Search

Abstract The growing population, decreasing arable land and fresh water supply questions the sustainability of terrestrial agriculture for securing safe nutrients supply, particularly starch- an essential ingredient for all staple foods. Here, we report the isolation, characterization and offshore production assessment of native starch from green seaweed Ulva ohnoi cultivated in seawater. Starch content varied from 1.59% to 21.44% depending on growth conditions and seasons. Our results show that nutrient starvation significantly increased the starch concentration up to 21.4% on dry weight basis. The extracted fraction contained 75.45% starch, and the starch extraction yield from the U. ohnoi biomass was 50.37%. Ulva starch granules are spherical, ovoid and irregularly shaped, 5–7 μm in size. Their gelatinization temperature is 69° C and they are susceptible to α-amylase and amyloglucosidase digestion. U. ohnoi biomass cultivated offshore for 13 months showed an average starch yield of 3.43 ton/ha/year (t·ha−1y−1). This study encourages the potential use of offshore produced biomass for sustainable starch supply as an alternative to current agricultural products, the production of which requires arable land and fresh water. Graphical abstract Unlabelled Image Highlights • Starch content of Ulva was 1.59% to 21.44% DW, rising with nutrient starvation. • Native granular starch extracted by food grade methods (75.4% purity, 50.37% yield). • Morphology, size, thermal properties and digestibility were studied. • Annual production of Ulva starch was monitored in offshore sea environment. • Average starch yield of 3.43 ton/ha/year (t·ha−1y−1) on DW basis was observed. [ABSTRACT FROM AUTHOR]

To foster the development of macroalgal biomass for biorefinery applications, we tested two orthogonal techniques for rapid phenotyping of the green macroalga Ulva based on its glucose, rhamnose, xylose and glucuronic acid contents as derived for reference by acid hydrolysis. Partial Least Squares (PLS) regression analyses, calculation of slopes and correlations across different spectral ranges/frequencies were used to predict the monosaccharide contents using two complementary methods: near infrared reflection spectroscopy (NIRS) and microelectromechanical systems (MEMS) resonating membrane vibrometry. Both methods were found to perform sufficiently well in monosaccharide mixtures and to enable quantitative assessment of different monosaccharide contents with the relative Root Mean Square Error of Prediction (%RMSEP) ranging from 8 to 16% (with similar accuracy when using PLS analyses). The best estimation was found for rhamnose and glucose contents, whereas xylose and uronic acid content predictions were found to be less accurate using PLS analyses. For the two latter components, slopes across different spectral ranges and frequencies at certain signals provided better estimates for their concentrations (e.g. for NIRS slopes: R 2 values in the range 0.55–0.66 and with higher accuracy for MEMS: between 0.75 and 0.90). This result is pivotal for opening new perspective to the construction of simple, multi-functional sensors for biomass downstream processing control in biorefinery and biometric applications. [ABSTRACT FROM AUTHOR]

Macroalgae are primary producers bearing key roles in the normal functioning of marine environments. The critical energy carriers that macroalgae produce are carbohydrates, which support marine ecosystems and are used in biorefineries. In this work, we quantified the monosaccharide content and diversity of macroalgal species common to the Eastern Mediterranean shores representing the three major seaweed divisions, namely, Chlorophyta ( Ulva sp. and Cladophora pellucida ), Rhodophyta ( Nemalion helminthoides , Galaxaura rugosa and Gracilaria sp.) and Ochrophyta ( Padina pavonica and Sargassum vulgare ). We found that the most abundant monosaccharide was different in 5 out of the 7 investigated species. The monosaccharide diversity profile was specific to each taxonomic group, especially in the first two orders of diversity, which correspond to Shannon entropy and Simpson concentration. The content of monosaccharides released by acid hydrolysis varied by 153% between Ulva sp., C. pellucida , G. rugosa , N. helminthoides , Gracilaria sp., P. pavonica , and S. vulgare collected from the same site. Ulva sp. collected at different sites at different months showed up to 79% variance in the total released monosaccharides, with up to 270% variance in the content of individual monosaccharides. The cultivation of Ulva sp. in a photobioreactor under more stable conditions reduced the diversity and the variability of the total carbohydrates to only 2%. By comparing amounts and types of monosaccharides derived from macroalgae, microalgae and terrestrial plants, it appears that Ulva sp. has the highest economic potential of all photosynthetic organisms, between $1733 kg − 1 and $3140 kg − 1 of Ulva biomass. [ABSTRACT FROM AUTHOR]

