The launch of national and international initiatives to reduce pollution, reliance on fossil fuels and increase the beneficiation of agricultural wastes has prompted research into sugar monomer production from lignocellulosic wastes. These sugars can subsequently be used in the production of biofuels and environmentally degradable plastics. This study investigated the use of synergistic combinations of commercial and pure enzymes to lower enzyme costs and loadings, while increasing enzyme activity in the hydrolysis of agricultural waste. Pineapple pomace was selected due to its current underutilisation and the substantial quantities of it produced annually, as a by-product of pineapple canning. One of the primary costs in beneficiating agricultural wastes, such as pineapple pomace, is the high cost of enzyme solutions used to generate reducing sugars. This can be lowered through the use of synergistic combinations of enzymes. Studies related to the inclusion of hemicellulose degrading enzymes with commercial enzyme solutions have been limited and investigation of these solutions in select combinations, together with pineapple pomace substrate, allows for novel research. The use of synergistic combinations of purified cellulosomal enzymes has previously been shown to be effective at releasing reducing sugars from agricultural wastes. For the present study, MannanaseA and XylanaseA from Clostridium cellulovorans were heterologously expressed in Escherichia coli BL21 (DE3) cells and purified with immobilised metal affinity chromatography. These enzymes, in addition to two commercially available enzyme solutions (Celluclast 1.5L® and Pectinex® 3XL), were assayed on defined polysaccharides that are present in pineapple pomace to determine their substrate specificities. The degree(s) of synergy and specific activities of selected combinations of these enzymes were tested under both simultaneous and sequential conditions. It was observed that several synergistic combinations of enzyme solutions in select ratios, such as C20P60X20 (20% cellulose, 60% pectinase and 20% xylanse), C20P40X40 (20% cellulose, 40% pectinase and 40% xylanase) and C20P80 (20% cellulose, 80% pectinase) with pineapple pomace could both decrease the protein loading, while raising the level of activity compared to individual enzyme solutions. The highest quantity of reducing sugars to protein weight used on pineapple pomace was recorded at 3, 9 and 18 hours with combinations of Pectinex® 3XL and Celluclast 1.5L®, but for 27 h it was combinations of both these commercial solutions with XynA. The contribution of XynA was significant as C20P60X20 displayed the second highest reducing sugar production of 1.521 mg/mL, at 36 h from 12.875 μg/mL of protein, which was the second lowest protein loading. It was also shown that certain enzyme combinations, such as Pectinex® 3XL, Celluclast 1.5L® and XynA, did not generate synergy when combined in solution at the initial stages of hydrolysis, and instead generated a form of competition called anti-synergy. This was due to Pectinex® 3XL which had anti-synergy relationships in select combinations with the other enzyme solutions assayed. It was also observed that the degree of synergy and specific activity for a combination changed over time. Some solutions displayed the highest levels of synergy at the commencement of hydrolysis, namely Celluclast 1.5L®, ManA and XynA. Other combinations exhibited the highest levels of synergy at the end of the assay period, such as Pectinex® 3XL and Celluclast 1.5L®. Whether greater synergy was generated at the start or end of hydrolysis was a function of the stability of the enzymes in solution and whether enzyme activity increased substrate accessibility or generated competition between enzymes in solution. Sequential synergy studies demonstrated an anti-synergy relationship between Pectinex® 3XL and XynA or ManA, as well as Pectinex® 3 XL and Celluclast 1.5L®. It was found that under sequential synergy conditions with Pectinex® 3 XL, XynA and ManA, that anti-synergy could be negated and high degrees of synergy attained when the enzymes were added in specific loading orders and not inhibited by the presence of other active enzymes. The importance of loading order was demonstrated under sequential synergy conditions when XynA was added before ManA followed by Pectinex® 3 XL, which increased the activity and synergy of the solution by 50%. This equates to a 60% increase in reducing sugar release from the same concentrations of enzymes and emphasises the importance of removing anti-synergy relationships from combinations of enzymes. It can be concluded that a C20P60X20 combination (based on activity) can both synergistically increase the reducing sugar production and lower the protein loading required for pineapple pomace hydrolysis. This study also highlights the importance of reducing anti-synergy in customised enzyme cocktails and how sequential synergy can demonstrate the order in which a lignocellulosic waste is degraded.

