No description available.

Microalgae synthesize and store large volumes of lipids (potentially over 25% of dry weight) which could provide a renewable source of biodiesel. Traditional extraction techniques often produce poor lipid yields particularly from microalgae with robust cell walls. This project investigated the role of power ultrasound as a cell disruption step in lipid extraction from four microalgal species. Nile Red staining was used to assess the time when ultrasound induced increased membrane permeability in each species and lipids were extracted using an ultrasound assisted Bligh and Dyer extraction method. A 20 kHz probe system (40% amplitude, 0.086 W/cm3) caused increased lipid recovery from dry biomass in all cases; D. salina (no cell wall) from 15 to 22.5% of dry biomass after 1 minute (26% when stressed with 35 g/L NaCl). C. concordia (thin cell wall) from 7.5 to 10.5% of dry biomass after 2 minutes (27% with 25% nitrogen reduction in growth media). N. oculata (thick cell wall) from 6.5 to 10% of dry biomass after 16 minutes (31.5% when stressed with 30 g/L NaCl). The stressed cultures yield could be improved to 35% when ultrasound was combined with S070 beating beads. Chlorella sp. (thick cell wall) from 6.3 to 8.7% of dry biomass, after 16 minutes (44% was achieved when harvested at day 9 instead of 15). A Dual Frequency Reactor (16 and 20 kHz, 0.01 W/cm3) flow system with S070 beads demonstrated that high lipid extraction yields could be achieved on a larger level with N. oculata. After 4:48 minutes sonication 24% lipid recovery was achieved. This system could theoretically increase daily microalgal oil production from 3.96 to 5.76 L per day when compared to conventional techniques, at an extra production cost of only 2.9 p/litre (1.5% increase). D. salina, N. oculata and C. concordia resumed normal growth following sonication at 20 kHz after 1-20 days (8 minutes treatment for D. salina, 60 minutes treatment for N. oculata and 16 minutes treatment for C. concordia). It was found that the supernatant of sonicated D. salina and C. concordia when added to established cultures were able to boost their growth.

Algae-derived biodiesel is currently under investigation as a suitable alternative to traditional fossil-fuels. Though it possesses many favorable characteristics, algae remains prohibitively expensive to mass produce and distribute. The most economical means of growing algae are large-scale open pond raceways. These, however, suffer from low culture densities; this fact impacts the cost directly through diminished productivity, as well as indirectly by raising costs due to the necessity of dewatering low culture density raceway effluent. Algae, as a photosynthetic organism, achieves higher culture densities when sufficient light is provided. In open ponds this can be accomplished by frequently cycling algae to the raceway surface. The current work examined delta wing vortex generators as a means of instigating this cycling motion. In particular the impact of spacing and angle of attack was analyzed. These vortex generators were found to significantly increase vertical mixing when placed in a series, developing precisely the motion desired. Their impact on power requirements was also examined. Specifically it was shown that increases in spacing and decreases in angle of attack result in lower power consumption. It was demonstrated that the most efficient mixing generation is achieved by larger spacings and smaller angles of attack. The impact that these devices had on raceway turbulence as measured by dissipation rate was also investigated and compared to published values for algae growth. Raceways were found to be significantly more turbulent than standard algae environments, and adding delta wings increased these levels further.

No description available.

