Sulfur reduction in sediments of marine and evaporite environments

Transformations of sulfur in sediments of ponds ranging in salinities from that of normal seawater to those of brines saturated with sodium chloride were examined. The chemistry of the sediment and pore waters were focused on with emphasis on the fate of sulfate reduction. The effects of increasing salinity on both forms of sulfur and microbial activity were determined. A unique set of chemical profiles and sulfate-reducing activity was found for the sediments of each of the sites examined. The quantity of organic matter in the salt pond sediments was significantly greater than that occurring in the adjacent intertidal site. The total quantitative and qualitative distribution of volatile fatty acids was also greater in the salt ponds. Volatile fatty acids increased with salinity

Glucose Tolerance in Lambs As Affected by Type of Ration

Metabolism of glucose is little understood in the ruminant animal. It has been demonstrated that little or no carbohydrate passes into the intestinal tract of adult ruminants on an all roughage ration (Heald 1951). Soluble carbohydrates of roughages are fermented to volatile fatty acids in the rumen. Available data show that 70% of total cellulose digestion occurs in the rumen and 30% in the cecum and large intestine with little or no cellulose digestion occurring in the small intestine (Hale, et al. 1947 and Gray 1951). The end products of cellulose digestion are the volatile fatty acids and not glucose. It has been estimated that up to 80% of the metabolizable energy of the feed is provided by the volatile fatty acids (McClymont, 1952). On an all roughage ration the source of blood glucose must, therefore, be from propionic acid which is liberally produced by rumen fermentation

The possibilities of the assessment of volatile fatty acids

Tato bakalářská práce se zabývá obecnou charakteristikou mastných kyselin, popisem struktury a názvosloví těkavých mastných kyselin, vlastnostmi a oblastmi jejich výskytu. Dále jsou zmapovány možnosti identifikace těkavých mastných kyselin, mezi které se řadí plynová chromatografie, plynová chromatografie-hmotnostní spektrometrie, vysokoúčinná kapalinová chromatografie, mikroextrakce pevnou fází, spektrofotometrie a izotachoforéza. Plynová chromatografie je nejvyužívanější metodou detekce těkavých mastných kyselin. Při stanovení se tyto látky vzhledem k jejich chemickým vlastnostem většinou převádějí na methylestery.This bachelor's thesis deals with common characteristics of fatty acids by description of the structure and terminology of volatile fatty acids, by description of the characteristics and areas of their occurrence. Then possibilities of identification of volatile fatty acids are charted, to which gas chromatography, gas chromatography-mass spectrometry, high performance liquid chromatography, solid phase microextraction, spectrophotometry and isotachophoresis belong. Gas chromatography is the most frequently used method of the detection of volatile fatty acids. During the assessment these substances are mostly converted to methylesters because of their chemical characteristics.

Impact of embalming and burial on decomposition rates and diffusion of volatile fatty acids in Kentucky

Six still-born fetal pigs were divided into two groups (three were embalmed, and three non-embalmed) to determine a postmortem interval on decomposing remains in eastern Kentucky. One pig from each group was placed on the surface, one from each group was interred at a depth of two feet, and one from each group was buried at four feet. This study focused on observing necrophagous insect succession as well as how far on both a horizontal and a vertical plane volatile fatty acids leach from a body. Soil samples were taken from near all specimens at the time of respective termination of the project in order to determine leaching distances. Results show that embalmed remains mummify, and, hence, attract more beetles than non-embalmed remains. Results also demonstrate that volatile fatty acids are not degraded by embalming fluid and leach out both vertically and horizontally, with higher concentrations running vertically. Soil associated with buried remains tend to retain higher concentrations of volatile fatty acids than do soils associated with surface remains

Mechanistic understanding of mixed-culture fermentations by metabolic modelling

Biorefineries are set to become an important agent in the shift towards a circular economy due to their potential to valorise organic wastes into marketable products. Anaerobic fermentations yielding volatile fatty acids are a key process in this production scheme as their products act as intermediates between the organic wastes and the final biorefinery products. However, their product selectivity is highly influenced by the environmental conditions and the mechanisms governing the process remain unknown. In this thesis, predictive tools were developed with the objective of understanding the mechanisms governing anaerobic fermentations and of designing processes targeting specific volatile fatty acids with high productivity

