Uma das desvantagens dos bio-óleos precursores do biodiesel é a alta carga de compostos oxigenados que diminuem seu poder de combustão, reduzindo sua eficiência e inviabilizando seu uso em larga escala. Nesse contexto, o processo de hidrodesoxigenação (HDO) é relevante, dado que elimina esses compostos através de uma reação catalítica e, portanto, aumenta o poder calorífico do combustível. Neste trabalho, estudou-se a HDO do guaiacol (2-metoxifenol) como composto modelo dos bio-óleos derivados da biomassa e avaliou-se o desempenho de catalisadores de Ni e Mo no processo. Estudou-se a performance de um catalisador suportado em SBA-15 - um material mesoporoso de sílica de alta área superficial - em comparação a de um catalisador tradicional suportado em gama-alumina. Para tal, utilizou-se um sistema contínuo em fase gasosa e reator de leito fixo. Utilizaram-se técnicas de caracterização de catalisadores, como adsorção de N2, MEV, MET, DRX, TPR-H2, FTIR, TPO-O2, Raman e TGA. Através das análises DRX e MET, comprovou-se que se formaram partículas de NiO e MoO3 de menor tamanho e mais dispersas no caso do catalisador de SBA-15, devido à menor interação com o suporte e maior área superficial, o que resultou em um grau de redução de 91,6 % deste catalisador, em comparação a 73,4 % do outro, analisados por TPR-H2. Os testes catalíticos mostraram que o catalisador de NiMo/SBA-15 supera o de alumina em termos de conversão no intervalo de 200 a 300 °C, com ciclohexeno e ciclohexano como principais produtos, em face à maior seletividade a catecol e fenol no NiMo/?-Al2O3. A 300 °C, o catalisador suportado em sílica alcançou taxas de 66,5 % para a HDO e 35,3 % HDA (hidrodesaromatização), enquanto o de alumina obteve somente 30,8 e 2,7 %, respectivamente. Finalmente, comprovou-se que o SBA-15 teve uma taxa de desativação por coque de 1,14 mgcoque gcat-1 h-1, 31 % menor que a taxa do catalisador de alumina, cujos depósitos foram de carbono grafítico bem estruturado e irreversível. Em vista dos resultados obtidos, esta dissertação apresenta as rotas e mecanismos de reação do guaiacol nos catalisadores estudados, conhecimento que é relevante para o desenvolvimento e aprimoramento de futuros catalisadores da HDO. / A key disadvantage of the bio-oils precursors of biodiesel is the high load of oxygenated compounds that reduce their heat of combustion, dropping their efficiency and making them unfeasible on a large scale. In light of that, the hydrodeoxygenation process (HDO) is relevant, since it eliminates these compounds through a catalytic reaction, thus increasing the calorific value of the fuel. In this work, the HDO of guaiacol (2-methoxyphenol) as a model compound of the bio-oils derived from biomass was studied and the performance of Ni-Mo catalysts was evaluated. A catalyst supported on SBA-15 - a high surface area mesoporous silica material - was compared to a traditional gamma-alumina-supported catalyst. For this purpose, a continuous gas phase setup with fixed bed reactor was employed. The catalysts properties were identified by N2 adsorption, SEM, TEM, XRD, H2-TPR, FTIR, O2-TPO, Raman and TGA techniques. Through XRD and TEM, it was verified that smaller and more dispersed NiO and MoO3 particles were formed in the case of the SBA-15 catalyst, due to the lower interaction with the support and the greater surface area, which resulted in a degree of reduction of 91.6% for this catalyst, as opposed to 73.4% for the other one, both analyzed by H2-TPR. The catalytic tests showed that the NiMo/SBA-15 outperforms the alumina catalyst in terms of conversion in the range of 200 to 300 °C, with cyclohexene and cyclohexane as main products, in contrast with major selectivity to catechol and phenol on NiMo/?-Al2O3. At 300 °C, the silica-supported catalyst achieved rates of 66.5% for HDO and 35.3% for HDA (hydrodearomatization), whereas alumina reached only 30.8 and 2.7%, respectively. Finally, it was shown that the SBA-15 catalyst had a coke deactivation rate of 1.14 mgcoke gcat-1 h-1, 31% lower than the alumina catalyst, whose coke deposits consisted of well-structured irreversible graphitic carbon. In view of the results, this dissertation proposes the routes and reaction mechanisms of guaiacol on the studied catalysts, knowledge that is pertinent for the development and improvement of future HDO catalysts.

Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Alicyclobacilli are endospore-forming, thermophilic, acidophilic bacteria (TAB) that survive the pasteurisation process and spoil acidic fruit juices through the production of the taint compound guaiacol. Guaiacol causes an undesirable odour with an unpleasant smoky, medicinal or phenolic-like taste. This thesis reports on the precursors, vanillin and vanillic acid metabolised to guaiacol by Alicyclobacillus spp. in fruit juice, the pathway of guaiacol production and the spoilage potential of contaminated fruit juices supplemented with these precursors. A high performance liquid chromatography method with UV-diode array detection (HPLC-DAD) was developed for the simultaneous detection and quantification of guaiacol and its precursors. Alicyclobacillus acidoterrestris FB2 was incubated at 45 °C for 7 d in Bacillus acidoterrestris (BAT) broth supplemented with ferulic acid, vanillin or vanillic acid. The cell concentrations were determined every 24 h and the concentration of the precursors and the production of guaiacol was determined using HPLC-DAD. The guaiacol production was also determined using the peroxidase enzyme colourimetric assay (PECA). Alicyclobacillus acidoterrestris produced guaiacol from vanillin and vanillic acid, confirming both vanillin and vanillic acid as precursors for guaiacol production by A. acidoterrestris FB2. Furthermore, a metabolic pathway directly from vanillin to guaiacol was identified in this study. However, guaiacol was not produced by A. acidoterrestris FB2 in the samples supplemented with ferulic acid and it is, therefore, not considered a direct precursor for guaiacol production by A. acidoterrestris. The spoilage potential of apple juice supplemented with either 10 mg L-1 or 100 mg L-1 vanillin or vanillic acid by A. acidoterrestris FB2 (106 cfu mL-1) was also evaluated. The production of guaiacol increased with the increase in vanillin or vanillic acid concentrations (in BAT broth and apple juice) indicating that the concentration of vanillin and vanillic acid present in fruit juice will influence the spoilage potential of the juice. Guaiacol concentrations in apple juice well above the best estimated threshold value of guaiacol for taste (0.24 – 2.00 μg L-1) and odour (0.50 - 2.32 μg L-1) was produced by A. acidoterrestris FB2 in the apple juice supplemented with 10 mg L-1 vanillin or vanillic acid. This indicates that fruit juice with a vanillin or vanillic acid concentration as low as 10 mg L-1 has the potential to spoil if the juice is contaminated with A. acidoterrestris. The concentrations of vanillin and vanillic acid in different fruit juices can be used to indicate if a specific fruit juice is susceptible to guaiacol spoilage by Alicyclobacillus spp. In the development of juice products and different blends of fruit juices, special care must be taken not to concentrate the amount of vanillin and vanillic acid present in the fruit juices. / AFRIKAANSE OPSOMMING: Alicyclobacilli is endospoor-vormende, termofiliese, asidofiliese bacterie (TAB) wat die pasteurisasie proses oorleef en suur vrugtesappe bederf met die produksie van ‘n taint komponent guaiakol. Guaiakol veroorsaak ‘n ongewensde reuk en onaangename rookagtige, medisinale of fenoliese smaak. Hierdie tesis doen verslag oor die voorloper komponente, vanillien en vanilliensuur in vrugtesappe wat gemetaboliseer word na guaiakol deur Alicyclobacillus spesies, die padweg van guaiakol produksie en die bederfbaarheid van gekontamineerde vrugtesap aangevul met hierdie voorloper komponente. ‘n Hoëprestasie vloeistof chromatografie metode met UV-deteksie (skanderend) (HPVC) is ontwikkel vir die gesamentlike deteksie en kwantifisering van guaiakol en die voorloper komponente. Alicyclobacillus acidoterrestris FB2 is geïnkubeer by 45 °C vir 7 d in Bacillus acidoterrestris (BAT) medium aangevul met feruliensuur, vanillien of vanilliensuur. Die sel konsentrasies is elke 24 h bepaal en die aangevulde komponente en die geproduseerde guaiakol is bepaal deur van HPVC gebruik te maak. Die guaiakol konsentrasies is ook bepaal deur van die peroksidase ensiem kolorimetriese bepaling (PEKB) gebruik te maak. Alicyclobacillus acidoterrestris het guaiakol geproduseer vanaf vanillien en vanilliensuur, dus is beide vanillien en vanilliensuur bevestig as voorlopers van guaiakol produksie deur A. acidoterrestris FB2. A padweg direk van vanillien na guaiakol is in hierdie studie geïdentifiseer. Guaiakol is nie geproduseer deur A. acidoterrestris FB2 in the monsters wat met feruliensuur aangevul is nie en feruliensuur is dus nie ‘n direkte voorloper van guaiakol produksie deur A. acidoterrestris. Die bederf potensiaal van appelsap aangevul met 10 mg L-1 of 100 mg L-1 vanillien of vanilliensuur deur A. acidoterrestris (106 kve mL-1) is ook geëvalueer. Die produksie van guaiakol het toegeneem met die toename in vanillien of vanilliensuur konsentrasies (in beide BAT en appelsap) wat aandui dat die konsentrasie vanillien en vanilliensuur teenwoordig in vrugtesap die bederfbaarheid van die sap sal beïvloed. Guaiakol konsentrasies in appelsap hoog bo die drumpel waardes van guaiacol vir smaak (0.24 – 2.00 μg L-1) en reuk (0.50 - 2.32 μg L-1) is geproduseer deur A. acidoterrestris FB2 in die appelsap monsters aangevul met 10 mg L-1 vanillien of vanilliensuur. Hierdie verskynsel dui aan dat vrugtesap met ‘n vanillien of vanilliensuur konsentrasies van so laag as 10 mg L-1 die potensiaal het om te bederf indien die sap gekontamineer is met A. acidoterrestris. Die konsentrasies van vanillien en vanilliensuur in verskillende vrugtesappe kan gebruik word om aan te dui of ‘n spesifieke vrugtesap ‘n hoë risiko het vir guaiakol bederf deur Alicyclobacillus spesies. Tydens die ontwikkeling van vrugtesap produkte en verskillende mengsels van vrugtesappe moet seker gemaak word dat die hoeveelhede vanillien en vanilliensuur in die sappe nie gekonsentreer word nie.

