A PDF of a demonstration project on "An Integrated System to Produce Food, Fuel, Energy in Hawai'i".
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Marine macroalgae are available in large quantities in many regions of the world and have been widely investigated as potential biosorbents for the removal of metals in wastewaters. However, few studies have been published on the biosorption of metals with seaweeds waste after the extraction of bioactive compounds.
This dissertation presents the study about: 1) the valorisation of macroalgae biomass based on the biorefinery concept giving rise to added-value byproducts like polyphenols and polysaccharides, and 2) the use of the produced waste to remove Cu(II) from contaminated wastewaters.
Chemical characterization of the two seaweeds studied, Ascophyllum nodosum and Ulva rigida, was performed. A.nodosum presented a higher percentage of ashes (13.8 ± 0.1 %) than U.rigida (10.9 ± 0.2 %). Regarding the percentage of polysaccharides, A. nodosum presented a lower percentage (45 ± 2 %) than U. rigida (48.7 ± 0.1 %). About the polyphenolic content, A. nodosum presented a higher value (0.95 mg GAE g-1) than U.rigida (0.33 mg GAE g-1).
FTIR analyses of Ascophyllum nodosum, before and after Cu(II) biosorption, identified some of the main functional groups that play a key role in metal biosorption: carboxyl functional group – COOH and alcohol functional group - OH. FTIR analyses of Ascophyllum nodosum were performed before and after extraction of polyphenols, indicating that the lack of this bioactive compounds reduced the hydroxyl stretches.
Preliminary biosorption tests for Cu(II) removal by Ascophyllum nodosum before and after extraction of polyphenols, present best results with A. nodosum virgin at pH values of 4 and 5. The adsorbed amount values obtained were in a range between 2.13- 2.25 mg g-1.
The biosorption kinetics was found to be fast, with more than 50% of Cu(II) maximum adsorption equilibrium capacity attained within 15 minutes and equilibrium reached after 30 minutes. This kinetic data was fitted to pseudo first-order and pseudo second-order models.
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The interest in seaweeds by humans seems to have originated over 1700 years ago when several seaweed species became used in ethnic cuisines. These initial applications enabled the start of farming in Japan, China and Korea. However, in Western countries, demand for seaweed polysaccharides began only after World War II, when the demand for agar, alginate and carrageenans developed. At the present time, many researchers and entrepreneurs predict a promising future for innovation in the seaweed industry. In this context, this special issue covers some advances and constraints that seaweed farming and the utilisation of its biomass face today.
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Seaweeds (macroalgae) play a key role in coastal ecosystems by providing space for marine microorganisms and higher organisms, as a nursery ground for fishes and maintain the overall biodiversity structure. Seaweeds are also considered as major primary producers in the reef ecosystems and form an important part of trophic structure. For environmental monitoring programme, seaweeds are used as good bioindicators to assess the pollutant level in marine waters. Besides, many seaweed species have phytochemicals and attain economic significance. This chapter describes the ecological significance of seaweed communities in coastal ecosystems and discusses the need for conservation of seaweed beds.
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The Irish Marine Institute has identified the potential of marine natural resources to be exploited as high value-added products. Marine biotechnology is at an early stage of development, and therefore, more of the potential global market is open for development by Ireland than is the case for other sectors. A key area of growth, both in Ireland and Europe is the use of seaweeds for various applications including bioremediation of heavy metal contaminated waters.
This thesis has demonstrated a method for identifying the most promising seaweeds for metal biosorption through the use of multiple analytical techniques. A comprehensive study of dead biomass of six locally derived seaweeds (Fucus vesiculosus, Fucus spiralis, Ulva lactuca, Ulva spp., Palmaria palmata and Polysiphonia lanosa) and three regionally significant metals (Cu (II), Cr (III) and Cr (VI)) was carried out. Fundamental investigations into metal binding were undertaken in order to determine the potential binding capacity of the seaweeds, the factors influencing binding and their potential mechanisms of binding. This work has adapted a number of analytical techniques previously used for seaweed analysis and modified them so that binding information supplementary to that found in the literature could be obtained. Studies indicated that seaweed is polyfunctional in nature with groups of varying affinities for metal ions. The quantity and distribution of these groups varied between species. Variations in experimental parameters were shown to influence the quantity of metal bound to the seaweeds, with optimum conditions dependent on the metal under investigation. Isotherm modelling revealed that Fucus vesiculosus and Polysiphonia lanosa were most effective in removing cations and anions respectively from solutions containing high residual metal concentrations while Palmaria palmata was superior for both cation and anion removal at low residual concentrations. Therefore, this implied that the most suitable seaweed biosorbent was ultimately dependent upon its final application. Changes in seaweed functional groups after metal binding were monitored using FTIR analysis with novel information on the timescale of Cu (II) binding presented.
Ion-exchange and complexation mechanisms were shown to occur for cation binding while a surface reduction mechanism was also apparent during anion binding. The use of multiple chemical modification techniques confirmed binding mechanisms and identified a methodology for capacity enhancement of the seaweeds. Important changes in surface morphology and binding mechanism were established using surface analysis techniques such as SEM/EDX and XPS while a novel methodology for seaweed surface analysis using SFM was also demonstrated.
