The increasing global demand of biofuels for energy security and reduction in climate change effects generate the opportunity to explore new biomass sources. Algae is a very promising source of biomass in this context as it sequester a significant quantity of carbon from atmosphere and industrial gases and is also very efficient in utilizing the nutrients from industrial effluents and municipal wastewater. Therefore cultivation of algal biomass provide dual benefit, it provides biomass for the production of biofuels and also save our environment from air and water pollution. The life cycle assessment (LCA) of algal biofuels suggests them to be environmentally better than the fossil fuels but economically it is not yet so attractive.
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Introduction: Phlorotannins, the phenolic compounds found in brown seaweeds, are a unique and diverse class of compounds showing a huge potential for food and pharmaceutical applications.
Objective: This review will give an account of the colorimetric assays used and a discussion of their quantitative and qualitative analytical shortcomings. It will also discuss other more complex and modern analytical chemistry methods that are currently being developed to study phlorotannins. The purpose of this review is to increase awareness of these bioactive compounds and promote further development of robust analytical methods for use in biology, food science, pharmacology and biomedical and cosmeceutical sciences.
Results: Whilst the biological activity and huge commercial potential of the phlorotannins has been widely reported throughout the literature, the chemical structures and reactivity of these compounds is still not well understood. The phlorotannin content of seaweed is usually characterised using colorimetric assays. However, although these methods give a reasonable overall estimation of the total phenolic content, they lack precision and specificity.
Conclusion: This review highlights the strengths and weaknesses of commonly used colorimetric assays. Novel techniques are highlighted using more selective chemistry to identify this class of compounds.
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Mesocosm experiments conducted for ecological purposes have become increasingly popular because they can provide a holistic understanding of the biological complexities associated with natural systems. This paper describes a new outdoor mesocosm designed for CO2 perturbation experiments of benthos. Manipulated the carbonate chemistry in a continuous flow-through system can be parallelized with diurnal changes, while irradiance, temperature, and nutrients can vary according to the local environment. A target hydrogen ion activity (pH) of seawater was sufficiently stabilized and maintained within 4 h after dilution, which was initiated by the ratio of CO2-saturated seawater to ambient seawater. Specifically, pH and CO2 partial pressure (pCO2) levels gradually varied from 8.05–7.28 and 375–2,691 μatm, respectively, over a range of dilution ratios. This mesocosm can successfully manipulate the pH and pCO2 of seawater, and it demonstrates suitability for ocean acidification experiments on benthic communities.
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Between the late 1960s and the early 1980s, several generations of phycologists in Hawaii and the Philippines, associated with M. S. Doty, contributed to developing a new approach, and to advance concepts in marine agronomy. This study reviews the approach and the main concepts contributed. Integrating these contributions with others, a basic conceptual framework for marine agronomy is presented.
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Algae are one of the most viable feedstock options that can be converted into different bioenergies viz., bioethanol, biobutanol, biodiesel, biomethane, biohydrogen, etc. owing to their renewable, sustainable and economic credibility features. Algal biomass to fuel biorefining process is generally classified into three categories as chemical, biochemical and thermochemical methods. The present article aims to provide a state-of-the-art review on the factors affecting the thermochemical conversion process of algal biomass to bioenergy. Further, reaction conditions of each techniques (torrefaction, pyrolysis, gasification and hydrothermal process) influence biochar, bio-oil and syngas yield were discussed. Reaction parameters or factors such as reactor temperature, residence time, pressure, biomass load/feedstock composition, catalyst addition and carrier gas flow affecting process efficiency in terms of product yield and quality were spotlighted and extensively discussed with copious literature. It also presents the novel insights on production of solid (char), liquid (bio-oil) and gaseous (syngas) biofuel through torrefaction, pyrolysis and gasification, respectively. It is found that the energy intensive drying was more efficient mode involved in thermochemical process for wet algal biomass. However other modes of thermochemical process were having unique feature on improving the product yield and quality. Among the various factors, reaction temperature and residence time were relatively more important factors which affected the process efficiency. The other factors signposted in this review will lay a roadmap to researchers to choose an optimal thermochemical conditions for high quality end product. Lastly, the perspectives and challenges in thermochemical conversion algae biomass to biofuels were also discussed.