Uma das desvantagens dos bio-óleos precursores do biodiesel é a alta carga de compostos oxigenados que diminuem seu poder de combustão, reduzindo sua eficiência e inviabilizando seu uso em larga escala. Nesse contexto, o processo de hidrodesoxigenação (HDO) é relevante, dado que elimina esses compostos através de uma reação catalítica e, portanto, aumenta o poder calorífico do combustível. Neste trabalho, estudou-se a HDO do guaiacol (2-metoxifenol) como composto modelo dos bio-óleos derivados da biomassa e avaliou-se o desempenho de catalisadores de Ni e Mo no processo. Estudou-se a performance de um catalisador suportado em SBA-15 - um material mesoporoso de sílica de alta área superficial - em comparação a de um catalisador tradicional suportado em gama-alumina. Para tal, utilizou-se um sistema contínuo em fase gasosa e reator de leito fixo. Utilizaram-se técnicas de caracterização de catalisadores, como adsorção de N2, MEV, MET, DRX, TPR-H2, FTIR, TPO-O2, Raman e TGA. Através das análises DRX e MET, comprovou-se que se formaram partículas de NiO e MoO3 de menor tamanho e mais dispersas no caso do catalisador de SBA-15, devido à menor interação com o suporte e maior área superficial, o que resultou em um grau de redução de 91,6 % deste catalisador, em comparação a 73,4 % do outro, analisados por TPR-H2. Os testes catalíticos mostraram que o catalisador de NiMo/SBA-15 supera o de alumina em termos de conversão no intervalo de 200 a 300 °C, com ciclohexeno e ciclohexano como principais produtos, em face à maior seletividade a catecol e fenol no NiMo/?-Al2O3. A 300 °C, o catalisador suportado em sílica alcançou taxas de 66,5 % para a HDO e 35,3 % HDA (hidrodesaromatização), enquanto o de alumina obteve somente 30,8 e 2,7 %, respectivamente. Finalmente, comprovou-se que o SBA-15 teve uma taxa de desativação por coque de 1,14 mgcoque gcat-1 h-1, 31 % menor que a taxa do catalisador de alumina, cujos depósitos foram de carbono grafítico bem estruturado e irreversível. Em vista dos resultados obtidos, esta dissertação apresenta as rotas e mecanismos de reação do guaiacol nos catalisadores estudados, conhecimento que é relevante para o desenvolvimento e aprimoramento de futuros catalisadores da HDO. / A key disadvantage of the bio-oils precursors of biodiesel is the high load of oxygenated compounds that reduce their heat of combustion, dropping their efficiency and making them unfeasible on a large scale. In light of that, the hydrodeoxygenation process (HDO) is relevant, since it eliminates these compounds through a catalytic reaction, thus increasing the calorific value of the fuel. In this work, the HDO of guaiacol (2-methoxyphenol) as a model compound of the bio-oils derived from biomass was studied and the performance of Ni-Mo catalysts was evaluated. A catalyst supported on SBA-15 - a high surface area mesoporous silica material - was compared to a traditional gamma-alumina-supported catalyst. For this purpose, a continuous gas phase setup with fixed bed reactor was employed. The catalysts properties were identified by N2 adsorption, SEM, TEM, XRD, H2-TPR, FTIR, O2-TPO, Raman and TGA techniques. Through XRD and TEM, it was verified that smaller and more dispersed NiO and MoO3 particles were formed in the case of the SBA-15 catalyst, due to the lower interaction with the support and the greater surface area, which resulted in a degree of reduction of 91.6% for this catalyst, as opposed to 73.4% for the other one, both analyzed by H2-TPR. The catalytic tests showed that the NiMo/SBA-15 outperforms the alumina catalyst in terms of conversion in the range of 200 to 300 °C, with cyclohexene and cyclohexane as main products, in contrast with major selectivity to catechol and phenol on NiMo/?-Al2O3. At 300 °C, the silica-supported catalyst achieved rates of 66.5% for HDO and 35.3% for HDA (hydrodearomatization), whereas alumina reached only 30.8 and 2.7%, respectively. Finally, it was shown that the SBA-15 catalyst had a coke deactivation rate of 1.14 mgcoke gcat-1 h-1, 31% lower than the alumina catalyst, whose coke deposits consisted of well-structured irreversible graphitic carbon. In view of the results, this dissertation proposes the routes and reaction mechanisms of guaiacol on the studied catalysts, knowledge that is pertinent for the development and improvement of future HDO catalysts.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers that are able to spoil acidic food and beverage products through the production of guaiacol and other taint compounds, which causes a medicinal off-flavour and/or odour in the products. This thesis reports on the comparison of methods used for the isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol production of different strains isolated from the South African fruit processing environment. Two methods for guaiacol detection were also evaluated and compared. Three isolation methods frequently used by South African fruit processors were compared with regards to their ability to isolate a strain of A. acidoterrestris from diluted peach juice concentrate. Method 1, the International Federation of Fruit Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and incubation of the membrane on K agar. The IFU Method No. 12 was the most effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%. These results support the use of the IFU Method No. 12 as a standard international method for the isolation and detection of species of Alicyclobacillus. Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A. acidocaldarius FB19, were analysed based on their growth characteristics and guaiacol production under optimum conditions. Strains were inoculated into BAT medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for 7 d. All the strains had similar growth patterns, with cell concentrations increasing rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an increase in spores as the cell density and competition for resources increased. All the strains were able to produce guaiacol in detectable concentrations [as measured by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the potential to cause product spoilage. Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers that are able to spoil acidic food and beverage products through the production of guaiacol and other taint compounds, which causes a medicinal off-flavour and/or odour in the products. This thesis reports on the comparison of methods used for the isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol production of different strains isolated from the South African fruit processing environment. Two methods for guaiacol detection were also evaluated and compared. Three isolation methods frequently used by South African fruit processors were compared with regards to their ability to isolate a strain of A. acidoterrestris from diluted peach juice concentrate. Method 1, the International Federation of Fruit Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and incubation of the membrane on K agar. The IFU Method No. 12 was the most effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%. These results support the use of the IFU Method No. 12 as a standard international method for the isolation and detection of species of Alicyclobacillus. Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A. acidocaldarius FB19, were analysed based on their growth characteristics and guaiacol production under optimum conditions. Strains were inoculated into BAT medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for 7 d. All the strains had similar growth patterns, with cell concentrations increasing rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an increase in spores as the cell density and competition for resources increased. All the strains were able to produce guaiacol in detectable concentrations [as measured by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the potential to cause product spoilage. iv The influence of temperature on the growth and guaiacol production of the Alicyclobacillus strains was also investigated and two guaiacol detection methods, the PECA and headspace gas-chromatography mass-spectrometry (HS GC-MS), were compared with regards to their ability to detect guaiacol. The strains were incubated at 25°C and 45°C for 6 d and samples analysed every 24 h. Growth of the A. acidoterrestris strains was slower at 25°C, and maximum cell concentrations were lower than at 45°C. A decrease in cell concentrations was observed in the A. acidocaldarius strains at 25°C, as this temperature is below their growth temperature range. All the strains were able to produce guaiacol at 45°C, with guaiacol only being detected once a cell concentration of 104-105 cfu.mL-1 had been reached. The maximum guaiacol concentrations detected at 45°C in the samples containing A. acidoterrestris were significantly higher than those detected in the A. acidocaldarius samples. At 25°C there was a longer lag phase before guaiacol was detected in the A. acidoterrestris samples, while no guaiacol was detected in the samples containing A. acidocaldarius. Because guaiacol is produced at ambient temperatures, cooling of products is recommended to control spoilage by A. acidoterrestris. The sensitivity of the two guaiacol detection methods also differed significantly and, therefore, the PECA is recommended for presence/absence detection of guaiacol, while HS GCMS is recommended where accurate quantification of guaiacol is required. Alicyclobacillus acidoterrestris FB2 was investigated for its ability to grow and produce guaiacol in white grape juice supplemented with vanillin at different concentrations. Alicyclobacillus acidoterrestris FB2 was inoculated into white grape juice concentrate diluted 1:10 with distilled water containing 0-500 mg.L-1 vanillin and incubated at 45°C for 6 d. Similar growth patterns were observed in all the samples, except in the sample containing 500 mg.L-1 vanillin, which had a longer lag phase of growth. Guaiacol concentrations, detected using the PECA, increased as the vanillin concentration increased, with the exception of the sample containing 500 mg.L-1 vanillin, where less guaiacol was detected than in the sample containing 250 mg.L-1 vanillin, due to growth inhibition caused by the higher vanillin concentration. A number of conditions need to be favourable for detectable guaiacol production to occur and it could, therefore, be possible to minimise or prevent guaiacol production by controlling or eliminating some of these factors. Good manufacturing practices should be employed in order to minimise contamination and, therefore, spoilage, by Alicyclobacillus