Browsing by Subject "Microalgae"
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Item Development of an effective swine manure-based algal cultivation system for biofuel & animal feed production and wastewater treatment(2013-03) Hu, BingMicroalgae have great potential to replace current crop feedstocks for biofuel and animal feed production. However, the algal industry is still far from being economically applicable. The dissertation was inspired by the idea of integrating algal biomass production and wastewater treatment. The overall objective of the study was to develop an effective algal cultivation system in which inorganic nutrients and organic substances in swine manure could be utilized by robust microalgae strains for the production of algal biomass with high lipids or protein contents. The first step in the study was bioprospecting for mixotrophic microalgae strains that adapted well to diluted swine manure. Through the multi-step screening strategy, two locally isolated microalgae strains, UMN271 and UMN266, were found to be facultative heterotrophic, manure-tolerant, and obviously robust in the algae storage including 98 UTEX strains and 50 indigenous strains. The two strains were identified as Chlorella sp. and Hindakia sp., respectively, through morphological observation and genetic identification, and were utilized for further studies in the dissertation. Since algae growth on highly diluted swine manure was still relatively low, a second step in the study was to assess the limiting factors of using anaerobically decomposed swine manure as nutrient supplement for algae cultivation. In the study, Chlorella sp. (UMN271) and Hindakia sp. (UMN266) were used to investigate the effects of two potential factors, which were trace elements and carbon compounds in swine manure, on algal growth and waste nutrient recovery. The results indicated that the algal growth and nutrient removal rates were independent of trace metal content in diluted swine manure, but were significantly improved when the initial liquid COD content in swine manure was high. Moreover, it was demonstrated that Chlorella sp. (UMN271) was able to utilize acetic, propionic and butyric acids, the main water-soluble organic carbon compounds in digested swine manure, for algal growth, lipid production, and waste nutrient removal. Therefore, it was considered that algal growth in highly diluted swine manure was limited by the deficiency of volatile fatty acids (VFAs). The third step was to modify anaerobic digestion process for liquid swine manure (LSM) rich in VFAs, so that the liquid effluent could be more suitable than the conventionally decomposed LSM effluent as nutrient for the cultivation of Chlorella sp. (UMN271). The results showed that the modified acidogenic digestion successfully promoted VFA concentrations in swine manure. The obtained acidogenically digested LSM supported the growth of Chlorella sp.(UMN271) in a 5-day batch experiment with higher algal growth rates and fatty acid contents in comparison with those on the conventionally decomposed LSM. High removal efficiencies on water-soluble nutrients, including COD, PO4-P, TN and NH3-N, were also observed for the raw, acidogenically digested manure sample (58.02%, 44.74%, 31.58%, and 44.73%, respectively). Finally, the fatty acid profile analysis showed that harvested algal biomass could be used as feedstock to produce high-quality biodiesel. In the fourth step, central composite design (CCD) was used to investigate the influences of two key parameters, namely wastewater dilution rate (DR) and hydraulic retention time (HRT), on algal biomass productivity and waste nutrient removal rates. According to the response surface analyses of the CCD results, statistically valid quadric models for the response variables, including algal biomass productivity and the liquid nutrient removal rates including COD, PO4-P, TN and NH3-N, were obtained. The regression analyses illustrated that both DR and HRT had significant influences on the five response variables. The optimal conditions estimated from the significant second-order quadratic models (p<0.05) were 8-fold DR and 2.26-d HRT. The final step was the development of an effective algal cultivation system for the semicontinuous production of algal biomass and waste nutrient removal. In the study, the predicted optimal conditions were applied in a bench-scale multi-layer photobioreactor (PBR) for algae growth on acidogenically digested swine manure. The 17-day semicontinuous cultivating experiment achieved high and stable algal productivity and nutrient removal rates, which fitted the predictive models well. Moreover, relatively high and stable protein and lipid contents (58.78% and 26.09% of the dry weight, respectively) were observed for the harvested algal sample, indicating the suitability of the algal biomass as ideal feedstock for both biofuel and animal feed production.Item Development of an Integrated Biological Wastewater Treatment System for the Full Utilization of High Nitrogen Livestock Waste(2023-01) Mataya, DmitriLivestock wastes such as Liquid Swine Manure (LSM), when discharged improperly, contribute to ground and surface water contamination. These wastes are also full of valuable nutrients that can be converted to bioproducts such as fertilizers, fuels, and feed. For this