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The present article reviews about the algae isolation, microalgae growth, types of cultivation, oil extraction, biodiesel characterization and the advantage of microalgae biomass and its other applications. A detailed review was undertaken on various microalgae harvesting methods, types of oil extraction and biodiesel production. The merits and demerits of open pond systems and photo-bioreactors cultivation are discussed briefly. The various microalgae species and its lipids used for biodiesel production were presented and compared with conventional feedstocks. This article also discusses the key process parameter for in-situ transesterification for biodiesel production such as molar ratio, stirring rate, moisture, reaction time, catalyst type and temperature. The fundamental characterization of the biodiesel and physiochemical properties such as flash point, cetane number, density, kinematic viscosity, pour and cloud point and calorific value were studied and compared with the results of conventional diesel. This study reports that oil from microalgae can be a suitable alternative than edible oils due to ease of growth, separation, and high lipid content. The properties of microalgae biodiesel meet ASTM standards. Overall, algae are not only a potential source for biofuel but can also be used in wastewater treatment, food additives, carbon sequestration, heath care, cancer treatment and aquaculture all of which are discussed in this review.
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In order to test the suitability of a site for the rearing of Macrocystis integrifolia. ten sporophytes were transplanted from a wild patch at Whiting Harbor. Sitka. Alaska. to a site located behind the Sheldon Jackson College salmon hatchery in Sitka. Growth and survival were compared at the locations from April 4 to May 28. 1987. Growth at Whiting Harbor was significantly greater than growth at Sheldon Jackson College (SJC). A freshwater lens at the SJC site is thought to have impaired growth of the upper blades on the plants. For this reason the SJC site is not suitable for M. integrifolia.
Attempts were made to artificially culture M. integrifolia at the SJC facility. Culturing from spore release through gametophyte stages to maturation and zygote fertilization was successful. However. culturing of the new sporophytes was not successful.
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Large-scale Sargassum blooms have been increasingly observed in coastal zones in recent years. Sargassum horneri (Turner) C. Agardh blooms (pelagic) have been observed in Jeju Island (Korea) and the southwest of the Korean Peninsula, causing serious problems for seaweed and abalone farms as well as for fisheries, tourism and recreational industries. The present study explored the physiological responses of attached and pelagic S. horneri populations cultivated under different nutrient concentrations (HN: 50 μM of nitrogen and 5 μM of phosphorus; LN: 5 μM of nitrogen and 0.5 μM of phosphorus) and photosynthetically active radiation (PAR) (H-PAR: 250; MPAR: 150; L-PAR: 50 μmol photons m− 2 s − 1 ) for 25 days. Relative growth rates (RGR) were significantly lower in the pelagic population than that in the attached population. All thalli from the pelagic population died within 20 days. Chlorophyll a and c, and carotenoids were significantly higher at HN than at LN, and decreased as PAR increased for both populations. For the attached population, photosynthetic rate, tissue nitrogen, and carbon and nitrogen removal were also significantly higher at HN than at LN. These results suggest that high nutrient and lower PAR increased the biomass accumulation of attached populations in coastal areas. Nutrient limitation and high PAR may accelerate senescence of the pelagic populations while traveling on the sea surface from their point of origin.
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The agar agar obtained from Gracilaria verrucosa growing in commercial quantities in Chilka Lake, Orissa was found to be having an yield of 23% and gel strength of 41 gm/cm . In order to exploit this agarophyte for the same with other agarophytes like Gelidlella acerosa and Gracilaria edulis in three different proportions was studied.
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The extraction and antioxidant activity of phlorotannins from the brown seaweeds Carpophyllum flexuosum, Carpophyllum plumosum and Ecklonia radiata was investigated to identify an optimised extraction process for novel anti-oxidant extracts. Subsequently, the composition of the most active phlorotannin extracts was de- termined. Microwave assisted extraction (MAE) using water was the most efficient extraction process with shorter processing times and a higher purity product than obtained with any of the other methods tested. MAE resulted in the fast, effective decomposition of the cellular structure, as identified through scanning electron microscopy (SEM), and this related directly to the efficiency of extraction. Phlorotannins extracted from C. flexuosum by MAE had the strongest antioxidant activity (62.1 mg gallic acid equivalents (GAE)/g dw of sea- weed) and more than 5.5-fold greater 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability than ascorbic acid after 7-day incubation periods at 30 °C and at 60 °C. Six major chemical species of phlorotannin, belonging to the fuhalol group, were identified within the MAE extract using NMR and HPLC-MS. The results confirm phlorotannins from C. flexuosum to be promising natural, bio-derived and bio-compatible antioxidants, while identifying the most effective method to extract the constituents and retain antioxidant activity.
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Marine Agronomy Group, CAFNRM, UH-Hilo
200 W. Kawili st., HI 96720, USA
Contact: Marine.Agronomy.Group@gmail.com
Funding for this web portal is provided by the World Wildlife Fund and the University of Hawaii-Hilo.