species. / AFRIKAANSE OPSOMMING: Bakterieë wat aan die genus Alicyclobacillus behoort, is termo-asidofiliese spoorvormers wat suur voedsel en drank produkte kan bederf deur die produksie van guaiakol en ander bederf verbindings, wat ‘n medisinale geur en/of reuk in die produkte veroorsaak. Hierdie tesis doen verslag oor die vergelyking van metodes wat vir die isolasie van spesies van Alicyclobacillus gebruik word, sowel as die groei kenmerke en guaiakol produksie van verskillende stamme wat uit die Suid- Afrikaanse vrugte prosesseringsomgewing geïsoleer is. Twee metodes vir die deteksie van guaiakol is ook geëvalueer en vergelyk. Drie isolasie metodes wat algemeen deur Suid-Afrikaanse vrugteprosesseerders gebruik word, is vergelyk ten opsigte van hul vermoë om H A. acidoterrestris stam uit verdunde perskesap konsentraat te isoleer. Metode 1, die Internasionale Federasie van Vrugtesap Produseerders (IFU) Metode No. 12, maak gebruik van spreiplating op Bacillus acidoterrestris (BAT) agar plate; Metode 2 behels gietplating met aartappel dekstrose agar (PDA) and Metode 3 maak gebruik van membraan filtrasie en inkubasie van die membraan op K agar. Die IFU Metode No. 12 was die mees effektiewe metode vir die isolasie van A. acidoterrestris, met H sel herwinning van 75.97%. Hierdie resultate ondersteun die gebruik van die IFU Metode No. 12 as H standaard internasionale metode vir die isolasie en deteksie van spesies van Alicyclobacillus. Sewe Alicyclobacillus stamme, insluitende die tipe stamme A. acidoterrestris DSM 3922T en A. acidocaldarius DSM 446T en vyf stamme geïsoleer uit ‘n Suid- Afrikaanse vrugte prosesseringsaanleg, A. acidoterrestris FB2, FB14, FB32, FB38 en A. acidocaldarius FB19, is geanaliseer met betrekking tot hul groei kenmerke en guaiakol produksie onder optimum toestande. Stamme is in BAT medium by pH 4.00, aangevul met 100 mg.L-1 vanillin, geïnokuleer en geïnkubeer teen 45°C vir 7 d. Al die stamme het soortgelyke groeipatrone getoon, met selgetalle wat vinnig toegeneem het van 0-24 h, gevolg deur ‘n stabilisering rondom maksimum selgetalle van 105-107 kve.mL-1. Selgetalle na hitte behandeling, gemeet as H aanduiding van spoorvorming, het toegeneem tot maksimum waardes van 105-107 kve.mL-1, wat aandui dat spore toegeneem het soos die seldigtheid en kompetisie vir voedingsbronne toegeneem het. Al die stamme kon guaiakol in bespeurbare konsentrasies produseer [soos gemeet deur die peroksidase ensiem kolorimetriese bepaling (PEKB)] en besit dus die potensiaal om produkte te bederf. Die invloed van temperatuur op groei en guaiakol produksie van die Alicyclobacillus stamme is ook ondersoek en twee guaiakol deteksie metodes, die PEKB en topspasie gas-kromatografie massa-spektrometrie (TS GK-MS) is vergelyk ten opsigte van hul vermoë om guaiakol op te spoor. Die stamme is geïnkubeer teen 25°C en 45°C vir 6 d en monsters is elke 24 h geanaliseer. Groei van die A. acidoterrestris stamme was stadiger by 25°C en maksimum selgetalle was laer as by 45°C. H Vermindering in selgetalle is waargeneem in die A. acidocaldarius stamme by 25°C, aangesien hierdie temperatuur buite hul groei temperatuur grense val. Al die stamme kon guaiakol produseer by 45°C, met guaiakol deteksie wat eers H aanvang geneem het nadat H sel konsentrasie van 104-105 kve.mL-1 bereik is. Die maksimum guaiakol konsentrasies wat by 45°C in die monsters met A. acidoterrestris opgespoor is, was beduidend hoër as die konsentrasies wat in die A. acidocaldarius monsters opgespoor is. By 25°C was daar H langer sloerfase voor guaiakol opgespoor is in die A. acidoterrestris monsters, terwyl geen guaiakol opgespoor is in die monsters wat A. acidocaldarius bevat het nie. Aangesien guaiakol by kamertemperatuur geproduseer word, word verkoeling van produkte aanbeveel ten einde bederf deur A. acidoterrestris te beheer. Die sensitiwiteit van die twee guaiakol deteksie metodes het ook beduidend verskil en dus word die gebruik van die PEKB aanbeveel vir teenwoordigheid/afwesigheid deteksie van guaiakol, terwyl TS GK-MS aanbeveel word waar akkurate kwantifisering van guaiakol vereis word. Ondersoek is ingestel na die vermoë van A. acidoterrestris FB2 om te groei en guaiakol te produseer in witdruiwesap aangevul met verskillende vanillin konsentrasies. Alicyclobacillus acidoterrestris FB2 is geïnokuleer in witdruiwesap konsentraat 1:10 verdun met gedistilleerde water wat 0-500 mg.L-1 vanillin bevat het en is geïnkubeer teen 45°C vir 6 d. Soortgelyke groeipatrone is waargeneem in al die monsters, behalwe die monster wat 500 mg.L-1 vanillin bevat het, wat H langer sloerfase van groei gehad het. Guaiakol konsentrasies, soos gemeet deur die PEKB, het toegeneem soos die vanillin konsentrasie toegeneem het, met die uitsondering van die monster wat 500 mg.L-1 vanillin bevat het, waar minder guaiakol opgespoor is as in die monster wat 250 mg.L-1 bevat het as gevolg van groei inhibisie veroorsaak deur die hoër vanillin konsentrasie. H Aantal toestande moet gunstig wees vir guaiakol produksie om plaas te vind en dit kan dus moontlik wees om guaiakol produksie te minimaliseer of te voorkom deur die beheer of uitskakeling van sommige van hierdie faktore. Goeie vervaardigingspraktyke moet in plek gestel word ten einde kontaminasie en bederf deur Alicyclobacillus spesies tot H minimum te beperk.

