Orientador: Alessandra Nara de Souza Rastelli / Resumo: O objetivo deste estudo in vitro foi avaliar a eficácia de diferentes técnicas de clareamento dental, através das análises de dureza e contéudo mineral do esmalte dental clareado. Diferentes protocolos foram testados após manchamento dos espécimes com (café), como segue: G1: Whiteness HP Maxx (FGM); G2: Whiteness HP Maxx (FGM) + LED Azul - Twin Flex Evolution (MMOptics); G3: Whiteness HP Maxx (FGM) + LED Violeta - Bright Max Whitening (MMOptics); G4: Peróxido de Hidrogênio a 10% (FGM); G5: Peróxido de Hidrogênio a 10% (FGM) + Led Violeta - Bright Max Whitening (MMOptics); G6: Peróxido de Carbamida a 22% (FGM); G7: Peróxido de Carbamida a 22% (FGM) + LED Violeta - Bright Max Whitening (MMOptics) e G8: LED Violeta - Bright Max Whitening (MMOptics). Foram obtidos oitenta (n=80) espécimes de (4x4x2mm) da face vestibular de incisivos bovinos, após foram seccionados ao meio em máquina de corte, separando cada espécime em duas metades, uma metade foi utilizada como espécime sem procedimento clareador (controle) e a outra metade como espécime com procedimento clareador (tratado). Foi realizada análise em profundidade no esmalte, afim de verificar as possíveis alterações na superficíe (S) e subsuperficie (P), assim, cento e sessenta (n=160) espécimes foram avaliados quanto microdureza Knoop (n =10) e espectroscopia Raman (n = 5). Os diferentes protocolos para clareamento dental foram aplicados de acordo com os fabricantes dos produtos e dos equipamentos. Os espécimes permaneceram em s... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this in vitro study was to evaluate the effectiveness of different dental bleaching techniques through microhardness analysis and mineral content of bleached dental enamel. Different protocols were tested after spotting the specimens with (coffee), as follows: G1: Whiteness HP Maxx (FGM); G2: Whiteness HP Maxx (FGM) + Blue LED - Twin Flex Evolution (MMOptics); G3: Whiteness HP Maxx (FGM) + Violet Led - Bright Max Whitening (MMOptics); G4: 10% Hydrogen Peroxide (FGM); G5: 10% Hydrogen Peroxide (FGM) + Violet Led - Bright Whitening (MMOptics); G6: 22% carbamide peroxide (FGM); G7: 22% Carbamide Peroxide (FGM) + LED Violet - Bright Max Whitening (MMOptics) and G8: Violet LED - Bright Max Whitening (MMOptics). Eighty (4x4x2mm) specimens were collected from the bovine incisal vestibular surface, after being sectioned in the cutting machine, separating each specimen into two halves, one half was used as a specimen without bleaching procedure (control) and the other half as a specimen with bleaching procedure (treated). To verify the possible changes in surface (S) and subsurface (P), one hundred and sixty (n = 160) specimens were evaluated for Knoop microhardness (n = 10) and Raman spectroscopy (n = 5). The different dental bleaching protocols were applied according to the manufacturers of the products and equipment. The specimens remain in artificial saliva at 37 ° C throughout the experiment period and are replaced weekly. Changes in bovine dental enamel were eva... (Complete abstract click electronic access below) / Mestre

O objetivo deste estudo clínico randomizado duplo cego boca-dividida foi avaliar, in vivo, a efetividade do condicionamento ácido prévio do esmalte e de géis clareadores a base de peróxido de hidrogênio (PH) de baixa concentração, associados a fontes de luz híbrida (LH), tendo como variáveis de reposta: sensibilidade dental, fluxo sanguíneo pulpar, grau de mudança e estabilidade de cor ao longo de 6 meses. Trinta e seis voluntários que se encaixaram nos critérios de inclusão e exclusão foram selecionados e randomizados em 3 grupos (n=12), de acordo com o protocolo clareador a ser utilizado. Dentro de cada grupo, um dos hemiarcos foi aleatoriamente selecionado para a realização do condicionamento ácido do esmalte, previamente a aplicação do gel clareador. Os géis que compunham os três protocolos clareadores foram: PH a 10% (experimental) associado a LH a base de LED violeta + laser de diodo (experimental); PH a 15% associado a LH a base de LED azul + laser de diodo; e PH a 35% sem ativação com fonte de luz. A sensibilidade foi avaliada com a escala VAS; a fluxometria pulpar, com o sistema Laser Doppler; e a cor pelo cálculo do ?E via espectrofotômetro. Os dados foram tratados pela análise de variância de medidas repetidas (ANOVA), Tukey e teste de Friedman (p<0,05). Com relação à