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Prospective of biodiesel production utilizing microalgae as the cell factories: A comprehensive discussion
NM Verma, S Mehrotra, A Shukla, BN Mishra
African Journal of Biotechnology , 2010,
Abstract: Microalgae are sunlight-driven miniature factories that convert atmospheric CO2 to polar and neutral lipids which after esterification can be utilized as an alternative source of petroleum. Further, other metabolic products such as bioethanol and biohydrogen produced by algal cells are also being considered for the same purpose. Microaglae are more efficient than the conventional oleaginous plants in capturing solar energy as they have simpler cellular organization and high capacity to produce lipids even under nutritionally challenged and high salt concentrations. Commercially, microalgae are cultivated either in open pond systems or in closed photobioreactors. The photobioreactor systems including tubular bioreactors, plate reactors and bubble column reactors have their own advantages as they provide sterile conditions for growing algal biomass. Besides, other culture conditions such as light intensity, CO2 concentration, nutritional balance, etc, in closed reactors remain controlled. On the other hand, though the open ponds provide a cost-effective option to utilize natural light facility for algal cells, the tough maintenance of optimal and stable growth conditions makes it difficult to manage the economy of the process. Further, these systems are much more susceptible to contamination with unwanted microalgae and fungi, bacteria and protozoa that feed on algae. Recently, some work has been done to improve lipid production from algal biomass by implementing in silico and in vitro biochemical, genetic and metabolic engineering approaches. This article represents a comprehensive discussion about the potential of microalgae for the production of valuable lipid compounds that can be further used for biodiesel production.
Isolation and Evaluation of Oil-Producing Microalgae from Subtropical Coastal and Brackish Waters  [PDF]
David K. Y. Lim, Sourabh Garg, Matthew Timmins, Eugene S. B. Zhang, Skye R. Thomas-Hall, Holger Schuhmann, Yan Li, Peer M. Schenk
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0040751
Abstract: Microalgae have been widely reported as a promising source of biofuels, mainly based on their high areal productivity of biomass and lipids as triacylglycerides and the possibility for cultivation on non-arable land. The isolation and selection of suitable strains that are robust and display high growth and lipid accumulation rates is an important prerequisite for their successful cultivation as a bioenergy source, a process that can be compared to the initial selection and domestication of agricultural crops. We developed standard protocols for the isolation and cultivation for a range of marine and brackish microalgae. By comparing growth rates and lipid productivity, we assessed the potential of subtropical coastal and brackish microalgae for the production of biodiesel and other oil-based bioproducts. This study identified Nannochloropsis sp., Dunaniella salina and new isolates of Chlorella sp. and Tetraselmis sp. as suitable candidates for a multiple-product algae crop. We conclude that subtropical coastal microalgae display a variety of fatty acid profiles that offer a wide scope for several oil-based bioproducts, including biodiesel and omega-3 fatty acids. A biorefinery approach for microalgae would make economical production more feasible but challenges remain for efficient harvesting and extraction processes for some species.
Current Status and Prospects of Biodiesel Production from Microalgae  [PDF]
Xiaodan Wu,Rongsheng Ruan,Zhenyi Du,Yuhuan Liu
Energies , 2012, DOI: 10.3390/en5082667
Abstract: Microalgae represent a sustainable energy source because of their high biomass productivity and ability to remove air and water born pollutants. This paper reviews the current status of production and conversion of microalgae, including the advantages of microalgae biodiesel, high density cultivation of microalgae, high-lipid content microalgae selection and metabolic control, and innovative harvesting and processing technologies. The key barriers to commercial production of microalgae biodiesel and future perspective of the technologies are also discussed.