Volatile fatty acids production from fish wastewater

In this work, two experiments were carried out to investigate the production of volatile fatty acids (VFAs) through the anaerobic degradation of a wastewater collected from a fish processing industry. The first experiment was carried out in batches, at different initial pH values (5, 6, 7, 8 and 9). Acetate and propionate were the main products obtained at the end of the experiment. The highest production of VFAs (5276 mg COD/L) was obtained at pH 8. The second experiment was performed in an anaerobic continuous reactor at pH 5.5. Several conditions were tested to improve the VFAs production such as different HRT (18 h, 12 h and 8 h), different feed´s dilution (50 x, 25 x, 10 x, 2 x and 1 x) and different feed´s salinity (2.8 g/L and 20 g/L of salt). The increase of feed´s salinity appear to be the best strategy, since the concentration of VFAs increased (457 mg COD/L with 2,8 mg/L of salt to 788 mg COD/L with 20 mg/L of salt) and the percentage of CH4 in the reactor decreased.El objetivo del trabajo fue la obtención de ácidos grasos volátiles (AGVs) a través de la degradación anaeróbica incompleta de un efluente procedente de una industria de procesamiento de pescado. Para ello se realizaron dos experimentos: El primero se llevó a cabo en un reactor anaerobio continuo. Durante el experimento se fueron variando distintos parámetros de operación: tiempo hidráulico de retención (TRH), dilución de la alimentación y salinidad de la misma, para encontrar las mejores condiciones para la producción de AGVs. El segundo experimento se llevó a cabo en ensayos por lotes a diferentes valores de pH: 5, 6, 7, 8 y 9. De esta forma se estudio cómo afectaban los distintos pHs a la producción de AGVs.Departamento de Ingeniería Química y Tecnología del Medio AmbienteGrado en Ingeniería Químic

Single cell oil production by oleaginous yeasts grown in synthetic and waste-derived volatile fatty acids

Four yeast isolates from the species—Apiotrichum brassicae, Candida tropicalis, Metschnikowia pulcherrima, and Pichia kudriavzevii—previously selected by their oleaginous character and growth flexibility in different carbon sources, were tested for their capacity to convert volatile fatty acids into lipids, in the form of single cell oils. Growth, lipid yields, volatile fatty acids consumption, and long-chain fatty acid profiles were evaluated in media supplemented with seven different volatile fatty acids (acetic, butyric, propionic, isobutyric, valeric, isovaleric, and caproic), and also in a dark fermentation effluent filtrate. Yeasts A. brassicae and P. kudriavzevii attained lipid productivities of more than 40% (w/w), mainly composed of oleic (>40%), palmitic (20%), and stearic (20%) acids, both in synthetic media and in the waste-derived effluent filtrate. These isolates may be potential candidates for single cell oil production in larger scale applications by using alternative carbon sources, combining economic and environmental benefits.This work was supported by the European project "VOLATILE-Biowaste derived volatile fatty acid platform for biopolymers, bioactive compounds and chemical building blocks" (Call H2020-NMBP-BIO-2016 Grant agreement No. 720777) and by the strategic programme UID/BIA/04050/2013 (POCI-01-0145-FEDER-007569) funded by national funds through the FCT I.P., by the ERDF through the COMPETE2020

Accumulation of Volatile Fatty Acids from Hydrothermally Treated Strawberry Extrudate through Anaerobic Fermentation at Different pH Values

The accumulation of volatile fatty acids (VFAs) through the anaerobic fermentation of organic waste, such as strawberry extrudate, is proposed for this work. A hydrothermal treatment was carried out, and it was proposed to break the complex matrix of the strawberry extrudate to favour the hydrolysis stage of the anaerobic digestion process. The production of volatile fatty acids from treated and untreated strawberry was evaluated by adjusting the pH to 5 and 9. After the hydrothermal treatment of the strawberry extrudate, an increase in the solubilisation of organic matter, such as sugars and phenols, was observed. In the production of VFAs by means of anaerobic digestion of the pretreated strawberry extrudate, a significant increase in the accumulation of volatile fatty acids was demonstrated at a pH of 9 with respect to the untreated strawberry extrudate. In addition, the operational pH also had a strong effect on the individual VFA profile. A stream enriched in acetic acid was obtained at a pH of 9 (around 65% of the VFAs), whereas the operation at a pH of 5 resulted in a more complex composition with a high percentage of propionic acid (29% of the VFAs).Ministry of Science and Innovation, Spain (MICINN) Spanish Government PID2020-116698RB-I0

