Use of multivariate experimental designs for optimizing the reductive degradation of an azo dye in the presence of redox mediators

The optimization of the anaerobic degradation of the azo dye Remazol golden yellow RNL was performed according to multivariate experimental designs: a 2² full-factorial design and a central composite design (CCD). The CCD revealed that the best incubation conditions (90% color removal) for the degradation of the azo dye (50 mg L- 1) were achieved with 350 mg L- 1 of yeast extract and 45 mL of anaerobic supernatant (free cell extract) produced from the incubation of 650 mg L- 1 of anaerobic microorganisms and 250 mg L- 1 of glucose. A first-order kinetics model best fit the experimental data (k = 0.0837 h- 1, R² = 0.9263).

Influence of chloride-mediated oxidation on the electrochemical degradation of the direct black 22 dye using boron-doped diamond and β-PbO2 anodes

The Direct Black 22 dye was electrooxidized at 30 mA cm-2 in a flow cell using a BDD or β-PbO2 anode, varying pH (3, 7, 11), temperature (10, 25, 45 °C), and [NaCl] (0 or 1.5 g L-1). In the presence of NaCl, decolorization rates were similar for all conditions investigated, but much higher than predicted through a theoretical model assuming mass-transport control; similar behavior was observed for COD removal (at pH 7, 25 °C), independently of the anode. With no NaCl, COD removals were also higher than predicted with a theoretical model, which suggests the existence of distinct dye degradation pathways.

TUNGSTOPHOSPHORIC ACID HETEROGENIZED ONTO NH4ZSM5 AS AN EFFICIENT AND RECYCLABLE CATALYST FOR THE PHOTOCATALYTIC DEGRADATION OF DYES

Materials based on tungstophosphoric acid (TPA) immobilized on NH4ZSM5 zeolite were prepared by wet impregnation of the zeolite matrix with TPA aqueous solutions. Their concentration was varied in order to obtain TPA contents of 5%, 10%, 20%, and 30% w/w in the solid. The materials were characterized by N2 adsorption-desorption isotherms, XRD, FT-IR, 31P MAS-NMR, TGA-DSC, DRS-UV-Vis, and the acidic behavior was studied by potentiometric titration with n-butylamine. The BET surface area (SBET) decreased when the TPA content was raised as a result of zeolite pore blocking. The X-ray diffraction patterns of the solids modified with TPA only presented the characteristic peaks of NH4ZSM5 zeolites, and an additional set of peaks assigned to the presence of (NH4)3PW12O40. According to the Fourier transform infrared and 31P magic angle spinning-nuclear magnetic resonance spectra, the main species present in the samples was the [PW12O40]3- anion, which was partially transformed into the [P2W21O71]6- anion during the synthesis and drying steps. The thermal stability of the NH4ZSM5TPA materials was similar to that of their parent zeolites. Moreover, the samples with the highest TPA content exhibited band gap energy values similar to those reported for TiO2. The immobilization of TPA on NH4ZSM5 zeolite allowed the obtention of catalysts with high photocatalytic activity in the degradation of methyl orange dye (MO) in water, at 25 ºC. These can be reused at least three times without any significant decrease in degree of degradation.

HYDROLYTIC DEGRADATION BEHAVIOR OF PLLA NANOCOMPOSITES REINFORCED WITH MODIFIED CELLULOSE NANOCRYSTALS

Bionanocomposites derived from poly(L-Lactide) (PLLA) were reinforced with chemically modified cellulose nanocrystals (m-CNCs). The effects of these modified cellulose nanoparticles on the mechanical and hydrolytic degradation behavior of polylactide were studied. The m-CNCs were prepared by a method in which hydrolysis of cellulose chains is performed simultaneously with the esterification of hydroxyl groups to produce modified nanocrystals with ester groups. FTIR, elemental analysis, TEM, XRD and contact angle measurements were used to confirm and characterize the chemical modifications of the m-CNCs. These bionanocomposites gave considerably better mechanical properties than neat PLLA based on an approximately 100% increase in tensile strength. Due to the hydrophobic properties of the esterified nanocrystals incorporated into a polymer matrix, it was also demonstrated that a small amount of m-CNCs could lead to a remarkable decrease in the hydrolytic degradation rate of the biopolymer. In addition, the m-CNCs considerably delay the degradation of the nanocomposite by providing a physical barrier that prevents the permeation of water, which thus hinders the overall absorption of water into the matrix. The results obtained in this study show the nanocrystals can be used to reinforce polylactides and fine-tune their degradation rates in moist or physiological environments.

