Presence of inclusions in high manganese steel are a major concern in the steel making industry, since these particles affect the processing and properties of the steel. During the refining of high manganese steel in the ladle furnace, the types of inclusions present and their growth in the liquid steel, or during solidification of the steel, caused by the addition of manganese and other alloying elements are to be examined. This research developed a kinetic model for the presence and growth of inclusions in the liquid high manganese steel for the ladle metallurgy process. The diffusion of dissolved elements, and the seed of inclusions for the growth and consumption of inclusions, were both addressed in the model. The present model for inclusions was coupled to the updated kinetic model for slag-steel reactions in the ladle furnace for high manganese steel. The coupled model allows for verifying the process analysis plant data for the highest manganese concentration presently available in the steel industry. Finally, an analysis of the coupled kinetic model was performed to compare the effect of the different processing conditions, and the presence and growth of inclusions in the high manganese steel from the ladle metallurgy process. / Thesis / Master of Applied Science (MASc)

Yes / Oxidative desulfurization process (ODS), enhanced with a novel metal oxide (Ag ions) as an active component over nano-zeolite that has not been reported in the literature, is used here to improve the fuel quality by removing mercaptan (as a model sulfur compound in the light naphtha). Nano-crystalline (nano-support (Nano-zeolite)) composite is prepared by Incipient Wetness Impregnation method loaded with a metal salt to obtain 0.5, 1 and 1.5% of Ag2O3 over Nano-zeolite. The new homemade nano-catalysts (Ag2O3/Nano-zeolite) prepared are characterized by Brunauer-Emmett-Teller (BET) (surface area, pore volume and pore size), X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), and Scanning Electron Microscopy (SEM) analysis. The ODS process is then used to evaluate the performance of the catalysts for the removal of sulfur at different reaction temperatures (80-140 °C) and reaction times (30-50 min) in a batch reactor using the air as oxidant. 87.4% of sulfur removal has been achieved using 1% silver oxide loaded on Nano zeolite (1% of Ag2O3/Nano-zeolite) giving a clear indication that our newly designed catalyst is highly efficient catalyst in the removal of sulfur compound (mercaptan) from naphtha. A new mechanism of chemical reaction for sulfur removal by oxygen using the new homemade catalyst (Ag2O3/Nano-zeolite) prepared has been suggested in this study. The best kinetic model parameters of the relevant reactions are also estimated in this study using pseudo first order technique based on the experimental results.

In biochemical networks, complex dynamical features such as superlinear growth and oscillations are classically considered a consequence of autocatalysis. For the large class of parameter-rich kinetic models, which includes Generalized Mass Ac- tion kinetics and Michaelis-Menten kinetics, we show that certain submatrices of the stoichiometric matrix, so-called unstable cores, are sufficient for a reaction network to admit instability and potentially give rise to such complex dynami- cal behavior. The determinant of the submatrix distinguishes unstable-positive feedbacks, with a single real-positive eigenvalue, and unstable-negative feedbacks without real-positive eigenvalues. Autocatalytic cores turn out to be exactly the unstable-positive feedbacks that are Metzler matrices. Thus there are sources of dynamical instability in chemical networks that are unrelated to autocatalysis. We use such intuition to design non-autocatalytic biochemical networks with su- perlinear growth and oscillations.

