Algae Biofuel Production Research Articles

Recent Advancement Of Algal Biofuel Production And Its Potential Uses

The utilization of diverse energy sources is linked to the growth of industry, agriculture, and transportation. After the third generation of biodiesel production began, it was anticipated that algae would emerge as the most advantageous source because it not only can accumulate large amounts of lipids but also has the potential to reduce the amount of agricultural land required for the production of biofuels and enhance air quality by capturing carbon dioxide. In contrast to the price of making biodiesel from crops, the cost of algal biomass cultivation and processing poses a significant issue. The first step is to use genetic engineering to boost the lipid content of algal cells. The promotion of enhanced lipid accumulation by stressing algae is related to the second way. The third direction entails looking for new, promising strains of algae that will differ from the currently recognized strains in their ability to collect biomass more quickly, have greater Triacylglycerols [TAG] concentrations, and accumulate saturated and unsaturated fatty acids in the right ratios. By defining the evolutionary relationships within the main taxonomic groups of algae, a new technique in the search for biotechnologically relevant strains of algae has recently been developed. These investigations have resulted in a significant cost decrease for the manufacture of biofuel based on algae biomass. All of this research aimed at improving algae biofuel production and exploring additional biofuel sources is crucial.

Using Algae for Biofuel Production: A Review

One of the greatest challenges of the 21st century is to obtain an ecological source of transport fuels. The production of biofuels based on feedstock obtained through the exploitation of arable land translates into an increase in food prices and progressive degradation of the environment. Unlike traditional agricultural raw materials, algae are a neutral alternative in many respects. They can even be obtained as waste from polluted water reservoirs. One of the manifestations of the deterioration of surface waters is the eutrophication of water reservoirs, which leads to an increase in the number of algae. Algae reaching the shores of water reservoirs can be used as a raw material for the production of biofuels, including biogas, bioethanol and biodiesel. However, it should be remembered that water blooms are a periodic phenomenon, appearing in the summer months. Therefore, in order to ensure the continuity of obtaining energy from biomass, it is necessary to conduct algae cultivation in artificial open tanks or photobioreactors. Accordingly, this review first briefly discusses the properties and possible applications of different species of algae in various industrial areas, and then describes the process of eutrophication and the presence of algae in eutrophicated reservoirs. Technologies of algal cultivation in various systems and technologies of algal biomass pretreatment were critically discussed. Various methods of obtaining biomass from algae were also reviewed, and the process conditions were summarized. Biofuels of various generations and raw materials from which they are obtained are presented in order to determine the possible future directions of development in this field. Parameters affecting the selection of algae species for the production of biofuels were also examined and presented. Overall, algal biofuels still face many challenges in replacing traditional fossil fuels. Future work should focus on maximizing the yield and quality of algae-derived biofuels while increasing their economic viability.

A comparative review on photo and mixotrophic mode of algae cultivation: Thermochemical processing of biomass, necessity of bio-oil upgrading, challenges and future roadmaps

Availability of renewable biomass for the production of bioenergy is need of hour as fossil-based energy consumption has led to both environmental and health problems. Algae biomass gains advantages over other biomasses (agriculture, sewage, forest, sludge, municipal waste) due to their availability, biomass generation in wastewater and negative carbon dioxide emission. In this review paper, we have explored the algae biomass cultivation routes, thermochemical conversion and upgradation of algal biomass. Photo bioreactors (tubular, bag, flat panel, etc) are preferred for microalgae cultivation in association with raceway open ponds for liquid hydrocarbons production. Algae biomass are processed through hydrothermal liquefaction (Temperature range of 220–320 °C, time of 60 min, pressure of 5–20 bar), pyrolysis (Temperature range of 320–420 °C) and co-liquefaction. The commonly upgradation techniques are catalytic cracking, hydrodeoxygenation, etc. Hydrodeoxygenation was performed to nullify the oxygen content of bio-oil, since in adverse case the bio-oil with higher content causes corrosion and coke formation in combustion engines. The algae biofuel production cost depends upon the conversion techniques and upgrading processes. Further in future this review provides strong base for exploring the aqueous phase obtained from thermochemical process for bio-hydrogen production via photo-catalytic reforming processes.