sensibilidade, foram encontradas diferenças significativas na interação tempo e grupo, mas não com relação ao ácido. Quanto à vascularização pulpar, o efeito de grupo não foi rejeitado, sendo o grupo de PH a 35% o que apresentou as menores medianas para as variações percentuais, porém os efeitos de ácido e tempo não foram significativos. Quanto à cor, diferenças significantes foram encontradas entre os grupos, mas não com relação ao uso do ácido, sendo o PH a 35% o que promoveu maior aumento do ?E. Conclui-se assim que o condicionamento ácido não foi capaz de favorecer a efetividade do clareamento em função do grau de mudança e estabilidade de cor, bem como não aumentou a sensibilidade e o fluxo sanguíneo da polpa dental. A concentração dos agentes clareadores foi determinante para o grau de mudança de cor e demonstrou influenciar a sensibilidade e o fluxo sanguíneo pulpar. / The aim of this double blind split-mouth randomized clinical study was to evaluate, in vivo, the effectiveness of prior acid etching on enamel and low concentration bleaching gels based on hydrogen peroxide (HP) associated with hybrid light (HL) sources, having as response variables: dental sensitivity, dental pulp vascularization and degree of color change and stability over 6 months. Thirty-six volunteers in agreement with the inclusion and exclusion criteria were selected and randomly divided into 3 groups (n = 12) according to the bleaching protocol to be used. Within each group, one of the sides was randomly selected for the execution of acid etching prior to the gel application. The three bleaching gels were: 10% HP (experimental) associated with HL-based violet LED/laser (experimental); 15% HP associated with HL-based blue LED/laser; and 35% HP without light activation. Sensitivity was evaluated with the VAS scale; pulp flowmetry by the use of the Laser Doppler system; and efficacy was evaluated by calculating the ?E via a spectrophotometer. Data were analyzed by analysis of variance for repeated measures (ANOVA), Tukeys and Friedman tests (p<0.05). Regarding sensitivity, significant differences were found in the interaction between the application time and group but not regarding etching. For dental pulp flowmetry, the group effect was not rejected, where the 35% HP showed the lowest medians for the percentile variations, but the effects of etching and time were not significant. For color, significant differences were found between the groups, but not between the sides with and without acid etching, where the 35% HP gel promoted the highest increase in ?E. It is therefore concluded that the etching was not able to favor the effectiveness of whitening due to color variation and stability, as well as not increasing sensitivity or pulp blood flow. The concentration of bleaching agents determined the degree of color change and influenced the sensitivity and blood flow of the dental pulp.

Este estudo in vitro avaliou a variação do pH de géis clareadores à base de peróxido de hidrogênio de diferentes concentrações e seu efeito sobre o esmalte bovino submetido à escovação simulada. Fragmentos de esmalte de dentes bovinos com 1,5cm x 0,5cm x 0,4cm, receberam o tratamento clareador e a escovação em uma metade, ficando a outra como controle; foram divididos aleatoriamente em nove grupos (n=10): G1 = controle; G2 = Whiteness HP 35% - 3 sessões (3x15); G3 = Whiteness HP 35% - 3 sessões (1x45); G4 = Lase Peroxide 35% - 1 sessão (4x730) + ativação com luz híbrida LED/Laser; G5 = Lase Peroxide 25% - 1 sessão (4x730) + ativação com luz híbrida LED/Laser; G6 = Lase Peroxide 15% - 1 sessão (4x730) + ativação com luz híbrida LED/Laser; G7 = Whitegold Office 35% - 3 sessões (1x45); G8 = Whiteness HP Blue Calcium 35% - 3 sessões (1x40); G9 = Whiteness HP Blue Calcium 20% - 3 sessões (1x50). A rugosidade aritmética (Ra) inicial, após clareamento e após escovação foi determinada pela média (µm) de 3 leituras com o rugosímetro Hommel Tester T 1000. Os valores de pH foram determinados pelo peagômetro digital Sentron Model 1001 nos tempos inicial e final independente do número de aplicações ou de sessões. Os espécimes foram armazenados em saliva artificial por 7 dias, submetidos à 100.000 ciclos de escovação simulada. Após 24 horas o desgaste superficial foi determinado (µm) novamente com o rugosímetro Hommel Tester T1000. Os dados da análise de pH foram submetidos a ANOVA um critério e teste de Tukey (p<0,05) com diferenças