Master of Science / Department of Grain Science and Industry / Subramanyam Bhadriraju / During heat treatment, the ambient temperature of grain-processing facilities is raised to 50-60°C for at least 24 hours to manage stored-product insects. Young larvae (first instars) of the red flour beetle, Tribolium castaneum (Herbst), are the most heat tolerant stage at 50-60°C. A thermal death kinetic (TDK) model predicted survival of T. castaneum young larvae exposed to six constant elevated temperatures between 42 and 60ºC. The model is based on logarithmic survival of T. castaneum as a function of time and logarithmic reduction in larval survival as a function of temperature. The model was validated with 12 independent temperature datasets collected during heat treatments of pilot-scale and commercial grain-processing facilities. Young larval survival in plastic boxes/vials with flour was used to validate model predictions. The heating rate to 50°C from the ambient among the 12 datasets ranged from 0.9-7.8°C/h. Mean absolute deviations between observed and predicted larval survival for 10 of the 12 datasets ranged from 2.1-11.4%; it was 16.2 and 18.3% for two other datasets. The TDK model can be used to predict survival of young larvae of T. castaneum based on time-dependent temperature profile obtained at any given location during heat treatment of grain-processing facilities. In three commercial grain-processing facilities heat treatments were conducted for 24-27.7 hours using forced-air gas heaters. Temperatures attained and survival of 20 eggs, 20 young larvae, and 20 adults of T. castaneum in bioassay vials at various locations were determined. Across all three facilities, 5 out of 2720 adults in 136 vials, 1 out of 960 young larvae in 48 vials, and 0 out of 1760 eggs in 88 vials were alive at the end of the heat treatment. In each facility, the time in hours for 1% predicted survival of T. castaneum young larvae was positively related to how quickly temperatures reached 50°C, and negatively related to rate of heating to 50°C from the ambient, time above 50°C in hours, and the maximum temperature. Bioassays with T. castaneum life stages and the TDK model can be used to gauge effectiveness of facility heat treatments.

BACKGROUND: Selection on proteins is typically measured with the assumption that each protein acts independently. However, selection more likely acts at higher levels of biological organization, requiring an integrative view of protein function. Here, we built a kinetic model for de novo pyrimidine biosynthesis in the yeast Saccharomyces cerevisiae to relate pathway function to selective pressures on individual protein-encoding genes. RESULTS: Gene families across yeast were constructed for each member of the pathway and the ratio of nonsynonymous to synonymous nucleotide substitution rates (dN/dS) was estimated for each enzyme from S. cerevisiae and closely related species. We found a positive relationship between the influence that each enzyme has on pathway function and its selective constraint. CONCLUSIONS: We expect this trend to be locally present for enzymes that have pathway control, but over longer evolutionary timescales we expect that mutation-selection balance may change the enzymes that have pathway control.

Thesis (MSc (Biochemistry))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: In Africa alone, Plasmodium, the causative agent of malaria is estimated to kill a child, under the age of five every thirty seconds140. The ability of the parasite to rapidly attain resistance, has resulted in immunity of the parasite to all, except one group of frontline drugs. The need to develop novel drugs, vaccines and prevention strategies that are accessible and affordable for third world countries is of the utmost importance to prevent needless human suffering and death. The glycolytic pathway is an attractive drug target since it is the principal source of ATP for the parasite. Many of the glycolytic enzymes have been studied and proposed as drug targets, but the importance of these enzymes for the function of the pathway as a whole has not been considered. It is known, from the frameworks of metabolic control analysis, that control of the flux and metabolite concentration can be divided among the individual steps. Differential control analysis of Plasmodium and erythrocyte glycolysis may reveal potential drug targets. These analyses require a detailed