reason, increasing attention has been focused on utilizing and treating this waste so that it can be discharged without detrimental environmental effects. In Chapter 1 the significance of this study and the purpose of each major component in the system are explained. Then Chapter 2 examines the obstacles apparent from literature to successful biological waste treatment as it regards each component. Finally in Chapter 3 a series of methods including thermal vacuum stripping pretreatment, mesophilic anaerobic digestion, microalgae treatment, and hydroponic cultivation are evaluated for full utilization of wastewater through nutrient removal and recovery, and a balance of mass and nutrients throughout the system is proposed. Overall, the system was capable of reducing the key nutrient parameters (COD, TN, ammonia, TP) to a large degree (>98%) while producing valuable side products. This approach has the potential to sustainably treat agricultural wastewater while offsetting treatment costs with the production of valuable bioproducts.Item Effects Of Algae Feeding On Mouse Metabolome(2017-09) Ma, YiweiAlgae have been investigated and developed as a source of food, dietary supplement, and biofuel, due to their chemical and nutrient composition. Algae consumption carries algal proteins, polyunsaturated fatty acids (PUFAs), vitamins, dietary fibers, and bioactive compounds into the biological systems of humans and animals, and therefore are expected to elicit metabolic and physiological responses. Numerous efforts have been undertaken to understand the health-promoting effects of algae consumption, such as their hypolipidemic, antioxidant, anti-obesity and anti-cancer properties. However, the metabolic events in algae-elicited effects were not examined in details in spite of the fact that these benefits are largely based on the metabolic interactions between algal components and the biological system. In this study, the influences of consuming green algae (Scenedesmus sp.) on the metabolic status of young mice was investigated through growth performance, blood chemistry, and liquid chromatography-mass spectrometry (LC-MS)-based metabolomics. Compared to the control diet, 5% algae promoted growth performance while 20% algae suppressed it. The growth performance was significantly increased by 5% algae but decreased by 20% algae feeding. Serum glucose, triacylglycerols (TAG), and blood urea nitrogen (BUN) levels were not affected by both treatments, but serum cholesterol level was dramatically decreased by 20% algae feeding. Metabolomic analysis of liver, serum, feces and urine samples revealed diverse influences of algae feeding on mouse metabolome, which are represented by the features as follows: 1). Urinary vitamins and fecal pigments are identified as robust exposure markers of algae feeding. 2). Despite the high-level protein in algae, the impacts of algae feeding on free amino acids in serum and the liver were quite limited. 3). Algae feeding increased the PUFA levels in serum and liver lipidomes and the free fatty acids in feces. 4). 5% algae increased the level of reduced glutathione (GSH) in the liver while 20% algae increased the level of oxidized glutathione (GSSG) in the liver and the levels of aldehydic lipid oxidation products (LOPs) in the liver and urine. 5). 5% algae selective increased the levels of intermediate metabolites, including adenosine monophosphate (AMP), adenylsuccinic acid, dephospho-CoA, and nicotinamide, in the liver while 20% algae increased the levels of carnitine and carnitine derivatives in the liver. 6). Algae feeding dramatically altered the microbial metabolism, as reflected by the increases in short-chain fatty acids (SCFAs) and primary bile salts in feces, the increases of branched fatty acids in urine, the decreases of secondary bile acids in feces, and the decrease of p-cresol metabolites in urine. Overall, multiple correlations between metabolite markers and growth performance in algae feeding were established in this study and could serve as a foundation for further mechanistic investigations on the biological effects of algae feeding.Item Heavy metals in wastewater: Their removal through algae adsorption and their roles in microwave assisted pyrolysis of algae.(2012-08) Zhao, YuanChlorella vulgaris was found as a good biosorbent for copper, zinc and aluminum. pH value, reaction time, initial metal and algal sorbents concentrations were considered as parameters affecting metal removal efficiency. In appropriate conditions, 85% of copper(II), 70% of zinc(II) and 99% of aluminum(III) could be removed from solutions by tested microalgae within 20 minutes. In following pyrolysis of the algae, metals were further concentrated in the charcoal. 