Biomedical subjects

I Angelidaki

Publications and source records attributed to I Angelidaki.

26 records · Page 2Linked to original sources

PubMed2000

Degradation of organic contaminants found in organic waste.

In recent years, great interest has arisen in recycling of the waste created by modern society. A common way of recycling the organic fraction is amendment on farmland. However, these wastes may contain possible hazardous components in small amounts, which may prevent their use in farming. The objective of our study has been to develop biological methods by which selected organic xenobiotic compounds can be biotransformed by anaerobic or aerobic treatment. Screening tests assessed the capability of various inocula to degrade two phthalates di-n-butylphthalate, and di(2-ethylhexyl)phthalate, five polycyclic aromatic hydrocarbons, linear alkylbenzene sulfonates and three nonylphenol ethoxylates under aerobic and anaerobic conditions. Under aerobic conditions, by selecting the appropriate inoculum most of the selected xenobiotics could be degraded. Aerobic degradation of di(2-ethylhexyl)phthalate was only possible with leachate from a landfill as inoculum. Anaerobic degradation of some of the compounds was also detected. Leachate showed capability of degrading phthalates, and anaerobic sludge showed potential for degrading, polycyclic aromatic hydrocarbons, linear alkylbenzene sulfonates and nonyl phenol ethoxylates. The results are promising as they indicate that a great potential for biological degradation is present, though the inoculum containing the microorganisms capable of transforming the recalcitrant xenobiotics has to be chosen carefully.

Biodegradation, Environmental↗

PubMed2000

Increase of anaerobic degradation of particulate organic matter in full-scale biogas plants by mechanical maceration.

Different concepts of implementation of mechanical pretreatment for enhancing the biogas potential from fibers in manure feedstock were evaluated by sampling before and after macerators at different biogas plants and from a fiber separation unit. An increase of the biogas potential of up to 25% by pretreatment of the whole feed in the macerator before the reactor was observed. Implementation concepts with a treatment of the fibers alone after separation from the manure showed to be not efficient due to a low recovery of organic matter in the fibers by the separation unit. The low operational costs of a macerator make it attractive to use this pretreatment method for a more complete degradation of particulate organic matter. Investigation of the size distribution of the fibers showed that a change in biogas potential was not correlated to a smaller size of the fibers. Results from the macerators indicate that the biodegradability of the fibers is rather enhanced by shearing which is not necessarily reflected by a change in fiber size.

Bacteria, Anaerobic↗

PubMed2000

Methods for increasing the biogas potential from the recalcitrant organic matter contained in manure.

The biogas potential of manure could be significantly increased by treatment of the recalcitrant organic matter (biofibers) contained in the manure. Several treatment methods were tested. Mechanical maceration resulted in an average increase of the biogas potential of approximately 17% as shown by the continuous stirred reactor experiment. In general the smaller the fibers the higher the biogas potential was. The best results showed an approximately 20% increase of the biogas potential with fibers smaller than 0.35 mm as measured by batch experiments. The increase was approximately 16% with fibers of size 2 mm. Chemical treatment of the fibers with bases such as NaOH, NH4OH or a combination of bases also resulted in an increased methane potential. However, combination of maceration and chemical treatment did not result in a further increase of the methane potential. There was not any significant difference of the biogas potential from fibers in the range 5-20 mm. Treatment of the fibers with hemicellulolytic or cellulolytic enzymes did not result in any significant increase of the methane potential. However, biological treatment of the fibers of the manure with the hemicellulose degrading bacterium B4 resulted in a significant increase of the biogas potential of manure. An increase of approximately 30% in methane potential was achieved compared to controls.