kinetic model of Plasmodium glycolysis, and the feasibility of constructing and validating such a model was the aim of this study. In this work we determined the feasibility of constructing and validating a detailed kinetic model for the Plasmodium falciparum glycolytic pathway. Whether the construction and validation of this kinetic model was feasible or not was decided on the basis of the ability to: i) culture and isolate sufficient asexual parasites for enzymatic and steady state assays , ii) obtain kinetic parameters such as Km and Vmax for each glycolytic enzyme, either from literature or experimentally, iii) measure glycolytic fluxes, iv) determine glycolytic intermediate concentrations, v) construct a kinetic model from the kinetic parameters and vi) validate it with steady state glycolytic fluxes and metabolite concentrations Each of the above criteria were successfully addressed. In summary, the kinetic parameters and glycolytic fluxes that were measured experimentally, were used to construct and partially validate a detailed kinetic model, respectively. Further validation of the model by means of steady state metabolite concentrations was shown to be possible with the development of a suitable protocol to measure the glycolytic intermediate concentrations. The model presented in this work may play an important role in drug target identification and improving the current understanding of host-parasite interactions and glycolytic regulation. / AFRIKAANSE OPSOMMING: Plasmodium, die parasiet wat malaria veroorsaak, is in Afrika alleen elke dertig sekondes verantwoordelik vir die afsterwe van ’n kind jonger as vyf jaar. Die parasiet se vermoë om vinnig weerstand op te bou het daartoe gelei dat Plasmodium weerstandbiedend is teen byna alle nuwe teen-malaria middels, behalwe vir ’n enkele toonaangewende groep. Die ontwikkeling van nuwe malaria teen-middels is van uiterste belang om lyding te voorkom. ’n Goeie teiken vir teen-malaria middels is die glikolitiese padweg omdat die metaboliese padweg essensieël is vir die produksie van ATP, die energiebron van die parasiet. Desondanks die feit dat meeste van die glikolitiese ensieme al goed bestudeer en as teiken voorgestel is, is dit steeds onduidelik hoe hierdie ensieme saam funksioneer om die metaboliese weg, as geheel, tot stand te bring. Metaboliese kontrole analise het aangetoon dat die glikolitiese beheer verdeel is tussen die onderskeie glikolitiese ensieme, m.a.w. geen enkele ensiematiese stap het volledige beheer oor die fluksie van die glikolitiese padweg nie. Die afsonderlike analise en vergelyking van Plasmodium - en rooibloedselglikolise met behulp van differensiële metaboliese kontrole analise sal moontlik gebruik kan word om gasheervriendelike teikens vir nuwe middels aan te toon. So ’n analise benodig ’n omvattende kinetiese model van Plasmodium glikolise. Derhalwe was die doel van hierdie studie om vas te stel hoe uitvoerbaar dit is om ’n kinetiese model van Plasmodium glikolise te konstrueer en te valideer. Die uitvoerbaarheid van die konstruksie en validering van die kinetiese model was geasseseer op grond van die vermoë om: i) parasietkulture te kweek en genoegsame parasiete, wat in die aseksuele fase is, te isoleer sodat ensiembepalings en bestendige toestand-bepalings gedoen kan word, ii) kinetiese parameters soos Km - en Vmax-waardes vir elke glikolitiese ensiem, hetsy vanuit literatuur of eksperimentele werk, te verkry, iii) glikolitiese fluksie te meet, iv) glikolitiese intermediaatkonsentrasies te bepaal, v) ’n kinetiese model van die bepaalde kinetiese parameters op te stel en vi) die model te valideer met glikolitiese flukswaardes en metaboliet- konsentrasies wat in die bestendige toestand verkry is. Elk van die bogenoemde kriteria was met sukses in hierdie studie aangespreek. Ter opsomming, die eksperimenteel bepaalde kinetiese parameters en glikolietiese flukswaardes was gebruik om onderskeidelik ’n gedetaileerde kinetiese model te konstrueer en gedeeltelik te valideer. Daar was getoon dat verdere validering van die model deur middel van bestendige toestand metabolietkonsentrasies moontlik is met die ontwikkeling van ’n geskikte protokol om glikolitiese intermediaatkonsentrasies te meet. Die model, soos opgestel in hierdie studie, kan moontlik ’n belangrike rol speel om teikens vir nuwe malaria teen-middels te identifiseer en om gasheer-parasiet interaksies en glikolitiese regulering beter te verstaan.