The use of seaweeds has a long history, as does the cultivation of a select and relatively small group of species. This review presents several aspects of seaweed production, such as an update on the volumes of seaweeds produced globally by both extraction from natural beds and cultivation. We discuss uses, production trends and economic analysis. We also focus on what is viewed as the huge potential for growing industrial-scale volumes of seaweeds to provide sufficient, sustainable biomass to be processed into a multitude of products to benefit humankind. The biorefinery approach is proposed as a sustainable strategy to achieve this goal. There are many different technologies available to produce seaweed, but optimization and more efficient developments are still required. We conclude that there are some fundamental and very significant hurdles yet to overcome in order to achieve the potential contributions that seaweed cultivation may provide the world. There are critical aspects, such as improving the value of seaweed biomass, along with a proper consideration of the ecosystem services that seaweed farming can provide, e.g. a reduction in coastal nutrient loads. Additional considerations are environmental risks associated with climate change, pathogens, epibionts and grazers, as well as the preservation of the genetic diversity of cultivated seaweeds. Importantly, we provide an outline for future needs in the anticipation that phycologists around the world will rise to the challenge, such that the potential to be derived from seaweed biomass becomes a reality. [ABSTRACT FROM PUBLISHER]

Marine macroalgal biomass is a promising sustainable feedstock for biorefineries. However, the development of macroalgal biomass for industrial cultivation and processing has been slow. In terrestrial plants, highthroughput phenotyping provides rapid imaging methods to select specimens with required properties, rapidly transforming traditional breeding techniques. To foster the development of macroalgal biomass for biorefinery applications, we developed a near-infrared spectrometrybased method for rapid phenotyping of the macroalga Ulva fasciata based on its glucose, rhamnose, xylose and glucuronic acid contents. Spectral slopes were calculated as indicative of major carbohydrate content change. In addition, different spectral indices were generated to distinguish between low and high contents of glucose, rhamnose, xylose and glucuronic acid in wet and dry biomass. Since glucose is a major monosaccharide in Ulva that is fermentable to bioethanol, as an example of future application, we developed a multivariate data analysis based on partial least squares regression to predict its content in dry and wet biomass samples solely from reflectance data. These methods could provide a useful, high-throughput tool to rapidly select thalli with high carbohydrate content for further propagation and to be used for feedstock development for marine biorefineries. [ABSTRACT FROM AUTHOR]

Fossil resources-free sustainable development can be achieved through a transition to bioeconomy, an economy based on sustainable biomass-derived food, feed, chemicals, materials, and fuels. However, the transition to bioeconomy requires development of new energy-efficient technologies and processes to manipulate biomass feed stocks and their conversion into useful products, a collective term for which is biorefinery. One of the technological platforms that will enable various pathways of biomass conversion is based on pulsed electric fields applications (PEF). Energy efficiency of PEF treatment is achieved by specific increase of cell membrane permeability, a phenomenon known as membrane electroporation. Here, we review the opportunities that PEF and electroporation provide for the development of sustainable biorefineries. We describe the use of PEF treatment in biomass engineering, drying, deconstruction, extraction of phytochemicals, improvement of fermentations, and biogas production. These applications show the potential of PEF and consequent membrane electroporation to enable the bioeconomy and sustainable development. [ABSTRACT FROM AUTHOR]