96.17% of Copper and 97.34% of Zinc stayed in the char portion. Metals in the algal feedstock improved the bioenergy production during microwave assisted pyrolysis of the algae by reducing heating time to about half of before. The presence of metals also significantly decreased the nitrogen containing compounds and the carbon dioxide output and increased the aromatics generation.Item Microalgae harvesting via co-culture with filamentous fungus(2013-07) Gultom, Sarman OktovianusMicroalgae harvesting is a labor- and energy-intensive process. For instance, classical harvesting technologies such as chemical addition and mechanical separation are economically prohibiting for biofuel production. Newer approaches to harvest microalgae have been developed in order to decrease costs. Among these new methods, fungal co-pelletization seems to be a promising technology. By co-culturing filamentous fungi with microalgae, it is possible to form pellets, which can easily be separated. In this study, different parameters for the cultivation of filamentous fungus (Aspergillus niger) and microalgae (Chlorella vulgaris) to efficiently form cell pellets were evaluated under heterotrophic and phototrophic conditions, including organic carbon source (glucose, glycerol and sodium acetate) concentration, pH, initial concentration of fungal spores, initial concentration of microalgal cells, concentration of ionic strength (Calcium and Magnesium) and concentration of salinity (NaCl). In addition, zeta-potential measurements were carried out in order to get a better understanding of the mechanism of attraction. It was found that 2 g/L of glucose, a fungus to microalgae ratio of 1:300, and uncontrolled pH (around 7) are the best culturing conditions for co-pelletization. Under these conditions, it was possible to achieve a high harvesting performance (>90%). In addition, it was observed that most pellets formed in the co-culture were spherical with an average diameter of 3.5 mm and in concentrations of about 5 pellets per mL of culture media. Under phototrophic conditions, co-pelletization required the addition of glucose as organic carbon source to sustain the growth of fungi and to allow the harvesting of microalgae. Zeta-potential measurements indicated that (i) both microalgae and fungi have low zeta-potential values regardless of the pH on the bulk (i.e. <-10 mV) (ii) fungi can have a positive electric charge at low pH (ie. pH=3). These values suggest that it might be possible that the degree of repulsion and dispersion between these organisms is low which facilitates the attraction between them.Item Strategies To Cultivate Microalgae On Eutrophic Wastewater For Nutrients Recycling And Biomass Production(2018-02) Lu, QianWastewater generated from industry may contain excessive nutrients, including nitrogen, phosphorus and organic carbon. On one hand, excessive nutrients in wastewater could cause environmental pollution and ecological disaster. On the other hand, these nutrients could be utilized for algae growth and algal biomass production. Unregulated discharge of eutrophic wastewater not only poses threats to water body, but also wastes the valuable nutrients in wastewater. This dissertation research focuses on the technologies and mechanisms to improve the efficiency of nutrients utilization by algae grown in eutrophic wastewater. The lack of ammonia limits algae growth in wastewater from food industry. In this study, a potential solution is to mix the wastewater from different resources to balance the nutrients profiles and promote the algae growth. The results showed that appropriate mixture of food industry wastewater effectively mitigated the bottleneck to algae growth and improved the nutrients removal efficiencies. Ammonia toxicity is a serious concern in the treatment of some wastewater. In this study, comparison of three common carbon sources, glucose, citric acid, and sodium bicarbonate, indicated that in terms of ammonia assimilation, glucose is the best carbon source. This result could be applied to the toxicity of ammonia enrichment to algae cultivation in eutrophic wastewater. A cooperation model between algae and wastewater-borne bacteria was reported by this dissertation research. Such a cooperation model increased the nutrients removal efficiencies and promoted the algae growth. A strain of beneficial aerobic bacteria, Acinetobacter sp., was isolated and its biochemical characteristics were explored. After treatment by co-cultivation of Acinetobacter sp. and Chlorella sp., residual nutrients in municipal wastewater were reduced to be under the permissible discharge limit. To fully utilize the nutrients in swine manure, it is always exploited to produce biogas by anaerobic digestion. However, the treatment of residual nutrients after anaerobic digestion is a critical issue. High turbidity and ammonia toxicity are two factors limiting the algae growth in anaerobically digested swine manure. This research developed a strategy to pretreat the anaerobically digested swine manure by cationic starch-assisted turbidity reduction and air bubbling-driven ammonia stripping.Item Thermochemical conversion of microalgae for biofuel production(2013-02) Du, ZhenyiConcerns about diminishing fossil fuels and increasing greenhouse gas emissions are driving many countries to develop renewable energy sources. In this respect, biomass may provide a carbon-neutral and sustainable solution. Microalgae have received growing interest recently because of their high productivity, high oil content and the ability to grow in a wide range of climates and lands. Pyrolysis is a thermochemical process in which biomass is thermally decomposed to a liquid product known as bio-oil. In this dissertation, pyrolysis and hydrothermal conversion techniques were applied to microalgae for biofuel production and an integrated algae-based biorefinery was proposed which includes algal biomass production, hydrothermal