Browsing by Subject "Inhibition"

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Anaerobic treatment of a biorefinery’s process-wastewater
(2024) Khan, Muhammad Tahir; Lemmer, Andreas
The phrase “one man's trash is another man’s treasure” perfectly embodies the concept of a circular bioeconomy, emphasizing the conversion of waste into valuable resources while embracing a zero-waste approach. In line with this perspective, the primary objective of the current research was to assess the suitability of a biorefinery’s process-wastewater as a potential feedstock for biogas plants by investigating its anaerobic biodegradability and exploring its biogas and methane production potentials. For such a specific purpose, the process-wastewater from a commercial-scale biorefinery specializing in 5-hydroxymethylfurfural (5-HMF) synthesis and refining was utilized. To fulfill the main objective, three independent sub-objectives were formulated. The initial investigation centered on assessing the biochemical methane potential (BMP) of the typical constituents present in process-wastewater, such as furans (5-HMF and furfural), phenols (syringaldehyde, vanillin, and phenol), and weak acids (levulinic and glycolic acid), as well as the full 5-HMF process-wastewater. The BMP assessments for each test substance were conducted separately at different concentrations (2, 4, 6, and 8 gCOD/L) and temperatures (37°C and 53°C) via the Hohenheim batch fermentation test. The model components at 2 gCOD/L, apart from phenol at 53°C, were efficaciously degraded, in most cases to such an extent, that supplementary methane generation was detected i.e. exceeding their maximum theoretical limits. However, increasing the concentrations of the test components in the assays resulted in diminishing methane conversion at both operating temperatures. Eventually, among the tested components, the 5-HMF process-wastewater was evaluated to be one of the most refractory substrates, following phenol, vanillin, and 5-HMF, when tested at its maximum load under mesophilic and thermophilic conditions. The subsequent investigation focused on examining the anaerobic decomposition of the 5-HMF process-wastewater and its main identified constituents, including 5-HMF, furfural, and levulinic acid in continuously operated anaerobic filters (AFs). The test substances were individually injected into the biofilm reactors operating at 43°C in a controlled manner with a randomized experimental design. This study yielded some unusual outcomes i.e., the test substrates exhibited satisfactory degradation, while at other instances, they hampered the process. Introducing butyric acid between the injected components revealed no signs of compromised consortia. The 5-HMF process-wastewater in this investigation emerged as the least favorable substrate for methane conversion. The culmination of the current research involved utilizing the 5-HMF process-wastewater as a sole feedstock for the fixed-bed reactors. Hence, necessary nutrients to support the existing microbial consortia in the AFs were added to the process-wastewater. Given its toxic nature, the substrate dosage was initiated from its reduced concentration of 10 gCOD/L and was gradually increased to 20, 30, 40, and 50 gCOD/L, with corresponding organic loading rates (OLRs) of 2, 4, 6, 8, and 10 gCOD/L.d, respectively, as the trial progressed. Despite meeting the nutrient requirements, the gas yields, in particular methane, were not remarkable. However, a noteworthy finding surfaced: as the gCOD/L of the fed substrate increased, so did the concentrations of the short-chained volatile fatty acids (SCVFAs) in the reactors. This observation led to the conclusion that the low methane yields were at the behest of the accumulation of SCVFAs in the AFs, at both mesophilic and thermophilic temperatures. Ultimately, the subpar performance of the process-wastewater as a substrate is considered to stem from its exceptionally high concentration of the pollutant 5-HMF, which significantly influences its overall characteristics, causing longer lag phases, especially at higher OLRs. This, in turn, triggers the inhibitory behavior, leading to reduced methane yields. Consequently, these factors render the 5-HMF process-wastewater a precarious choice for biogas plants in terms of efficient energy recovery. While AFs are well-suited technology for treating high-strength wastewaters, for the substrate such as 5-HMF process-wastewater, it might be beneficial to increase retention times by decreasing the OLRs. Additionally, reducing the strength via dilution combined with these adjusted process parameters could further enhance its decomposition. Anaerobic digestion (AD), traditionally used for energy recovery from (bio)wastes, has potential beyond biogas production in the bioeconomy. This research showed that the highly recalcitrant 5-HMF process-wastewater can be a viable source for producing SCVFAs through AD. Furthermore, the Muttenz biorefinery could utilize the filtration byproducts to produce levulinic acid, aligning with a cascading biorefinery approach.
