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The rapid development of the bioethanol industry globally demonstrates the importance of bioethanol as an alternate energy source to the depleting fossil fuels. To decrease costs and avoid undue pressure on the global food supply, the renewable lignocelluloses appear to be a better substrate for bioethanol production compared to others being investigated. This study investigated the conversion of lignocellulosic material, sugarcane bagasse, to ethanol by the use of Zymomonas mobilis and Pichia stipitis. The investigation of fermentation characteristics of the two strains revealed that their performance on the ethanol production was closely related to the viable cell concentration in the medium. The increase of inoculum size to five fold resulted in an increase in the system co-efficiency to 2.2 fold and 5.2 fold respectively for Z. mobilis and P. stipitis. A theoretical value de (the cell instantaneous ethanol production rate) was introduced to describe the ethanol productivity based on biomass. System co-efficiency proved to be only affected by the viable cell concentration (xC) and de, regardless of ethanol re-assimilation. Immobilized culture of Z. mobilis and P. stipitis showed distinct differences in their characteristics. The bacterium acclimatized to the interior of gel beads; the biomass concentration within the beads increased greater than 10 fold during the reuse of the beads, resulting in an improved fermentation performance. The immobilized P. stipitis gave a similar system co-efficiency level of approximately 0.5 g/l/h under different culture conditions; cell growth in the medium was considerably more vigorous compared to that within the beads. P. stipitis sole-culture on the glucose/xylose medium with a high inoculum size showed a comparable fermentation efficiency with the best result of the co-culture processes. Fermentation of 50.0 g/l of sugar mixture (30.0 g/l glucose and 20.0 g/l xylose) was completed in 20 h with an ethanol yield of 0.44 g/g. No catabolite repression due to glucose was observed for the xylose assimilation. Co-culture of immobilized Z. mobilis and free cells of P. stipitis proved to be the best fermentation scheme on the glucose/xylose sugar mixture co-fermentation. The removal of Z. mobilis after the utilization of glucose improved the stability of the performance. The best result showed that 50.0 g/l sugars were fully converted to ethanol within 19 h, giving an ethanol yield of 0.49 g/g, which is 96% of the theoretical rate. When co-cultured, viable cells of Z. mobilis inhibited the cell activity of P. stipitis, and were capable of growing to high concentration levels without an appropriate carbon source. Acid and enzymatic hydrolysates of sugarcane bagasse showed similar fermentability, but the hydrolysate without overliming significantly inhibited both cell growth and ethanol production of P. stipitis. The co-culture process on the hydrolysate medium successfully utilized 53.56 g/l sugars (32.14 g/l glucose and 21.42 g/l xylose) in 26 h with a yield of 0.43 g/g; this value further increased to 0.49 g/g when ethanol peaked at 40 h. A high cell density proved to be an effective method to improve the system co-efficiency for ethanol production. For the fermentation processes on the sugar medium, results achieved in this study, 10.54 g/l/h for Z. mobilis free cell culture on glucose, 0.755 g/l/h for P. stipitis free cell culture on xylose, 1.092 g/l/h for P. stipites free cell culture on the glucose/xylose mixture and 1.277 g/l/h for glucose/xylose co-fermentation using co-culture, are higher than the best values reported in the literature in batch culture. In the fermentation of the hydrolysate, the system co-efficiency of 0.879 g/l/h achieved with co-culture is comparable to the best values reported for the fermentation of lignocellulosic hydrolysates. / Master of Science (Hons)

Submitted in fulfillment of the requirements Of the degree of Masters in applied science: Biotechnology, Durban University of Technology, Durban, South Africa, 2016. / Anaerobic dark fermentation is an efficient biological process to produce hydrogen from waste material. In South Africa, this technology has not been explored adequately to extract energy from biological wastes. Within the KwaZulu Natal region of South Africa, the sugar industry is a prominent venture that produces mass quantities of sugarcane bagasse amongst other waste products. This by-product can be an ideal source of substrate for biohydrogen generation. In this study, sugarcane bagasse was used as the main substrate for biohydrogen production by anaerobic fermentation using sewage sludge as the inoculum. Different pre-treatment methods were employed to maximize the release of fermentable sugars from the lignocellulosic biomass. Among the different pre-treatment methods employed, the maximum sugar yield (294.4 mg/g) was achieved with 0.25% H2SO4 for 60 minutes at 121°C. Prior to inoculation, the sewage sludge was also subjected to thermal pre-treatment to eliminate methanogens. Thermal pre-treatment of inoculum sludge for 30 min was effective in eliminating methanogens. Fluorescence in situ hybridization was used to positively identify the hydrogen producing bacteria present before and after treatment. The pre-treated substrate and inoculum was integrated into a dark fermentation process to further optimize the effect of pH, substrate to biomass, iron and magnetite nanoparticles on hydrogen production. The maximum hydrogen production (1.2 mol/mol glucose) was achieved at a pH range of 5-6, a substrate to biomass ratio of 3.5, and iron and magnetite nanoparticle concentration of 200 mg/L. Microbial analysis using quantitative polymerase chain reaction has confirmed the dominance of Clostridium spp. in the reactor. The highest hydrogenase gene activity (number of copies of hydrogenase gene expression/ng DNA) was recorded in the reactor supplemented with magnetite nanoparticles with lowest being in the raw sludge. There was a direct positive correlation between the hydrogenase gene copy number and the hydrogen yield obtained at different reactor conditions. Scanning electron microscopy was a useful to visually analyse the interaction of microorganisms with activated sludge. This study highlights the significance of anaerobic microorganisms from waste sludge being able to utilize agricultural waste material to produce biohydrogen which could be further scaled up for continuous hydrogen production. In addition, statistical tools used to predict the possible sugar (Design of experiments) and hydrogen yields (Gompertz model) produced would be helpful in saving time during full-scale operation of biohydrogen producing reactors. / M