BIOFUELS FROM ALGAE AS A DIRECTION FOR THE DEVELOPMENT OF THE «GREEN» ECONOMY: THE CURRENT STATE AND PROSPECTS

The article describes environmental aspects of the impact of traditional energy sources on the environment. It is substantiated that energy needs and environmental problems lead to the search for alternative renewable fuels. A comparative analysis of the structure of general supply between traditional and alternative energy sources is done. The current state of production and use of traditional fuels and prospects for the production of biofuels in Ukraine are analyzed. The projected structure of the use of traditional and alternative fuels according to the Energy Strategy of Ukraine until 2035 «Safety, energy efficiency, competitiveness» is presented. The classification of biofuels is provided depending on raw materials: first, second and third generation. Unlike biofuels from crops such as sugar cane and corn (first-generation biofuels), as well as animal and vegetable wastes (second-generation), algae-derived fuels (third-generation biofuels) have many benefits. In particular, this is a greater potential for biofuel production compared to previous systems: a variety of possible fuels (biodiesel, bioethanol, biobutanol, biogas and even jet fuel); flexible production technologies. Algae cultivation technologies have been studied: especially cultivation in open reservoirs or in more advanced closed ponds and bioreactors. It is substantiated that algae are most often used for biodiesel production; a comparison of different technologies for its production is made. The foreign experience of algae biofuel production and its usage by various automobile companies and enterprises, as well as the prospects of algae biofuel production in Ukraine are presented. Despite the prospects for the production of the third-generation biofuels, there we think, that the issue of investigation has been not been studied properly by scientists and Ukrainian producers don’t have basic knowledge.

Utilizing high-purity carbon dioxide sources for algae cultivation and biofuel production in the United States: Opportunities and challenges

Carbon dioxide (CO2) supply is an important consideration for algae production systems, and using high-purity CO2 eliminates the need for purification processes. This study assessed the challenges and opportunities inherent in using waste high-purity CO2 to produce algae in the United States. The United States’ upper Midwest region is rich in high-purity CO2 from corn ethanol production. However, its climate is not as favorable for algae production as that on the Gulf Coast. This study assessed the tradeoffs between these factors by comparing algae biofuel production with and without high-purity CO2 across these two regions. Monthly algae cultivation was modeled in open ponds co-located with high-purity CO2 sources in the Midwest and along the Gulf Coast, where many steam methane reforming and ammonia production facilities are located. This revealed that, by avoiding the energy-intensive carbon-capture process, an algae site that sources carbon from a high-purity CO2 source would achieve a 9–39% reduction in life-cycle greenhouse gas (GHG) emissions and a 9–37% reduction in life-cycle fossil energy use compared to a similar site using dilute CO2 for algae cultivation. The results also suggest that during warm months an algae pond in the Midwest would achieve results that are comparable to GHG emissions from a pond on the Gulf Coast. Furthermore, several Midwest algae ponds investigated in this study create less local water stress than those located along the Gulf Coast. The abundant high-purity CO2 from corn ethanol plants thus creates a potential opportunity for algae cultivation in the Midwest. This study illustrated the interplay between algae productivity, CO2 delivery, GHG emissions, and water stress in siting algae ponds.

Integration of Algal Biofuel Production with Municipal Wastewater Treatment: a Review

The integration of algae-based wastewater treatment and biofuel production has been of growing research interest in recent years. This article reviewed recent researches in algae biofuel production and the integration of algal wastewater treatment and biofuel production. The methods to algal biofuel production, biofuel productivity, and removal rate of treated municipal wastewater were summarized in this review. Chlorella is largely used, especially in biodiesel and bioethanol production. Spirulina is more often used to produce biogas. The removal rate of NH4+-N can be high in this integration. The most common biofuel products in this integration are biomethane and lipid. Traces of the integration are numerous on laboratory basis and limited in commercial use for now. The barrier to apply it from lab to commercial use may include a high cost during algae harvesting as well as land use and availability. Possible solutions and research gaps are outlined in this article.

Balancing Water Sustainability and Productivity Objectives in Microalgae Cultivation: Siting Open Ponds by Considering Seasonal Water-Stress Impact Using AWARE-US.

