No description available.

Essential to the entire field of Organic Chemistry is the nature of the carbon to carbon bond. Our current concepts and guiding principles concerning it are almost solely constructed from aliphatic compounds, certain simple ring species, and aromatic systems. Except for special cases, aliphatic and aromatic types are felt to be mildly strained or free from internal tension while the alicylic small and medium ring compounds are the so-called strained molecules. These strained compounds involve bending back or compression of two of the four carbon bonds from an equilibrium position. Distortions of more complex origin occur in the paracyclophanes and hexahelicine, etc. The theory considering strain of two of the four carbon bonds might well be extended to include three bonds. Simple caged compound core types testing three-bond strain. are the tetrahedron, trigonal prism , and cube. The successful synthesis of a unique compound, 4-methyl tricyclo[1.1.0.02-4] butane-1,2,3-tricarboxylic acid containing the three-bond strained tetrahedral core was reported by Beesley, Thorpe, and Ingold thirty eight years ago. With the exception of unsuccessful efforts by Woodward and Larson, this area of chemistry has remained virtually inactive since that time. Our reinvestigation of this remarkable synthesis has revealed method omissions vital to acquiring the compounds leading to l. These methods, a preliminary objective of this research and apparently commonplace in the laboratory of Thorpe, particularly involved the preparation of 1,1,1-ethane triacetic acid, II, and triethyl tribromo-1,1,1-ethane triacetate, III. The tri acid II was very difficult to purify by crystallizing with the techniques of frequent present-day use. Thorpe made no mention of temperature in his accounts, but obtained the acid in good condition. Our work has shown the acid can be easily purified by crystallizing from 50 % hydrochloric acid solution at 65°-70° C. This higher purity product can then be brominated with phosphorus pentabromide under special conditions. These are only partially stated by Thorpe. Our work has shown that III can be brominated by making phosphorus pentabromide in situ with slow bromine addition to a mixture of II and phosphorus tribromide. Compounds necessary to the acquisition of II and III are ethyl isodehydracetate IV, ethyl β-methyl glutaconate V, and ethyl a-cyano β,β-dimethylpropane tricarboxylate VI . Discussion of the plausible reasons for method omissions, the synthesis deletions and results of greater interest, reaction schemes leading each compound to it's successor, and the experimental details of compounds II through VI are presented in the Thesis. Appended is a proposed manuscript for publishing in the Journal of the American Chemical Society.

No description available.

No description available.