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This thesis deals with description of preparation and use of monomers and copolymers for gel polymer electrolytes usable in electrochemical power sources. This thesis is divided in theoretical and experimental part. The theoretical part describes electrolytes focused on gel polymer electrolytes, measuring methods and materials used for experiments. The experimental part deals with calculation of composition of polymer electrolytes, method of preparation and evaluation of measured results. The method of applying GPE to a negative LTO electrode and a positive NMC electrode is described too. Linear Sweep Voltammetry (LSV) and Potentiostatic Electrochemical Impedance Spectroscopy (PEIS), Cyclic Voltammetry (CV) and Galvanostatic Cycling with Potential Limitation (GCPL) were chosen for measurement of properties.

Thousand of new substances with unknown environmental effect are produced and used daily. Many of them are deliberately or by negligence released and deposited into the environment where they could undergo different transport and degradation mechanisms. They are able to affect different types of organisms, as well as humans. For this reason, the awareness of the problems, associated with pollution of all environmental compartments is growing. The environmental impact of monomer formaldehyde resins, which are produced for commercial use, on the environment were studied in this research. For the purposes of ecotoxicological evaluation samples of melamine-formaldehyde and urea-formaldehyde resin were chosen and three toxicity tests were run: acute test with measurement of inhibition of the mobility of Daphnia magna, the acute test with luminescent bacteria Vibrio fischeri and acute test with measurement of inhibition of oxygen consumption by activated sludge. For more comprehensive assessment of the impact of these substances on the environment, biodegradability was also determined. Both tested substances showed minor hazardous impact to testing organisms and it can be concluded, that these substances should not present a significant risk to the environment.

No description available.