Marine algal biofuel is considered a promising solution for energy and environmental challenges. Macroalgal biomass has the potential for bypassing the shortcoming of first and second generation of biomass from food crop and lignocellulosic sources. In this review, we summarize the findings in this domain in the past two decades with a focus on the process of saccharification and fermentation of macroalgae for transportation biofuels. In general, macroalgae contains high levels of carbohydrates, almost no or comparatively less lignin than in terrestrial plants, which makes it a very promising source for liquid biofuel production via bioconversion. After harvest, macroalgal biomass goes through several process units, including pre-treatment and/or saccharification and fermentation to be converted to biofuel, e.g., bioethanol. We also propose strategies for further studies to realize macroalgae biomass potential for transportation bioenergy production. [ABSTRACT FROM AUTHOR]

Biorefineries aim to provide sustainable production of food and generation of low carbon energy in the next decades. Current strategies for biorefinery reply mostly on the classic terrestrial agriculture for biomass production. However, land availability, competition with food crops and total energy balance are challenging limiting factors for terrestrial bioenergy crop production. Off-shore macroalgae production could provide alternative, sustainable feedstocks for biorefineries without competition with food crops. Increasing the yields of off-shore macroalgae cultivation systems could further improve the total energy balance of the marine biorefineries. In this work, based on the fundamental principle of timing differences between light harvesting and carbon fixation in algae, we developed a theoretical framework for increasing the yields of off-shore macroalgae biomass using external mechanical mixing. We show that for a given physiological parameter of macroalgae light harvesting and carbon fixation, mixing could allow for increase of the total energy gain by two orders of magnitude. The overall biorefinery to biofuel efficiency, however, is constrained by drag and macroalgae thallus size. [ABSTRACT FROM AUTHOR]

AbstractUlva, a genus of green macroalgae commonly known as sea lettuce, has long been recognized for its nutritional benefits for food and feed. As the demand for sustainable food and feed sources continues to grow, so does the interest in alternative, plant-based protein sources. With its abundance along coastal waters and high protein content, Ulva spp. have emerged as promising candidates. While the use of Ulva in food and feed has its challenges, the utilization of Ulva in other industries, including in biomaterials, biostimulants, and biorefineries, has been growing. This review aims to provide a comprehensive overview of the current status, challenges and opportunities associated with using Ulva in food, feed, and beyond. Drawing on the expertise of leading researchers and industry professionals, it explores the latest knowledge on Ulva’s nutritional value, processing methods, and potential benefits for human nutrition, aquaculture feeds, terrestrial feeds, biomaterials, biostimulants and biorefineries. In addition, it examines the economic feasibility of incorporating Ulva into aquafeed. Through its comprehensive and insightful analysis, including a critical review of the challenges and future research needs, this review will be a valuable resource for anyone interested in sustainable aquaculture and Ulva’s role in food, feed, biomaterials, biostimulants and beyond. [ABSTRACT FROM AUTHOR]

The last years have seen the emergence of the bioeconomy. Assessment of these new technologies is a significant challenge. We develop a unique dynamic programming framework to assess the value of the investment in a multi-stage supply chain with the production of bio-feedstock and its processing into multiple outputs. The system allows for adaptive learning in all supply chain stages, which creates a positive learning effect of co-outputs. We apply the framework to macroalgae (seaweed) farming and biorefinery processing into proteins and sugars for the Philippines and Ireland as representatives of developing and developed economies with emerging supply chains. We run Monte Carlo simulations to analyze the uncertainty of learning and prices. The key results indicate that the macroalgae sector that builds on traditional technologies is quite viable. Developing a new algae industry that generates proteins and other high-value products requires significant investment and depends on the dynamics of learning and prices. Even though the production of high-value chemicals is not yet viable, it gains profitability potential from learning of feedstock farming that is currently produced for the lower value application. The learning is much more valuable in feedstock production and processing into proteins than low-value chemicals currently produced (carrageenan). • Original dynamic, two-stage supply chain model with non-linear cost functions, learning, and heterogenous coproducts. • Analysis of impact of learning effects and prices on investment decision in a supply chain of aquaculture. • The co-production allows financing learning in both stages of the supply chain that may transform the non-viable product into a profitable in the long run. • If the combined impact of learning is greater than the discount effect, than the investment in a technology can be profitable even if prices decline. • Payback period in Asia is short, while in the West long-term investment is vital for high learning rates to reach profitability. [ABSTRACT FROM AUTHOR]