Microalgae have great potential as an energy and feed resource. Here we evaluate the water use associated with freshwater algae cultivation and find it is possible to scale U.S. algae biofuel production to 20.8 billion liters of renewable diesel annually without significant water-stress impact. Among potential sites, water-stress is significantly more variable than algae productivity across location and season. Thus, it is possible to reduce water-stress impact, quantified as water scarcity footprint, through the choice of algae site location. We test three site-selection criteria based on (1) biomass productivity, (2) water-use efficiency, and (3) water-stress impact and find that adding water-stress constraints to productivity-based ranking of suitable sites reduces water-stress impact by 97% and water consumption by half, compared with biomass-productivity ranking alone, with little productivity impact (<1.7% per-site on average). With 20.8 billion liters, algae could meet 19.7% of U.S. jet fuel demand with a freshwater demand of less than 1.4% of U.S. irrigation consumption. Evaluating water-stress impact is important because the impact of unit water consumption on water stress varies significantly across regions and seasons. Considering seasonal water balances allows producers to understand the combined seasonal effects of hydrologic flows and productivity, thereby avoiding potential short-term water stress.

Assessment of algal biofuel resource potential in the United States with consideration of regional water stress

Algae is a promising feedstock for biofuels. Because scaling up the production of algae-based biofuels consumes a significant amount of water, it is important to consider the impact it has on water stress. This study evaluates the potential for algae-derived biofuel production in the United States (US) and considers regional water stress. We used the Biomass Assessment Tool (BAT) to identify potential sites in the US that meet land, biomass productivity, and CO2 co-locating criteria. We quantify the water stress impacts of algal biofuel production in terms of water scarcity footprint using water consumption from BAT, and the water stress indicator from Available Water Remaining for the US (AWARE-US) system. We assess long-term (20 billion gal per year [BGY]) and near-term (5 BGY by 2030) renewable diesel (RD) production targets. To select suitable algae sites, we consider biomass yield and water use with and without water stress constraints. We found that ranking sites based on biomass yield results in a high water stress impact (24.5 × 103 US equivalent BGY [BGYe]) for the long-term RD target. If we instead rank sites on water use efficiency, water consumption decreases on average by 62%, with an average reduction in biomass yield of 25%. To reconcile tradeoffs between biomass yield and water stress impacts, water stress indicator (AWARE-US) that represents relative water availability by region can be applied while considering biomass yield. This strategy removes sites located in water-stressed areas and keeps high-productivity sites. For the long-term RD target, this reduces water stress impacts by 55% (13.8 BGYe) without lowering yield or 97% (24.2 BGYe) with moderately lower (4%) yield, compared to the sites ranked by biomass yield alone. The results demonstrate that incorporating water stress into energy-scale algae biofuel production planning is key to achieving synergies between biofuel yield and fresh water stress impacts.

Economic viability of multiple algal biorefining pathways and the impact of public policies

This study presents an extensive systems-level multi-pathway sustainability assessment of algae biofuel production that demonstrates the necessity of high-value co-products, examines the impact of public policy scenarios, and identifies improvements and pathway directions required for economic viability. Engineering process models for several fuel and co-product pathways were leveraged to perform high fidelity techno-economic analysis. These pathways included: baseline hydrothermal liquefaction; protein extraction followed by hydrothermal liquefaction; fractionation into high-value chemicals with fermentation followed by hydrothermal liquefaction for fuels; and a small-scale first-of-a-kind plant coupled with a wastewater treatment facility. From these models, it was shown that hydrothermal liquefaction as a fuel-only pathway is not economically viable. Likewise, the benefits of coupling with wastewater water treatment are insignificant compared to the impact of reduced facility size resulting in increased capital costs. These models were also used to examine public policy scenarios, uniquely presenting their impact on the breakeven cost of fuel production and sensitivity to scenario assumptions. Specifically, depreciation type was shown to be irrelevant for writeoffs faster than 10 years. Due to discounting, short-term subsidies were found to capture 50% of the subsidy value in 6 years with an additional 24 years required for full subsidy valuation. Integration of a carbon economy was shown to decrease biofuel production costs, particularly for the protein pathway due to the co-product accounting. Finally, a metric of normalized costs was used to compare algal biorefineries to corn and cellulosic ethanol production, showing that algal systems are uniquely different due to significantly higher capital costs, though operational costs are comparable. This work demonstrates that, to reach economic viability, algal biofuel production must either utilize higher value non-fuel co-products or achieve drastic reductions in capital costs.

