With ever-growing environmental concerns, petrochemical and fine chemical industries face an omnipresent issue in recovering acetic acid from its aqueous solutions. The recovery of acetic acid through the esterification process is a very viable option. However, esterification reactions are typically restricted by equilibrium limitations, and face challenges with product purification. Reactive distillation is an emerging technology that has an extremely attractive potential as a process alternative for carrying out equilibrium limited chemical reactions. Although the reactive distillation process has been successfully commercialised for the manufacture of hIgh commodity chemicals e.g. methyl tertiary butyl ether (MTBE) and methyl acetate, its potential as a separation tool for the recovery of acetic acid using iso-amyl alcohol has not been exploited.

Selective corrosion of type 316L austenitic stainless steel welds during the production of organic acids resulted in losses in production due to unscheduled downtimes to perform repairs. Estimated corrosion rates of type 316L filler material welds were an order of magnitude higher than that of the base material. Alternative higher alloyed commercial filler materials were evaluated under actual production conditions. The evaluated filler materials were types 316L, 317L, 309L, 309MoL, 2205, 2507, 625, 825 and 904L. The effect of nitrogen on the corrosion properties of type 309L filler material was evaluated by manipulating the nitrogen concentration of the shielding gas during MIG welding. These changes in nitrogen concentration did not influence the corrosion resistance of the type 309L filler material. No correlation could be established between the corrosion rates, analysed chemical composition of the product and operating temperature during production. In almost all the cases where the chemical composition of the filler material was comparable with that of the base material the corrosion rates of the filler materials were higher than that base material. It might be expected that the ferrite phase with higher molybdenum and chromium should be more corrosion resistant while the austenite should be less resistant. This was, however, not the case with the corrosion of type 309L filler material. It would thus appear that in this case nickel enrichment of the austenite phase had a larger influence on the corrosion resistance of the austenite phase than the chromium and molybdenum had on the corrosion resistance of the ferrite phase. It appears that nickel and molybdenum had the largest contribution to the corrosion resistance of stainless steels welds under these operating conditions. It is, however, believed that a certain minimum concentration of chromium is also required to provide corrosion resistance to these alloys in hot organic acid environments. In contrast with the fact that a substantial alloying content is required to improve corrosion resistance of the filler material, the small difference in composition between ferrite and austenite phases, due to micro segregation, appeared to affect the corrosion resistance on micro scale. This is illustrated by the micrographs, which show corrosion to etch out the dendrite structure. Since the morphology of the austenite and ferrite phases is so similar, it could not always be conclusively established which one of the two phases corroded selectively. Analyses performed on the austenite and ferrite phases did not indicate a concentration difference within the phases itself. However, there were significant differences in the concentration of elements between the phases, with the austenite stabilising elements reporting to the austenite phase and the ferrite stabilizing elements reporting to the ferrite phase, in line with thermodynamic predictions. In the case of the filler materials following the austenite mode of solidification, no significant concentration differences were detected within the matrix. Although all highly alloyed high nickel alloyed filler materials (types 904L, 825 and 625) corroded at a lower rate than the type 316L base material, type 625 filler material was the filler material of choice due to the lack of any pitting of the weld. Pitting was detected in both the 825 and 904L filler materials. Galvanic corrosion was not noted at any of the weld/HAZ interfaces and in no case did the type 316L parent metal adjacent to the weld corrode preferentially to the material further away from the weld. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Materials Science and Metallurgical Engineering / unrestricted

No description available.

Integrating ultrafiltration (UF) membranes in lieu of traditional media filters within conventional surface water coagulation-flocculation-sedimentation processes is growing in popularity. UF systems are able to produce low turbidity filtered water that meets newer drinking water standards. For typical drinking water applications, UF membranes require periodic chemically enhanced backwashes (CEBs) to maintain production; and citric acid is a common chemical used for this purpose. Problems may arise when the backwash recycle stream from a citric acid CEB is blended with raw water entering the coagulation basin, a common practice for conventional surface water plants. Citric acid is a chelating agent capable of forming complexes that interfere with alum or ferric chloride coagulation. Interference with coagulation negatively affects settled water quality. Acetic acid was investigated as a potential substitute for citric acid in CEB applications. A jar testing study was conducted to compare the impacts of both citric acid and acetic acid on the effectiveness of aluminum sulfate (alum) and ferric chloride coagulants. Citric acid was found to adversely affect coagulation at lower acid to coagulant (A/C) molar ratios than acetic acid, and a coagulation interference threshold was identified for both acids based on settled water turbidity goals recommended by the U.S. Environmental Protection Agency (EPA). Pilot testing was conducted to assess the viability of acetic acid as a UF CEB chemical. Acetic acid CEBs maintained pilot performance in combination with sodium hypochlorite CEBs for filtering a raw California surface water. It is believed that this is the first ultrafiltration membrane process application of acetic acid CEBs for municipal potable water production in the United States.