Thesis (PhD (Biochemistry))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In the last decade a need arose to find a theoretical framework capable of gaining a quantitative understanding of ecosystems. Control analysis was proposed as a suitable candidate for the analysis of ecosystems with various theoretical applications being developed, i.e. trophic control analysis (TCA) and ecological control analysis (ECA). We set out to test the latter approach through experimental means by applying techniques akin to enzyme kinetics of biochemistry on a simple ecosystem between Saccharomyces cerevisiae and Gluconobacter oxydans. However, this exercise was far more complex than we originally expected due to the extra metabolic activities presented by both organisms. Nevertheless, we derived suitable kinetic equations to describe the metabolic behaviour of both organisms, with regards to the activities of interest to us, from pure culture experiments. We developed new techniques to determine ethanol and oxygen sensitivity of G. oxydans based on its obligately aerobic nature. These parameters were then used to build a simple kinetic model and a more complex model incorporating oxygen limited metabolism we observed at higher cell densities of G. oxydans. Our models could predict both situations satisfactorily for pure cultures and especially the more complex model could describe the lack of linearity observed between metabolic activity and cell density at higher cell densities of G. oxydans. Mixed populations of S. cerevisiae and G. oxydans reached quasi-steady states in terms of ethanol concentration and acetate flux, which was a positive indication for the application of control analysis on the ecosystem. However, the theoretical models based on parameters derived from pure culture experiments did not predict mixed culture steady states accurately. Careful analysis showed that these parameters were mostly under-estimated for G. oxydans and overestimated for S. cerevisiae. Hence, we calculated the kinetic parameters for mixed population assays directly from the experimental data obtained from mixed cultures. We could calculate the control coefficients directly from the experimental data of mixed population studies and compare it with those from theoretical models based on 3 different parameter sets. Our analysis showed that the yeast had all the control over the acetate flux while control over the steady-state ethanol was shared. The strength of our approach lies in designing our experiments with a control analysis approach in mind, but we have also shown that even for simple ecosystems this approach is non-trivial. Despite the various experimental challenges, this approach was very rewarding due to the extra information obtained especially regarding control structure with regards to the steady-state ethanol concentration. / AFRIKAANSE OPSOMMING: In die afgelope dekade het daar ’n behoefte ontstaan na ‘n teoretiese raamwerk om tot ‘n kwantitatiewe begrip van ekosisteme te kom. As kandidaat vir so tipe raamwerk is kontrole analise voorgestel gepaardgaande met die ontwikkeling van verskeie teoretiese toepassings, i.e. trofiese kontrole analise en ekologiese kontrole analise. In hierdie tesis het ons laasgenoemde aanslag eksperimenteel ondersoek op ‘n eenvoudige ekosisteem, tussen Saccharomyces cerevisiae en Gluconobacter oxydans, deur gebruik te maak van tegnieke vanuit ensiemkinetika van biochemie. Hierdie strategie was egter baie meer kompleks as wat oorspronklik verwag is as gevolg van verdere metabolise aktiwiteite aanwesig in beide organismes. Ons het egter steeds daarin geslaag om kinetiese vergelykings af te lei, vanuit suiwer kulture, wat die metaboliese gedrag van beide organismes beskryf vir die aktiwiteite van belang vir ons studie. Ons het nuwe tegnieke, gebaseer op die aerobiese natuur van G. oxydans, ontwikkel om die sensitiwiteit van G. oxydans vir etanol en suurstof te bepaal. Hierdie parameters is gebruik om eers ’n eenvoudige model en toe ‘n meer gevorderde model, wat die suurstof-beperkte metabolisme van G. oxydans by hoër biomassa te beskryf, op te stel. Beide modelle was baie effektief in die voorspelling van die situasies waarvoor hulle ontwikkel is vir die suiwer kulture waar veral die meer gevorderde model die gebrek aan ‘n linieêre verband tussen die metabolisme van G. oxydans en biomassa by hoër biomassa kon beskryf. ’n Bemoedigende aanduiding dat kontrole analise toegepas kon word op die ekosisteem was dat mengkulture van S. cerevisiae en G. oxydans het quasi-bestendige toestande bereik het in terme van etanol konsentrasies en asetaat-fluksie. Die teoretiese modelle gebaseer op die parameters afgelei vanaf suiwer kulture kon egter nie die bestendige toestande in mengkulture akkuraat voorspel nie. Nadere ondersoek het aangedui dat die parameters meesal onderskat is vir G. oxydans en oorskat is vir S. cerevisiae. Gevolglik het ons die kinetiese parameters vir mengkulture direk van eksperimentele data van die mengkulture bereken. Verder kon ons die kontrole koeffisiente ook direk vanaf die eksperimentele data van mengkulture bereken en vergelyk met dié bereken vanuit die teoretiese modelle gebaseer op drie verskillende paremeter-stelle. Ons analise het gewys dat die gis alle beheer op die asetaat-fluksie uitoefen en dat die beheer oor die etanol-konsnetrasie gedeel is tussen die twee organismes. Die krag van ons aanslag lê daarin dat die eksperimente ontwerp is met ‘n kontrole analise in gedagte, maar ons het ook bewys dat hierdie aanslag selfs vir eenvoudige ekosisteme nie triviaal is nie. Ten spyte van die eksperimentele uitdagings, was die aanslag baie waardevol as gevolg van die ekstra inligting verkry met spesifieke klem op die kontrole-struktuur met betrekking tot die etanol konsentrasie by bestendige toestand.