Potency of Microalgae as Biodiesel Source in Indonesia  [cached]
H Hadiyanto,W Widayat,Andri Cahyo Kumoro
International Journal of Renewable Energy Development (IJRED) , 2012,
Abstract: Within 20 years, Indonesia should find another energy alternative to substitute current fossil oil. Current use of renewable energy is only 5% and need to be improved up to 17% of our energy mix program. Even though, most of the area in Indonesia is covered by sea, however the utilization of microalgae as biofuel production is still limited. The biodiesel from current sources (Jatropha, palm oil, and sorghum) is still not able to cover all the needs if the fossil oil cannot be explored anymore. In this paper, the potency of microalgae in Indonesia was analysed as the new potential of energy (biodiesel) sources.
Microalgae Lipid and Biodiesel Production: A Brazilian Challenge  [PDF]
Carolina T. Miranda, Roberta F. Pinto, Daniel V. N. de Lima, Carolina V. Viegas, Simone M. da Costa, Sandra M. F. O. Azevedo
American Journal of Plant Sciences (AJPS) , 2015, DOI: 10.4236/ajps.2015.615254
Abstract: Global increases in atmospheric CO2 and climate change are drawing considerable attention to identify sources of energy with lower environmental impact than those currently in use. Biodiesel production from microalgae lipids can, in the future, occupy a prominent place in energy generation because it represents a sustainable alternative to petroleum-based fuels. Several species of microalgae produce large amounts of lipids per biomass unit. Triacylglycerol is the fatty acid used for biodiesel production and the main source of energy reserves in microalgae. The current literature indicates that nutrient limitations can lead to triacylglycerol accumulation in different species of microalgae. Further efforts in microalgae screening for biodiesel production are needed to discover a native microalgae that will be feasible for biodiesel production in terms of biomass productivity and oil. This revision focuses in the biotechnological potential and viability of biodiesel production from microalgae. Brazil is located in a tropical region with high light rates and adequate average temperatures for the growth of microalgae. The wide availability of bodies of water and land will allow the country to produce renewable energy from microalgae.
Screening of Microalgae for Biodiesel Feedstock  [PDF]
Xi Chen, Guoqiang He, Zhiping Deng, Nan Wang, Wei Jiang, Sanfeng Chen
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.47044
Abstract:

Three heterotrophic microalgae identified as Scenedesmus sp. Y5, Scenedesmus sp. Y7 and Chorellasp. Y9 were isolated and screened from natural water based on biomass yield and lipid productivity. Fatty acids’ composition analysis showed that both Y5 and Y7 mainly contained C16:0, C18:1 (n - 9), C18:2 (n - 6) and C18:3 (n - 3) and Y9 mainly contained C16:0, C18:0 and C18:2 (n - 6), suggesting that these microalgae can be ideal feedstock for biodiesel. Considering the specific growth rate and lipid productivity, the culture conditions were optimized for Scenedesmus sp. Y5, Scenedesmus sp. Y7 and Chorellasp. Y9. Based on the optimization of cultural conditions, all of these three microalgae were tested in fed-batch fermentation, and their biomass productivities were 4.960 g·L-1·d-1, 5.907 g·L-1·d-1 and 4.038 g·L-1

TUBULAR PHOTOBIOREACTOR FOR MICROALGAE BIODIESEL PRODUCTION  [PDF]
Nkongolo Mulumba,Ihab H. Farag
International Journal of Engineering Science and Technology , 2012,
Abstract: Biodiesel production from algae is a promising technique. Microalgae have the potential to produce 5,000-15,000 gallons of biodiesel/(acre-year). However, there are challenges; these include high yieldof algae biomass with high lipid content and the effective technique to harvest the grown algae, extract the algal oil and transesterify the oil to biodiesel. In this project Tubular PhotoBioReactor (TPBR) was designed and achieved a ten times increase in algae concentration. It produced 1g of dry algal biomass per liter of medium within 12 days, with a lipid content of 12% approximately. Healthy algal culture grew well in the TPBR reaching 56x106 cells/mL of culture medium. The 10 fold increase is higher than those reported for open ponds and helical photobioreactor.
