Matching Items (12)

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Automated monitoring and control systems for an algae photobioreactor

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There has been considerable advancement in the algae research field to move algae production for biofuels and bio-products forward to become commercially viable. However, there is one key element that

There has been considerable advancement in the algae research field to move algae production for biofuels and bio-products forward to become commercially viable. However, there is one key element that humans cannot control, the natural externalities that impact production. An algae cultivation system is similar to agricultural crop farming practices. Algae are grown on an area of land for a certain time period with the aim of harvesting the biomass produced. One of the advantages of using algae biomass is that it can be used as a source of energy in the form of biofuels. Major advances in algae research and development practices have led to new knowledge about the remarkable potential of algae to serve as a sustainable source of biofuel. The challenge is to make the price of biofuels from algae cost-competitive with the price of petroleum-based fuels. The scope of this research was to design a concept for an automated system to control specific externalities and determine if integrating the system in an algae cultivation system could improve the algae biomass production process. This research required the installation and evaluation of an algae cultivation process, components selection and computer software programming for an automated system. The results from the automated system based on continuous real time monitored variables validated that the developed system contributes insights otherwise not detected from a manual measurement approach. The implications of this research may lead to technology that can be used as a base model to further improve algae cultivation systems.

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Date Created
  • 2014

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Improvement strategies for the production of renewable chemicals by Synechocystis sp PCC 6803

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Synechocystis sp PCC 6803 is a photosynthetic cyanobacterium that can be easily transformed to produce molecules of interest; this has increased Synechocystis’ popularity as a clean energy platform. Synechocystis has

Synechocystis sp PCC 6803 is a photosynthetic cyanobacterium that can be easily transformed to produce molecules of interest; this has increased Synechocystis’ popularity as a clean energy platform. Synechocystis has been shown to produce and excrete molecules such as fatty acids, isoprene, etc. after appropriate genetic modification. Challenges faced for large–scale growth of modified Synechocystis include abiotic stress, microbial contamination and high processing costs of product and cell material. Research reported in this dissertation contributes to solutions to these challenges. First, abiotic stress was addressed by overexpression of the heat shock protein ClpB1. In contrast to the wild type, the ClpB1 overexpression mutant (Slr1641+) tolerated rapid temperature changes, but no difference was found between the strains when temperature shifts were slower. Combination of ClpB1 overexpression with DnaK2 overexpression (Slr1641+/Sll0170+) further increased thermotolerance. Next, we used a Synechocystis strain that carries an introduced isoprene synthase gene (IspS+) and that therefore produces isoprene. We attempted to increase isoprene yields by overexpression of key enzymes in the methyl erythritol phosphate (MEP) pathway that leads to synthesis of the isoprene precursor. Isoprene production was not increased greatly by MEP pathway induction, likely because of limitations in the affinity of the isoprene synthase for the substrate. Finally, two extraction principles, two–phase liquid extraction (e.g., with an organic and aqueous phase) and solid–liquid extraction (e.g., with a resin) were tested. Two–phase liquid extraction is suitable for separating isoprene but not fatty acids from the culture medium. Fatty acid removal required acidification or surfactant addition, which affected biocompatibility. Therefore, improvements of both the organism and product–harvesting methods can contribute to enhancing the potential of cyanobacteria as solar–powered biocatalysts for the production of petroleum substitutes.

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Date Created
  • 2013

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Towards improving electron recovery and Coulombic efficiency of microbial electrochemical cells fed with fermentable electron donors

Description

The microbial electrochemical cell (MXC) is a novel environmental-biotechnology platform for renewable energy production from waste streams. The two main goals of MXCs are recovery of renewable energy and production

The microbial electrochemical cell (MXC) is a novel environmental-biotechnology platform for renewable energy production from waste streams. The two main goals of MXCs are recovery of renewable energy and production of clean water. Up to now, energy recovery, Coulombic efficiency (CE), and treatment efficiency of MXCs fed with real wastewater have been low. Therefore, the overarching goal of my research was to address the main causes for these low efficiencies; this knowledge will advance MXCs technology toward commercialization.

First, I found that fermentation, not anode respiration, was the rate-limiting step for achieving complete organics removal, along with high current densities and CE. The best performance was achieved by doing most of the fermentation in an independent reactor that preceded the MXC. I also outlined how the efficiency of fermentation inside MXCs can be enhanced in order to make MXCs-based technologies cost-competitive with other anaerobic environmental biotechnologies. I revealed that the carbohydrate and protein contents and the BOD5/COD ratio governed the efficiency of organic-matter fermentation: high protein content and low BOD5/COD ratio were the main causes for low fermentation efficiency.

