Cultivation Of Oleaginous Microalgae Research Articles

Intensifying outdoor cultivation of oleaginous microalgae in photobioreactors for simultaneous wastewater bioremediation and low-cost production of renewable biodiesel feedstocks

Oleaginous microalgae are gaining increasing attention for simultaneous wastewater bioremediation and biofuel feedstock production. In this study, four oleaginous species of microalgae including Chlamydomonas sp. WWP, Scenedesmus sp. HP56, Haematococcus sp., and Nannochloropsis sp., were screened for their growth and lipid production at 30, 35, and 40 °C, under light intensity at 3, 4, and 5 klux. Among the strains screened, Haematococcus sp. grew best and gave comparable high growth at 30 °C and 35 °C (0.7–0.8 g/L) indicating its thermotolerant characteristic, and the optimal light intensity was found at 4 klux. Haematococcus sp. also grew well using unsterile secondary effluent from the seafood processing plant and produced high biomass (0.53–0.57 g/L) and lipids (0.17–0.19 g/L), especially in the column photobioreactor (CP). The repeated-batch outdoor cultivation mode showed that CP equipped with four-blade baffles was most efficient for the production of biomass (0.40–0.63 g/L) and lipids (0.15–0.30 g/L) during 4 cycles. The microalga also removed total nitrogen and total phosphorus from secondary effluent by 70.59% and 94.97%, respectively. The fatty acid compositions in microalgal lipids were C16-C18, especially palmitic acid, oleic acid, and linolenic acid, which show superior fuel properties, suggesting their promising use as biodiesel feedstocks. These strategies may have a significant impact not only on bioremediation of industrial effluent but also low-cost production of microalgae-based biodiesel feedstocks.

Cultivation of Oily Microalgae for the Production of Third-Generation Biofuels

Biofuel production by oleaginous microalgae is a promising alternative to the conventional fossil fuels. Many microalgae species have been investigated and deemed as potential renewable sources for the production of biofuel, biogas, food supplements and other products. Oleaginous microalgae, named for their ability to produce oil, are reported to store 30–70% of lipid content due to its metabolic properties under nutrient starvation conditions. This review presents the assortment of the research studies focused on biofuel production from oleaginous microalgae. The new methods and technologies developed for oleaginous microalgae cultivation to improve their biomass content and lipid accumulation capacity were reviewed. The production of renewable, carbon neutral, bio-based or microalgae-based transport fuels are necessary for environmental protection and economic sustainability. Microalgae are a significant source of renewable biodiesel because of their ability to produce oils in the presence of sunlight more efficiently than that of crop oils. This review will provide the background to understanding the bottlenecks and the need for improvement in the cultivation or harvesting process for oleaginous microalgae.

Integrated lipid production, CO2 fixation, and removal of SO2 and NO from simulated flue gas by oleaginous Chlorella pyrenoidosa.

CO2, SO2, and NO are the main components of flue gas and can cause serious environmental issues. Utilization of these compounds in oleaginous microalgae cultivation not only could reduce air pollution but could also produce feedstock for biodiesel production. However, the continuous input of SO2 and NO inhibits microalgal growth. In this study, the toxicity of simulated flue gas (15% CO2, 0.03% SO2, and 0.03% NO, balanced with N2) was reduced through automatic pH feedback control. Integrated lipid production and CO2 fixation with the removal of SO2 and NO was achieved. Using this technique, a lipid content of 38.0% DW was achieved in Chlorella pyrenoidosa XQ-20044. The lipid composition and fatty acid profile indicated that lipid production by C. pyrenoidosa XQ-20044 cultured with flue gas is suitable as a biodiesel feedstock; 81.2% of the total lipids were neutral lipids and 99.5% of the total fatty acids were C16 and C18. The ratio of saturated fatty acids to monounsaturated fatty acids in the microalgal lipid content was 74.5%. In addition, CO2, SO2, and NO from the simulated flue gas were fixed and converted to biomass and lipids with a removal efficiency of 95.9%, 100%, and 84.2%, respectively. Furthermore, the utilization efficiencies of CO2, SO2, and NO were equal to or very close to their removal efficiencies. These results provide a novel strategy for combining biodiesel production with biofixation of flue gas.