As the global population rises to an estimated 9.4bn by 2050, the pressure for food, fuel and freshwater will continue to increase. Current renewable energy technologies are not widely applicable to the transport sector, which requires energy dense liquid fuels that drop into our existing infrastructure. Algal biofuels promise significantly higher yields than plants, without the displacement of valuable agricultural resources and have the potential to meet the global demand for transport fuel. Fossil fuel energy is largely ‘a legacy of algal photosynthesis’, with algae accounting for ~50% of global CO2 fixation today. In addition, these curious organisms show remarkable diversity in form, behaviour and composition. Recently there has been a global resurgence of interest in microalgae as a resource of biomass and novel products. With the present level of technology, knowledge and experience in commercial scale aquaculture, the capital cost and energy investment for algal biomass production is high. Culturing, harvesting and disrupting microalgal cells account for the largest energy inputs with more positive energy balances requiring low energy designs for culture, dewatering and extraction, efficient water and nutrient recycling with minimal waste. Little is known about the variable cell wall of microalgae, which presents a formidable barrier to the extraction of microalgal products. Staining, transmission electron microscopy (TEM) and enzymatic digestion were all utilised in an attempt to visualise, digest and characterise the cell wall of stock strains of Chlorella spp. and Pseudochoricystis ellipsoidea. The presence of algaenan, a highly resistant biopolymer, rendered staining and enzymatic digestion techniques ineffective. TEM revealed that algaenan is present in the outer walls of microalgae in a variety of conformations which appeared to impart strength to cells. A preliminary investigation utilising Fusarium oxysporum f.sp. elaeidis as a novel source of enzymes for the digestion of algaenan has also been described. Methods were developed for the mutagenesis of Chlorella emersonii and P. ellipsoidea using EMS and UV with the intent of generating cell-wall mutants. Although no viable cell wall mutants were produced, a viable pale mutant of C. emersonii was recovered 5 from UV mutagenesis. Growth rates of the pale mutant were significantly slower than the wild type, yet FAME profile was largely unaffected. Fluorescence activated cell sorting (FACS) was also investigated as a means for the rapid screening of mutagenized cells for cell wall mutants. In an attempt to reduce cooling costs of closed-culture systems, temperature tolerant species of microalgae were sought by bioprospecting the thermal waters of the Roman Baths. Numerous methods for isolation and purification of microalgae from the Baths were employed, ultimately yielding seven diverse isolates including cyanobacterial, eukaryotic, filamentous and single celled species. Despite some species possessing an increased tolerance to higher temperatures, none showed marked temperature tolerance coupled with high productivity. Further improvements to the culture conditions may have improved the productivity at higher temperatures. All seven isolates were deposited to the Culture Collection of Algae and Protozoa (CCAP). A variety of extraction methods including soxhlet, beadbeating, sonication and microwaving was investigated for efficacy of extracting fatty acid methyl esters (FAMEs) from C. emersonii. Beadbeating proved most effective in the extraction of FAMEs from C. emersonii. Microwaving showed potential as a rapid method of extraction yet was coupled with degradation of FAMEs, requiring further method development to resolve this issue. Method development has been a significant component of the work described in this thesis.

Green macroalgae represent an attractive source of renewable carbon. Conversion of algal biomass to useful products requires depolymerization of the cell wall polysaccharides cellulose and ulvan. Cellulose saccharification has been widely studied and involves synergistic action of endoglucanases, exoglucanases, and β-glucosidases. The enzymatic depolymerization of ulvan has not received the same attention and additional studies are required in order to fully understand the mechanisms involved in its biodegradation. Synthetic biology offers the possibility of importing modules such as biomass-degrading systems and biofuel producing pathways from different organisms into a genetically tractable host such as Escherichia coli. In this study it was shown that E. coli expressing the glycosidase CHU2268 of Cytophaga hutchinsonii grows well on cello-oligosaccharides such as cellohexaose, and co-expression with the endoglucanase CenA of Cellulomonas fimi allows growth on untreated crystalline cellulose. Moreover, a model for ulvan utilization was built for the first time based on a polysaccharide utilization locus from the alga-associated flavobacterium Formosa agariphila. It was also shown that F. agariphila, is able to grow using biomass from the green macroalga Ulva lactuca as its sole carbon source, and enzymes with ulvanase activity are induced by the presence of this alga in the culture medium. Enzymes for ulvan depolymerization from F. agariphila, including an ulvan lyase, xylanases and rhamnosidases, were cloned using the PaperClip DNA assembly method and expressed in active form in E. coli. Furthermore, a secretion system based on the use of the Antigen 43 was successfully used to secrete an active ulvan lyase using E. coli and ribosome binding sites of different strengths were studied and used to optimize the system. These results represent a first step for the design of a microorganism capable of utilizing green macroalgal biomass for the production of biofuels and other valuable bio-products.

No description available.

No description available.