Liquid biofuel production from volatile fatty acids

The production of renewable fuels and chemicals reduces the dependency on fossil fuels and limits the increase of CO2 concentration in the atmosphere only if a sustainable feedstock and an energy efficient process are used. The thesis assesses the possibility to use municipal and industrial waste as biomass feedstock to have little of no competition with food production, and to save greenhouse gasses emissions. Waste is a complex substrate with a diverse composition and high water content. It can be homogenized without losing its initial energy value by anaerobic conversion to volatile fatty acids. Using VFA gives the opportunity to process cheap and abundantly present biomass residues to a fuel and chemical instead of sugar containing crops or vegetable oil. This thesis describes the feasibility to convert VFA to compounds with a higher energy content using mixed culture fermentations by eliminating of oxygen and/or increasing the carbon and hydrogen content. At high hydrogen pressure, protons and electrons release via the reduction of organic products such as VFA becomes thermodynamically more attractive. Three VFA reduction reactions were studied: hydrogenation to an alcohol with 1) hydrogen and 2) an electrode as electron donor, and 3) by chain elongation with hydrogen and ethanol. Based on concentration, production rate and efficiency, elongation of acetate with hydrogen and/or ethanol was the best technique to convert VFA into a fuel. In a continuous flow CSTR, 10.5 g L-1 caproic acid and 0.48 g L-1 caprylic acid were produced with ethanol and/or hydrogen at a specific MCFA production activity of 2.9 g caproate and 0.09 g caprylate per gram VSS d-1. The products were selectively removed by calcium precipitation and solvent extraction with ethyl hexanoate and petroleum ether. Microbial characterization revealed that the microbial populations were stable and dominated by relatives of Clostridium kluyveri. VFA could also be reduced to alcohols. Acetic, propionic and butyric acids were biohydrogenated with hydrogen and acetic acid also with an electrode. Observed alcohol concentrations were 0.62 g L-1 ethanol, 0.49 g L-1 propanol and 0.27 g L-1 n-butanol. Methanogenesis was successfully inhibited after thermal pre-treatment incubated at pH 6, while acetate reduction was enhanced. In the second study, ethanol (0.084 g L-1) was produced at the cathodic compartment of a bioelectrochemical system, in which the electron transport was mediated by methyl viologen. The ethanol production activity at the cathode was only of very short term, since the mediator irreversibly reacted at the surface of the cathode. Of the two VFA conversion processes, biohydrogenation and chain elongation, chain elongation was a more dominant process that consumes ethanol with acetate to medium chain fatty acids. With this technology, wet organic waste can be converted to biofuels carbon and energy efficient. The technology is promising due to the good fuel and separation properties of medium chain fatty acids, and the possibility to produce them at high concentrations and specific production rates comparable to other anaerobic conversions. <br/

Volatile fatty acids production from fish wastewater

In this work, two experiments were performed to investigate the production of volatile fatty acids (VFAs) through the anaerobic degradation of an effluent formed by cleaning, cooking and brine wastewaters collected from a fish processing industry. The first experiment was carried out in an anaerobic continuous reactor at pH 8. Several strategies were tested to improve the VFAs production such as different HRT (18 h, 14 h, 8 h and 6 h), different feed´s dilution (50 x, 10 x, 2 x and 1 x) and different feed´s salinity (2.8 g/L and 20 g/L). For several HRT and dilutions, the concentration of VFAs was very low and methane (CH4) was detected in the reactor. The increase of feed´s salinity appear to be a good strategy, since the concentration of VFAs increased (401 mg COD/L with 2.8 g/L of salt to 900 mg COD/L with 20 g/L of salt) and the percentage of CH4 in the reactor decreased. The second experiment was carried out in batches at different initial pH values (5, 6, 7, 8 and 9). Acetate and propionate were the main products obtained at the end of the experiment. The highest production of VFAs (1583 mg COD/L) was obtained at pH 6.Departamento de Ingeniería Química y Tecnología del Medio AmbienteGrado en Ingeniería Químic