estatísticas. O teste de Kruskal Wallis e Dunn (p<0,05) aplicado sobre a variação da rugosidade e desgaste apontou diferenças estatísticas entre os grupos. Os géis clareadores apresentaram uma tendência de diminuição dos valores de pH do tempo inicial para o tempo final. Os géis clareadores apresentaram um tendência de diminuição dos valores de pH do tempo inicial para o tempo final, assim como os géis com valores de pH mais próximos dos valores ácidos tendem a levar a superfície do esmalte à uma maior susceptibilidade ao aumento da rugosidade e desgaste superficial, quando submetido à escovação simulada. / This in vitro study evaluated the variation of the pH of bleaching gels, roughness and the wear on bovine enamel, after various in office bleaching protocols and brushing. Ninety fragments of enamel, measuring 15mm x 5mm, were randomly divided into nine groups (n=10) according to bleaching procedure: G1: control; G2: 35% hydrogen peroxide (HP) (Whiteness HP, FGM) 3x15, 3 sessions with one week between each; G3: 35% HP (Whiteness HP, FGM) 1x45, in 3 sessions; G4: 35% HP (Lase Peroxide, DMC) + hybrid light (HL) (LED/Diode laser, Whitening Lase II, DMC Equipments), 4x730 (6 of HL activation), in 1 session; G5: 25% HP (Lase Peroxide II, DMC) + HL, 4x730 (6 of HL activation), in 1 session; G6: 15% HP (Lase Peroxide Light, DMC) 4x730 (6 of HL activation), in 1 session; G7: 35% HP (Whitegold Office, Dentsply) 3x15, in 3 sessions; G8: 35% HP (Whiteness HP Blue Calcium, FGM) 1x40, in 3 sessions; G9: 20% HP (Whiteness HP Blue Calcium, FGM) 1x50, in 3 sessions. The pH values were determined using a pH meter (Sentron Model 1001, Sentron) during the initial and final gel application times. The surface roughness (Ra) was evaluated with a rugosimeter (Hommel Tester T 1000) before and after bleaching, and after brushing (100,000 strokes). The rugosimeter was used to evaluate wear surface after 24 hours brushing. The data were submitted to one-way ANOVA and Tukey tests for pH values, Kruskall Wallis and Dunns test in relation to wear and surface roughness (p<0.05). It could be concluded that the pH values tended to decrease from the initial to final bleaching. After tooth brushing, bleaching procedures with highly acidic products provided a significant increase in enamel wear and surface roughness.

Orientador: Andréa Abi Rached Dantas / Resumo: Após o clareamento dental, radicais livres permanecem na estrutura dental interferindo negativamente na adesão, além disso também geram redução da resistência dental à fratura. Sugere-se que substâncias antioxidantes podem ser capazes de reverter tais efeitos. Assim, esse estudo buscou avaliar os efeitos da solução de alfatocoferol em diferentes concentrações sobre a resistência à fratura, formação de camada híbrida e resistência de união adesiva de dentes tratados endodonticamente e clareados. Foram realizados 3 experimentos. Experimento 1: 60 incisivos bovinos receberam tratamento endodôntico e foram distribuídos em 6 grupos (n=10): G1 - coroas apenas restauradas; G2 - coroas clareadas e restauradas; G3 - coroas clareadas e aplicação de solução de ascorbato de sódio 10%; G4 ao G6: coroas clareadas e aplicação das soluções de alfatocoferol nas concentrações de 15%, 20% e 25%, respectivamente. Os espécimes foram submetidos ao teste de resistência à fratura em máquina de ensaios mecânicos (EMIC). Experimento 2: 60 incisivos bovinos foram tratados endodonticamente, distribuídos e tratados, de acordo com o grupo, de forma idêntica ao experimento 1. Os espécimes foram seccionados na junção cemento-esmalte e no sentido vestíbulo-lingual, lixados e polidos, passaram por processo de desproteinização com ácido clorídrico 18% e hipoclorito de sódio 5%. Em seguida, foram moldados com silicona de adição e vasados com resina epóxi. Os modelos obtidos foram analisados em microscópio eletr... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: After dental bleaching, free radicals remain at the dentin, which causes reduces at adhesive and fracture resistance. To minimize these undesirable effects, the use of antioxidants to neutralize free radicals before the final restoration is recommended. This study evaluated the effects of alphatocopherol solution at different concentrations on the fracture resistance, hybrid layer and shear bond strength of endodontically treated teeth subjected to tooth bleaching. Three experiments were done. Experiment 1: 60 bovine incisors were endodontically treated and then divided into 6 groups (n=10): G1 - the teeth immediately restored with composite resin; G2 - the teeth were bleached and immediately restored; G3 - the teeth received treatment similar to that used for G2, but with 10% sodium ascorbate gel applied after the bleaching protocol; G4 to G6: the teeth received treatment similar to that used for G3, rather than sodium ascorbate, it was applied alphatocopherol at concentrations of 15%, 20% and 25%, respectively. Teeth were subjected to a fracture resistance test in an electromechanical testing machine (EMIC). Experiment 2: 60 bovine incisors were endodontically treated, distributed and treated identically to experiment 1. The specimens were sectioned at the cementum-enamel junction and in the vestibular-lingual direction, sanded and polished, and then it was made the deproteinization with 18% hydrochloric acid and 5% sodium hypochlorite. Then, they were molded with addition / Mestre

Atualmente, o setor sucroenergético está se tornando cada vez mais competitivo, o que de fato é incentivado, principalmente, pela representativa demanda e exigências do mercado externo. Ao se analisar a produção do açúcar refinado, podem-se encontrar barreiras para a sua ampla aceitação nacional e internacional devido ao método de clarificação empregado, uma vez que este é realizado através da queima de enxofre elementar em câmaras de combustão. O uso do sulfito acima dos limites permitidos pode ocasionar potenciais problemas de saúde pública. Neste sentido, o Brasil tem realizado estudos sobre a adoção de novas tecnologias para a substituição da sulfitação, sem alteração da qualidade do açúcar refinado a ser produzido. Partindo deste pressuposto, fez-se a avaliação do uso do peróxido de hidrogênio (H2O2) em solução comercial (35% v/v) como reagente alternativo ao dióxido de enxofre para obtenção de açúcar refinado com menor cor ICUMSA. Para isso, na calda de açúcar do tipo VHP, foram testadas doses distintas de peróxido de hidrogênio, aliadas a diferentes pH e temperaturas frente a um Delineamento composto central composto central, permitindo a otimização e o acompanhamento das transformações decorrentes do processo. Com isso, obteve-se como melhores condições o pH 7,5 e 10, temperaturas entre 50 e 70 °C e dosagens entre 500 e 797,6 ppm de H2O2. A análise a partir da cinética química da peroxidação da calda permitiu observar maiores reduções da cor ICUMSA em geral nos tempos de 50 a 75 minutos e nos 30 primeiros minutos para os pontos extremos de pH, temperatura e dose de H2O2. A degradação de sacarose não foi um fator expressivo quanto ao tempo, pois a mesma na maioria dos casos foi degradada nos 5 primeiros minutos e após esse tempo se mantinha sem muitas alterações, sendo mais vulnerável as condições de pH 3,32 e 11,68, altas temperaturas (83,6 °C) e máxima dosagem H2O2 (1000 ppm) aplicados. Além de favorecer a redução da cor ICUMSA da calda, o H2O2 também se mostrou como um bom agente antimicrobiano, principalmente quando associado às altas temperaturas. Agindo com maior intensidade na diminuição da carga bactériana do que na diminuição da carga fungica. A rede neural artificial (RNA) mostrou um bom ajuste e indicou a variável °Brix (teor de sólidos solúveis) como a que apresentou maior influência na redução da cor ICUMSA e a variável tempo a que menor influenciou na redução de cor. / Nowadays, the sugar-energy industry is becoming increasingly competitive, which indeed is encouraged mainly by representative demand and requirements of foreign markets. When analyzing the production of refined sugar can be found barriers to their widespread international acceptance due to the clarification method employed, since this is performed by burning elemental sulfur in combustion boilers. The use of sulfite above the permitted limits can result in potential public health problems. In this regard, Brazil has conducted studies on the adoption of new technologies to replace the sulfite, without changing the quality of the produced refined sugar. On that basis, it was done the evaluation of the use of hydrogen peroxide (H2O2) in commercial solution (35% v/v) as an alternative reagent to sulfur dioxide to obtain refined sugar with less ICUMSA color. For this the sugar liquor VHP different doses of hydrogen peroxide were tested, together with different pH and temperatures outside a central composite design, enabling optimization and monitoring