A bi-objective stochastic location-inventory-routing model for microalgae-based biofuel supply chain

This paper introduces a viable two-objective model for the design of algae biofuel production and distribution network with integrated formulation of location, inventory and routing decisions. The model consists of an algae biomass production facility, several distribution facilities, multiple extraction sites, and transport vehicles. In this model, the system implementation cost and its pollution impacts via CO2 emission are considered simultaneously. Our model allows the decision maker to determine the number and location of distribution facilities, the allocation of extraction sites to these facilities, the routes by which extraction sites need to be served, and the minimum inventory level that should be maintained at each distribution facility to achieve the mentioned objectives. In an attempt to bridge the gaps in the literature, the paper tries to incorporate the uncertainty in parameters and also a queueing system into integrated formulation of location, inventory and routing decisions and develop a viable model with economic and environmental objectives considered simultaneously. Since the proposed model belongs to the class of NP-hard problems, two multi-objective metaheuristic algorithms, namely MOPSO and NSGA-II, are tested for solving the formulated model. For this purpose, Taguchi method is used to set the parameters of these algorithms, and then their results are compared in terms of five evaluation criteria. These comparisons show that, for the formulated model, NSGA-II outperforms MOPSO in the majority of evaluation criteria. Finally, the proposed model is evaluated with the real data related to the implementation of an algae biofuel production and distribution network in Iran and the results are further examined. The results demonstrate the good performance of the proposed model.

Risk analysis and development of algae biofuel from aquatic and terrestrial systems

Production of algae biofuel from aquatic and terrestial systems are global emerging strategies for the reduction of the overreliance on fossil fuel based on its potentials to promote the green environment, which can be a panacea to the global warming, climate change and other earthly challenges affecting global evolution. Algae as bioenergetic resource has the capacity to solve the uneven energy supply of developing countries. This study adopts an exploratory research appraoch and uses a contextual SWOT model to assess what needs to be done on the premise of the prevailing situation in Nigeria and strategically analyzes the risk and potential benefits of biodiesel production from algae. The model helps to examine the strength, weaknesses, opportunities, and threats of the algae biofuel production and utilization peculiar to Nigeria. The result showed that there are prospects for the algae biofuel implementation in Nigeria, though with various limitations. Some of the challenges anticipated could be resolved with adequate government and private stakeholders support in terms of policies, funding and sustainable management. The main focus of this paper is on micro-algae, known for their rapid growth rate and suitability as feedstock for biodiesel (third generation of bio energy). With Nigeria’s total economic dependence on petroleum oils, algae derived biofuel could provide options as well as aid environmental sustainability.

Lipid metabolism and potentials of biofuel and high added-value oil production in red algae

Biomass production is currently explored in microalgae, macroalgae and land plants. Microalgal biofuel development has been performed mostly in green algae. In the Japanese tradition, macrophytic red algae such as Pyropia yezoensis and Gelidium crinale have been utilized as food and industrial materials. Researches on the utilization of unicellular red microalgae such as Cyanidioschyzon merolae and Porphyridium purpureum started only quite recently. Red algae have relatively large plastid genomes harboring more than 200 protein-coding genes that support the biosynthetic capacity of the plastid. Engineering the plastid genome is a unique potential of red microalgae. In addition, large-scale growth facilities of P. purpureum have been developed for industrial production of biofuels. C. merolae has been studied as a model alga for cell and molecular biological analyses with its completely determined genomes and transformation techniques. Its acidic and warm habitat makes it easy to grow this alga axenically in large scales. Its potential as a biofuel producer is recently documented under nitrogen-limited conditions. Metabolic pathways of the accumulation of starch and triacylglycerol and the enzymes involved therein are being elucidated. Engineering these regulatory mechanisms will open a possibility of exploiting the full capability of production of biofuel and high added-value oil. In the present review, we will describe the characteristics and potential of these algae as biotechnological seeds.

Post Treatment of Primary and Secondary Effluent by Chlorococcum sp.

The potential of algae biofuel production in conjunction with wastewater treatment is considered an alternative energy source, which is recently proposed. The scope of this study was to investigate the use of Chlorococcum sp. in wastewater treatment and the evaluation of algal biomass and lipid production. The experiments were conducted using a 30-L open pond. The pond was fed with primary and secondary treated wastewater from an activated sludge treatment plant. Experiments were conducted under controlled environmental conditions in order to investigate the removal of nutrients, biomass growth, and algal lipid content. The pond initialy treated secondary effluent at hydraulic retention time (HRT) from 2.5 to 6 days, and radiation intensity of 100 μmol m−2 s−1. With the primary effluent as substrate, the pond was operated at an HRT of 30 days, and radiation intensity of 100 and 200 μmol m−2 s−1. The growth rate of microalgae treating the secondary effluent was greater at low HRT, compared to higher HRTs. The highest biomass concentration was observed when the pond was treating the primary effluent. Nitrates removal with the secondary effluent was up to 98 %, and the lower removal efficiencies were observed at low HRTs. The higher lipid content of Chlorococcum sp. was observed when the pond was fed with the secondary effluent.