A novel approach using low-cost Citrus limetta waste for mixotrophic cultivation of oleaginous microalgae to augment automotive quality biodiesel production

The present study reports the use of Citrus limetta (CL) residue for cultivating Chlorella sp. mixotrophically to augment production of biodiesel. The cultivation of Chlorella sp. using CL as media was carried out by employing a fed-batch technique in open tray (open tray+CL) and in software (BioXpert V2)-attached automated photobioreactor (PBR+CL) systems. Data showed the limit of nitrogen substituent and satisfactory organic source of carbon (OSC) in CL, causing > 2-fold higher lipid content in cells, cultivated in both the systems than in control. For the cells grown in both the systems, ≥ 3-fold enhancement in lipid productivity was observed than in control. The total fatty acid methyl ester (FAME) concentrations from lipids extracted from cells grew in PBR+CL and in open tray+CL techniques were calculated as 50.59% and 38.31%, respectively. The PBR+CL system showed improved outcomes for lipid content, lipid and biomass productivity, FAME characteristics and physical property parameters of biodiesel than those obtained from the open tray+CL system. The physical property parameters of biodiesel produced from algal cells grown in PBR+CL were comparable to existing fuel standards. The results have shown lower cold filter plugging point (- 6.57 °C), higher cetane number (58.04) and average oxidative stability (3.60 h). Collectively, this investigation unveils the novel deployment of CL as a cost-effective feedstock for commercialisation of biodiesel production.

Photoautotrophic cultivation of oleaginous microalgae and co-pelletization with filamentous fungi for cost-effective harvesting process and improved lipid yield

Oleaginous microalga Scenedesmus obliquus SIT06 was selected as potential biodiesel feedstocks due to its high lipid content and suitable fatty acid composition for production of biodiesel with high oxidative stability and high cetane number. The important factors for cultivating microalgae in photoautotrophic mode were optimized through response surface methodology (RSM). The highest microalgal biomass obtained was 1.99 ± 0.12 g L−1 with a high lipid content of 40.86 ± 0.32%. To simplify harvesting process of microalgal cells, pellet-forming filamentous fungi were inoculated into the late log-phase of microalgae culture. Among the fungi tested, Cunninghamella echinulata TPU 4652 most effectively harvested the microalgal cells with the highest flocculation efficiency of 92.7%. Moreover, the biomass and lipids of microalgae-fungi pellets were as high as 4.45 ± 0.06 and 1.21 ± 0.08 g L−1, respectively. The extracted lipids were mainly composed of C16:0, C18:0, and C18:1, and their estimated fuel properties meet with the international standards indicating their potential use as biodiesel feedstocks. This study has shown the strategies not only to simplify the harvesting process but also to increase the lipid yield and tailor the lipid composition.

Effective biogas upgrading and production of biodiesel feedstocks by strategic cultivation of oleaginous microalgae

This study has shown the strategies to upgrade biogas and produce lipids as biodiesel feedstocks by cultivation of oleaginous microalgae. Three important growth factors for microalgae including light intensity, nitrogen source and CO2 supply, were strategically stepwise-increased during cultivation. The stepwise-increasing of CO2 supply was suitable for cell growth and lipid production while the stepwise-increasing of light intensity was more suitable for CO2 removal efficiency. Among the strategies attempted, the simultaneous stepwise-increasing of all three growth factors most effectively enhanced the performance of microalgae. Through this strategy, >96% of CO2 was continuously removed from biogas and the CH4 content in the purified biogas was >98%. This process also generated microalgal biomass at 4.40 ± 0.04 g L−1 with a lipid content of 34.10 ± 2.26%. The CO2 removal rate by this process was as high as 6.50 ± 0.21 g-CO2 day−1 per 1 L microalgal culture. The microalgal lipids contained long chain fatty acids (C16C18) >94% and their prospect fuel properties indicated their suitable use as biodiesel feedstocks. The integrated processes and strategies in this study would contribute greatly to the production of biogas and biodiesel feedstocks.

Energy-efficient outdoor cultivation of oleaginous microalgae at northern latitudes using waste heat and flue gas from a pulp and paper mill

Energy efficient cultivation is the major bottleneck for microalgal biomass production on a large scale and considered very difficult to attain at northern latitudes. In this study an unconventional method for industrial microalgae cultivation for bio-oil production using pulp and paper mill waste resources while harvesting only once a year was performed, mainly in order to investigate the energy efficiency of the process. Algae were cultivated for three months in 2014 in covered pond systems with access to flue gas and waste heat from the industry, and the biomass was recovered as thick sediment sludge after dewatering. The cultivation systems, designed to manage the waste resources, reached a promising photosynthetic efficiency of at most 1.1%, a net energy ratio (NER) of 0.25, and a projected year-round energy biomass yield per area 5.2 times higher than corresponding rapeseed production at the location. Thus, microalgae cultivation was, for the first time, proven energy efficient in a cold continental climate. Energy-rich indigenous communities quickly out-competed the oleaginous monocultures used for inoculation. The recovered biomass had higher heating values of 20–23MJkg−1 and contained 14–19% oil dominated by C16 followed by C18 fatty acids. The cultivation season at 59°15′N, 14°18′E was projected to be efficient for 10months and waste heat drying of the biomass is suggested for two winter months. The technique is proposed for carbon sequestering and energy storage in the form of microalgal sludge or dry matter for later conversion into biochemicals.