Algae are a promising new source of oil for biodiesel. They are aquatic organisms that do not require cropland, and they can produce many useful side-products for bioenergy, aquaculture, and nutraceutical production. To be cost-effective, algae need high and reliable oil productivities; however, there is still a great deal to learn about the effects of culturing conditions on algae growth rates and lipid production. These culturing conditions include light intensity, gas flow, use of CO₂, and culture volume. An extensive database of published research on algae growth rates and lipid contents under a wide variety of environmental conditions was prepared. By graphing data from 116 publications on 132 microalgae species, several key trends were identified relating to culturing parameters and algae biomass and lipid production. In addition, data from 131 publications on 128 microalgae species were graphed to look at presence of flagella, nutrient limitation, lipid productivity, and productivity tradeoffs. Moreover, cell size information was gathered for 146 species. The interactions between culture variables are complex, so it is difficult to quantify the degree to which each culture variable affects algae growth rates and lipid production. Therefore, several multivariate analyses were performed to generate a set of general and simple predictive models to assess specific growth rates, maximum lipid contents, and volumetric lipid productivities. These models were used to determine which culture parameters were significant predictors of algae growth rates and lipid production, and the contribution of each environmental parameter was quantified. In addition to models for algae in general, genera specific models were prepared for Chlorella, Isochrysis, Nannochloropsis, Phaeodactylum, and Tetraselmis. These models show high predictive capabilities, and they greatly extend the range of species-specific multiple regression models available. Furthermore, one Tetraselmis model was validated using Tetraselmis impellucida growth experiments in a large novel photobioreactor.

[pt] Com a crescente demanda – nacional e internacional – por biocombustíveis e a pressão internacional para redução da emissão de gases de efeito estufa, o Brasil teria muito a ganhar, do ponto de vista econômico e ambiental, com um aumento na eficiência e oferta de biocombustíveis. O advento da produção de biocombustíveis produzidos em fazendas de alga possibilita uma relação de simbiose com usinas de cana-de-açúcar. Tais algas se alimentam, entre outras substâncias, de dióxido de carbono, e a abundante biomassa de cana queimada em caldeiras, aliada à incidência solar privilegiada no Brasil, fazem da utilização de algas em usinas de cana uma possibilidade de conversão de emissões de gás de efeito estufa em biocombustível. Essa dissertação tem como objetivo estimar o resultado da implantação de uma fazenda de algas em uma usina de cana-de-açúcar. A usina em questão sofreu vistoria e fez-se o levantamento da produção de energia renovável e as emissões atmosféricas dos principais gases de efeito estufa (CH4, N2O e CO2), através da metodologia de Avaliação de Ciclo de Vida (ACV). A meta, a partir desta análise e com o uso de dados primário de uma empresa que instala fazendas de alga, é estimar o acréscimo de biocombustível gerado por algas e o decréscimo das emissões de GEE no processo produtivo. Os resultados obtidos na Usina Estudada mostram que caso a mesma implantasse uma fazenda de algas em seu parque industrial, sua eficiência energética na produção de energia através do etanol quase triplicaria ao passo em que emitiria quatro vezes menos poluentes em sua cadeia de produção. Caso a usina optasse por gerar exclusivamente Biodiesel, produziria Biodiesel (B100) para 19 anos de subsistência com um combustível 78,4 por cento menos poluente em termos de GEE. Aproximações mostram que caso a totalidade da lavoura de cana implante fazendas de algas no Brasil, apenas o Biodiesel gerado neste processo seria equivalente à quase 70 por cento da produção Brasileira de diesel de 2012. / [en] With the demand for Biofuels growing – in Brazil and abroad – and with worldwide efforts to reduce greenhouse gas (GHG) emissions, Brazil would have much to gain, from an environmental and economic point of view, from increasing the efficiency and offer of biofuels. The advent of biofuels produced in algae farms enabled a symbiotic relationship with ethanol plants. Such algae feeds off, among other things, Carbon Dioxide, and the abundant biomass burned in ethanol plants boilers, along with Brazil s privileged solar incidence, and this regime permits such farms to convert GHG to biofuel. The objective of this study was to investigate an ethanol plant as a productive system to understand how the addition of an algae farm could change the status quo of energy efficiency and emission of pollutant gases. The system analyzed includes the sugarcane sowing, the plantation handling, the harvesting, the industrial activities, and the Ethanol distribution. The goal, from this analysis and using primary data from a company that installs algae farms, is to estimate the increase of biofuel generated by algae and decrease GHG emissions in the production process. The results obtained in Plant Studied show that an algae farm in its industrial grounds would better its energy efficiency in almost threefold, while generating four times less atmospheric pollution in their production chain. If the plant chose to produce exclusively Biodiesel, production of B100 Biodiesel would be enough for the industry s diesel needs for 19 years, with a 78.4 percent cleaner fuel in terms of GHG emissions. Approximations show that if all the sugar cane fields implant algae farms in Brazil, the Biodiesel generated in this process would be equivalent to almost 70 percent of the Brazilian production of diesel from 2012.