Dissertation (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: L-Malic and tartaric acid are the most prominent organic acids in wine and playa crucial role in winemaking processes and wine quality, including the organoleptic quality and the physical, biochemical and microbial stability of wine. The production of premium wines depends on the oenologist's skill to accurately adjust wine acidity to obtain the optimum balance with other wine components to produce wine with optimum colour and flavour. Strains of Saccharomyces, in general, rarely degrade L-malic acid completely in grape must during alcoholic fermentation, with relatively minor modifications in total acidity during vinification. The degree of L-malic acid degradation, however, varies from strain to strain. Some strains of Saccharomyces are known to be able to degrade a higher percentage of L-malic acid, but the underlying reason for this phenomenon is unknown. The underlying mechanisms of this phenomenon have been partially revealed during preliminary transcriptional regulation research during this study. In contrast, S. pombe cells can effectively degrade up to 29 gil L-malic acid via the malo-ethanolic pathway that converts L-malic acid to pyruvate and CO2, and ultimately to ethanol under fermentative conditions. A number of reasons for the weak degradation of L-malic acid in Saccharomyces cerevisiae have been postulated. Firstly, S. cerevisiae lacks the machinery for the active transport of L-malic acid found in S. pombe and relies on rate-limiting simple diffusion for the uptake of extracellular L-malic acid. Secondly, the malic enzyme of S. cerevisiae has a significantly lower substrate affinity for L-malic acid (Km = 50 mM) than that of S. pombe (Km = 3.2 mM), which contributes to the weaker degradation of L-malic acid in S. cerevisiae. Lastly, the mitochondrial location of the malic enzyme of S. cerevisiae, in contrast to the cytosolic S. pombe malic enzyme, suggests that the S. cerevisiae malic enzyme is inherently subject to the regulatory effects of fermentative metabolism. The malate permease gene tmael) and the malic enzyme gene (mae2) of S. pombe was therefore cloned and co-expressed in single or multi-copy under regulation of the constitutive S. cerevisiae 3-phosphoglycerate kinase (PGK1) promoter and terminator sequences in a laboratory strain of S. cerevisiae. This introduced a strong malo-ethanolic phenotype in S. cerevisiae where L-malic acid was rapidly and efficiently degraded in synthetic and Chardonnay grape must with the concurrent production of higher levels of ethanol. Functional expression of the malo-ethanolic pathway genes of S. pombe in a laboratory strain of S. cerevisiae paved the way for the genetic modification of industrial wine yeast strains of Saccharomyces for commercial winemaking. A prerequisite for becoming an inherited component of yeast is the stable integration of the malo-ethanolic genes into the genome of industrial wine yeast strains. Genetic engineering of wine yeasts strains of Saccharomyces is, however, complicated by the homothallic, multiple ploidy and prototrophic nature of industrial strains of Saccharomyces. Transformation and integration of heterologous genes into industrial strains of Saccharomyces require the use of dominant selectable markers, i.e. antibiotic or toxic compound resistance markers. Integration of these markers into the yeast genome is, however, not acceptable for commercial application due to the absence of long-term risk assessment and consumer resistance. A unique strategy for the integration of the S. pombe mae} and mae2 expression cassettes without the incorporation of any non-yeast derived DNA sequences was. The malo-ethanolic cassette, containing the S. cerevisiae PGK} promoter and terminator regions together with the S. pombe mae] and mae2 open reading frames, was integrated into the VRA3 locus of an industrial strain of Saccharomyces bayanus EC 1118 during co-transformation with a phleomycin-resistance plasmid, pUT332. After initial screening for phleomycin resistance, S. bayanus EC1118 transformants were cured of the phleomycin-resistance plasmid, resulting in the loss of non-yeast derived DNA sequences. After correct integration of the mae] and mae2 expression cassettes was verified, small-scale vinification in synthetic and Chardonnay grape must with stable transformants resulted in rapid and complete degradation of L-malic acid during the early stages of alcoholic fermentation. Integration and expression of the malo-ethanolic genes in S. bayanus ECll18 had no adverse effect on the fermentation ability of the yeast, while sensory evaluation and chemical analysis of the Chardonnay wines indicated an improvement in wine