DIRECT INFUSION ESI-MS APPLIED IN THE DETECTION OF BYPRODUCTS DUE TO REDUCTIVE DEGRADATION OF ACETAMIPRID BY ZERO-VALENT IRON

This study investigated the reductive degradation of acetamiprid (5 mg L-1) in aqueous medium (at pH 2.0) induced by zero-valent iron (50 mg). The process was monitored using high-performance liquid chromatography (HPLC) to determine the degradation rate as a function of reaction time, and direct infusion electrospray ionization mass spectrometry (DI-ESI-MS) to search for (and potentially characterize) any possible byproducts formed during degradation. The results obtained via HPLC showed that after 60 min, the degradation of the substrate reached nearly 100% in an acidic medium, whereas the mineralization rate (as determined by total organic carbon measurements) was as low as 3%. Data obtained by DI-ESI-MS showed that byproducts were formed mainly by insertions of hydrogen atoms into the nitrile, imine, and pyridine ring moieties, in addition to the observation of chlorine substitution by hydrogen replacement (hydrodechlorination) reactions.

Thermal degradation behaviour of some polydithiooxamide metal complexes

The thermal decomposition behavior of the Fe(II), Co(II), Ni(II) and Zn(II) complexes of polydithiooxamide has been investigated by thermogravimetric analysis (TGA) at a heating rate of 20°C min-1 under nitrogen. The Coats-Redfern integral method is used to evaluate the kinetic parameters for the successive steps in the decomposition sequence observed in the TGA curves. The processes of thermal decomposition taking place in the four complexes are studied comparatively as the TGA curves indicate the difference in the thermal decomposition behavior of these complexes. The thermal stabilities of these complexes are discussed in terms of repulsion among electron pairs in the valence shell of the central ion and electronegativity effects.

Photoelectrocatalytical degradation of basic blue 41 dye using nanoporous semiconductor of Ti/TiO2

O presente trabalho investiga a degradação fotoeletrocatalítica do corante Azul Básico 41 (AB 41) amplamente utilizado na tintura de fibras sintéticas, utilizando um semicondutor Ti/TiO2 como fotoanodo. 100% de degradação foi obtida após 60 min de tratamento de 8,33x10-5 mol L-1 do corante em 0,1 mol L−1 Na2SO4, pH 2 sob densidade de corrente de 0,40 mA cm−2 e irradiação UV. Ainda foi obtido 80% de remoção de carbono orgânico total, cuja oxidação segue uma reação de pseudo-primeira ordem com constante de velocidade inicial de -0,040 mim-1 e uma eficiência de corrente de 51%. Os resultados são superiores á fotocatálise convencional nas mesmas condições sem a polarização do fotoanodo que leva a 65% de mineralização sob constante de velocidade de -0,024 mim-1.

Pulsed corona discharge as an advanced oxidation process for degradation of organic