La pyrolyse rapide de biomasse lignocellulosique produit des bio-huiles avec des rendements élevés mais ces liquides contiennent de nombreux composés oxygénés, une acidité élevée et de ce fait sont instables. Un hydrotraitement poussé de ces huiles est nécessaire avant qu'elles puissent être utilisées comme combustibles liquides. Afin de réduire le coût et d'améliorer les performances de l'hydrotraitement ultérieur, plusieurs stratégies ont été proposées pour réduire les teneurs en oxygène et en acides, comme l'ajout d'un lit catalytique après la pyrolyse. La conversion catalytique des vapeurs de pyrolyse permet une désoxygénation partielle avant la condensation des vapeurs. Dans ce contexte, nous avons étudié la conversion de molécules modèles, l'acide acétique et le gaïacol, sur différents catalyseurs acides afin d'identifier des phases actives performantes et de comprendre les mécanismes réactionnels. Dans un deuxième temps, un test de pyrolyse semi-continu combiné avec un réacteur catalytique a été conçu et mis en place et les meilleurs catalyseurs acides sélectionnés pour les molécules modèles ont été testés pour la conversion de bois de hêtre. Après conversion, un protocole de séparation des fractions a été appliqué et les fractions gaz, liquide et solide ont été caractérisées par différentes méthodes (?-GC, GC×GC, GPC, RMN…). Une attention particulière a été portée à la quantification des monomères dans la fraction liquide par GC×GC. Les bilans massiques atteignent plus de 90% et des bilans carbones ont été également réalisés dans les différentes fractions. L'ensemble des caractérisations et la comparaison entre pyrolyse avec et sans étape catalytique permet d'améliorer la compréhension du rôle du catalyseur dans la conversion des vapeurs de pyrolyse / Fast pyrolysis of biomass yields bio-oils with high levels of oxygen-containing components, high acidity and low stability. Further upgrading of these oils is necessary before they can be used as liquid fuels. Several low-cost strategies have been proposed for reducing the oxygen and acid contents including the catalytic conversion of pyrolytic vapors before vapor condensation. In this context, a first step in this work was the study of model molecules conversion, acetic acid and guaiacol, on different acid catalyst to understand reaction mechanisms and determine the best catalyst. In a second time, a semi-continuous pyrolysis test combined with a catalytic reactor was built and use to test the best acid catalysts found on model molecules, for the conversion of beech wood chips. A product recovery protocol was implanted to recover all the gas, liquid and solid fractions. Those fractions were characterized in depth by various techniques (?-GC, GC×GC, GPC, RMN…). A special focus was made on the quantification of monomers in the bio-oils by GC×GC. Mass balance reached 90% and carbon balance were established for some experiments. The performed characterizations as well as the comparison between catalytic and thermal experiments allowed to get more insights in the role of the catalyst on pyrolytic vapors conversion

Elevada disponibilidade de bário (Ba) no meio de cultivo pode resultar em severa toxidez nas plantas. A toxidez causada pelo metal pesado nas plantas pode ser amenizada pelo fornecimento de nutrientes, particularmente o enxofre (S). Objetivou-se avaliar os parâmetros produtivos, sintomas visuais, estado nutricional, índice SPAD, indicadores de estresse (malondialdeído, peróxido de hidrogênio e prolina) e a atividade de enzimas do sistema antioxidante (glutationa redutase, superóxido dismutase, catalase, ascorbato peroxidase e guaiacol peroxidase) do capim tanzânia (Panicum maximum Jacq. cv. Tanzânia) cultivado com combinações de doses de S e de Ba na solução nutritiva, em casa de vegetação, em dois ciclos de crescimento das plantas. As plantas foram submetidas às combinações de cinco doses de S (0,1; 1,0; 1,9; 2,8 e 3,7 mmol L-1) com cinco doses de Ba (0,0; 2,5; 5,0; 10,0 e 20,0 mmol L-1), utilizando esquema fatorial fracionado (52), em blocos ao acaso, com seis repetições e seis plantas por unidade experimental. Os parâmetros produtivos e o estado nutricional das plantas foram severamente afetados pelas combinações de S e Ba em ambos os ciclos de crescimento. O aumento na dose de Ba na solução nutritiva prejudicou acentuadamente o crescimento e o estado nutricional das plantas, principalmente na área foliar, e nos nutrientes potássio e magnésio, enquanto o aumento da dose de S amenizou o efeito tóxico do metal. Maiores concentrações de malondialdeído foram observadas nas plantas que apresentaram maior acúmulo do metal pesado. As atividades das enzimas glutationa redutase, catalase e ascorbato peroxidase foram mais altas nas plantas cultivadas com baixo fornecimento de S, enquanto a atividade da guaiacol peroxidase foi aumentada com incremento das doses de Ba e de S. / High