pretreatment, catalytic pyrolysis of microalgae into biofuels, and recycling of the wastewater from conversion as low-cost nutrient source for algae cultivation. In Chapter 3, Microwave-assisted pyrolysis (MAP) of Chlorella sp. was carried out with char as microwave reception enhancer. The results indicated that the maximum biooil yield of 28.6% was achieved under the microwave power of 750 W. The bio-oil properties were characterized with elemental, gas chromatography-mass spectrometry (GC-MS), gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG) analysis. The algal bio-oil had a density of 0.98 kg/L, a viscosity of 61.2 cSt, and a higher heating value (HHV) of 30.7 MJ/kg. The GC-MS results showed that the bio-oils were mainly composed of aliphatic hydrocarbons, aromatic hydrocarbons, phenols, long chain fatty acids and nitrogenated compounds, among which aliphatic and aromatic hydrocarbons (account for 22.18 % of the total GC-MS spectrum area) are highly desirable compounds as those in crude oil, iii gasoline and diesel. The results indicate that fast growing algae are a promising source of feedstock for advanced renewable fuels production via MAP. To further elucidate the pyrolysis mechanism of microalgae, the different roles of three major components (carbohydrates, proteins, and lipids) in microalgae were investigated on a pyroprobe. In Chapter 4, cellulose, egg whites, and canola oil were employed as the model compounds of the three components, respectively. Non-catalytic pyrolysis was used to identify and quantify some major products and several pyrolysis pathways of algal biomass were also postulated by analysis and identification of pyrolysis products from the model compounds. Algal bio-oil contains oxygenates and nitrogenates which can lower the heating values and lead to NOx emissions, and thus upgrading processes towards reducing nitrogen and oxygen are necessary. Catalytic pyrolysis was then carried out with HZSM-5 for the production of aromatic hydrocarbons at different temperatures and catalyst to feed ratios. The aromatic yields of all feedstocks were significantly improved when the catalyst to biomass ratio increased from 1:1 to 5:1. Egg whites had the lowest aromatic yield among the model compounds under all reaction conditions, which suggests that proteins can hardly be converted to aromatics with HZSM-5. Lipids, although only accounted for 12.33% of Chlorella, contributed about 40% of aromatic production from algal biomass. Based on the preliminary catalytic pyrolysis results, a detailed catalyst screening study was carrier out to evaluate the performance of different zeolites for the production of aromatic hydrocarbons in Chapter 5. Three zeolites with different crystal structures (H-Y, H-Beta and H-ZSM5) were used to study the effect of catalyst type on the aromatic yield. All three catalysts significantly increased the aromatic yields from pyrolysis of microalgae and egg whites compared with non-catalytic runs, and H-ZSM5 was most effective with a yield of 18.13%. Three H-ZSM5 with silica-to-alumina (Si/Al) ratios of 30, 80 and 280 were used to study the effect of Si/Al ratio on the aromatic yield. The maximum yield was achieved at the Si/Al ratio of 80, which provides moderate acidity to achieve high aromatic production and reduce coke formation simultaneously. Aromatic production increased with the incorporation of copper or gallium to HZSM-5. However, other metals studied either had no significant influence or led to a lower aromatic yield. Based on the results in Chapter 4 and Chapter 5, nitrogenates are very resistant to catalytic conversion and the aromatic hydrocarbon yield from proteins was the lowest among the three major components of microalgae. However, since nitrogen is an essential element for algal growth, recycling of this nutrient will be important to achieving sustainable algal feedstock production. Therefore, hydrothermal pretreatment (HP) was employed to reduce the nitrogen content in Nannochloropsis oculata feedstock by hydrolyzing proteins without requiring significant energy inputs. The effects of reaction conditions on the yield and composition of pretreated algae were investigated by varying the temperature (150−225 °C) and reaction time (10−60 min). Compared with untreated algae, pretreated samples had higher carbon contents and enhanced heating values under all reaction conditions and 6−42% lower nitrogen contents at 200 °C−225 °C for 30−60 min. The pyrolytic bio-oil from pretreated algae contained less nitrogen-containing compounds than that from untreated samples. The bio-oil contained mainly (44.9% GCMS peak area) long-chain fatty acids (C14−C18) which can be more readily converted into hydrocarbon fuels in the presence of simple catalysts. Additionally, the feasibility of using recovered nutrients from HP for cultivation of microalga Chlorella vulgaris was v investigated. Different dilution multiples of 50, 100 and 200 were applied to the recycled process water from HP and algal growth was compared among these media and a standard growth medium BG-11. Algae achieved a biomass concentration of 0.79 g/L on 50× process water after 4 days. Algae removed total nitrogen, total phosphorus and chemical oxygen demand by 45.5-59.9%, 85.8-94.6% and 50.0-60.9%, respectively, on different diluted process waters. The