No description available.

Programmed cell death in animals, plants and protists is in part regulated by a variety of proteases, including cysteine aspartyl proteases, (caspases, paracaspases and metacaspases), cathepsins, subtilisin-like serine proteases, vacuolar processing enzymes and the proteasome. The role of different proteases in the cell death responses of the fungi is however largely unknown. A greater understanding of the fungal cell death machinery may provide new insights into the mechanisms and evolution of PCD and potentially reveal novel targets for a new generation of antifungal drugs. The role of a metacaspase encoding gene, MCA1, in the cell death response of the human pathogen Candida albicans pathogen has been investigated by functional analysis. MCA1 deletion not only alters the sensitivity of cells to a number of cell death stimuli, it also enhances virulence in an insect model. C. albicans shows altered cell and colony morphology on Lee’s medium. Evidence is presented to suggest that these functions appear to be dependent upon active mitochondria. In this study it has also been shown that key caspase substrates may be conserved between humans and the yeasts Saccharomyces cerevisiae and Candida albicans. Many substrates, particularly those which are essential, have retained their caspase cleavage motifs. 14 protease mutants displayed altered activity against caspase 1, 3, 6 or 8 substrates during acetic acid-induced PCD and caspase 1-like activity appeared to be particularly associated with PCD. Using a novel bioinformatic analysis of experimental LC-MS/MS data, changes in the degradation patterns of the proteome (destructome) following acetic acid-induced cell death have been investigated in wild-type yeast. In addition, potential native substrates of the yeast Mca1 have also been identified. The future challenge is to characterise the destructome of different proteases under a range of cell death conditions. In this way it may be possible to identify key components of the cell death machinery and their substrates and so reveal the most promising targets for future therapeutics.

Previous research of colonies formed by yeast Saccharomyces cerevisiae growing on glycerol agar medium revealed two major cell types of U and L cells that are formed within these colonies. This colonial cell differentiation seem to be caused by communication among yeast cells as well as whole colonies and affected by changes in the environment (for example changes in nutrients). Studies of U and L cells showed that U cells are more resistant against biological, chemical and physical stresses than L cells. The aim of this thesis was to isolate U and L cell types and investigate their resistance against selected low molecular weight chemical substances produced in Ehrlich pathway. Ehrlich pathway was discovered in 1907 and was classified as amino acid catabolic pathway in yeast S. cerevisiae. The low molecular intermediates are formed in Ehrlich pathway which are called fusel (original name from German) alcohols and acids. These chemical substances are widely used in food industry and cosmetics especially because of their aroma. Several studies provided indications that these chemical substances may affect development of colonies and important yeast functions such as switching to the pseudohypfal growth of S. cerevisiae cells. Some chemical substances of the Ehrlich pathway were selected and their effects on...