Next, I showed how a high ammonium concentration can provide kinetic and metabolic advantages or disadvantages for anode-respiring bacteria (ARB) over their competitors, particularly methanogens. When exposed to a relatively high ammonium concentration (i.e., > 2.2 g total ammonia-nitrogen (TAN)/L), the ARB were forced to divert a greater electron flow toward current generation and, consequently, had lower net biomass yield. However, the ARB were relatively more resistant to high free ammonia-nitrogen (FAN) concentrations, up to 200 mg FAN/L. I used FAN to manage ecological interactions among ARB and non-ARB in an MXC fed with fermentable substrate (glucose). Utilizing a combination of chemical, electrochemical, and genomic tools, I found that increased FAN led to higher CE and lower methane (CH4) production by suppressing methanogens. Thus, managing FAN offers a practical means to suppress methanogenesis, instead of using expensive and unrealistic inhibitors. My research findings open up new opportunities for more efficient operation of MXCs; this will enhance MXC scale-up and commercial applications, particularly for energy-positive treatment of waste streams containing recalcitrant organics.

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Date Created
  • 2016

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Approaches to engineering Synechocystis for biofuel production with emphasis on electron transport modifications

Description

The basic scheme for photosynthesis suggests the two photosystems existing in parity with one another. However, cyanobacteria typically maintain significantly more photosystem I (PSI) than photosystem II (PSII) complexes. I

The basic scheme for photosynthesis suggests the two photosystems existing in parity with one another. However, cyanobacteria typically maintain significantly more photosystem I (PSI) than photosystem II (PSII) complexes. I set out to evaluate this disparity through development and analysis of multiple mutants of the genetically tractable cyanobacterium Synechocystis sp. PCC 6803 that exhibit a range of expression levels of the main proteins present in PSI (Chapter 2). One hypothesis was that the higher abundance of PSI in this organism is used to enable more cyclic electron flow (CEF) around PSI to contribute to greater ATP synthesis. Results of this study show that indeed CEF is enhanced by the high amount of PSI present in WT. On the other hand, mutants with less PSI and less cyclic electron flow appeared able to maintain healthy levels of ATP synthesis through other compensatory mechanisms. Reduction in PSI abundance is naturally associated with reduced chlorophyll content, and mutants with less PSI showed greater primary productivity as light intensity increased due to increased light penetration in the cultures. Another question addressed in this research project involved the effect of deletion of flavoprotein 3 (an electron sink for PSI-generated electrons) from mutant strains that produce and secrete a fatty acid (Chapter 3). Removing Flv3 increased fatty acid production, most likely due to increased abundance of reducing equivalents that are key to fatty acid biosynthesis. Additional components of my dissertation research included examination of alkane biosynthesis in Synechocystis (Chapter 4), and effects of attempting to overexpress fibrillin genes for enhancement of stored compounds (Chapter 5). Synechocystis is an excellent platform for metabolic engineering studies with its photosynthetic capability and ease of genetic alteration, and the presented research sheds light on multiple aspects of its fundamental biology.

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Date Created
  • 2017

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Towards biohybrid artificial photosynthesis

Description

A vast amount of energy emanates from the sun, and at the distance of Earth, approximately 172,500 TW reaches the atmosphere. Of that, 80,600 TW reaches the surface with 15,600

A vast amount of energy emanates from the sun, and at the distance of Earth, approximately 172,500 TW reaches the atmosphere. Of that, 80,600 TW reaches the surface with 15,600 TW falling on land. Photosynthesis converts 156 TW in the form of biomass, which represents all food/fuel for the biosphere with about 20 TW of the total product used by humans. Additionally, our society uses approximately 20 more TW of energy from ancient photosynthetic products i.e. fossil fuels. In order to mitigate climate problems, the carbon dioxide must be removed from the human energy usage by replacement or recycling as an energy carrier. Proposals have been made to process biomass into biofuels; this work demonstrates that current efficiencies of natural photosynthesis are inadequate for this purpose, the effects of fossil fuel replacement with biofuels is ecologically irresponsible, and new technologies are required to operate at sufficient efficiencies to utilize artificial solar-to-fuels systems. Herein a hybrid bioderived self-assembling hydrogen-evolving nanoparticle consisting of photosystem I (PSI) and platinum nanoclusters is demonstrated to operate with an overall efficiency of 6%, which exceeds that of land plants by more than an order of magnitude. The system was limited by the rate of electron donation to photooxidized PSI. Further work investigated the interactions of natural donor acceptor pairs of cytochrome c6 and PSI for the thermophilic cyanobacteria Thermosynechococcus elogantus BP1 and the red alga Galderia sulphuraria. The cyanobacterial system is typified by collisional control while the algal system demonstrates a population of prebound PSI-cytochrome c6 complexes with faster electron transfer rates. Combining the stability of cyanobacterial PSI and kinetics of the algal PSI:cytochrome would result in more efficient solar-to-fuel conversion. A second priority is the replacement of platinum with chemically abundant catalysts. In this work, protein scaffolds are employed using host-guest strategies to increase the stability of proton reduction catalysts and enhance the turnover number without the oxygen sensitivity of hydrogenases. Finally, design of unnatural electron transfer proteins are explored and may introduce a bioorthogonal method of introducing alternative electron transfer pathways in vitro or in vivo in the case of engineered photosynthetic organisms.

