 were searched for using Medline and Scopus. The included studies were randomized trials that measured the bioavailability of CUR, dCUR and bdCUR in healthy participants. Estimates were calculated using a random-effects model. Fifteen trials were included in the study, representing a total of 50 interventions, i.e., each trial investigated several curcuminoid formulations, in 762 participants. The relative bioavailabilities were calculated using the inverse variance method. dCUR was 2.32 (95% CI:1.70, 3.13) times more bioavailable than CUR, while bdCUR was 2.57 (95% CI: 1.58, 4.16) times more bioavailable than CUR, with some heterogeneity across the formulations used. Using an in vitro gastro-intestinal digestion model with pure curcuminoids, we showed that dCUR solubilization efficiency was 4.8 and 5.3 times higher than that of CUR and bdCUR, respectively (p < 0.001), while its micellization efficiency was 10.3 and 5.1 times higher than that of CUR and bdCUR, respectively (p < 0.001). Conclusions: bdCUR and dCUR display greater bioavailability in humans compared to CUR. A subgroup analysis by formulation is undergoing investigation and will be presented. For dCUR, this difference is partly explained by higher in vitro bioaccessibility. Uptake efficiency measurements of pure curcuminoids and of curcuminoids from in vitro digestion fluids are undergoing investigation and will be presented. bdCUR and dCUR might therefore represent relevant alternatives to CUR for the systematic delivery of curcuminoids.
The effect of enzyme additives on the anaerobic digestion of energy crops
(2014) Brulé, Mathieu; Jungbluth, Thomas
The mechanisms governing the efficiency of commercial fiber-degrading enzyme additives at improving the anaerobic digestion of energy crops were investigated. Standard batch digestion trials (BMP-assays) were performed using the Hohenheim Biogas Test (HBT) on maize straw, maize corn, and rye silage with different inocula. These BMP-assays showed no significant effect of enzyme additives (including commercial cellulase, xylanase, pectinase, laccase) on the methane production rate. However, batch digestion trials performed on grass silage under suboptimal conditions with inoculum of weak bacterial activity revealed significant increases of methane production up to 40%. In another experiment semi continuous acidogenic fermentation was performed in laboratory digesters with maize silage and water added for dilution at OLR 4 kg VS/(m3 × d), HRT 5 days, with the medium kept in the pH range 5 5.5 through quicklime addition. Enzyme additives at a dosage of 10 g/kg substrate VS significantly increased VFA release (+10%) as well as gas production, including H2 production (+20%). The results show that the efficiency of enzyme additives in anaerobic digestion depends on substrate (fibre length and composition) and process parameters (retention time, loading rate, pH, efficiency of bacterial substrate degradation).