Advanced oxidation processes (AOPs) have been studied and developed to suffice the effective removal of refractory and toxic compounds in polluted water. The quality and cost of wastewater treatment need improvements, and electric discharge technology has a potential to make a significant difference compared to other established AOPs based on energy efficiency. The generation of active oxidant species such as ozone and hydroxyl radicals by high voltage discharge is a relatively new technology for water treatment. Gas-phase pulsed corona discharge (PCD), where a treated aqueous solution is dispersed between corona-producing electrodes free of the dielectric barriers, was developed as an alternative approach to the problem. The short living radicals and ozone formed in the gas phase and at the gas-liquid interface react with dissolved impurities. PCD equipment has a relatively simple configuration, and with the reactor in an enclosed compartment, it is insensitive towards gas humidity and does not need the gas transport. In this thesis, PCD was used to study and evaluate the energy efficiency for degrading various organic compounds, as well as the chemistry of the oxidation products formed. The experiments investigate the aqueous oxidation of phenol, humic substances, pharmaceutical compounds (paracetamol, ibuprofen, indomethacin, salicylic acids, -estradiol), as well as lignin degradation and transformation to aldehydes. The study aims to establish the influence of initial concentration of the target pollutant, the pulsed discharge parameters, gas phase composition and the pH on the oxidation kinetics and the efficiency. Analytical methods to measure the concentrations of the target compounds and their by-products include HPLC, spectrophotometry, TOC and capillary electrophoresis. The results of the research included in this summary are presented in the attached publications and manuscripts accepted for publication. Pulsed corona discharge proved to be highly effective in oxidizing each of the target compounds, surpassing the closest competitor, conventional ozonation. The increase in oxidation efficiencies for some compounds in oxygen media and at lower pulse repetition frequencies shows a significant role of ozone. The role of the ·OH radicals was established in the surface reactions. The main oxidation products, formation of nitrates, and the lignin transformation were quantified. A compound specific approach is suggested for optimization of the PCD parameters that have the most significant impact on the oxidation energy efficiency because of the different characteristics and responses of the target compound to the oxidants, as well as different admixtures that are present in the wastewater. Further studies in the method’s safety (nitration and nitrosation of organic compounds, nitrite and nitrate formation enhancement) are needed for promoting the method.

Imidazolinone Degradation in Soil in Response to Application History

Accelerated herbicide degradation consists in its faster degradation in areas where it has been previously applied, due to the adaptation of microbial population to that particular compound. Accelerated degradation can reduce herbicide persistence and reduce its efficacy in soil. The objective of this study was to investigate if imidazolinone herbicides have enhanced microbial degradation in rice paddy soils. A laboratory experiment was conducted, evaluating the CO2 evolution rate from soils with and without history of herbicide application (imazapyr + imazapic and imazethapyr + imazapic), incubated with imidazolinone herbicides: imazethapyr, imazapyr, imazapic, imazamethabenz, imazamox and an untreated check. The amount of CO2 released from the soil was measured. As a result, the prior application of imidazolinones does not stimulate microbial degradation of herbicides from the same chemical group.

Fructan degradation and hydrolytic activity in tuberous roots of Viguiera discolor Baker (Asteraceae), a herbaceous species from the cerrado

Fructans of the inulin type are the major reserve carbohydrates in tuberous roots of Viguiera discolor, a perennial herb native to the cerrado. Changes in molecular mass of the polymer, followed by releasing free fructose suggested that hydrolysis could be related to the sprouting of the buds after the dormant period, when aerial parts of the plant are naturally absent. Excision of aerial parts resulted in the increase of fructan 1-exohydrolase (1-FEH) activity in tuberous roots after sprouting. 1-FEH was partially purified from this material by binding to ConA-Sepharose and the highest activity was detected at pH 5.4 and between 20 and 40 °C. Values of Km for V. discolor inulin could not be determined since no saturation was observed up to 10%. The study of the kinetics of the 1-FEH activity showed that it does not follow Michaelis-Menten and apparently presents allosteric behaviour, as data fits in the Hill equation. The 1-FEH from V. discolor is a glycoprotein, more active on low molecular mass fructans than on high molecular mass inulin from the same species.