Estudos têm mostrado a incidência de mastite bovina associada à alga Prototheca zopfii. O objetivo deste trabalho foi estudar a interação da P. zopfii com neutrófilos recuperados de leite bovino e avaliar o efeito do sistema ácido indol-3-acético/peroxidase de raiz forte (AIA/HRP) sobre a viabilidade deste microrganismo em experimentos in vitro. A P. zopfii foi recuperada de vacas com mastite clínica e, no laboratório, foram realizadas a caracterização molecular, morfológica e crescimento exponencial do microrganismo. Em seguida, neutrófilos recuperados de leite bovino foram incubados na ausência e na presença de P. zopfii opsonizada e foram avaliadas a produção de peróxido de hidrogênio, enzimas antioxidantes dos neutrófilos e microrganismo, e a capacidade fagocitária. Em outro estudo, a P. zopfii foi incubada com o sistema AIA/HRP e foram avaliadas a viabilidade por unidades formadoras de colônias (UFC), atividade de enzimas antioxidantes, integridade de membrana por exclusão com azul de Trypan e integridade do DNA. Os resultados foram analisados pela análise de variância com significância de 5% usando o teste Tukey. Foram observados diversos tamanhos celulares da P. zopfii, presença de autofluorescência, crescimento exponencial ao longo do tempo de incubação em que não foi possível determinar o início da fase de morte. Ainda, foram encontrados os genótipos 1, 2 e 3 nos isolados em estudo. A produção de peróxido de hidrogênio pelos neutrófilos na presença da alga foi estimulada 5 vezes em relação ao controle, estimulou a atividade das enzimas catalase (CAT) em 21% e glutationa redutase (GR) em 27% e não houve diferença significativa quanto à atividade de CAT, GR e superóxido dismutase (SOD) produzido pela P. zopfii. Também foi verificado que a P. zopfii não foi englobada pelo neutrófilo. O sistema AIA/HRP inibiu o crescimento do microrganismo em 45, 82 e 88% nos tempos de 4, 6 e 9 horas de incubação; a atividade da SOD, CAT, Glutationa Peroxidase (GPx) e GR aumentou respectivamente em 90, 120, 150% e 3,4 vezes; houve redução da viabilidade da P. zopfii em 10, 15, 20, 25 e 32% após os tempos de 4, 6, 8, 10 e 12 horas de incubação; e não afetou a integridade do DNA após 6 horas de incubação. Conclui-se que a P. zopfii é altamente resistente frente aos neutrófilos e demonstrou ser susceptível quanto ao efeito microbicida do sistema AIA/HRP. / Studies have shown the incidence of bovine mastitis associated with the algae Prototheca zopfii. The objective of this work was to study the interaction of P. zopfii with neutrophils recovered from bovine milk and to evaluate the effect of system indole-3-acetic acid/horseradish peroxidase (IAA/HRP) on the viability of this microorganism in vitro experiment. P. zopfii was recovered from cows with clinical mastitis and both the molecular and morphological characterization were performed besides the evaluation of exponential growth of the microorganism in the laboratory. Next, neutrophils recovered from bovine milk were incubated in the absence and presence of opsonized P. zopfii and were evaluated the production of hydrogen peroxide, antioxidant enzymes on neutrophils and microorganism, and phagocytic capacity. In another study, P. zopfii was incubated with the system IAA/HRP and the viability assessed by colony forming units (CFU), antioxidant enzymes activity, membrane integrity by exclusion with Trypan blue and DNA integrity. The results were analyzed by analysis of variance with a 5% significance using the Tukey test. Results from P. zopfii characterization showed various cellular sizes, presence of autofluorescence, exponential microorganism growth throughout the incubation time and was not possible to determine the beginning of the death. Moreover it was found genotypes 1, 2 and 3 in the isolates in study. The production of hydrogen peroxide by neutrophils in the presence of algae was stimulated 5 times compared to the control, increase the activity of catalase (CAT) in 21% and glutathione reductase (GR) in 27% was seen in neutrophils; and there was no significant difference in CAT, GR and superoxide dismutase (SOD) activity produced by P. zopfii. P. zopfii was not engulfment by neutrophils. The system IAA/HRP inhibited the growth of the microorganism in 45, 82 and 88% in the times of 4, 6 and 9 hours of incubation, the activity of SOD, CAT, glutathione peroxidase (GPx) and GR increased respectively by 90, 120, 150%, and 3.4 times, decreased the viability of P. zopfii 10, 15, 20, 25 and 32% after the times of 4, 6, 8, 10 and 12 hours of incubation, and did not affect the integrity of DNA after 6 hours of incubation. As a conclusion, P. zopfii is highly resistant to the neutrophils and demonstrated to be susceptible to the effect microbicidal of system IAA/HRP.

