Marine macroalgae have evolved a different mechanism to maintain physiological concentrations of essential metal ions and non-essential metals. The objective of the present work was to evaluate the antioxidant response and DNA damage of copper and cadmium ions in three halophytes, namely, Acanthophora spicifera, Chaetomorpha antennina, and Ulva reticulata. Accumulation of copper was significantly higher (P < 0.05) than that of cadmium. Biochemical responses showed that copper was considerably more toxic than cadmium (P < 0.05). Decreases in glutathione content and fluctuations of super oxide dismutase, catalase, and glutathione peroxidase activities were observed corresponding to time and concentration of exposure. Interestingly, it was also observed that antioxidant levels decreased as a result of metal accumulation, which may be due to free radicals generated by copper and cadmium in seaweeds. The present study also showed that copper and cadmium increased oxidative stress and induced antioxidant defense systems against reactive oxygen species. The order of toxicity for metals in the studied seaweeds was U. reticulata > A. spicifera > C. antennina. DNA damage index analysis supported that copper was significantly (P < 0.05) more toxic than cadmium. Bioaccumulation, biochemical responses, and DNA damage observed in the here analyzed marine macroalgae after exposure to selected metals indicate that these marine organisms represent useful bioindicators of marine pollution.
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Strategies for sustainably increasing sugarcane productivity without any negative implications to the environment are challenging. In the present investigation, field trials were conducted to demonstrate the potential of an agro-technique involving foliar applications of Kappaphycus alvarezii seaweed based biostimulant in combination with recommended rate of synthetic fertilizers (RRF) for sustainably enhancing sugarcane production and mitigating environmental impacts. Kappaphycus seaweed extract (KSWE) applied at 5% concentration enhanced cane productivity by 12.5 and 8%, respectively, in plant and ratoon crops. Interestingly, the treatment involving 6.25% KSWE +50% RRF showed yield parity (p < 0.05) with control (water+100% RRF) in ratoon while there was 7.9% reduction over control in plant crop with a concomitant savings of 50% RRF. These results revealed that KSWE application in addition to recommended rate of fertilizer application, can reduce gap between potential and real yield which otherwise requires application of incremental inputs in the form of synthetic fertilizers to obtain similar yields. The findings confirmed our hypothesis that the use of KSWE not only results in hypothetical savings in the incremental application of synthetic fertilizers but also can be used for achieving target yields sustainably. The sugar yield too was enhanced thus increasing the returns on investment. The technique is practically feasibility and scalability. The potential of the KSWE in lowering GHGs is manifested by the way of saving at least 260 kg CO2 equivalents (Mg cane production)−1 ha−1 when applied at 5% concentration. This would translate in to savings of ca. 9.3 million Mg of CO2 equivalents if one assumes employing KSWE for at least 10% of the total cane production in India for the year 2015–16. Therefore, the present study advocates a paradigm shift in policy to encourage use of biostimulants in the context of mitigating adverse effects of global climate change and expecting better returns from sugarcane cultivation.
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Utilisable crude protein (uCP), methane (CH4) production and other fermentation parameters were analysed in vitro for a diet in which grass silage was replaced by different levels of seaweed protein fractions prepared from three seaweed species: Saccharina latissima, Alaria esculenta and Palmaria palmata. Ten fractions from these three species in which the protein content had been increased and the salt content reduced by simple processing were tested, with inclusion levels in the diet based on the nitrogen content of the fractions. Following an extraction procedure, four fractions from Saccharina latissima, three from Alaria esculenta and one from Palmaria palmata, were incrementally included in the diet by replacing high quality silage with approximately 0, 0.15, 0.30 and 0.45 g/g DM, while two high-protein fractions of Palmaria palmata were tested at replacement levels of 0, 0.075, 0.15 and 0.225 g/g DM. To estimate fermentation parameters, 500 mg of each diet were incubated in bottles with 60 mL buffered rumen fluid. Estimated uCP increased linearly with increasing replacement rate of grass silage with seaweed protein fractions (from 158 g/kg DM to 206 g/kg DM on average for all fractions). Increasing protein fraction from the brown seaweed Saccharina latissima in the diet significantly increased true organic matter digestibility (OMD) (from on average 0.786 to 0.821). Organic matter digestibility decreased with increasing level of Alaria esculenta fractions (from on average 0.785 to 0.733), which also gave a linear decrease in CH4 production (from on average 45.3 to 38.5 mL/g organic matter). As a result of decreased CH4 production and OMD, total volatile fatty acid concentration decreased with increasing level of Alaria esculenta fractions (from on average 69.5 to 63.0 mmol/L). Thus, positive and species-specific effects of seaweed on estimated uCP and fermentation parameters were observed in vitro when protein fractions remaining after an extraction procedure on seaweed partly replaced grass silage in the feed ration.