barium (Ba) availability in growth medium can cause severe toxicity in plants. Nutrient supply may mitigate heavy metal phytotoxicity, especially the sulphur (S) supply. The study was carried out to evaluate the plant growth, visual symptoms, nutritional status, indicators of stress (malondialdehyde, hydrogen peroxide and proline) and activities of the antioxidant enzymes (glutathione reductase, superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) in Tanzania guineagrass (Panicum maximum Jacq. cv. Tanzania) grown with combinations of S rates and Ba rates in nutrient solution, in a greenhouse, for two growth periods. Plants received nutrient solutions where combinations of five S rates (0.1, 1.0, 1.9, 2.8 and 3.7 mmol L-1) with five Ba rates (0.0, 2.5, 5.0, 10.0 and 20.0 mmol L-1) were used in a fractionated factorial (52), in randomized block design, with six replications and six plants per experimental unit. Plant production and nutritional status were highly affected by combinations of S and Ba rates, in both growth periods. Increase on Ba rates impaired growth, mainly on leaf area production. Barium rates impaired nutritional status, mainly on potassium and calcium, while increasing on S rates alleviated Ba toxic effects. High concentrations of malondialdehyde was observed in plants with increase of Ba application. The activities of catalase and ascorbate peroxidase were high in plants grown with low S availability, while guaiacol peroxidase activity was enhanced by increasing Ba and S rates in the nutrient solution.

Elevada disponibilidade de bário (Ba) no meio de cultivo pode resultar em severa toxidez nas plantas. A toxidez causada pelo metal pesado nas plantas pode ser amenizada pelo fornecimento de nutrientes, particularmente o enxofre (S). Objetivou-se avaliar os parâmetros produtivos, sintomas visuais, estado nutricional, índice SPAD, indicadores de estresse (malondialdeído, peróxido de hidrogênio e prolina) e a atividade de enzimas do sistema antioxidante (glutationa redutase, superóxido dismutase, catalase, ascorbato peroxidase e guaiacol peroxidase) do capim tanzânia (Panicum maximum Jacq. cv. Tanzânia) cultivado com combinações de doses de S e de Ba na solução nutritiva, em casa de vegetação, em dois ciclos de crescimento das plantas. As plantas foram submetidas às combinações de cinco doses de S (0,1; 1,0; 1,9; 2,8 e 3,7 mmol L-1) com cinco doses de Ba (0,0; 2,5; 5,0; 10,0 e 20,0 mmol L-1), utilizando esquema fatorial fracionado (52), em blocos ao acaso, com seis repetições e seis plantas por unidade experimental. Os parâmetros produtivos e o estado nutricional das plantas foram severamente afetados pelas combinações de S e Ba em ambos os ciclos de crescimento. O aumento na dose de Ba na solução nutritiva prejudicou acentuadamente o crescimento e o estado nutricional das plantas, principalmente na área foliar, e nos nutrientes potássio e magnésio, enquanto o aumento da dose de S amenizou o efeito tóxico do metal. Maiores concentrações de malondialdeído foram observadas nas plantas que apresentaram maior acúmulo do metal pesado. As atividades das enzimas glutationa redutase, catalase e ascorbato peroxidase foram mais altas nas plantas cultivadas com baixo fornecimento de S, enquanto a atividade da guaiacol peroxidase foi aumentada com incremento das doses de Ba e de S. / High barium (Ba) availability in growth medium can cause severe toxicity in plants. Nutrient supply may mitigate heavy metal phytotoxicity, especially the sulphur (S) supply. The study was carried out to evaluate the plant growth, visual symptoms, nutritional status, indicators of stress (malondialdehyde, hydrogen peroxide and proline) and activities of the antioxidant enzymes (glutathione reductase, superoxide dismutase, catalase, ascorbate peroxidase and guaiacol peroxidase) in Tanzania guineagrass (Panicum maximum Jacq. cv. Tanzania) grown with combinations of S rates and Ba rates in nutrient solution, in a greenhouse, for two growth periods. Plants received nutrient solutions where combinations of five S rates (0.1, 1.0, 1.9, 2.8 and 3.7 mmol L-1) with five Ba rates (0.0, 2.5, 5.0, 10.0 and 20.0 mmol L-1) were used in a fractionated factorial (52), in randomized block design, with six replications and six plants per experimental unit. Plant production and nutritional status were highly affected by combinations of S and Ba rates, in both growth periods. Increase on Ba rates impaired growth, mainly on leaf area production. Barium rates impaired nutritional status, mainly on potassium and calcium, while increasing on S rates alleviated Ba toxic effects. High concentrations of malondialdehyde was observed in plants with increase of Ba application. The activities of catalase and ascorbate peroxidase were high in plants grown with low S availability, while guaiacol peroxidase activity was enhanced by increasing Ba and S rates in the nutrient solution.