A pesquisa propôs avaliar o desempenho e o comportamento de reatores seqüenciais em batelada com biomassa suspensa e imobilizada, em escala de bancada, na remoção de compostos de nitrogênio. Tais sistemas foram testados como tratamento complementar de reatores sulfetogênico e metanogênico utilizados no tratamento de água residuária industrial com alta concentração de sulfato e amônia. Visou o desenvolvimento de uma estratégia de operação que viabilizasse o uso dos próprios constituintes da água residuária para a maximização da eficiência do tratamento. O estudo foi dividido em 3 etapas principais. Na etapa 1 (181 dias de operação), o reator com biomassa suspensa foi mantido com 4 fases alternadas aeróbio/anóxico e ciclo de 24 horas, e verificou-se a presença da desnitrificação endógena (eficiência de remoção de nitrogênio de 65 \'+ OU -\' 27%). Para a etapa 2 (127 dias de operação), o reator de biomassa suspensa foi submetido ao tempo de ciclo de 12 horas, com uma fase aeróbia (6 horas) e com posterior fase anóxica (6 horas). Nessa etapa adicionou-se efluentes dos reatores metanogênico e sulfetogênico, ricos em ácidos voláteis (ácido acético), com intuito de acelerar o processo desnitrificante. Os resultados obtidos foram baixos em termos de remoção de nitrogênio (42 \'+ OU -\' 21%). Para a etapa 3 (134 dias de operação), foram ensaiados vários meios suportes, através de técnica de microsensores de oxigênio dissolvido, a fim de verificar a formação de biofilme específico (nitrificante/desnitrificante) e optou-se pelo uso do carvão mineral no reator com biomassa imobilizada. Nesta última etapa, foi mantida a estratégia operacional adotada na etapa 2 (ciclo 12 horas), bem como a adição de parcela do afluente na fase anóxica. A remoção de nitrogênio, com períodos aeróbio e anóxico e ciclo de 12 horas, mostrou-se viável no reator com biomassa imobilizada (eficiência de remoção de nitrogênio de 72 \'+ OU -\' 13%). Ao final dos ensaios experimentais, realizaram-se modelagens cinéticas que permitiram a compreensão dos processos convencionais e não convencionais ocorridos nas várias etapas para remoção de nitrogênio, tais como desnitrificação em fase aeróbia e o processo ANAMMOX. / The purpose of this research was to evaluate the performance and the behavior of sequential batch reactors with suspended and immobilized biomass, in benches scale, for the nitrogen composite removal. Such systems had been tested as sulphetogenic and methanogenic reactors complementary treatment, used in an industrial waste water treatment with high sulphate and ammonia concentrations. The research aimed for the development of an operation strategy that could make possible the use of the proper waste water constituent for the improvement of the treatment efficiency. The study was divided into 3 main stages. In stage 1 (181 days of operation), the reactor with suspended biomass was kept with 4 alternating phases aerobic/anoxic and a 24-hour cycle was used, and the endogenous denitrification was verified (nitrogen removal efficiency of 65 \'+ OU -\' 27%). For stage 2 (127 days of operation), the suspended biomass reactor was submitted to a cycle of 12 hours, with an aerobic phase (6 hours) and posterior anoxic phase (6 hours). In this stage effluent of the methanogenic and sulphetogenic reactors, rich in volatile acid (acetic acid), was added to accelerate the denitrify process. The achieved results had been low in terms of nitrogen removal(42 \'+ OU -\' 21%). For stage 3 (134 days of operation), some supports media was tested through dissolved oxygen microsensors technique, in order to check the specific biofilm formation (nitrificant/denitrificant) and the mineral coal was opted to be used in the immobilized biomass reactor. In this last stage it was adopted an operational strategy similar in stage 2 (12 hours cycle), as well as the addition of part of the affluent in the anoxic phase. The nitrogen removal, with aerobic and anoxic periods and 12 hours cycle, revealed feasible in the reactor with immobilized biomass (nitrogen removal efficiency of 72 \'+ OU -\' 13%). In the end of the experimental tests, kinetic modelings were done and had allowed the understanding of conventional and not conventional processes occurred in the stages for nitrogen removal, such as desnitrification in aerobic phase and ANAMMOX process.