Biochemical methane potential of a biorefinery’s process-wastewater and its components at different concentrations and temperatures
(2022) Khan, Muhammad Tahir; Huelsemann, Benedikt; Krümpel, Johannes; Wüst, Dominik; Oechsner, Hans; Lemmer, Andreas
A sustainable circular bioeconomy requires the side streams and byproducts of biorefineries to be assimilated into bioprocesses to produce value-added products. The present study endeavored to utilize such a byproduct generated during the synthesis of 5-hydroxymethylfurfural as a potential feedstock for biogas production. For this purpose, biochemical methane potential tests for the full process-wastewater, its components (5-hydroxymethylfurfural, furfural, levulinic acid, and glycolic acid), together with furfural’s metabolites (furfuryl alcohol and furoic acid), and phenols (syringaldehyde, vanillin, and phenol), were conducted at mesophilic and thermophilic temperatures to assess their biodegradability and gas production kinetics. 0.1, 0.2, 0.3, and 0.4 g COD of the test components were added separately into assays containing 35 mL of inoculum. At their lowest concentrations, the test components, other than the process-wastewater, exhibited a stimulatory effect on methane production at 37 °C, whereas their increased concentrations returned a lower mean specific methane yield at either temperature. For similar component loads, the mesophilic assays outperformed the thermophilic assays for the mean measured specific methane yields. Components that impaired the anaerobic process with their elevated concentrations were phenol, vanillin, and 5-hydroxymethylfurfural. Poor degradation of the process-wastewater was deduced to be linked to the considerable share of 5-hydroxymethylfurfural in the process-wastewater governing its overall characteristics. With excessive recalcitrant components, it is recommended to use such waste streams and byproducts as a substrate for biogas plants operating at moderate temperatures, but at low rates.
Glucocorticoid-induziertes Wachstum von Tumorzellen
systematische Quantifizierung, Signalmechanismen und Inhibition
(2010) Gündisch, Sibylle; Jeremias, Irmela
Glucocorticoids (GCs) like Dexamethasone (Dex) are widely used in cancer patients, as cytotoxic drugs in hematopoetic tumors or adjuvants in solid tumors to reduce severe side effects. Nevertheless, GCs are accused to reduce anti-cancer treatment efficiency. Due to preliminary works in our research group the suspicion arose that GCs are able to induce proliferation of tumor cells. The present work provides the first systematic quantification of the proproliferative effects of GCs on tumor cells. Enhanced tumor cell growth was validated by repetitive microscopy, impedance analysis, investigation of DNA synthesis rate, enzymatic activity as well as absolute cell number. It could be proven that 6 out of 10 cell lines from solid tumors showed enhanced proliferation after stimulation with Dex, whereas this phenotype was not limited to one tumour entity or a common origin. In vivo, Dex significantly promoted tumor cell growth in a preclinical mouse model with a lung carcinoma cell line. Furthermore the effect of GCs was detected on 139 primary, patient-derived acute childhood leukemia cells. In 15% GCs were able to increase the in vitro survival of the tumor cells and one sample showed even GC-induced proliferation. Accordingly the anti-apoptotic and pro-proliferative effects of GCs could be proven not only on established solid tumor cell lines but also on primary hematopoetic tumor cells. Knockdown studies in cells of solid tumors showed that GC-induced proliferation was mediated by the glucocorticoid receptor and was further transmitted by the proteinkinases Akt and p38-MAPK. GC-induced proliferation could be prevented by induction of apoptosis which was caused either by clinically applicable substances, as for example Vincristine, or by inducible expression of the pro-apoptotic molecule Caspase-3. To sum up, the present work identified GC-induced proliferation of tumor cells as a new, tumor cell directed side effect of GCs. Of direct translational relevance, our data argue towards a restricted use of GCs during anti-cancer therapy as well as the need for preclinical and clinical studies which demonstrate a more effective and safer application of GCs during anti-cancer therapy.
Mono-digestion of 5-Hydroxymethylfurfural process-wastewater in continuously operated anaerobic filters: A cascade utilization approach
(2023) Khan, Muhammad Tahir; Krümpel, Johannes; Wüst, Dominik; Lemmer, Andreas
A proper remedy for the overexploitation of biomass and biobased materials in the bioeconomy is the valorization of biorefineries’ side streams into meaningful products. Hence, in pursuit of a cascade utilization of renewables, a unique biorefinery byproduct was investigated for its biogas potential, specifically methane, in continuously operated anaerobic filters. For this purpose, 5-Hydroxymethylfurfural process-wastewater, after supplementation of necessary nutrients, was diluted down to 10, 20, 30, 40, and 50 gCOD/L concentrations and thereafter tested individually at 43 °C and 55 °C. Maximum methane conversion efficiency at either temperature was observed for test substrates with 10 gCOD/L and 20 gCOD/L concentrations. At 43 °C, the anaerobic filters exhibited their highest biogas yields when supplied with the 30 gCOD/L feedstock. Further exposure of the mesophilic and thermophilic consortia to the ensuing 5-Hydroxymethylfurfural process-wastewater dilutions compromised the stability of the anaerobic process due to the soaring concentrations of short-chained volatile fatty acids. The supplementation of necessary nutrients to unlock the methane potential of the given recalcitrant substrate appears insufficient. Techniques like micro aeration, photolysis, or the use of activated carbon in the fixed bed might have the ability to enhance the biochemical methane conversion of such feedstock; otherwise, the introduction of trace elements alone may be adequate if aiming for platforms (volatile fatty acids) via anaerobic technologies.