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Date Created
  • 2014

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Impact of viral infectivity on phototrophic microbes for biofuel applications

Description

Research in microbial biofuels has dramatically increased over the last decade. The bulk of this research has focused on increasing the production yields of cyanobacteria and algal cells and improving

Research in microbial biofuels has dramatically increased over the last decade. The bulk of this research has focused on increasing the production yields of cyanobacteria and algal cells and improving extraction processes. However, there has been little to no research on the potential impact of viruses on the yields of these phototrophic microbes for biofuel production. Viruses have the potential to significantly reduce microbial populations and limit their growth rates. It is therefore important to understand how viruses affect phototrophic microbes and the prevalence of these viruses in the environment. For this study, phototrophic microbes were grown in glass bioreactors, under continuous light and aeration. Detection and quantification of viruses of both environmental and laboratory microbial strains were measured through the use of a plaque assay. Plates were incubated at 25º C under continuous direct florescent light. Several environmental samples were taken from Tempe Town Lake (Tempe, AZ) and all the samples tested positive for viruses. Virus free phototrophic microbes were obtained from plaque assay plates by using a sterile loop to scoop up a virus free portion of the microbial lawn and transferred into a new bioreactor. Isolated cells were confirmed virus free through subsequent plaque assays. Viruses were detected from the bench scale bioreactors of Cyanobacteria Synechocystis PCC 6803 and the environmental samples. Viruses were consistently present through subsequent passage in fresh cultures; demonstrating viral contamination can be a chronic problem. In addition TEM was performed to examine presence or viral attachment to cyanobacterial cells and to characterize viral particles morphology. Electron micrographs obtained confirmed viral attachment and that the viruses detected were all of a similar size and shape. Particle sizes were measured to be approximately 50-60 nm. Cell reduction was observed as a decrease in optical density, with a transition from a dark green to a yellow green color for the cultures. Phototrophic microbial viruses were demonstrated to persist in the natural environment and to cause a reduction in algal populations in the bioreactors. Therefore it is likely that viruses could have a significant impact on microbial biofuel production by limiting the yields of production ponds.

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Date Created
  • 2014

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Phosphorus recovery from microbial biofuel residual using microwave peroxide digestion and anion exchange

Description

Biofuel from microbial biomass is a viable alternative to current energy production practices that could mitigate greenhouse gas levels and reduce dependency on fossil fuels. Sustainable production of microbial biomass

Biofuel from microbial biomass is a viable alternative to current energy production practices that could mitigate greenhouse gas levels and reduce dependency on fossil fuels. Sustainable production of microbial biomass requires efficient utilization of nutrients like phosphorus (P). P is a limited resource which is vital for global food security. This paper seeks to understand the fate of P through biofuel production and proposes a proof-of-concept process to recover P from microbial biomass. The photosynthetic cyanobacterium Synechocystis sp. PCC 6803 is found to contain 1.4% P by dry weight. After the crude lipids are extracted for biofuel processing, 92% of the intercellular P is found within the residual biomass. Most intercellular P is associated with nucleic acids which remain within the cell after lipids are extracted. Phospholipids comprise a small percentage of cellular P. A wet chemical advanced oxidation process of adding 30% hydrogen peroxide followed by 10 min of microwave heating converts 92% of the total cellular P from organic-P and polyphosphate into orthophosphate. P was then isolated and concentrated from the complex digested matrix by use of resins. An anion exchange resin impregnated with iron nanoparticles demonstrates high affinity for P by sorbing 98% of the influent P through 20 bed volumes, but only was able to release 23% of it when regenerated. A strong base anion exchange resin sorbed 87% of the influent P through 20 bed volumes then released 50% of it upon regeneration. The overall P recovery process was able to recover 48% of the starting intercellular P into a pure and concentrated nutrient solution available for reuse. Further optimization of elution could improve P recovery, but this provides a proof-of-concept for converting residual biomass after lipid extraction to a beneficial P source.