Devido à sua vasta biodiversidade, o Brasil dispÃe de uma grande variedade de resÃduos agrÃcolas e agroindustriais, cujo bioprocessamento à de grande interesse econÃmico e social. Entre os biocombustÃveis produzidos em todo o mundo, o etanol produzido no Brasil a partir da cana de aÃÃcar possui lugar de destaque, apresentando notÃvel evoluÃÃo durante as ultimas dÃcadas, alcanÃando assim maturidade e consistÃncia. Contudo, estima-se que a produÃÃo de etanol atravÃs dessa matÃria-prima nÃo seja suficiente para atender a demanda mundial. Neste contexto, o objetivo deste trabalho foi avaliar a produÃÃo de etanol a partir do suco de caju. Para tal fim, inicialmente, avaliou-se a necessidade de suplementaÃÃo do suco de caju para a sua posterior fermentaÃÃo. Nesta etapa, foi observado que nÃo se faz necessÃria a suplementaÃÃo do suco de caju com nutrientes, pois o mesmo in natura jà apresenta todos os nutrientes necessÃrios para o crescimento do microrganismo. Posteriormente, estudou-se o efeito da temperatura na produÃÃo de etanol, avaliando a fermentaÃÃo na faixa de 26 a 42ÂC. Os melhores resultados de rendimento (0,5 g.g-1), produtividade (4,9 g.L-1.h-1), eficiÃncia (92,8%) e produÃÃo mÃxima de etanol (49,3 g.L-1), foram obtidos quando se conduziu a fermentaÃÃo na faixa de 30 a 38ÂC. Os modelos de Monod e Arrhenius foram utilizados para descrever a dependÃncia dos parÃmetros cinÃticos com a temperatura, sendo os resultados obtidos satisfatÃrios. O potencial do suco de caju como fonte de aÃÃcares para a produÃÃo de etanol foi avaliado por diferentes cepas de leveduras dos gÃneros Saccharomyces e Kluyveromyces. Os resultados mostraram que as cepas de Saccharomyces foram bastante superiores quando comparadas Ãs Kluyveromyces quanto à produÃÃo mÃxima de etanol. A levedura que apresentou melhores resultados para os parÃmetros cinÃticos avaliados foi a Saccharomyces cerevisiae CCA008. Por ultimo, para determinar o efeito da concentraÃÃo inicial de substrato na produÃÃo de etanol, estudou-se a faixa de 70, 90, 110, 130 e 150 g.L-1 de substrato inicial. A concentraÃÃo que apresentou melhores resultados para os parÃmetros estudados foi 90 g.L-1. O modelo cinÃtico que conseguiu chegar mais prÃximos dos dados experimentais e assim descrever o processo mais fielmente foi o modelo proposto por Ghose & Thyagi. Com estes resultados, conclui-se que o uso do suco de caju como substrato para a produÃÃo de etanol trarà benefÃcios econÃmicos, pois estaremos utilizando um substrato de baixo custo, e ambientais, jà que o mesmo à um resÃduo agroindustrial proveniente da produÃÃo de castanha de caju. / Despite its big biodiversity, Brazil has a great variety of agriculturists and agroindustrials which its bioprocess has a lot of economic and social interest. Among all the ethanol produced all over the world, the ethanol produced in Brazil made of cane of sugar has great distinction. Its evolution on the last decade is remarkable reaching its maturity and consistency. Within all it is estimated that the ethanol produced with that material is not enough to be spread and supply worldwide. The object of this article is to evaluate the production of the ethanol made with cashew apple juice. In this stage, it was observed that it is not necessary to supplement the cashew apple juice to posterior fermentation because the juice already shows all the nutrients necessary for the growth of the microorganism. Later there was a study showing that the temperature in the production of ethanol evaluating its fermentation between 26 and 42ÂC. The best results of revenue (0,5 g.g-1), productivity (4,9 g.L-1.h-1), efficiency (92,8%) and the maximum production of ethanol (49,3 g.L-1), It was gained when the