flavour compared to the control wines, without the production of any off-flavours. / AFRIKAANSE OPSOMMING: L-Appelsuur en wynsteensuur is die mees prominente organiese sure in wyn en speel 'n kritiese rol in die wynbereidingsproses en organoleptiese wynkwaliteit, insluitende die fisiese, biochemiese en mikrobiese stabiliteit van wyn. Die produksie van hoë-kwaliteit wyne berus op die vermoë van 'n wynmaker om die suurinhoud korrek aan te pas om sodoende 'n gebalanseerde produk met optimale geur en kleur te produseer. Saccharomyces rasse kan gewoonlik nie appelsuur volledig tydens alkoholiese gisting benut nie en dra dus nie noemenswaardig tot 'n verlaging van die totale suurinhoud van wyn by nie. Die mate van appelsuur afbraak deur Saccharomyces wissel egter van ras tot ras. Sekere Saccharomyces rasse kan 'n groter persentasie appelsuur afbreek, maar die onderliggende rede vir hierdie verskynsel is onbekend. Die onderliggende meganismes vir hierdie verskynsel is gedurende hierdie studie uitgelig na afloop van voorlopige transkripsionele regulerings studies op die malaatensiemgeen. In teenstelling hiermee kan S. pombe tot 29 gIl appelsuur via die malo-alkoholiese padweg afbreek waartydens appelsuur na pirodruiwesuur en CO2, en uiteindelik na alkoholonder fermentatiewe toestande omgeskakel word. Verskeie redes vir die swak afbraak van appelsuur deur Saccharomyces cerevisiae is voorgestel. Eerstens beskik S. cerevisiae nie oor 'n meganisme vir die aktiewe transport van appelsuur, soos in die geval van S. pombe nie, en is aangewese op die stadige opname van appelsuur deur eenvoudige diffusie. Tweedens het die S. cerevisiae malaatensiem 'n baie laer substraataffiniteit vir appelsuur (Km = 50 mM) in vergelyking met die van S. pombe (Km = 3.2 mM), wat verder bydra tot die swak afbraak van appelsuur in S. cerevisiae. Laastens dra die mitochondriale ligging van die S. cerevisiae malaatensiem in teenstelling met die sitoplasmiese ligging van die S. pombe malaatensiem, verder by tot die swak afbraak van appelsuur, aangesien die mitochondria onder fermentatiewe toestande negatief gereguleer word. Die malaatpermease geen (maely en malaatensiem geen (mae2) van S. pombe is gevolglik gekloneer en heteroloog in 'n laboratoriumras van S. cerevisiae onder die beheer van die konstitutiewe 3-fosfogliseraat kinase (PGKI) promoter- en termineerdervolgordes uitgedruk. 'n Sterk malo-alkoholiese fenotipe was duidelik tydens fermentasies met die rekombinante gis in sintetiese en Chardonnay druiwemos, met 'n gepaardgaande verhoging in alkoholvlakke. Funksionele uitdrukking van die malo-alkoholiese gene van S. pombe in 'n S. cerevisiae laboratoriumras het die weg vir die genetiese modifisering van industriële wynrasse van S. cerevisiae vir kommersiële wynfermentasie gebaan. Om 'n integrale deel van die gis te word, moet die malo-alkoholiese gene stabiel in die genoom van industriële wynrasse geïntegreer word. Genetiese manipulering van industriële wynrasse word egter bemoeilik deur die homotalliese, multi-ploïediese en prototrofiese aard van industriële Saccharomyces rasse. Transformasie en integrasie van heteroloë gene in industriële Saccharomyces rasse vereis die gebruik van dominante merkers, bv. weerstandbiedendheid teen antibiotika of ander gifstowwe. Integrasie van hierdie merkers in die gisgenoom is egter nie vir kommersiële toepassing aanvaarbaar nie weens die afwesigheid van langtermyn risikobepalings en verbruikersweerstand. Tydens hierdie studie is daar dus gepoog om industriële wynrasse met 'n unieke strategie geneties te verbeter sodat slegs gis-DNA tydens die integrasie van die S. pombe mae1 en mae2 uitdrukkingskassette in die gisgenoom opgeneem word. Die Malo-alkoholiese integrasiekasset wat slegs die S. pombe mae1, mae2 oopleesrame en die S. cerevisiae PGK1 promoter en termineerdervolgordes bevat, is in die URA3 lokus van Saccharomyces bayanus ECll18 geïntegreer tydens parallelle transformasie met 'n 'phleomycin' weerstandbiedendheidsplasmied. Na seleksie van transformante op 'phleomycin' -bevattende media, is die S. bayanus EC 1118 transformante in nieselektiewe kondisies opgegroei sodat verlies van die 'phleomycin' plasmied kon plaasvind. Integrasie van die mae1 en mae2 uitdrukkingskassette is bevestig en kleinskaalse fermentasies in sintetiese en druiwemos het 'n vinnige en doeltreffende afbraak van appelsuur in die vroeë fases van die alkoholiese fermentasie getoon. Integrasie en uitdrukking van die malo-alkoholiese gene in S. bayanus ECl118 het geen nadelige effek op die fermentasievermoë van die gis getoon nie, terwyl sensoriese en chemiese ontleding van die Chardonnay wyne 'n verbetering in aroma relatief tot die kontrole wyne getoon het, met die afwesigheid van enige afgeure.

