Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 112-121).

Includes bibliographical references (p. 93-95).

Orientador: Telma Teixeira Franco / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química. / Made available in DSpace on 2018-08-20T23:25:42Z (GMT). No. of bitstreams: 1 Vidotti_AnnamariaDoriaSouza_M.pdf: 2006384 bytes, checksum: cae5b036525c63c6b285732d6f067476 (MD5) Previous issue date: 2012 / Resumo: Rotas heterotróficas a partir de microalgas apresentam ganhos significativos de produtividade em biomassa quando comparadas aos sistemas fotossintéticos convencionais, estando a glicose e o acetato entre as fontes de carbono mais comuns desse tipo de cultivo. Neste contexto, o objetivo do presente estudo foi desenvolver cultivos heterotróficos axênicos para a microalga Chlorella vulgaris, utilizando a glicose e o acetato de sódio como fontes de carbono exógeno, avaliando o efeito de inibição por substrato, bem como a modelagem dos perfis de crescimento de biomassa e consumo de substrato. A influência da concentração inicial de substrato na produção de biomassa pela C. vulgaris foi investigada, sendo obtidas cinéticas de crescimento do microrganismo submetido a concentrações iniciais de glicose entre 2 e 100 g.L-1, e de acetato de sódio, entre 2 e 20 g.L-1. Foi verificado que a concentração inicial de substrato influenciou significativamente o rendimento celular final, e que apesar dos dois substratos avaliados terem se mostrado fontes de carbono adequadas, a utilização de maiores concentrações iniciais, 100 g.L-1 e 20 g.L-1 de glicose e acetato de sódio, respectivamente, acarretaram na inibição do crescimento da C. vulgaris. Os modelos matemáticos testados representaram adequadamente a cinética de inibição, sendo que os resultados indicaram que a concentração ótima de glicose para o cultivo heterotrófico da C. vulgaris foi 5,8 ± 0,3 g.L-1 e de acetato de sódio foi 3,5 ± 0,2 g.L-1. Os resultados evidenciaram ainda que os procedimentos adotados no controle da contaminação foram efetivos para a manutenção da axenia dos cultivos. Pela comparação do desempenho cinético, foi constatada uma superioridade (maior que 50%) da glicose como substrato em comparação com o acetato de sódio. E no estudo de aumento de produtividade de biomassa para cultivos com acetato, foi obtido um aumento de 70% neste parâmetro com a batelada alimentada, e uma concentração final de biomassa 2,5 vezes maior do que a melhor concentração celular alcançada em shaker / Abstract: Heterotrophic microalgal routes show significant productivity gains in biomass when compared with the conventional photosynthetic systems, being glucose and acetate among the most common carbon sources such in this kind of cultivation. In this context the objective of this study was to develop axenic cultures for heterotrophic microalgae Chlorella vulgaris using glucose and sodium acetate as exogenous carbon sources, evaluating the effect of substrate inhibition, as well as the modeling of the biomass growth profiles and substrate consumption. The influence of the initial substrate concentration in the biomass production by C. vulgaris was investigated, being obtained kinetics growth of the microorganism subjected to initial glucose concentrations between 2 and 100 g/L-1, and sodium acetate between 2 and 20 g/L-1. It was found that the initial substrate concentration significantly affected the final cell yield and that although the two have been shown to be tested substrates carbon sources suitable, the use of larger initial concentrations of 100 and 20 g.L-1 of glucose and sodium acetate, respectively, resulted in inhibiting the growth of C. vulgaris. The mathematical models tested represented adequately the kinetics of inhibition, and the results indicated that the optimum concentration of glucose to heterotrophic cultivation of C. vulgaris is 5,8 ± 0,3 g.L-1 and for the sodium acetate this value is 3,5 ± 0,2 g.L-1. The results showed also that the procedures used in contamination control have been effective for the maintenance of the axenic of crops. By comparing the performance, kinetic superiority was observed (more than 50%) for the systems using glucose as substrate in comparison with the systems using sodium acetate. Finally, in the study of increasing of productivity of biomass for crops with acetate, was obtained a 70% increase in this parameter with the fed batch operation, and a final biomass concentration 2.5 times greater than the best cell concentration achieved in shake flasks / Mestrado / Desenvolvimento de Processos Químicos / Mestra em Engenharia Química

No description available.