fermentation was conducted between 30 to 38ÂC. The models of Monod and Arrhenius were used to describe the dependence of the kinetic parameter with the temperature, showing the results to be satisfactory. The potential of the cashew apple juice being a source of sugar for the production of ethanol was evaluated by different sources of the genders Saccharomyces and Kluyveromyces. The results showed that the strains of Saccharomyces were higher when compared to the Kluyveromyces to the maximum production of ethanol. The strain that showed the best results for the kinetic parameter that was evaluated was Saccharomyces cerevisiae CCA008. At last, to determine the effect of the initial concentrate substratum in the production of ethanol, it was studied the range of 70, 90, 110, 130 and 170 g.L-1 of initial substratum. The one that showed the best results for the parameters studied was 90 g.L-1. The kinetic model that came closer to the ones experimented and could explain the process best was the model proposed by Ghose & Thyagi. In conclusion, with those results shows that the cashew apple juice used in the production of ethanol will bring great economic benefits because it is a product of low cost and economic as well as to the environment being a agroindustial product deriving from the production of the cashew nut.

Nanotubes have numerous potential applications in areas such as biotechnology, electronics, photonics, catalysis and separations. There are several challenges to be overcome in order to realize their potential, such as: (1) Synthesis of monodisperse (in diameter and in length) single-walled nanotubes; (2) Quantitative understanding of the mechanism of formation and growth of nanotubes; (3) Capability to engineer the nanotube size; (4) Low temperature synthesis process; and (5) Synthesis of impurity free nanotubes. Our investigation focuses on a class of metal oxide (aluminosilicate/germanate) nanotubes, which are; single walled nanotubes with monodisperse inner and outer diameters, can be synthesized in the laboratory by a low temperature (95ºC) process in mildly acidic aqueous solutions, and their formation timescales is hours, which makes it convenient as a model system to study the mechanisms of nanotube formation. This work is focused on obtaining a qualitative and quantitative understanding of the mechanism of formation of aluminosilicate and aluminogermanate nanotubes. In order to achieve this overall objective, this thesis consists of the following aspects: (1) A systematic phenomenological study of the growth and structural properties of aluminosilicate and aluminogermanate nanotubes. The constant size and increasing nanotube concentration over the synthesis time strongly suggest that these nanotubular are assembled through self-assembly process. (II) Investigation of the mechanism of formation of single-walled aluminogermanate nanotubes provided the central phenomena underlying the formation of these nanostructures: (1) the generation (via pH control) of a precursor solution containing chemically bonded precursors, (2) the formation of amorphous nanoscale (~ 6 nm) condensates via temperature control, and (3) the self-assembly of short nanotubes from the amorphous nanoscale condensates. (III) Synthesis of mixed metal oxide (aluminosilicogermanate) nanotubes with precise control of elemental composition, diameter and length of the product nanotubes. (IV) Preliminary work towards generalization of the kinetic model developed for aluminogermanate nanotubes to a larger class of metal oxide nanotubes. It was found that the size of nanotubes is dependent on the amount of precursors that can be packed in a single ANP and in turn depends on the size of the ANP.