Polyesters are an important class of polymers in many applications ranging from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications, such as lightweight strength materials in construction, electronics, and automotive parts. Poly(ethylene terephthalate) (PET), a semicrystalline aromatic polyester, is commercially the most common and widely used polyester. However, the inability to reuse polyesters such as PET over multiple reprocessing cycles in the same application remains a challenge due to the susceptibility of the polymer to thermal, hydrolytic, and oxidative degradation during melt processing. The various degradation modes result in a drop in molecular weight, loss of key physical properties, and release of volatile compounds. Furthermore, the vast issue of plastic accumulation and pollution in diverse ecosystems, landfills, and waste streams underscores the burgeoning need to create a closed loop—responsible materials management from the cradle to the grave—through these materials' continual reuse and recycling. Additionally, most feedstock monomers used in polyester synthesis primarily come from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment, so finding alternative sources for polyester monomers is paramount. This dissertation addresses key polyester challenges by designing and synthesizing alicyclic polyesters. First, we synthesized a series of alicyclic polyesters using various ratios of two regioisomers of a previously unexplored alicyclic monomer, bicyclohexyldimethanol (BCD). We learned from this alicyclic polyester series that we could tailor properties such as morphology and elongation while raising the glass transition temperatures (Tg) and lower melting temperatures (Tm) of the polymers based on the regioisomer composition. Furthermore, the regioisomer that led to polymers with semicrystalline morphologies inspired us to apply it to PET as a copolymer, with the goal of increasing PET's stability under melt processing conditions by lowering Tm. Next, we synthesized a series of alicyclic copolyesters with different BCD compositions in the polymer. The results showed that the presence of the alicyclic rings of BCD lowers the melting temperature and enhances the stability of the polymer in the melt compared to PET. These results directed us toward synergistically combining the benefits of alicyclic monomers with sustainable biobased monomers to enhance polyester properties, thereby decoupling fossil fuels from polymer feedstock production. Accordingly, we explored naturally ubiquitous, structurally diverse, and chemically modifiable terpenes present in the resin exudate of conifers. Specifically, we derived alicyclic diacid and diol monomers from the terpene verbenone and used them to synthesize a series of biobased alicyclic polyesters. The polymer series exhibited a range of morphologies, Tg's, as well as enhanced stabilities. The semicrystalline composition exhibited higher Tg and slightly lower Tm than PET while possessing exceptional stability in the melt over PET. / Doctor of Philosophy / Polyesters are important materials widely used today. They are very large molecules composed of a basic chemical unit linked together in a repeating fashion to make a long chain. The nature of the links between the basic units is referred to as an ester link, and materials are described as polyester when the number of these links is large. The applications of polyesters range from common-use objects—such as packaging containers, clothing, and upholstery—to more advanced applications in construction, transportation, and defense—such as body armor, seat belts, and lightweight strength materials and coatings in construction. The properties of its basic structural unit enable the wide breadth of applications of polyesters. A significant challenge that faces polyesters is the inability to reuse the material in the same application multiple times. The material must be reprocessed by melting at high temperatures to be reused. This melting breaks down the polyester chain, weakening the material and rendering it unsuitable for continued use. The need to reuse polyesters is an important area of concern because of the growing problem of plastic accumulation and pollution in diverse ecosystems and landfills. If these materials are continually reused, they will not accumulate as environmental waste. Furthermore, the basic starting unit that makes up polyesters largely comes from fossil fuels. Fossil fuel extraction processes release gases and particulate matter that adversely affect health, climate, and the environment. The issues of polyester breakdown in the melt and fossil fuel use to make the polyester can be addressed in two ways. First, reinforcing the polyester through changes to the basic structural unit can prevent the breakdown of the material when melted, thereby enabling its reuse over multiple cycles. Second, reducing the dependence on fossil fuels to make the basic structural unit of the polyester can be accomplished by using more renewable biobased sources instead. This dissertation seeks to address these two challenges. In the first approach, we investigate the effect of using a special cyclic structure in the polyester make-up to reinforce its stability when melted and enable its reuse. Next, we use plant materials to derive these unique structures to reduce the dependence on fossil fuels and mitigate the environmental, climate, and health effects of fossil fuel use.

An introduction is given to the background theory and scientific literature of the major subject areas of interest in this thesis, namely the chemistry of free radical and anionic polymerisation, molecular weight control in each type of polymerisation, polymerisation reactors, computer simulation of polymerisation processes and polymer characterisation by gel permeation chromatography. A novel computer model has been devised, based on the analysis of the polymerisation process in terms of the reaction extent of each reactant and the use of generation functions to describe the concentration of living and dead polymeric species, for the free radical, solution polymerisation of methylmethacrylate in a CSTR. Both heat and mass balance expressions have been described. Conversion, Mn and Mw were monitored. To test the model a reactor was designed and constructed. A detailed description of the reactor and the experimental conditions used for the validation of the model are given. The results of these studies are presented and excellent agreement is shown between model predictions and experiments up to 30% conversion for Mn w and % conversion. A similar study is described for the anionic polymerisation of styrene in tetrahydrofuran as solvent, in a CSTR. In this work the computer model becomes 'stiff' when realistic rate constants are introduced in the kinetic expressions. Experimental difficulties were encountered in obtaining reproducible results in the anionic work. A new approach of using 'scavengers' as protecting agents for the living chains is described. A scavenger was successfully employed in the preparation of block copolymers using a tubular reactor. Block copolymerisation, in addition to providing a means of checking the number of the 'living' chains inside the reactor, is of interest in its own right. All the experimental findings are discussed in relation to the currently accepted views found in the scientific literature.

No description available.

No description available.

No description available.