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Background: Nutritional well-being is the prerequisite condition for a sustainable improvement in human wel- fare. Human gut microbiota plays a magnificent role in balancing the condition of metabolic syndrome man- agement. Currently, the gut microbiome mediated immune system is gaining attention for the treatment of several health ailments such as diabetes, gastrointestinal disorders, and malnourishment. Bioactive compounds from marine polysaccharides from seaweeds are found beneficial for enhancing the activity of gut microbes. Scope and approach: There were limited reviews in recent times to discuss the updates on extraction, purification and biological activities of dietary fibers using non-conventional methods. The present review inspects on the proximal and structural composition of seaweed polysaccharides and their methods of extraction and pur- ification aspects. It also focuses on the immune modulating mechanisms of prebiotic-probiotic synergetic in- teraction by stimulating beneficial gut microbial activity and by the production of short-chain fatty acids. The mutual relationship between prebiotics and probiotics that leads to a healthy gut was targeted in the present review.
Key findings and conclusions: Marine seaweeds polysaccharides are the untapped bioresources to be explored for its biotherapeutic properties of dietary fibers. The practical complications on extracting polysaccharides by a single technique could be overcome by adopting the strategy of utilizing combinatorial extraction and pur- ification techniques. Its prebiotic effect aids in the enhancement of gut microbial activity by exhibiting the properties of non-digestibility, fermentability, and pathogen inhibition potential. The impending benefits of dietary fiber from seaweed polysaccharides as prebiotics for formulating functional food ingredients along with probiotic microbes to exhibit immunomodulation applications. Therefore, intended human clinical trials should be carried out to evaluate and discover the probiotic-prebiotic relationship in the human gut, which could step out the research to the next level in the medicinal world.
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This review discusses anaerobic production of methane, hydrogen, ethanol, butanol and electricity from microalgal biomass. The amenability of microalgal biomass to these bioenergy conversion processes is compared with other aquatic and terrestrial biomass sources. The highest energy yields (kJ g1 dry wt. microalgal biomass) reported in the literature have been 14.8 as ethanol, 14.4 as methane, 6.6 as butanol and 1.2 as hydrogen. The highest power density reported from microalgal biomass in microbial fuel cells has been 980 mW m2. Sequential production of different energy carriers increases attainable energy yields, but also increases investment and maintenance costs. Microalgal biomass is a promising feedstock for anaerobic energy conversion processes, especially for methanogenic digestion and ethanol fermenta- tion. The reviewed studies have mainly been based on laboratory scale experiments and thus scale-up of anaerobic utilization of microalgal biomass for production of energy carriers is now timely and required for cost-effectiveness comparisons.
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To suffice the escalating global energy demand, microalgae are deemed as high potential surrogate feedstocks for liquid fuels. The major encumbrance for the commercialization of microalgae cultivation is due to the high costs of nutrients such as carbon, phosphorous, and nitrogen. Meanwhile, the organic-rich anaerobic digestate which is difficult to be purified by conventional techniques is appropriate to be used as a low-cost nutrient source for the economic viability and sustainability of microalgae production. This option is also beneficial in terms of reutilize the organic fraction of solid waste instead of discarded as zero-value waste. Anaerobic digestate is the side prod- uct of biogas production during anaerobic digestion process, where optimum nutrients are needed to satisfy the physiological needs to grow microalgae. Besides, the turbidity, competing biological contaminants, ammonia and metal toxicity of the digestate are also potentially contributing to the inhibition of microalgae growth. Thus, this review is aimed to explicate the feasibility of utilizing the anaerobic digestate to cultivate microalgae by evaluat- ing their potential challenges and solutions. The proposed potential solutions (digestate dilution and pre- treatment, microalgae strain selection, extra organics addition, nitrification and desulfurization) corresponding to the state-of-the-art challenges are applicable as future directions of the research.
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The potential of algal biomass as a source of liquid and gaseous biofuels is a highly topical theme, with over 70 years of sometimes intensive research, and considerable financial investment. A wide range of unit operations can be combined to produce algal biofuel, but as yet there is no successful commercial system producing such biofuel. This suggests that there are major technical and engineering difficulties to be resolved before economically viable algal biofuel production can be achieved.
Both gasification and anaerobic digestion have been suggested as promising methods for exploiting bioenergy from biomass and 2 major projects have been funded in the UK on the gasification and anaerobic digestion of seaweed, MacroBioCrude and SeaGas.
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Polysaccharides present in several seaweeds (Kappaphycus alvarezii, Calliblepharis jubata, and Chondrus crispus—Gigartinales, Rhodophyta; Gelidium corneum and Pterocladiella capillacea—Gelidiales, Rhodophyta; Laurencia obtusa—Ceramiales, Rhodophyta; Himanthalia elongata, Undaria pinnatifida, Saccorhiza polyschides, Sargassum vulgare, and Padina pavonica— Phaeophyceae, Ochrophyta) are analyzed by spectroscopic techniques. The nature of the polysaccharides (with extraction and without any type of extraction) present in these seaweeds was determined with FTIR-ATR and FT-Raman analysis of extracted phycocolloids and ground dry seaweed.
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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.