Characterization and classification of highly productive microalgae strains discovered for biofuel and bioproduct generation

This paper describes the characteristics of microalgal strains that originated out of an isolation and screening project included within the National Alliance for Advanced Biofuels and Bioproducts (NAABB). The project's goal was to identify new potential platform strains with high growth rates and/or lipid productivities. To classify the best performing strains, we conducted a combined microscopic and phylogenetic analysis. Among the best performing strains were many coccoid green algae. Several strains belong to the species Acutodesmus (Scenedesmus) obliquus and to the species Chlorella sorokiniana, thus expanding on existing germplasm. Identified at the genus level were some Desmodesmus strains and one Ankistrodesmus strain. Several strains were classified as belonging to the genus Coelastrella, a taxon reported for the first time for North America. Multiple additional strains had ambiguous identities, with some strains possibly representing novel species. Reporting on the above strains, some of which have been tested successfully in outdoor ponds and most of which are deposited at the University of Texas Culture Collection of Algae, is a step forward in expanding the biological resources available for algae biofuel production.

Impact of nitrogen limitation on biomass, photosynthesis, and lipid accumulation in Chlorella sorokiniana

Induction of oil accumulation in algae for biofuel production is often achieved by withholding nitrogen. How- ever, withholding nitrogen often reduces total biomass yield. In this report, it is demonstrated that Chlorella sorokiniana will not only accumulate substantial quantities of neutral lipids when grown in the absence of nitrogen but will also exhibit unimpeded growth rates for up to 2 weeks. To deter- mine the physiological basis for the observed increase in oil and biomass accumulation, we compared photosynthetic and respiration rates and chlorophyll, lipid, and total energy con- tent under ammonia replete and deplete conditions. Under N- depleted growth conditions, there was a 64 % increase in total energy density and a ∼20-fold increase in oil accumulation relative to N-replete growth leading to a 1.6-fold greater total energy yield in N-depleted than in N-replete cultures. We pro- pose that the higher energy accumulation in N-depleted cul- tures is due to enhanced photosynthetic energy capture and conversion associated with reduced chlorophyll levels and reduced self-shading as well as a shift in metabolism leading to the accumulation of oils.

Evaluation of Microalgae Biofuel Production Potential and Cultivation Sites Using Geographic Information Systems: A Review

Geographic Information System (GIS) tools have been used to strategically locate bioenergy facilities and optimize the relationship between biomass supply and demand, aiming to minimize overall fuel production costs. Microalgae, also termed third generation bioenergy feedstocks, are discussed for their potential to meet future energy demands. This study reviews literature on GIS applications to locate algae cultivation sites and estimate algae biofuel potential. To highlight the diversity of results, a quantitative comparison for the US studies is presented. We found two major assumptions that primarily limited the algae biofuel production potential estimates: (1) the production technology (open pond or photobioreactor), and (2) the number and type of resources considered, such as land type, CO2, water source, water quality, etc. All studies used binary (a location is either unsuitable or suitable) suitability models to determine areas for algae production. Most studies considered water, land, and CO2 resources, while some also accounted for infrastructure, soil properties, and work force requirements. We found that potential cultivation area in the USA is most sensitive to the constraints of CO2 availability and land cost. This review explains the wide range of algal biofuel potential estimates (from 0.09 to over 600 billion L yr−1) by identifying underlying assumptions, methodologies, and data. The highly variable outputs indicate the need for a comprehensive analysis of different criteria individually and in combination to estimate realistic biofuel potential. The results suggest that with models becoming increasingly detailed in considering resources and conversion/production technologies, further decrease in estimated theoretical production potential is expected under available technology.