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

The world of energy is changing. With rising energy costs and concerns over the supply of energy materials, more research is being conducted into alternative sources of fuel and microalgae is one of the sources being researched, although much research had been conducted on it as a part of the Aquatic Species Program from the 1970s to the early 1990s. With the emergence of microalgae as a source of alternative energy, the need for an economic analysis of microalgae has arisen. This research studies the economic feasibility of the design and operation of a microalgae production facility in two Texas locations (Pecos and Corpus Christi) and in southeastern New Mexico using a stochastic simulation model. It examines the production levels needed for the facility to be profitable and also some facility designs necessary for that profitability. It also measures several annual financial indicators so that potential investors have some estimates of the future profitability of the microalgae industry. The results show that for microalgae to become a viable commercial operation, production must be improved beyond the current levels and the levels suggested by the literature. Production needs to be at least 0.8 g/L/day with 40 percent oil content and 24 inches of water depth. Production must be improved through increasing growth rates and oil contents at greater water depths. Production can be improved through nutrient and carbon dioxide usage, two elements that are being heavily researched. Water usage will become a major focus because of the limited resources and the quantities necessary to operate a commercial-scale facility. With the necessary improvements in technology and research, microalgae could prove to be a viable source of alternative energy.

Abstract This study is to elucidate the possibility of DNA fragment identification method in the forensic detection of marine microalgae (Chlorella sp. and Nannochloropsis oculata) from human (Homo sapiens) body by 3% agarose gel electrophoresis of amplification fragments via PCR-amplified ribosomal gene small subunit (SSU) rDNA molecules as primers, which are specific nucleotide segments on conserved regions (18S rDNA region (NS1-NS2 primers))on SSU rDNA and on variable regions (internal transcribed spacer (ITS) regions (primer 2/primer 5 for ITS1 region and primer 3/primer 4 for ITS2 region)). NS1-NS2-amplified PCR fragments are 550 bp for C. sp., 550 bp for N. oculata and 600 bp for human. ITS1-amplified PCR fragments are 1, 2 and 4 bands for C. sp. (350 bp), N. oculata (400 and 450 bp) and human (300, 450, 500 and 580 bp), respectively, while ITS2-amplified PCR fragments are 1, 2 and 1 bands for C. sp. (430 bp), N. oculata (430 and 600 bp) and human (400 bp), respectively. By using human-specific primers (AmpFlSTR® Profilerä PCR Amplification Kit), only human can be identified in the sample containing C. sp., N. oculata and human DNA, whereas C. sp. and N. oculata can not be detected, indicating the prevention of algal interference in human-specific primer-PCR procedures via AmpFlSTR® Profilerä PCR Amplification Kit. Detection limits of C. sp. and N. oculata DNA were 50 and 10 pg, respectively. The results of present investigation show that algae can be distinguished from human by NS1-NS2-amplified PCR fragments but not between C. sp. and N. oculata, while C. sp., N. oculata and human can be distinguished by ITS1- or ITS2-amplified PCR fragments. Evidently, the specificity of DNA segments in marine microalgal and human DNA provides the base for investigation of cause of death in drowning case in the marine environment.