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Date Created
  • 2012

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The potential of coastal marine filtration as a feedstock source for biodiesel

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Second-generation biofuel feedstocks are currently grown in land-based systems that use valuable resources like water, electricity and fertilizer. This study investigates the potential of near-shore marine (ocean) seawater filtration as

Second-generation biofuel feedstocks are currently grown in land-based systems that use valuable resources like water, electricity and fertilizer. This study investigates the potential of near-shore marine (ocean) seawater filtration as a source of planktonic biomass for biofuel production. Mixed marine organisms in the size range of 20µm to 500µm were isolated from the University of California, Santa Barbara (UCSB) seawater filtration system during weekly backwash events between the months of April and August, 2011. The quantity of organic material produced was determined by sample combustion and calculation of ash-free dry weights. Qualitative investigation required density gradient separation with the heavy liquid sodium metatungstate followed by direct transesterification and gas chromatography with mass spectrometry (GC-MS) of the fatty acid methyl esters (FAME) produced. A maximum of 0.083g/L of dried organic material was produced in a single backwash event and a study average of 0.036g/L was calculated. This equates to an average weekly value of 7,674.75g of dried organic material produced from the filtration of approximately 24,417,792 liters of seawater. Temporal variations were limited. Organic quantities decreased over the course of the study. Bio-fouling effects from mussel overgrowth inexplicably increased production values when compared to un-fouled seawater supply lines. FAMEs (biodiesel) averaged 0.004% of the dried organic material with 0.36ml of biodiesel produced per week, on average. C16:0 and C22:6n3 fatty acids comprised the majority of the fatty acids in the samples. Saturated fatty acids made up 30.71% to 44.09% and unsaturated forms comprised 55.90% to 66.32% of the total chemical composition. Both quantities and qualities of organics and FAMEs were unrealistic for use as biodiesel but sample size limitations, system design, geographic and temporal factors may have impacted study results.

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Date Created
  • 2011

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Examining the impacts of switchgrass derived biofuels on U.S. biofuel policy and the potential environmental ethical dilemmas

Description

Overall, biofuels play a significant role in future energy sourcing and deserve thorough researching and examining for their best use in achieving sustainable goals. National and state policies are supporting

Overall, biofuels play a significant role in future energy sourcing and deserve thorough researching and examining for their best use in achieving sustainable goals. National and state policies are supporting biofuel production as a sustainable option without a holistic view of total impacts. The analysis from this research connects to policies based on life cycle sustainability to identify other environmental impacts beyond those specified in the policy as well as ethical issues that are a concern. A Life cycle assessment (LCA) of switchgrass agriculture indicates it will be challenging to meet U.S. Renewable Fuel Standards with only switchgrass cellulosic ethanol, yet may be used for California's Low Carbon Fuel Standard. Ethical dilemmas in food supply, land conservation, and water use can be connected to biofuel production and will require evaluation as policies are created. The discussions around these ethical dilemmas should be had throughout the process of biofuel production and policy making. Earth system engineering management principles can help start the discussions and allow anthropocentric and biocentric viewpoints to be heard.

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Date Created
  • 2014

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Characterization of novel adsorbents for recovery of biofuels

Description

Due to depletion of oil resources, increasing fuel prices and environmental issues associated with burning of fossil fuels, extensive research has been performed in biofuel production and dramatic progress has

Due to depletion of oil resources, increasing fuel prices and environmental issues associated with burning of fossil fuels, extensive research has been performed in biofuel production and dramatic progress has been made. But still problems exist in economically production of biofuels. One major problem is recovery of biofuels from fermentation broth with the relatively low product titer achieved. A lot of in situ product recovery techniques including liquid-liquid extraction, membrane extraction, pervaporation, gas stripping and adsorption have been developed and adsorption is shown to be the most promising one compared to other methods. Yet adsorption is not perfect due to defect in adsorbents and operation method used. So laurate adsorption using polymer resins was first investigated by doing adsorption isotherm, kinetic, breakthrough curve experiment and column adsorption of laurate from culture. The results indicate that polymer resins have good capacity for laurate with the highest capacity of 430 g/kg achieved by IRA-402 and can successfully recover laurate from culture without causing problem to Synechocystis sp.. Another research of this paper focused on a novel adsorbent: magnetic particles by doing adsorption equilibrium, kinetic and toxicity experiment. Preliminary results showed excellent performance on both adsorption capacity and kinetics. But further experiment revealed that magnetic particles were toxicity and inhibited growth of all kinds of cell tested severely, toxicity probably comes from Co (III) in magnetic particles. This problem might be solved by either using biocompatible coatings or immobilization of cells, which needs more investigation.

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Date Created
  • 2012