Low Cost Alternative Fuel from Biomass

A major challenge for next decades is development of competitive renewable energy sources, highly needed to compensate fossil fuels reserves and reduce greenhouse gas emissions. Among different possibilities, which are currently under investigation, there is the exploitation of unicellular algae for production of biofuels and biodiesel in particular. Microalgae have the ability of accumulating large amount of lipids within their cells which can be exploited as feedstock for the production of biodiesel. The lipid content of different species of microalgae can range from 30%-70% of their dry weight. In this project a microalgae with lipid content of 60.095% was used. This means that 26gms of oil was obtained from 42gms of microalgae sample from which 17.624gm of biodiesel (FAME) was found at the end of transesterification. Algae biofuels avoid some of the previous drawbacks associated with crop-based biofuels as the algae do not compete with food crops. The favorable growing conditions found in many developing countries has led to a great deal of speculation about their potentials for reducing oil imports, stimulating rural economies, and even tackling hunger and poverty. Strong research efforts are however still needed to fulfill this potential and optimize cultivation systems and biomass harvesting.

Low Cost Alternative Fuel from Biomass

A major challenge for next decades is development of competitive renewable energy sources, highly needed to compensate fossil fuels reserves and reduce greenhouse gas emissions. Among different possibilities, which are currently under investigation, there is the exploitation of unicellular algae for production of biofuels and biodiesel in particular. Microalgae have the ability of accumulating large amount of lipids within their cells which can be exploited as feedstock for the production of biodiesel. The lipid content of different species of microalgae can range from 30%-70% of their dry weight. In this project a microalgae with lipid content of 60.095% was used. This means that 26gms of oil was obtained from 42gms of microalgae sample from which 17.624gm of biodiesel (FAME) was found at the end of transesterification. Algae biofuels avoid some of the previous drawbacks associated with crop-based biofuels as the algae do not compete with food crops. The favorable growing conditions found in many developing countries has led to a great deal of speculation about their potentials for reducing oil imports, stimulating rural economies, and even tackling hunger and poverty. Strong research efforts are however still needed to fulfill this potential and optimize cultivation systems and biomass harvesting.

The Selective Use of Hypochlorite to Prevent Pond Crashes for Algae-Biofuel Production.

Although algae-biofuels have many advantages including high areal productivity, algae can be preyed upon by amoebas, protozoans, ciliates, and rotifers, particularly in open pond systems. Thus, these higher organisms need to be controlled. In this study, Chlorella kessleri was used as the algal culture and Brachionus calyciflorus as the source of predation. The effect of sodium hypochlorite (bleach) was tested with the goal of totally inhibiting the rotifer while causing minor inhibition to the alga. The 24-hr LC50 for B. calyciflorus in spring water was 0.198 mg Cl/L while the 24-hr LC50 for C. kessleri was 0.321 mg Cl/L. However, chlorine dissipates rapidly as the algae serves as reductant. Results showed a chlorine dosage between 0.45 to 0.6 mg Cl/L and a dosing interval of two hours created the necessary chlorine concentrations to inhibit predation while letting the algae grow; thus giving algae farmers a tool to prevent pond crashes. Water Environ. Res., 87 (2015).

Altered lipid composition and enhanced lipid production in green microalga by introduction of brassica diacylglycerol acyltransferase 2.

Higher lipid biosynthesis and accumulation are important to achieve economic viability of biofuel production via microalgae. To enhance lipid content, Chlamydomonas reinhardtii was genetically engineered with a key enzyme diacylglycerol acyltransferase (BnDGAT2) from Brassica napus, responsible for neutral lipid biosynthesis. The transformed colonies harbouring aph7 gene, screened on hygromycin-supplemented medium, achieved transformation frequency of ~120±10 colonies/1×10(6) cells. Transgene integration and expression were confirmed by PCR, Southern blots, staining lipid droplets, proteins and spectro-fluorometric analysis of Nile red-stained cells. The neutral lipid is a major class (over 80% of total lipids) and most significant requirement for biodiesel production; this was remarkably higher in the transformed alga than the untransformed control. The levels of saturated fatty acids in the transformed alga decreased to about 7% while unsaturated fatty acids increased proportionately when compared to wild type cells. Polyunsaturated fatty acids, especially α-linolenic acid, an essential omega-3 fatty acid, were enhanced up to 12% in the transformed line. Nile red staining confirmed formation of a large number of lipid globules in the transformed alga. Evaluation of long-term stability and vitality of the transgenic alga revealed that cryopreservation produced significantly higher quantity of lipid than those maintained continuously over 128 generations on solid medium. The overexpression of BnDGAT2 significantly altered the fatty acids profile in the transformed alga. Results of this study offer a valuable strategy of genetic manipulation for enhancing polyunsaturated fatty acids and neutral lipids for biofuel production in algae.