Offshore grown macroalgae biomass could provide a sustainable feedstock for biorefineries. However, tools to assess its potential for producing biofuels, food and chemicals are limited. In this work, we determined the net annual primary productivity (NPP) for Ulva sp. (Chlorophyta), using a single layer cultivation in a shallow, coastal site in Israel. We also evaluated the implied potential bioethanol production under literature based conversion rates. Overall, the daily growth rate of Ulva sp. was 4.5 ± 1.1%, corresponding to an annual average productivity of 5.8 ± 1.5 g DW m −2 day −1 . In comparison, laboratory experiments showed that under nutrients saturation conditions Ulva sp. daily growth rate achieved 33 ± 6%. The average NPP of Ulva sp . offshore was 838 ± 201 g C m −2 year −1 , which is higher than the global average of 290 g C m −2 year −1 NPP estimated for terrestrial biomass in the Middle East. These results position Ulva sp. at the high end of potential crops for bioenergy under the prevailing conditions of the Eastern Mediterranean Sea. We found that with 90% confidence, with the respect to the conversion distribution, the annual ethanol production from Ulva sp. biomass, grown in a layer reactor is 229.5 g ethanol m −2 year −1 .This translates to an energy density of 5.74 MJ m −2 year −1 and power density of 0.18 W m −2 . Growth intensification, to the rates observed at the laboratory conditions, with currently reported conversion yields, could increase, with 90% confidence, the annual ethanol production density of Ulva sp. to 1735 g ethanol m −2 year −1 , which translates to an energy density of 43.5 MJ m −2 year −1 and a power density 1.36 W m −2 . Based on the measured NPP, we estimated the size of offshore area allocation required to provide biomass for bioethanol sufficient to replace 5–100% of oil used in transportation in Israel. We also performed a sensitivity analysis on the biomass productivity, national CO 2 emissions reduction, ethanol potential, feedstock costs and sizes of the required allocated areas. [ABSTRACT FROM AUTHOR]

Economic and environmental developments in the last decades call for the displacement of fossil fuels to alternative energy sources. Biofuels are considered as a part of the solution for this challenge. Sustainable raw materials for the production of transportation biofuels such as biodiesel, biobutanol and bioethanol, can be obtained from algal biomass. In particular, marine macroalgal biomass is a promising feedstock for transportation biofuels because of (the) its fast growth and its potential cultivation on seawater, avoiding competition of resources with conventional agriculture of terrestrial plants used for food. In addition, dissolved inorganic nutrients like nitrogen, phosphorous and carbon are taken up by macroalgae, helping to alleviate eutrophication in seas and oceans. Using biological, chemical and engineering advances in the last decades, technologies to provide cost efficient cultivation, harvesting, extraction and processing of sustainable biofuels have to be elaborated. This paper provides a review of macroalgae based biorefineries with offshore cultivation and consequent biomass conversion into transportation liquid biofuels. We discuss the methods for offshore cultivation, harvesting, and conversion of macroalgae biomass into liquid transportation biofuels. Based on the current information and global experience, we present local perspectives specific for France, Germany, Norway, the Netherlands and Israel on the potential use of Exclusive Economic Zone for transportation biofuels production. Marketable suggestions for future research need to include all stakeholders of a given site for offshore biorefinery development. [ABSTRACT FROM AUTHOR]