A Brachiaria brizantha é considerada uma das forrageiras preferidas entre os agropecuaristas por possuir elevada produção de forragem, tolerância ao calor e ao déficit hídrico, alta resposta à aplicação de fertilizantes, produção em grande massa de raízes e sementes, resistência à cigarrinha das pastagens (exceto as pertencentes ao gênero Mahanarva) e boa competição com plantas invasoras. É considerada a principal fonte de alimento para bovinos, sendo utilizada tanto na cria, recria, como na engorda dos animais. As bactérias fixadoras de nitrogênio ou diazotróficas são procariotos capazes de reduzir o N2 a NH3, forma assimilável pelos organismos, e também podem produzir hormônios vegetais, como ácido-indol-acético, que estimulam o crescimento radicular da planta. Estes micro-organismos apresentam grande importância para a manutenção dos ecossistemas. Sua associação com as raízes de plantas e seu efeito promotor quando associados à Brachiaria brizantha possibilitaria a recuperação de áreas de pastagens que apresentam deficiência de nitrogênio, o que é um mecanismo ainda pouco explorado. Com o objetivo de estudar esta possibilidade, foram escolhidas três áreas (Nova Odessa-SP, São Carlos- SP e Campo Verde-MT), preferencialmente onde o nitrogênio era limitante, constituídas por pastagem de Brachiaria brizantha para a amostragem de solo e raiz. Os três locais demonstraram a ocorrência de diazotróficos, após o isolamento e cultivo das bactérias em meio de cultivo semisólido sem adição de nitrogênio na forma combinada (JNFb). Foram obtidas 110 estirpes bacterianas e, após sorteio aleatório, 72 isolados foram mantidos para realização de testes a fim de se avaliar o potencial biotecnológico das bactérias. Destes, 10 demonstraram atividade da nitrogenase quando submetidos ao método de aumento na concentração de nitrogênio total (Ntotal) em meio de cultura. 57 isolados foram capazes de reduzir o gás acetileno a etileno quando submetidos à técnica de redução de acetileno. As estirpes bacterianas C4 (Pseudomonas sp.) e C7 (Azospirillum sp.), isoladas da rizosfera de Brachiaria brizantha da área de Campo Verde-MT, se destacaram das demais por apresentar atividade da nitrogenase muito superior até a de bactérias diazotróficas que foram incluídas na avaliação como testemunhas positivas. Outros 68 isolados produziram o hormônio vegetal ácido-indol-acético quando cultivados em meio de cultivo LB, na presença de triptofano. A produção variou de 0,39µg/mL a 195 µg/mL de AIA. Todos os 72 isolados foram utilizados em experimento em casa de vegetação para avaliar o efeito de inoculação em B. brizantha quando com eles inoculada. Avaliaram-se a matéria seca da parte aérea e raiz e o teor de nitrogênio total da parte aérea através do método micro-Kjeldhal. Nenhum isolado diferiu significativamente do controle sem inoculação bacteriana que continha a mesma dose de nitrogênio fornecido às plantas. O seqüenciamento parcial do gene 16S rRNA dos 72 isolados permitiu a caracterização de sete grupos genotípicos: Stenotrophomonas sp, Pseudomonas sp., Xanthomonas sp., Bacillus sp., Rhizobium sp, Sphingomonas sp. e Azospirillum sp. O gênero Stenotrophomonas sp. predominou (69%) nas três áreas de estudo. / Brachiaria brizantha is considered one of preferred fodders among farmers for having high forage yield, tolerance to heat and drought, high response to fertilizer application, large production of root mass and seeds, resistance to grassland leafhopper (except those belonging to the genus Mahanarva) and good competition with weeds. It is considered the main source of food for cattle, being used in the raising, breeding, and fattening of animals. The nitrogen fixing bacteria or diazotrophs are prokaryotes able to reduce N2 to NH3, which is assimilated by organisms, and may also produce plant hormones such as indole-acetic acid, which stimulates root growth. These micro-organisms have great importance for the maintenance of ecosystems. Their association with plant roots and their promoting effect when combined with Brachiaria brizantha enable recovery of nitrogen-deficient grazing areas, which is a mechanism still little explored. Therefore, three areas were chosen (Nova Odessa-SP, Sao Carlos-SP and Campo Verde-MT), preferably where nitrogen was limiting, consisting of Brachiaria brizantha from which samples of soil and roots were collected. The three sites showed the occurrence of diazotrophs after the isolation and cultivation of bacteria in semi-solid culture medium with no nitrogen added in the combined form (JNFb). It was obtained 110 bacterial strains and, after the raffle random, 72 were kept isolated for testing in order to assess the biotechnological potential of bacteria. From which, 10 showed nitrogenase activity when subjected to the method of total nitrogen concentration increase (N-total) in the culture medium. 57 isolates were able to reduce acetylene to ethylene when subjected to the acetylene reduction technique. The strains C4 (Pseudomonas sp.) and C7 (Azospirillum sp.), isolated from the rhizosphere of Brachiaria brizantha in the area of Campo Verde-MT, stood out from the others by presenting nitrogenase activity far superior to that of diazotrophs recommended as positive controls. Other 68 isolates produced the plant hormone indole-acetic acid when grown in LB culture medium in the presence of tryptophan. Production ranged from 0.39 g/mL to 195 g/mL of IAA. All 72 isolates were used in an experiment in a greenhouse to evaluate the effect of inoculation on B. brizantha. Evaluations were carried out on dry matter of shoot and root and total nitrogen content of the shoot through the micro-Kjeldahl method. None of the isolates differed significantly from the control without bacterial inoculation which contained the same amount of nitrogen supplied to plants. Partial sequencing of the 16S rRNA of the 72 isolates allowed the characterization of seven genotype groups: Stenotrophomonas sp., Pseudomonas sp., Xanthomonas sp., Bacillus sp., Rhizobium, Sphingomonas sp. and Azospirillum sp. The genus Stenotrophomonas sp. predominated (69%) in the three study areas.