of changes resulting from the process. Thus there was obtained as the best pH conditions 7.5 to 10, temperatures between 50 and 70 °C and dosages between 500 and 797.6 ppm H2O2. The analysis from the chemical kinetics of the peroxidation of the liquor has observed greater reductions in ICUMSA color in general in the time of 50 minutes to 75 minutes and in the first 25 minutes to the extremes of pH, temperature and H2O2 dose. As for sucrose degradation was not a significant factor, since it in most cases was first degraded within 5 minutes and after this time remained without many changes, being more vulnerable conditions (3.32 and 11.68), high temperatures (83.6 °C) and H2O2 maximum dosage (1000 ppm) applied. In addition to further reduce color ICUMSA H2O2 Liquor also showed such a good antimicrobial agent, particularly when combined with high temperatures. Acting with more intensity in the decrease of bacteria than the reduction of fungi. The artificial neural network (ANN) showed good fit and indicated the variable ° Brix (soluble solids) as the one with the greatest influence in reducing the ICUMSA color and variable time that less influenced the color reduction.

Vanadium is commonly used as an agent to make tools rust-resistant. As a transition metal, it can be used as a catalyst due to its ability to change oxidation states. VO(HEDTA)-1, a complex of the vanadyl ion, VO2+ and HEDTA (N-(2-Hydroxyethyl)ethylenediamine-N,N’,N’-triacetic acid) was readily formed. This complex containing vanadium in the +4 oxidation state was reacted with hydrogen peroxide to form a vanadate complex. This vanadate complex was formed as a first step in simulating the vanadate(V)-dependent haloperoxidases in marine algae, a yet uncharacterized reaction. Electron absorption spectroscopy (UV-Vis) was used to observe the oxidation of V(IV) in the complex to V(V) through the color change of the complex from blue to yellow. This color change was observed through the formation of a peak at 450nm. By changing the initial concentrations of VO(HEDTA)-1, hydrogen peroxide, and hydronium ion, the change in absorbance at 450nm during the first minutes of the reaction was correlated with time to determine the initial rates for each reactant. Using this method, a rate equation for the reaction was determined. The rate of reaction was determined to be first order with respected to VO(HEDTA)-1 and H2O2, and 1/2 order with respect to H+. This half-order indicates that the hydronium ion is engaged in a reversible reaction. The involvement of hydroxyl radicals produced by the reaction, as shown by the effect of free radical scavengers to inhibit the reaction was also studied.

Orientador: Luciano Tavares Angelo Cintra / Coorientador: André Luiz Fraga Briso / Banca: Denise Pedrini Ostini / Banca: Renata Oliveira Samuel / Resumo: Novos produtos estão sendo desenvolvidos com o propósito de atenuar os efeitos dos compostos utilizados em procedimentos clareadores. O objetivo do presente estudo foi avaliar in vivo o potencial terapêutico do gel de Biosilicato® (BS) sobre o tecido pulpar de molares de ratos Wistar, por meio das análises histológica e imunoistoquímica, assim como analisar in vitro, a penetração do H2O2 e a eficácia clareadora em dentes bovinos. Para isso, este estudo foi dividido em 2 partes. Parte 1: Segmento in vivo: 50 hemi-maxilas de 25 ratos foram divididas aleatoriamente em 5 grupos (n=10): Controle- não recebeu qualquer tratamento; CLA- recebeu 30 min do gel clareador H2O2 35%; BS-CLA- recebeu 20 min do gel de BS, seguido de 30 min do H2O2 35%; CLA+BS- recebeu 30 min de uma mistura do H2O2 35% com o gel BS (1:1); CLA+H2O- recebeu 30 min de uma mistura do H2O2 35% com água destilada (1:1). Após 2 dias, os animais foram mortos e as hemi-maxilas separadas para análise histológica em H.E. Foram atribuídos escores à inflamação e os dados submetidos aos testes de Kruskal-Wallis e Dunn e teste de Mann-Whitney (p<0,05). Segmento in vitro: 50 discos de dentes bovinos foram acoplados em câmaras pulpares artificiais, e divididos em 5 grupos (n=10) que receberam os mesmos tratamentos que o segmento in vivo. A penetração do H2O2 por esmalte e dentina foi quantificada baseada na reação deste com o corante violeta leucocristal. A alteração de cor foi analisada pelo sistema CIELab, nos períodos: ant... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: New products are being developed with the purpose of mitigating the effects of the compounds used in bleaching procedures. The objective of the present study was to evaluate in vivo the therapeutic potential of Biosilicate® (BS) gel on the pulp tissue of Wistar rats by means of histological and immunohistochemical analysis, as well as to analyze in vitro, the penetration of H2O2 and bleaching efficiency in bovine teeth. For this, this study was divided into 2 parts. Part 1: In vivo segment: 50 hemi-maxilla of 25 rats were randomly divided into 5 groups (n = 10): Control- received no treatment; CLA- received 30 min of the 35% H2O2 bleaching gel; BS-CLA- received 20 min of BS gel, followed by 30 min of 35% H2O2; CLA+BS- received 30 min of a mixture of 35% H2O2 with the BS gel (1:1); CLA+H2O- received 30 min of a mixture of 35% H2O2 with distilled water (1:1). After 2 days, the animals were killed and the hemi-maxils separated for histological analysis in H.E. Inflammation scores and data submitted to the Kruskal-Wallis and Dunn tests and Mann-Whitney test (p<0.05) were assigned. Segment in vitro: 50 discs of bovine teeth were coupled in artificial pulp chambers, and divided into 5 groups (n=10) that received the same treatments as the in vivo segment. The penetration of H2O2 by enamel and dentin was quantified based on the reaction of this with the leucocrystal violet dye. The color change was analyzed by the CIELab system, in the periods: before the bleaching session - (T0), i... (Complete abstract click electronic access below) / Mestre

Probiotics are living organisms which exert a beneficial health effect when consumed in sufficient numbers. Consumer interest in probiotics has increased dramatically in recent years prompting an increase in production and development of functional foods. One major problem is the decreased viability of probiotic bacteria during functional food production and storage and subsequent digestion due to environmental stresses. The most common probiotic strains belong to the genus Lactobacillus or Bifidobacterium. Due to the anaerobic nature of these bacteria, they lack the required defense mechanisms for oxidative stress inherent in aerobic microorganisms. This study examined the oxidative stress responses of six strains of Bifidobacterium, which are commonly used as probiotics in functional foods.The first phase of the study investigated the innate and inducible hydrogen peroxide (H2O2) stress response of Bifidobacterium longum strains NCC2705 and D2957, Bifidobacterium longum ssp. infantis ATCC 15697, and Bifidobacterium animalis ssp. lactis strains BL-04, DSM10140 and RH-1. Strains were screened for survival at increasing concentrations of H2O2 and lethal and sublethal concentrations were determined for each. In the second phase, B. animalis ssp. lactis strains BL-04 and DSM10140 and B. longum strains NCC2705 and D2957 were treated with a sublethal H2O2 concentration and RNA samples were collected for transcriptome analysis after 5 min and either 20 or 60 min. Statistical analysis was performed to identify genes that increased or decreased in expression during H2O2 treatment compared to control cells.Results showed that survival was species and strain dependent and that strains which naturally survived higher H2O2 concentrations had a larger number of differentially expressed genes early on during H2O2 exposure. Some of the protective genetic systems that were activated during H2O2 stress are mechanisms which perform basic cellular functions under normal conditions such as deoxuynucleotide synthesis. Under stress conditions, these systems can be used to detoxify oxidative free radicals. Also a number of genes involved in sugar transport and energy production for the cell showed increased expression, which reveals the increased energy needs of the cells during oxidative stress.During testing, it was found that two B. animalis ssp. lactis strains, BL-04 and DSM10140, had differing levels of survival and gene expression during H2O2 exposure despite having almost identical genome sequences. It was determined that one possible cause of the differences was a genetic deletion in a gene that allows the cell to incorporate extracellular fatty acids into the cell membrane instead of synthesizing them.Results from this project have increased the understanding of oxidative stress responses in bifidobacteria and highlighted possible methods to increase bacterial survival during food manufacture, storage, and human digestion.