fatty acid methyl ester yields for algae grown on the process water were 11.2% (50×), 11.2% (100×) and 9.7% (200×), which were significantly higher than 4.5% for BG-11 grown algae. In addition, algae cultivated on process water had 18.9% higher carbon and 7.8% lower nitrogen contents than those on BG-11, indicating that they are very suitable as biofuel feedstocks. In summary, HP is a low cost and efficient way to reduce the nitrogen content in microalgae without significant energy inputs. The recovered aqueous nutrients from HP can be recycled for algal cultivation. Pretreated microalgae were very hydrophobic with reduced nitrogen content and retained 73 to 99% lipids of the starting microalgae. These lipids can be easily converted into hydrocarbon fuels in the presence of simple catalysts, such as HZSM5 zeolite.Item Understanding Cyanobacteria-based Biofertilizers in Soil-Water and Soil-Plant Systems(2021-10) Alvarez De La Hoz, AdrianaGrowing pressures to increase agricultural productivity amid rising environmental impacts and global climate threats call for critical strategies that preserve the soil resource and improve sustainability. Microalgae, including cyanobacteria, are emerging as promising platforms to enhance soil structure and fertility and reduce our reliance on chemical fertilizers. To advance applications, further understanding is needed with different strains, plants, agroecological regions and types of soil including Mollisols, which are among the most productive soils in the world. This dissertation reviewed aspects of microalgae that might be applied in agriculture and evaluated effects of soil inoculations with the dinitrogen (N2)-fixing cyanobacterium Anabaena cylindrica UTEX 1611 on a Mollisol from the U.S. Upper Midwest. First, a comprehensive literature review supported microalgae as renewable resources for the potential development of biofertilizers, organic fertilizers, biostimulants, biocontrol agents, and soil conditioners. Furthermore, experiments with cyanobacterial soil inoculations described effects on soil structure and nutrient dynamics, soil loss and water nutrient levels after high-intensity rain simulations, and soil mineralization of cyanobacterial biomass. The results revealed changes in soil structural components that might be resistant to wind and water erosion, potential for reducing rainfall-induced soil loss, and a gradual nutrient release from the cyanobacterial biomass. High-intensity rain simulations also indicated depth-related positive changes in soil microbial dynamics that persisted after consecutive rains. Finally, experiments with a local variety of spring wheat consistently evidenced improvements in soil nutrients, microbial biomass, and microbial activity, and demonstrated that cyanobacteria, and a mixture with a local green microalga, supplied nitrogen (N) to support plant growth and partially replace urea. These findings provide insights on the positive role cyanobacteria might have as resources to enhance the sustainability and resiliency of agricultural systems.Item Utilization of Dairy Wastewater for Sustainable Produciton(2019-08) Luzzi, SianeInefficient use of nitrogen and phosphorus leads to anthropogenic eutrophication of rivers, lakes, and oceanic basis worldwide, causing an environmental problem that can trigger a death cycle of an entire water body. Microalga, one of the organisms that benefits from the excessive nutrient runoff and uses the sunlight to catalyze reactions that cause eutrophication, can also be part of a solution. The study presented in this thesis represents a possible integrated solution for the nutrients accumulated, especially in dairy farms. This work shows how it is possible to treat dairy wastewater in large volumes, using plastic photobioreactors with an initial inoculum of microalgae, in this case Chlorella sp., in a mixotrophic solution (since the dairy wastewater used in this study was not sterilized). It was also shown that in pilot-scale, ratio 1:10 (dairy wastewater in water) was capable of removing high amounts of nutrients, up to 97.55% of ammonium, 39.27% of nitrate, and 27.05% of phosphate. The 1:10 was also capable of producing competitive biomass amounts when comparing to the controls, 1.575 ± 0.599 g.L^(-1) and 1.315 ± 0.240 g.L^(-1). Moreover, none of the treatments (control, controlN, 1:10, 1:10N, 1:30 and 1:30N) were significantly different from each other, considering the nutrients (〖NH〗_4^+, 〖PO〗_4^(3-), 〖NO〗_3^-) removal rates and biomass, when adding or not extra CO2. In addition, a study was carried to evaluate the taste preference of calves fed Chlorella sp. produced in the previous steps. Sterilized biomass was used for feeding trials with six Holstein and crossbred dairy heifer calves. No mycotoxins were found in the biomass and many heavy metals were tested, having the levels below the maximum content recommended for animal feeding. The microalgae biomass produced had a protein content of 49.2%, 2.32% of fat, 38.5% of carbohydrates, and around 10% of different minerals and nutrients. They were fed 0, 30, and 60 g of Chlorella sp. daily in a sequential elimination study. No difference were found for dry matter intake of calves fed 0, 30, or 60 g of Chlorella sp., indicating that microalgae may be added to the rations of calves without any adverse effects.