Stability of Natural Colorants of Plant Origin

In recent years, there have been studies that show a correlation between the hyperactivity of children and use of artificial food additives, including colorants. This has, in part, led to preference of natural products over products with artificial additives. Consumers have also become more aware of health issues. Natural food colorants have many bioactive functions, mainly vitamin A activity of carotenoids and antioxidativity, and therefore they could be more easily accepted by the consumers. However, natural colorant compounds are usually unstable, which restricts their usage. Microencapsulation could be one way to enhance the stability of natural colorant compounds and thus enable better usage for them as food colorants. Microencapsulation is a term used for processes in which the active material is totally enveloped in a coating or capsule, and thus it is separated and protected from the surrounding environment. In addition to protection by the capsule, microencapsulation can also be used to modify solubility and other properties of the encapsulated material, for example, to incorporate fat-soluble compounds into aqueous matrices. The aim of this thesis work was to study the stability of two natural pigments, lutein (carotenoid) and betanin (betalain), and to determine possible ways to enhance their stability with different microencapsulation techniques. Another aim was the extraction of pigments without the use of organic solvents and the development of previously used extraction methods. Stability of pigments in microencapsulated pigment preparations and model foods containing these were studied by measuring the pigment content after storage in different conditions. Preliminary studies on the bioavailability of microencapsulated pigments and sensory evaluation for consumer acceptance of model foods containing microencapsulated pigments were also carried out. Enzyme-assisted oil extraction was used to extract lutein from marigold (Tagetes erecta) flower without organic solvents, and the yield was comparable to solvent extraction of lutein from the same flowers. The effects of temperature, extraction time, and beet:water ratio on extraction efficiency of betanin from red beet (Beta vulgaris) were studied and the optimal conditions for maximum yield and maximum betanin concentration were determined. In both cases, extraction at 40 °C was better than extraction at 80 °C and the extraction for five minutes was as efficient as 15 or 30 minutes. For maximum betanin yield, the beet:water ratio of 1:2 was better, with possibly repeated extraction, but for maximum betanin concentration, a ratio of 1:1 was better. Lutein was incorporated into oil-in-water (o/w) emulsions with a polar oil fraction from oat (Avena sativa) as an emulsifier and mixtures of guar gum and xanthan gum or locust bean gum and xanthan gum as stabilizers to retard creaming. The stability of lutein in these emulsions was quite good, with 77 to 91 percent of lutein being left after storage in the dark at 20 to 22°C for 10 weeks whereas in spray dried emulsions the retention of lutein was 67 to 75 percent. The retention of lutein in oil was also good at 85 percent. Betanin was incorporated into the inner w1 water phase of a water1-in-oil-inwater2 (w1/o/w2) double emulsion with primary w1/o emulsion droplet size of 0.34 μm and secondary w1/o/w2 emulsion droplet size of 5.5 μm and encapsulation efficiency of betanin of 89 percent. In vitro intestinal lipid digestion was performed on the double emulsion, and during the first two hours, coalescence of the inner water phase droplets was observed, and the sizes of the double emulsion droplets increased quickly because of aggregation. This period also corresponded to gradual release of betanin, with a final release of 35 percent. The double emulsion structure was retained throughout the three-hour experiment. Betanin was also spray dried and incorporated into model juices with different pH and dry matter content. Model juices were stored in the dark at -20, 4, 20–24 or 60 °C (accelerated test) for several months. Betanin degraded quite rapidly in all of the samples and higher temperature and a lower pH accelerated degradation. Stability of betanin was much better in the spray dried powder, with practically no degradation during six months of storage in the dark at 20 to 24 °C and good stability also for six months in the dark at 60 °C with 60 percent retention. Consumer acceptance of model juices colored with spray dried betanin was compared with similar model juices colored with anthocyanins or beet extract. Consumers preferred beet extract and anthocyanin colored model juices over juices colored with spray dried betanin. However, spray dried betanin did not impart any off-odors or off-flavors into the model juices contrary to the beet extract. In conclusion, this thesis describes novel solvent-free extraction and encapsulation processes for lutein and betanin from plant sources. Lutein showed good stability in oil and in o/w emulsions, but slightly inferior in spray dried emulsions. In vitro intestinal lipid digestion showed a good stability of w1/o/w2 double emulsion and quite high retention of betanin during digestion. Consumer acceptance of model juices colored with spray dried betanin was not as good as model juices colored with anthocyanins, but addition of betanin to real berry juice could produce better results with mixture of added betanin and natural berry anthocyanins could produce a more acceptable color. Overall, further studies are needed to obtain natural colorants with good stability for the use in food products.

Importance of hyaluronan biosynthesis and degradation in cell differentiation and tumor formation

Hyaluronan is an important connective tissue glycosaminoglycan. Elevated hyaluronan biosynthesis is a common feature during tissue remodeling under both physiological and pathological conditions. Through its interactions with hyaladherins, hyaluronan affects several cellular functions such as cell migration and differentiation. The activities of hyaluronan-synthesizing and -degrading enzymes have been shown to be regulated in response to growth factors. During tumor progression hyaluronan stimulates tumor cell growth and invasiveness. Thus, elucidation of the molecular mechanisms which regulate the activities of hyaluronan-synthesizing and -degrading enzymes during tumor progression is highly desired.