Effect of gamma irradiation on lipid accumulation and expression of regulatory genes involved in lipid biosynthesis in Chlorella sp.

Microalgae are promising species with high potential for biodiesel production. Large-scale cultivation of oleaginous microalgae in industrial effluents and municipal wastewater provides dual benefits of biodiesel production and wastewater treatment. Such approach to biodiesel production does not interfere with conventional agricultural resources and practices. Microalgae can accumulate lipid under various stress conditions. In this study, gamma irradiation was used for the first time as a stressor to trigger lipid accumulation in two strains of Chlorella sorokiniana. Gamma irradiation enhanced the lipid content of more than 40% of biomass. Intracellular reactive oxygen species generated by gamma ray exposure was measured by 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) staining under flow cytometry. Cytoplasmic lipid droplets were observed by Nile red staining using fluorescence microscopy. Expression patterns of regulatory genes involved in lipid biosynthesis, namely acetyl-CoA carboxylase and diacylglycerol acyl transferase, were upregulated immediately after irradiation and were highest 3 days post irradiation. This novel strategy of using gamma radiation as a faster and extremely potent stressor for triggering lipid biosynthesis in microalgae has immense potential in industrial biodiesel production.

Strategies to improve methane content in biogas by cultivation of oleaginous microalgae and the evaluation of fuel properties of the microalgal lipids

This study aimed to improve methane content in biogas by feeding biogas through the culture of oleaginous microalgae. As oleaginous microalgae have ability to mitigate CO2 into lipids and accumulate at the content >20%, this process not only contributes to CO2 removal from biogas but also producing microalgal biofuel. Among the species tested, Scenedesmus sp. and marine Chlorella sp. are suitable for this purpose. However, Scenedesmus sp. was selected due to the higher CO2 removal ability and the optimized conditions were as follows: gas flow rate of 0.3 L h−1 per 1 L- microalgal culture inoculated with 107 microalgal cells mL−1, added with KNO3 0.8 g L−1 as nitrogen source and illuminated at 5.5 klux light intensity. Under these conditions, methane content in biogas was increased from 60% up to >90% coupled with lipid productivity of 88.57 mg L−1 day−1. With the strategy of stepwise-increasing gas flow rate to support the increasing biomass, the final biomass and lipid productivity were 1.25 and 1.79 folds increased. CO2 removal rate was as high as 5.097 g-CO2 day−1 per 1 L-microalgal culture. Fuel properties calculated based on fatty acid composition indicated high oxidation stability and high ignition quality of the microalgal lipids-derived biodiesel.

Cultivation of oleaginous microalgae for removal of nutrients and heavy metals from biogas digestates

Cultivation of microalgae in anaerobically digested effluent is beneficial for removal of nutrients, such as nitrogen and phosphorus, and heavy metals at reduced cost and generation of biomass to produce biofuels. In the present study, four strains of oleaginous microalgae, separated from fresh water in South China, were evaluated for their ability to remove nitrogen and phosphorus. The results showed that Scenedesmus sp. (GN 171) was capable of removing nitrogen and phosphorous in BG-11 medium at the rates of 97% and 99%. Two types of anaerobically digested effluents, i.e., grass anaerobically digested effluent and molasses wastewater anaerobically digested effluent, were chosen as the nutrient sources. These anaerobically digested effluents diluted in BG-11 medium or with tap water were used as the substitute medium to cultivate GN 171; other pretreatment methods, such as sterilization and dilution ratio, were also taken into consideration. A ratio of 1/3 for unsterilized grass anaerobically digested effluent/tap water mixture (designated as G4) was the optimal proportion for growth of GN 171 and removal of nitrogen and phosphorus at a large scale. The dry weight of GN 171 reached 3.2 g L−1, and the total lipid, carbohydrate and protein contents were 34%, 30% and 16% in G4. The efficacies for removal of total nitrogen, ammonia nitrogen, phosphorus and selected heavy metals were generally satisfactory. It seems possible to use ADE, rather than any artificial medium, as the sole nutrient source for microalgae production.