No description available.

<p><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a></a><a>ABSTRACT</a></p> <p>Phenols are ubiquitous in our surroundings including biological molecules such as L-Dopa metabolites, food components, such as whiskey and liquid smoke, etc. This dissertation describes a new method for detecting phenols, by reaction with Gibbs reagent to form indophenols, followed by mass spectrometric detection. Unlike the standard Gibbs reaction which uses a colorimetric approach, the use of mass spectrometry allows for simultaneous detection of differently substituted phenols. The procedure is demonstrated to work for a large variety of phenols without <i>para</i>‐substitution. With <i>para</i>‐substituted phenols, Gibbs products are still often observed, but the specific product depends on the substituent. For <i>para</i> groups with high electronegativity, such as methoxy or halogens, the reaction proceeds by displacement of the substituent. For groups with lower electronegativity, such as amino or alkyl groups, Gibbs products are observed that retain the substituent, indicating that the reaction occurs at the <i>ortho</i> or <i>meta</i> position. In mixtures of phenols, the relative intensities of the Gibbs products are proportional to the relative concentrations, and concentrations as low as 1 μmol/L can be detected. The method is applied to the qualitative analysis of commercial liquid smoke, and it is found that hickory and mesquite flavors have significantly different phenolic composition.</p> <p>In the course of this study, we used this technique to quantify major phenol derivatives in commercial products such as liquid smoke (catechol, guaiacol and syringol) and whiskey (<i>o</i>-cresol, guaiacol and syringol) as the phenol derivatives are a significant part of the aroma of foodstuffs and alcoholic beverages. For instance, phenolic compounds are partly responsible for the taste, aroma and the smokiness in Liquid Smokes and Scotch whiskies. </p> <p>In the analysis of Liquid Smokes, we have carried out an analysis of phenols in commercial liquid smoke by using the reaction with Gibbs reagent followed by analysis using electrospray ionization mass spectrometry (ESI-MS). This analysis technique allows us to avoid any separation and/or solvent extraction steps before MS analysis. With this analysis, we are able to determine and compare the phenolic compositions of hickory, mesquite, pecan and apple wood flavors of liquid smoke. </p> <p>In the analysis of phenols in whiskey, we describe the detection of the Gibbs products from the phenols in four different commercial Scotch whiskies by using simple ESI-MS. In addition, by addition of an internal standard, 5,6,7,8-tetrahydro-1-napthol (THN), concentrations of the major phenols in the whiskies are readily obtained. With this analysis we are able to determine and compare the composition of phenols in them and their contribution in the taste, smokey, and aroma to the whiskies.</p> <p>Another important class of phenols are found in biological samples, such as L-Dopa and its metabolites, which are neurotransmitters and play important roles in living systems. In this work, we describe the detection of Gibbs products formed from these neurotransmitters after reaction with Gibbs reagent and analysis by using simple ESI‐MS. This technique would be an alternative method for the detection and simultaneous quantification of these neurotransmitters. </p> <p>Finally, in the course of this work, we found that the positive Gibbs tests are obtained for a wide range of <i>para</i>-substituted phenols, and that, in most cases, substitution occurs by displacement of the <i>para</i>-substituent. In addition, there is generally an additional unique second-phenol-addition product, which conveniently can be used from an analytical perspective to distinguish <i>para</i>-substituted phenols from the unsubstituted versions. In addition to using the methodology for phenol analysis, we are examining the mechanism of indophenol formation, particularly with the <i>para</i>-substituted phenols. </p> <p>The importance of peptides to the scientific world is enormous and, therefore, their structures, properties, and reactivity are exceptionally well-characterized by mass spectrometry and electrospray ionization. In the dipeptide work, we have used mass spectrometry to examine the dissociation of dipeptides of phenylalanine (Phe), containing sulfonated tag as a charge carrier (Phe*), proline (Pro) to investigate their gas phase dissociation. The presence of sulfonated tag (SO₃^-) on the Phe amino acid serves as the charge carrier such that the dipeptide backbone has a canonical structure and is not protonated. Phe-Pro dipeptide and their derivatives were synthesized and analyzed by LCQ-Deca mass spectroscopy to get the fragmentation mechanism. To confirm that fragmentation path, we also synthesized dikitopeparazines and oxazolines from all combinations of the dipeptides. All these analyses were confirmed by isotopic labeling experiments and determination and optimization of structures were carried out using theoretical calculation. We have found that the fragmentation of Phe*Pro and ProPhe* dipeptides form sequence specific b₂ ions. In addition, not only is the ‘mobile proton’ involved in the dissociation process, but also is the ‘backbone hydrogen’ is involved in forming b₂ ions. </p> <p> </p>