Ageing is a progressive impairment of function causing decreased defense against environmental challenges and increased risk of many diseases. The development of ageing and ageing-related diseases might be attenuated by nutrients such as carotenoids and polyunsaturated fatty acids. In the present study, for the first time, two nutrient-rich marine microalgae, namely Haematococcus pluvialis (HP) and Schizochytrium mangrovei (SM) were studied for their anti-ageing effects both in vitro and in vivo. Results of nutritional profile analysis confirmed that HP is rich in astaxanthin (AX) (978.9 μg/g). Using rat adrenal medulla pheochromocytoma (PC12) cells as an in vitro model, AX exhibited significant protective effects against oxidative stress induced by H2O2 or amyloid β-peptide (Aβ). To testify whether AX conveys such effects to HP, the anti-ageing property of HP was subsequently investigated on Drosophila melanogaster. In the group of SODn108 mutant fruit flies, lifespan elongation effect was observed, where HP may play as a complement of the defective endogenous antioxidant system to extend the lifespan and ameliorate the age-related decline of locomotor function. On the other hand, a long-term intake of HP (20 mg/mL) induced early mortality of wild type fruit flies, which was associated with the decreased enzymatic activities of CuZn-superoxide dismutase (SOD1) and Mn-superoxide dismutase (SOD2) as well as mRNA down-regulation of SOD1, SOD2, and Catalase (CAT). Further study showed that HP supplementation contributed to the defense of wild type OR fruit flies against chronic but not intensive oxidative stress. The observed ‘bifacial effect’ could be resulted from ‘hormesis’ responses, suggesting the therapeutic instead of the preventive potential of HP against ageing-related diseases. Another microalga SM was found to contain abundant docosahexaenoic acid (DHA) (53 mg/g). The in vitro studies showed that SM failed to protect PC12 cells under H2O2-induced oxidative stress due to its poor anti-oxidative activity. However, from in vivo studies, the SM supplementation significantly extended the lifespan of both wild type and SODn108 mutant fruit flies and ameliorated the age-related decline of locomotor function. Further studies revealed that the observed activities were associated with the mRNA up-regulation of endogenous stress-defending genes such as SOD1 and SOD2, as well as the down-regulation of methuselah (MTH) gene. It has been proposed that antioxidants may protect DHA against oxidative damage. To determine whether there is a synergistic effect for HP and SM, a mixture of these two algal samples was evaluated for its effects on the lifespan of D. melanogaster. Results showed that the wild type fruit flies fed with the mixture had no elevated survival rate, tentatively suggesting that the increased nutritional complexity may trigger elevated metabolic rate and lead to shortened lifespan. In conclusion, results of the present study demonstrated the anti-ageing properties of nutrient-rich microalgae both in vitro and in vivo, suggesting SM possesses the potential to be used as a preventive diet supplementation, while HP may be a suitable candidate as therapeutic agents. Based on these findings, the health benefits of nutrient-rich microalgae for the elderly as well as patients with ageing-related diseases were proposed. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Heterotrophic fermentation is a widely used means in the biotechnological, pharmaceutical and food industries for the large-scale production of desired products. However, two problems are often encountered during its application: the limitation of dissolved oxygen level in high cell density cultures, and the high cost of the carbon substrates for supporting growth. In this study these issues are solved through the expression of the hemoglobin gene from Vitreoscilla (VHb), which is known to be able to facilitate intracellular oxygen delivery, and the use of low-cost waste carbon sources for fermentation, respectively. Aurantiochytrium sp. MP4 (non-pigmented) and SK4 (pigmented) were chosen for the present study because of members of this genus has been consideredas potential producers of biodiesel as well asastaxanthin in recent years. VHb gene was successfully expressed in Aurantiochytrium sp. MP4 and SK4, and three transformants of MP4 (TMP4-VHb1, TMP4-VHb10 and TMP4-VHb24) and one transformant of SK4 (TSK4-VHb2) were obtained, respectively. TMP4-VHb24 andTSK4-VHb2 were selected for further study. It was found that VHb expression led to higher maximum biomass under microaerobic conditions and improved oxygen utilization in high cell density fermentation. Moreover, under aerobic conditions, there was an increase of total cellular fatty acid content by 10% and 44%forTMP4-VHb24 and TSK4-VHb2,respectively, and the pigmented strain TSK4-VHb2 produced 9-fold higher astaxanthin content than the control (i.e., SK4), showing that heterologous expression of VHb as a promising approach to improving growth or secondary metabolite biosynthesis in the fermentation process. The mechanism underlying the effects of VHb expression was further investigated using TMP4-VHb24. Expression of VHb led to a higher adenylate energy charge and hence higher metabolically available energy in the cells, especially at the late exponential phase. In addition, VHb expression promoted the rate of consumption of NADH during the period from the late exponential phase to the stationary phase, in which NADH carried electrons from the oxidation of carbon substrates in energy pathways for ATP synthesis. VHb also increased the resistance of the host cells to nitrosative stress, but not to oxidative stress. In terms of utilization of cheap carbon substrates, TMP4-VHb24 and TSK4-VHb2were found to grow well on the waste carbon sources including cane molasses and crude glycerol. Under such conditions, however, the contents of fatty acids and astaxanthin were generally lowered compared to the use of glucose-based media. Therefore, the growth and product synthesis in TMP4-VHb24 was further optimized using the response surface methodology, and it was found to be effective. In conclusion, the expression of VHb in Aurantiochytrium sp. MP4 and SK4 was effective in relieving limitation on the growth due to low oxygen availability at high cell density cultivation, while increasing the cellular astaxanthin and fatty acid biosyntheses under aerobic conditions. Also, the VHb-expressing strains were able to utilize low-cost waste carbon sources, and the response surface methodology could be employed to optimize fermentation effectively in order to lower the cost of fermentation. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

This study investigated the extraction of lipids and β-carotene from microalgae using microemulsions as an alternative to current solvents. Type I and type IV microemulsions composed of 4% lecithin, sorbitan monooleate, PEG-6-caprylic glycerides, and ethyl caprate were able extract lipids from lyophilized microalgae better than hexane and ethyl caprate. HPLC quantified the extracted β-carotene, with type IV microemulsions extracting the most β-carotene at 0.137±0.074% (w/w) of the total microalgae biomass after an hour. The growth recovery of the microalgae after extraction was observed over 2 weeks. Variability in the data prevented definite conclusions about the ability of algae to grow after extraction. The type IV extractions consistently showed some signs of survival. After two weeks, a pale-green colour was observed in the 15min and 1h extractions. This study showed that microemulsions can successfully extract lipids from microalgae; future work would apply microemulsion formulations to live algal cells for in-situ extraction.