Fatty Acids, Volatile↗

PubMed1999

A comprehensive model of anaerobic bioconversion of complex substrates to biogas

A dynamic model describing the anaerobic degradation of complex material, and codigestion of different types of wastes, was developed based on a model previously described (Angelidaki et al., 1993). In the model, the substrate is described by its composition of basic organic components, i.e., carbohydrates, lipids, and proteins, the concentration of intermediates such as volatile fatty acids and long-chain fatty acids, and important inorganic components, i.e., ammonia, phosphate, cations, and anions. This allows dynamic changes of the process during a shift of substrate composition to be simulated by changing the input substrate data. The model includes 2 enzymatic hydrolytic steps, 8 bacterial steps and involves 19 chemical compounds. The model also includes a detailed description of pH and temperature characteristics. Free ammonia, acetate, volatile fatty acids, (VFA) and long-chain fatty acids (LCFA) constitute the primary modulating factors in the model. The model was tested with success in lab-scale reactors codigesting manure with glycerol trioleate or manure with gelatin. Finally, the model was validated using results from a full-scale biogas plant codigesting manure together with a proteinous wastewater and with bentonite-bound oil, which is a waste with high content of lipids. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1995

Isomerization of n- and i-butyrate in anaerobic methanogenic systems.

Studies of the degradation of the two isomeric forms of butyrate in different anaerobic environments showed isomerization between n- and i-butyrate. Degradation rates were similar for the different examined systems and degradation rates for n-butyrate degradation were generally higher than for i-butyrate. Degradation rates for n-butyrate ranged from 0.52 to 1.39 day-1, while the rates for i-butyrate were from 0.46 to 1.15 day-1. Production of isomers was not observed when the volatile fatty acid degradation was inhibited by addition of bromoethane sulfonic acid, indicating that isomerization was coupled to the methanogenic degradation of the acid. The degree of isomerization observed during n-butyrate degradation was similar to the degree during i-butyrate degradation. Experiments indicated that the isomerization degree was higher for the thermophilic than for the mesophilic inocula.

Anaerobiosis↗

PubMed1995

Establishment and Characterization of an Anaerobic Thermophilic (55(deg)C) Enrichment Culture Degrading Long-Chain Fatty Acids.

A thermophilic, long-chain fatty acid-oxidizing culture was enriched. Stearate was used as the substrate, and methane and carbon dioxide were the sole end products. Cultivation was possible only when a fed-batch system was used or with addition of activated carbon or bentonite. The enrichment culture consisted of a short rod and two bacteria antigenically related to Methanobacterium thermoautotrophicum (Delta)H and Methanosarcina thermophila TM-1.

Journal Article↗

PubMed1990

Effects of lipids on thermophilic anaerobic digestion and reduction of lipid inhibition upon addition of bentonite.

The effect of bentonite-bound oil on thermophilic anaerobic digestion of cattle manure was investigated. In digestor experiments, addition of oil was found to be inhibitory during start-up and the inhibitory effect was less pronounced when the oil was added in the form of bentonite-bound oil compared to when the oil was added alone. After adaptation of the digestors, very rapid degradation of oil was observed and more than 80% of the oil was degraded within a few hours after daily feeding. In batch experiments, glyceride trioleate was found to be inhibitory to thermophilic anaerobic digestion when the concentrations were higher than 2.0 g/l. However, addition of bentonite (a clay mineral) at concentrations of 0.15% and 0.45% was found to partly overcome this inhibition. Addition of calcium chloride in concentration of 3 mM (0.033% w/v) showed a similar positive effect on the utilization of oil, but the effect was lower than with bentonite.

Anaerobiosis↗

PubMedDate not supplied

Codigestion of manure and organic wastes in centralized biogas plants: status and future trends.

Centralized biogas plants in Denmark codigest mainly manure, together with other organic waste such as industrial organic waste, source sorted household waste, and sewage sludge. Today 22 large-scale centralized biogas plants are in operation in Denmark, and in 2001 they treated approx 1.2 million tons of manure as well as approx 300,000 of organic industrial waste. Besides the centralized biogas plants there are a large number of smaller farm-scale plants. The long-term energy plan objective is a 10-fold increase of the 1998 level of biogas production by the year 2020. This will help to achieve a target of 12-14% of the national energy consumption being provided by renewable energy by the year 2005 and 33% by the year 2030. A major part of this increase is expected to come from new centralized biogas plants. The annual potential for biogas production from biomass resources available in Denmark is estimated to be approx 30 Peta Joule (PJ). Manure comprises about 80% of this potential. Special emphasis has been paid to establishing good sanitation and pathogen reduction of the digested material, to avoid risk of spreading pathogens when applying the digested manure as fertilizer to agricultural soils.

Animals↗