High Lipid Induction in Microalgae for Biodiesel Production  [PDF]
Kalpesh K. Sharma,Holger Schuhmann,Peer M. Schenk
Energies , 2012, DOI: 10.3390/en5051532
Abstract: Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. High lipid productivity of dominant, fast-growing algae is a major prerequisite for commercial production of microalgal oil-derived biodiesel. However, under optimal growth conditions, large amounts of algal biomass are produced, but with relatively low lipid contents, while species with high lipid contents are typically slow growing. Major advances in this area can be made through the induction of lipid biosynthesis, e.g., by environmental stresses. Lipids, in the form of triacylglycerides typically provide a storage function in the cell that enables microalgae to endure adverse environmental conditions. Essentially algal biomass and triacylglycerides compete for photosynthetic assimilate and a reprogramming of physiological pathways is required to stimulate lipid biosynthesis. There has been a wide range of studies carried out to identify and develop efficient lipid induction techniques in microalgae such as nutrients stress (e.g., nitrogen and/or phosphorus starvation), osmotic stress, radiation, pH, temperature, heavy metals and other chemicals. In addition, several genetic strategies for increased triacylglycerides production and inducibility are currently being developed. In this review, we discuss the potential of lipid induction techniques in microalgae and also their application at commercial scale for the production of biodiesel.
Current Status and Outlook in the Application of Microalgae in Biodiesel Production and Environmental Protection  [PDF]
Junfeng Rong,Hui Chen,Qiang Wang
Frontiers in Energy Research , 2014, DOI: 10.3389/fenrg.2014.00032
Abstract: Microalgae have been currently recognized as a group of the most potential feedstocks for biodiesel production due to high productivity potential, efficient biosynthesis of lipids, and less competition with food production. Moreover, utilization of microalgae with environmental purposes (CO2 fixation, NOx, and wastewater treatment) and biorefinery has been reported. However, there are still challenges that need to be addressed to ensure stable large-scale production with positive net energy balance. This review gives an overview of the current status of the application of microalgae in biodiesel production and environmental protection. The practical problems not only facing the microalgae biodiesel production but also associated with microalgae application for environmental pollution control, in particular biological fixation of greenhouse gas (CO2 and NOx) and wastewater treatment are described in detail. Notably, the synergistic combination of various applications (e.g., food, medicine, wastewater treatment, and flue gas treatment) with biodiesel production could enhance the sustainability and economics of the algal biodiesel production system.
Cultivating Microalgae in Domestic Wastewater for Biodiesel Production  [cached]
Soha S.M. MOSTAFA,Emad A. SHALABY,Ghada I. MAHMOUD
Notulae Scientia Biologicae , 2012,
Abstract: The objective of this study was to evaluate the growth of nine species of microalgae (green and blue green microalgae) on domestic waste water samples obtained from Zenein Waste Water Treatment Plant (ZWWTP), Giza governorate, Egypt. The species were cultivated in different kind of waste water; before treatment; after sterilization; with nutrients with sterilization and with nutrients without sterilization. The experiment was conducted in triplicate and cultures were incubated at 25±1°C under continuous shaking (150 rpm) and illumination (2000 Lux) for 15 days. pH, electric conductivity (EC), optical density (OD) , dry weight (DW), were done at the time of incubation and at the end of experiment, in addition to determine the percentage of lipid and biodiesel. The data revealed that, domestic waste water with nutrient media (T3) was promising for cultivation of five algal species when compared with conventional media, Moreover, domestic waste water after sterilization (T2) was selected media for cultivation of Oscillatoria sp and Phormedium sp. However, T1 media (waste water without treatment) was the promising media for cultivation of Nostoc humifusum. The biodiesel produced from algal species cultivated in waste water media ranged from 3.8 to 11.80% when compared with the conventional method (3.90 to 12.52%). The results of this study suggest that growing algae in nutrient rich media offers a new option of applying algal process in ZWWTP to mange the nutrient load for growth and valuable biodiesel feedstock production.
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