Bacterial community structure and petroleum hydrocarbon degradation in the Baltic Sea

The Baltic Sea is unique by its biological, geochemical and physical features. The number of species of larger organisms is small and the species composition is distinctive. On the contrary microbial communities are diverse. Because of the low salinity levels, bacterial communities differ from the ones in the oceans. Knowing the structure of these communities better and how they response to different environmental conditions helps us to estimate how different factors affect the balance and function of the Baltic Sea ecosystem. Bacteria are the key players when it comes to natural biogeochemical processes and human-induced phenomena like eutrophication, oil spills or disposal of other harmful substances to the sea ecosystem. In this thesis, bacterial community structure in the sea surface microlayer and subsurface water of the Archipelago Sea were compared. In addition, the effect of diatom derived polyunsaturated aldehydes on bacterial community structure was studied by a mesocosm experiment. Diesel, crude oil and polycyclic aromatic hydrocarbon degradation capacity of the Baltic Sea bacteria was studied in smaller scale microcosm experiments. In diesel oil experiments bacteria from water phase of the Archipelago Sea was studied. Sediment and iron manganese concretions collected from the Gulf of Finland were used in the crude oil and polycyclic aromatic hydrocarbon experiments. The amount of polycyclic aromatic hydrocarbon degradation genes was measured in all of the oil degradation experiments. The results show how differences in bacterial community structure can be seen in the sea surface when compared to the subsurface waters. The mesocosm experiment demonstrated how diatom-bacteria interactions depend on other factors than diatom derived polyunsaturated aldehydes, which do not seem to have an effect on the bacterial community structure as has been suggested in earlier studies. The dominant bacterial groups in the diesel microcosms differed in samples taken from a pristine site when compared to a site with previous oil exposure in the Archipelago Sea area. Results of the study with sediment and iron-manganese concretions indicate that there are diverse bacterial communities, typical to each bottom type, inhabiting the bottoms of the Gulf of Finland capable to degrade oil and polycyclic aromatic hydrocarbon compounds.  

An animal experimental study of porous magnesium scaffold degradation and osteogenesis

Our objective was to observe the biodegradable and osteogenic properties of magnesium scaffolding under in vivo conditions. Twelve 6-month-old male New Zealand white rabbits were randomly divided into two groups. The chosen operation site was the femoral condyle on the right side. The experimental group was implanted with porous magnesium scaffolds, while the control group was implanted with hydroxyapatite scaffolds. X-ray and blood tests, which included serum magnesium, alanine aminotransferase (ALT), creatinine (CREA), and blood urea nitrogen (BUN) were performed serially at 1, 2, and 3 weeks, and 1, 2, and 3 months. All rabbits were killed 3 months postoperatively, and the heart, kidney, spleen, and liver were analyzed with hematoxylin and eosin (HE) staining. The bone samples were subjected to microcomputed tomography scanning (micro-CT) and hard tissue biopsy. SPSS 13.0 (USA) was used for data analysis, and values of P<0.05 were considered to be significant. Bubbles appeared in the X-ray of the experimental group after 2 weeks, whereas there was no gas in the control group. There were no statistical differences for the serum magnesium concentrations, ALT, BUN, and CREA between the two groups (P>0.05). All HE-stained slices were normal, which suggested good biocompatibility of the scaffold. Micro-CT showed that magnesium scaffolds degraded mainly from the outside to inside, and new bone was ingrown following the degradation of magnesium scaffolds. The hydroxyapatite scaffold was not degraded and had fewer osteoblasts scattered on its surface. There was a significant difference in the new bone formation and scaffold bioabsorption between the two groups (9.29±1.27 vs 1.40±0.49 and 7.80±0.50 vs 0.00±0.00 mm3, respectively; P<0.05). The magnesium scaffold performed well in degradation and osteogenesis, and is a promising material for orthopedics.