An oleaginous filamentous microalgae Tribonema minus exhibits high removing potential of industrial phenol contaminants

Discharge of industrial phenol contaminants could cause great harm on natural environment. Through oleaginous microalgae cultivation in phenolic wastewater, pollutants can be phototrophically biofixed into biomass as feedstock for bioenergy production. It was firstly reported in this study that, an oleaginous filamentous microalgae Tribonema minus exhibited strong environmental phenol removal ability. T. minus filaments showed 449.46mgg−1 of phenol-uptake capacity, obviously higher than those strains with low phenol absorption such as Scenedesmus dimorphus. And phenols could be removed efficiently at the initial phenol concentration up to 700mgL−1. Simultaneously, through T. minus growth, phenol concentration could be decreased from 100mgL−1 to the range of 0.1–0.5mgL−1, which meet industrial discharge need of phenol contaminants in most countries. So Tribonema minus is a potential algal specie to help the construction of integrated process for both oleaginous biomass production and bioremediation of phenol contaminants.

Physiological responses of freshwater oleaginous microalgae Desmodesmus sp. NMX451 under nitrogen deficiency and alkaline pH-induced lipid accumulation

Many microalgae are reported to accumulate TAG under high concentrations of bicarbonate and nitrogen deficiency, but their physiological responses remain unknown and the associated applied technology is rarely explored. We found that single high concentration of bicarbonate did not enhance lipid content, except when combined with nitrogen limitation in Desmodesmus sp. NMX451, and the lipid contents obtained were independent from nitrogen limitation and alkalinity stress. Further analysis showed that adding bicarbonate not only retarded the cell cycle, repressed starch accumulation but also promoted polar lipid content. Nitrogen limitation meantime caused protein and chlorophyll degradation with a corresponding increase in total lipid content. Following the aforementioned insights, combined cultivation was performed at an outdoor 5 L scale, and higher biomass and lipid productivities were obtained. These results suggest that bicarbonate can be used as a "trigger" for rapid lipid accumulation in microalgae during nitrogen depletion, and this is an effective new strategy for the cultivation of oleaginous microalgae.

Microalgal oil production for use in rice farms in Albufera (València) region

In the Albufera (Valencia) region of Spain, rice has been farmed for nearly 500 years. Post-harvest flooding of rice fields has become an integral element of wetland refuge for migratory birds. The steady rise in the cost of purchased inputs is causing considerable economic stress to the viability of rice farming in this region. In 2011, it has been estimated the cost of purchased diesel accounted for about 15% of the gross revenue from grain sales. Setting aside about 1.6% of the 14,350-hectare paddy fields for the dedicated yearround cultivation of oleaginous microalgae appears to be sufficient for the entire annual need of diesel fuel. The isolated crude microalgal oil could be used directly in diesel farm equipment, with only minor modifications of the diesel engine required for the optimisation of performance and minimisation of the emission of pollutants. The net economic gain would be nearly €2 million annually.

Effects of iron on fatty acid and astaxanthin accumulation in mixotrophic Chromochloris zofingiensis

The integration of oleaginous microalgae cultivation with high-value products is considered a low-cost approach for manufacturing algae-based biodiesel. The objective of this study was to investigate the potential of using Fe(II) to produce fatty acids and astaxanthin in mixotrophic Chromochloris zofingiensis. Fatty acid biosynthesis was less sensitive than astaxanthin formation to the changes in Fe(2+) concentrations. However, the enhancement and inhibition of fatty acids formation were concomitant with an increase and a decrease in the production of astaxanthin, respectively. The highest contents of astaxanthin and total fatty acids were simultaneously obtained at 0.2mM Fe(2+) with the corresponding values of 2.2mgg(-1) (i.e., 25.8mgl(-1)) and 41.8% dry weight (i.e., 5gl(-1)).

Differential fatty acid profiles of Chlorella kessleri grown with organic materials

AbstractBACKGROUND: Integration of oleaginous microalgae cultivation with wastewater treatment is considered a low‐cost approach for manufacturing algae‐based biodiesel. However, autotrophic microalgae cannot survive in organic wastewater where the effluent is usually turbid and sunlight cannot penetrate into the wastewater. Thus mixotrophic microalgae should be explored. The objective of this study was to investigate the potential of using mixotrophic Chlorella kessleri to produce fatty acids from organic materials.RESULTS: Results revealed that mixotrophic C. kessleri fatty acids display much greater productions (up to 54.67% of cell dry weight) and more suitable compositions for biodiesel production (moderate carbon chain length mainly with C16 and C18, down to 1.17 ∇/mol of unsaturation degree) than autotrophic ones. A suitable final pH (near neutral) after nitrate‐depletion and a high organic carbon consumption seemed to be the key factors manipulating fatty acids production under whichever organic substrate tested.CONCLUSION: These characteristics increase the acceptability in using mixotrophic C. kessleri as a potential easy‐control candidate in biodiesel production. If fed with available organic effluent of wastewater as the nutrient supply, C. kessleri may have great potential for profitable biodiesel. © 2012 Society of Chemical Industry