"October, 2005" / Coursework / Bibliography: leaves 97-105. / xvi, 136 leaves : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (D.Clin.Dent.)--University of Adelaide, Dental School (Endodontics), 2005

Recently, metal nanoparticles have attracted the attention of researchers in several fields of study due to their high surface area and other unique properties. Using metal nanoparticles as a component of an in situ chemical oxidation (ISCO) system is emerging and hence very little information is available. In this research, nano zero valent iron (nZVI) particles and iron-based bimetallic zero valent nanoparticles (BZVNs) were employed to activate some common peroxygens (hydrogen peroxide (H2O2), persulfate (S2O82-), and peroxymonosulfate (HSO5-)) to degrade hazardous organic compounds. Aqueous and soil slurry batch systems were used along with a one-dimensional physical model. The results from the aqueous batch systems showed that nZVI is a promising activator for S2O82- compared to other conventional iron activators (e.g., granular-ZVI and Fe2+). For example, the initial trichloroethylene (TCE) reaction rate by nZVI activated S2O82- was 1.11 x 10-4 M L-1 min-1 compared to an initial reaction rate of 6.25 x 10-5 M L-1 min-1, 5.18 x 10-6 M L-1 min-1, and 1.8 x 10-7 M L-1 min-1 for Fe2+ activated S2O82-, granular-ZVI activated S2O82-, and non-activated S2O82-, respectively. However, the surfaces of nZVI particles were passivated quickly following exposure to S2O82-, causing the reaction rate to reduce to a magnitude representative of an un-activated S2O82- system. An iron-sulfate (FeSO4) complex was formed on the surfaces of the nZVI particles following exposure to S2O82- compared to the iron oxyhydroxide (FeOOH) layer that was present on fresh nZVI surfaces. BZVNs showed better treatment effectiveness than nZVI particles as activators for H2O2, S2O82-, and HSO5-. For example, the TCE reaction rate constant for nano-Ag-Fe0 activated H2O2 was 9 to 18 fold higher than that for nZVI activated H2O2. Of the nine different BZVNs investigated as activators, the greatest TCE degradation was achieved by nano-Pd-Fe0 and nano-Zn-Fe0 activated S2O82- system, nano-Co-Fe0 activated HSO5- system, and nano-Ag-Fe0 activated H2O2 system. For all of these systems, an increase in the dosage of nanoparticles and peroxygens increased TCE degradation. The activated H2O2 system showed a lower TCE degradation rate compared to either the activated S2O82- or the activated HSO5- systems, suggesting that a bridged group complex is formed between the activators and H2O2. The dissolved TCE concentration remaining in the soil slurry batch systems after using the nano-Pd-Fe0 activated S2O82- system was two to three fold higher than that in an aqueous batch system. Furthermore, for five different aquifer materials used, the higher mass of aquifer materials the lower the TCE degradation, indicating that the aquifer materials compete with a target organic compound in the presence of activated S2O82-. A linear relationship was observed between the organic carbon (OC) content and the initial TCE decomposition rate. Although there is no direct evidence of the effect of OC on the treatment system, it is suggested that the OC may result in scavenging the generated free radicals or by directly consuming persulfate. In the one-dimensional physical model systems, bimetallic nanoparticles were mobile in a non-geological porous medium and relatively immobile in a geological porous medium. In the non-geological porous medium, we found that adding a second metal (e.g., Pd) to nano-Fe0 particles significantly improved their functionality and performance (e.g., mobility and suspension). For example, the results from mobility experiments using columns packed with glass beads showed that the effluent iron concentration was <6 % of the influent iron concentration for the nano-Fe0 particles, while it was ~100 % for the nano-Pd-Fe0 particles. In the geological porous medium, based on visual inspection, nano-Pd-Fe0 particles could not travel more than a few centimeters into columns packed with CFB Borden sand, and no iron was detected in the effluent. To overcome the delivery issue in porous media, nano-Pd-Fe0 particles were injected to create a zone of activation to activate S2O82- for the treatment of TCE source zone. However, we found that the TCE mass destruction was only 9 % higher in the nano-Pd-Fe0 activated S2O82- system compared to the non-activated S2O82- system as revealed by the effluent chloride concentration. In addition, the activation zone composed of nano-Pd-Fe0 particles was rapidly deactivated after exposure to persulfate as visually observed by color change, indicating that the longevity of the activation zone is limited. This research effort provides a contribution to the field of ISCO by evaluating the potential utility and applicability of a new class of activators for some common peroxygens.