Submitted in fulfillment of the academic requirements for the Masters in Applied Sciences (Chemistry), Durban University of Technology, Durban, South Africa, 2016. / The main aim of this work was to produce levulinic acid (LA) from sugarcane bagasse (SB) and since there is approximately 3 000 000 tons of bagasse produced per annum by 16 factories that are located on the north coast of Kwa-Zulu Natal, after the extraction of sugar. For this project fructose was firstly used for the production of LA, thereafter SB was used to produce LA. Cellulose was extracted from sugarcane bagasse using two types of pre-treatments namely (i) acid-alkali pre-treatment and (ii) liquid hot water (LHW). In the latter method acid hydrolysis and enzymatic hydrolysis was used to hydrolyse cellulose to glucose. For the acid-alkali pre-treatment work, two types of bagasse was used namely (i) mill-run bagasse and (ii) depithed bagasse and for the LHW a mill-run bagasse (pellets form) was used. In both pre-treatment methods the glucose solution was then acid catalysed by two different acids (i) an environment friendly acid, methanesulfonic acid (MSA) and (ii) sulphuric acid, producing levulinic acid. The results showed that MSA and sulphuric acid produced almost the same yield of LA but, MSA is preferred for the production of LA since it is less toxic and less corrosive than sulphuric acid. / M

Thesis (M.S. (Hons.))-- University of Western Sydney, 2008. / A thesis sumitted to the University of Western Sydney in fulfilment of the requirements for the degree of Masters of Science (Honours), School of Natural Sciences, College of Health and Science. Includes bibliography.

Orientador: Alcides Lopes Leão / Coorientador: Ivana Cesarino / Banca: Carla dos Santos Riccardi / Banca: Lucia Helena Innocentini Mei / Resumo: As preocupações ambientais e o esgotamento dos combustíveis fósseis resultaram em um interesse crescente em materiais ambientalmente amigáveis, à base de polímeros naturais. Esforços estão sendo feitos para introduzir a lignina em compostos plásticos, tais como polipropileno, com o objetivo de produzir materiais com boas características mecânicas e, ao mesmo tempo, ambientalmente amigáveis. A lignina é uma matéria-prima amplamente disponível na natureza, que contém alta densidade de compostos aromáticos, os quais são atualmente, em sua maioria, derivados do petróleo. No entanto, grande parte da lignina é utilizada para geração de energia e pode ser um potencial agente poluidor se não destinada de forma adequada. Desse modo, é importante encontrar uma maneira econômica de converter esse polímero natural em materiais de alto valor agregado, como compósitos com alto desempenho mecânico e térmico. Neste estudo, compósitos de polipropileno e de lignina kraft de pinus (LKI) e de bagaço de cana (LBC) foram submetidos à extrusão, e os corpos de prova foram produzidos pelo processo de injeção. Os materiais produzidos foram analisados quanto às propriedades mecânicas, térmicas (TGA, DSC, HDT), química (FTIR), reológica (índice de fluidez) e morfológica (MEV). Os objetivos desta pesquisa foram desenvolver novos compósitos de polipropileno contendo lignina e proporcionar propriedades mecânicas comparáveis aos polipropilenos comerciais, além de obter compósito com alto grau de afinidade e... / Abstract : Environmental concerns and the depletion of fossil fuels resulted in a growing interest in environmentally friendly materials based on natural polymers. Efforts are being made to introduce the lignin in plastic composites such as polypropylene, in order to produce materials with good mechanical characteristics and at the same time environmentally friendly. Lignin is a biopolymer widely available which contains high density of aromatic compounds. Nowadays, the aromatic compounds are almost exclusively derived from petroleum. However, the lignin is used mainly to generate energy and can be a pollution potential if not properly treated. Lignin, however, can improve the performance of composites. Moreover, it is important to find an economical way to convert lignin into high value-added materials. In this study, blends of polypropylene, pine kraft lignin (LKI) and sugar cane bagasse lignin (LBC) were subjected to extrusion and the specimens were produced by injection process. The materials produced were analyzed for their mechanical, thermal (TGA, DSC, HDT), chemical (FTIR), rheological (melt flow index) and morphological (SEM) properties. The objective of this research was to develop new lignin-based polypropylene composite with mechanical properties comparable to commercial polypropylene. The results showed that the incorporation of lignin in polypropylene matrix resulted in composites, in general, with properties suitable for various industrial segments, especially those in which mechanical and thermal properties are crucial, such as the replacement of engineering plastics and polypropylene mineral ... / Mestre