No Brasil, diariamente, são descartadas 2,3 toneladas de meios de cultura potencialmente contaminados com microorganismos. A resolução RDC No 306/2004 da Agência Nacional de Vigilância Sanitária preconiza que os resíduos devem ser tratados antes do descarte, visando à redução da carga microbiana. Foram desenvolvidos 2 métodos para avaliar a sensibilidade e a eficiência, assim como a concentração ideal, de um agente químico (biocida) contra microorganismos contaminantes. O método de difusão com Perfurador Circular de Ágar (PCA) e o método com Perfurador Linear de Ágar (PLA) foram testados com 13 cepas de microorganismos. O biocida avaliado foi a combinação de hipoclorito de sódio (NaClO) com ácido acético (CH3COOH). A partir destes resultados, foi desenvolvido um equipamento automatizado para processar a redução da carga microbiana (SADEMC) dos meios de cultura contaminados. A redução da carga microbiana foi avaliada pelo método quantitativo da reação da transcriptase reversa com detecção em tempo real. O método PCA mostrou ser reprodutível e eficiente para medir a inibição do crescimento bacteriano de um biocida. A concentração mínima de biocida capaz de reduzir o crescimento microbiano foi de 250 ppm para a solução aquosa de NaClO a 0,25% e de 200 ppm para a de CH3COOH a 0,2%. No SADEMC, foi possível processar 4,6kg de meios de culturas em 100 litros da concentração mínima eficaz do biocida por 15 minutos, e atingir uma redução da carga microbiana de, aproximadamente, 1,4E10 unidades formadoras de colônias. Podemos concluir que o SADEMC promove uma redução de carga microbiana compatível com os níveis exigidos pela RDC No. 306; fornece biossegurança na sua manipulação e que resulta em plástico reciclável. / In Brazil, daily, 2.3 tons of potentially contaminated cultured medium with microorganisms are discarded. The RDC 306 resolution from the Brazilian National Health Department rules out that residue must be treated prior to discart in order to reduce microbial load. Two methods were developed to evaluate the sensitivity, efficiency and ideal concentration of a chemical agent (biocide) against microorganisms. The Ágar\'s Diffusion Method by Circular Perforator (PCA) and by Linear Perforator (PLA) were tested with 13 microorganism lines and the biocide composed by Sodium Hypochlorite (NaClO) and its combination with Acetic Acid (CH3COOH). The microbial load reduction was evaluated by the real time reverse transcription-polymerase chain reaction. From the in vitro data, an automatic equipment to process the potentially contaminated culture media (SADEMC) was developed. The PCA method was reproductive and efficient to measure the bacterial growth inhibition induced by the biocide. The minimum biocide concentration capable to reduce the microbial growth was a solution of 0.25% NaClO (250 ppm) and 0.2% CH3COOH (200 ppm). In the SADEMC, the direct exposition of 4.6 kg of culture media in 100 liters of biocide for a period of 15 minutes is capable to reduce the microbial load in approximately 1,4E10 of colony-forming unit. We may conclude that the SADEMC is able to promote a microbial load reduction more intense than the one demanded by the RDC 306 resolution. In addition to that, the SADEMC contemplates personnel safety and allows recycling the plastic residues