A complete, sensitive and selective procedure was developed for gas chromatographic determination of perfluoroalkyl carboxylic acids (PFCAs, C5 - C12) in river water samples. A rapid and simple derivatization procedure was developed and optimized at first, using isobutyl chloroformate (IBCF) to convert the acids into the more volatile isobutyl esters. The second task was to find the most suitable stationary phase for separation of perfluoroalkyl carboxylic acids by GC. The retention characteristics of PFCA isobutyl esters were measured and compared on 9 different stationary phases. The physical-chemical parameters of analyte interactions with stationary phase were monitored on selected column Rtx-200MS, and these parameters were compared with a non-fluorinated homologue - octanoic acid. A sensitive GC-MS system was used with negative chemical ionization, which is suitable for the selected type of fluorinated analytes. The developed method exhibits very low limits of detection and determination of PFCA isobutyl esters: 0.05 - 9.7 ng mL-1 (LOD) and 0.16 - 32.2 ng mL-1 (LOQ). An optimum pre-concentration technique was found for real water samples, where SPE SupelTM-Select HLB cartridges were used. In these cartridges, PFCAs were captured as ion- pairs with enrichment factor of 400. The recoveries of...

This study evaluated the potential of the aerobic Mycobacterium strain JS6O to grow on a variety of organic acid substrates, and the possible effects an organic acid would have on the degradation rate of vinyl chloride (VC). A series of batch growth tests were designed to determine the time it took to consume the substrate and the overall increase in biomass. Strain JS6O was found capable of growth on acetate, propionate, and butyrate, but could not grow on formate or lactate. Acetate was chosen for further study because strain JS6O consumed acetate the most rapidly of all the organic acids tested, and acetate is a common product of fermentation reactions in the subsurface. Strain JS6O was confirmed to grow on both ethylene and vinyl chloride as the sole carbon and energy source. Comparatively, strain JS6O's rate of growth on VC is much slower than that of ethylene. With acetate as an augmenting growth substrate, ethylene and VC utilization rates increased by 30% and 48%, respectively. Since acetate and VC are often found together in contaminated chlorinated ethene plumes, this makes a strong case for natural attenuation of VC by strain JS6O. A series of kinetic tests were implemented to determine the K[subscript s] and k[subscript max] of strain JS6O for ethylene, VC, and c-DCE. The K[subscript s] and k[subscript max] for ethylene determined through NLSR methods was similar to the values published in Coleman et al. (2002), supporting the maintenance of a pure culture throughout the experimental work. When strain JS6O was exposed to the isomers of DCE (trans-1,2-dichloroethylene (t-DCE), cis-1,2-dichloroethylene (c-DCE), and 1,1-dichloroethylene (1,1-DCE)) the cells were unable to grow on these compounds. However, when growing on acetate, strain JS6O cometabolized c-DCE and t-DCE, but not 1,1-DCE, with c-DCE transformed more rapidly than t-DCE. Transformation of c-DCE was also observed with growth on VC and ethylene. The presence of c-DCE was shown to partially inhibit VC degradation, but had no effect on ethylene degradation. The cometabolism results with acetate further indicate that strain JS6O is a good candidate for natural attenuation of multiple chlorinated ethenes in the subsurface. / Graduation date: 2006

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (Ph.D.) in Food and Nutrition Sciences--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 66-76).

Bio-conversion of agricultural wastes provides a viable solution to multiple environmental problems as well as production of natural products. Apple processing for manufacturing juice, pies and sauce results in significant volumes of underutilized by-products. This study aims to optimize the method for producing fermentable sugars from apple processing by-products. The conditions required for pre-treatment, polyphenol removal and enzymatic hydrolysis were optimized. The optimized conditions for dilute sulfuric acid-based hydrothermal pre-treatment were acid concentration of 1.5% (w/v) at 91 oC for 16 min. The final yield of 12.7% fermentable sugars (glucose, fructose and galacturonic acid) was obtained after multistep hydrolysis using commercial cellulase, pectinase and ?-glucosidase at 9, 38 and 8 enzyme units/g FW, respectively. The other optimum conditions were temperature of 40 oC, pH at 4.0 and 24 h of reaction time. These fermentable sugars can further be converted into bio-ethanol and organic acids using specific yeast and bacteria.