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Increasing crop productivity for food security is a challenging task without compromising the environmental integrity. In this scenario, seaweed based plant biostimulants are one of the potential sources for sustainably improving crop productivity and mitigating climate change. However, in order to quantitatively express the environmental benefits it becomes imperative to estimate the impacts resulting from their production. Thus the present study was undertaken to determine the various impacts across nineteen environmental categories that resulted from production of 1000 L of Gracilaria seaweed extract-a potent plant biostimulant by using life cycle assessment methodology. The environmental impacts were apportioned between seaweed extract and downstream product (agar) on the basis of price allocation. Among the three different steps involved in production of the extract, the processing module contributed to higher proportion of impacts across different evaluated environmental impact categories and it ranged from 65 to 99% of the total impacts. Electricity requirement, shed and blowmoulding sub-processess within the processing step contributed to bulk of the evaluated environmental impact categories. Plastics used in packaging of the extract as well as those used in cultivation module contributed to more than 50% of impacts across 8 out of the 19 evaluated environmental impact categories. Thus, in order to render the product even more sustainable we would recommend the use of biodegradable products for making the raft as well as for packaging. In addition, marketing of the extract as a concentrate would further lower the environmental burden associated with the transport and packaging, thus rendering the SWE even more sustainable.
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Macroalgae, or seaweeds, are a rich source of components which may exert beneficial effects on the mammalian gut microbiota through the enhancement of bacterial diversity and abundance. An imbalance of gut bacteria has been linked to the development of disorders such as inflammatory bowel disease, immunodeficiency, hypertension, type-2-diabetes, obesity, and cancer. This review outlines current knowledge from in vitro and in vivo studies concerning the potential therapeutic application of seaweed-derived polysaccharides, polyphenols and peptides to modulate the gut microbiota through diet. Polysaccharides such as fucoidan, laminarin, alginate, ulvan and porphyran are unique to seaweeds. Several studies have shown their potential to act as prebiotics and to positively modulate the gut microbiota. Prebiotics enhance bacterial populations and often their production of short chain fatty acids, which are the energy source for gastrointestinal epithelial cells, provide protection against pathogens, influence immunomodulation, and induce apoptosis of colon cancer cells. The oral bioaccessibility and bioavailability of seaweed components is also discussed, including the advantages and limitations of static and dynamic in vitro gastrointestinal models versus ex vivo and in vivo methods. Seaweed bioactives show potential for use in prevention and, in some instances, treatment of human disease. However, it is also necessary to confirm these potential, therapeutic effects in large-scale clinical trials. Where possible, we have cited information concerning these trials.
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The potential of algal biomass as a source of liquid and gaseous biofuels has been the subject of considerable research over the past few decades, with researchers strongly agreeing that algae have the potential of becoming a viable aquatic energy crop with a higher energy potential compared to that from either terrestrial biomass or municipal solid waste. However, neither microalgae nor seaweed are currently cultivated solely for energy purposes due to the high costs of harvesting, concentrating and drying. Anaerobic digestion of algal biomass could theoretically reduce costs associated with drying wet biomass before processing, but practical yields of biogas from digestion of many algae are substantially below the theoretical maximum. New processing methods are needed to reduce costs and increase the net energy balance. This review examines the biochemical and structural properties of seaweeds and of microalgal biomass that has been produced as part of the treatment of wastewater, and discusses some of the significant hurdles and recent initiatives for producing biogas from their anaerobic digestion.
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Brown seaweeds are rich in polyphenols with a basic building block of 1,3,5-trihydroxybenzene (phloroglucinol) and were investigated as a bioresource for the extraction of polyphenols for biopolymers and bioproducts. Spe- cies of seaweed with high contents of polyphenols were identified through meta-analysis and selected for the comparative assessment of the extraction efficiency of polyphenols using microwave assisted (MAE) vs. conven- tional solid-liquid (SLE) extraction. Out of ten species from Australia and New Zealand screened by SLE, Carpophyllum flexuosum (8.6%) and C. plumosum (7.5%) had the highest contents of polyphenols and were select- ed for MAE along with commercially available Ecklonia radiata. C. flexuosum was identified as the key species for extraction of polyphenols, with a 70% increase in yield using optimized MAE (aqueous, biomass:solvent ratio 1:30, 160 °C, 3 min) compared to SLE. The cell-wall bound fraction of polyphenols in brown seaweed may be larg- er than previously thought and is accessible through MAE.
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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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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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The tetrasporophyte of Asparagopsis armata has been previously established as a novel seaweed biofilter for integrated land-based mariculture. The species growth and biofiltration rates were much higher than the values described in the literature for Ulva spp., the most common seaweed biofilter. However, a validation of the advantage of one species over the other requires a study of the performances of these two species in the same system at the same time. In this work, we compared the biofiltration performance and biomass yield of A. armata and Ulva rigida cultivated in the effluents of a fish farm in southern Portugal. Comparisons were performed at different water renewal rates and in two seasons of the year. The maximum total ammonia nitrogen (TAN) removal rates were similar for both species in December (2.7 and 2.8 g TAN m–2 day–1 for U. rigida and A. armata, respectively) and higher for A. armata (6.5 g TAN m–2 day–1 ) than for U. rigida (5.1 g TAN m–2 day–1 ) in May. Higher differences were observed when estimating the nitrogen biofiltration through the organic nitrogen yield (N yield) of the biomass produced, particularly in May. This estimate is directly related with the biomass yield and the N content in the tissue which were always higher for A. armata than for U. rigida. In December, the maximum biomass yields were 71 g dry weight (DW) m–2 day–1 for A. armata and 44 g DW m–2 day–1 for U. rigida, while in May, the yield of A. armata was 125 g DW m–2 day–1 and of U. rigida was 73 g DW m–2 day–1 . This study confirmed that A. armata is indeed a more efficient biofilter than U. rigida. To the best of our knowledge, the production rates reported here are the highest ever reported for macroalgae cultivated in tanks.
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