Marine macroalgae are an attractive source of alternative protein. However, protein extraction from macroalgae is challenging. In this work, we investigated a combination of enzymatic cell wall degradation and high voltage Pulsed Electric Fields (PEF), to enhance yields of water-soluble-protein extraction from the green marine macroalga Ulva sp. The combined process showed a considerably higher protein extraction yield (19.6 ± 0.33%) compared to that of PEF alone (10.8 ± 0.37%) and enzyme pretreatment alone (9.7 ± 0.42%). Moreover, the water-soluble-protein extract obtained by PEF, which followed enzymatic cell wall degradation, had significant antioxidant activity. These results indicate that PEF combined with enzymatic pretreatment could contribute to protein extraction yields from Ulva sp., as a part of sustainable seaweed biorefinery. Although several previous works reported on methods for protein extraction from seaweeds for food application, the commercialization of the seaweed proteins is challenging due to multiple challenges in the extraction process development. In this work we show that a combination of enzymes for cell wall degradation with high voltage pulsed electric fields for membrane permeabilization lead to higher yields of water-soluble proteins. Both enzyme treatment and PEF are scalable processes, which do not modify proteins chemically, potentially leading to higher quality of the extract in comparison to standard alkaline extraction with a need to treat chemical waste. • Protein extraction from macroalgae Ulva sp. is challenging. • A combination of cellulase with Pulsed Electric Fields to extract protein was investigated. • The combined process showed 19.6 ± 0.33% protein extraction yield. • The water-soluble-protein extract had significant antioxidant activity. • The specific energy consumed relative to the wet mass of Ulva sp. was 79.1 ± 1.44 kJ kg−1 [ABSTRACT FROM AUTHOR]

Macroalgae are potential feedstock for biorefineries. However, integration of macroalgae into biorefinery network requires new processing technologies that will lead to energy efficient and zero waste conversion of macroalgae biomass into food, chemicals and fuels. Here we report on the selective extraction of proteins from green macroalgae from Ulva genus by electroporation with energy efficient pulsed electric field (PEF) process. We show that application of 75 pulses with an average electric field strength of 2.964 ± 0.007 kV cm − 1 , and pulse duration 5.70 ± 0.30 μs, delivered at approximately 0.5 Hz, combined with hydraulic pressing of the treated samples for 5 min with force of 45 daN cm − 2 led to the total protein concentration of 59.13 ± 3.82 μg mL − 1 in the extracted juice. The final temperature of the extracted juice was 35.50 ± 2.02 °C. The energy consumption of the process is 251 ± 3 kWh kg − 1 of protein. We show that PEF process is selective and its extraction efficiency and damage are protein specific. [ABSTRACT FROM AUTHOR]

• Hydrothermal processing of the whole Ulva sp. biomass vs. extracted carbohydrate fractions of starch and cellulose. • Glucose is a major released monosaccharide with hydrothermal deconstruction. • Most of the glucose is released from starch. • Whole biomass hydrolysis preferred for PHA fermentation with Haloferax mediterranei. • The highest ash-free hydrochar yield was from Ulva cellulose. In the fermentation and bioenergy industry, terrestrial biomass is usually fractionated and the collected components, such as starch, are processed separately. Such a separation has not been reported for seaweeds. In this work, the direct hydrothermal processing of the whole green seaweed Ulva sp. biomass is compared to processing of separated starch and cellulose, to find the preferable route for monosaccharide, hydrochar, and polyhydroxyalkanoates (PHA) production. Glucose was the major released monosaccharide. A significant share of the glucose yield comes from the starch fraction. The highest hydrochar yield with the lowest ash content was obtained from the separated cellulose fraction. The highest PHA yield was obtained using a whole Ulva sp. hydrolysate fermentation with Haloferax mediterranei. Economic analysis shows the advantage of direct Ulva sp. biomass fermentation to PHA. The co-production of glucose and hydrochar does not add significant economic benefits to the process under plausible prices of the two outputs. [ABSTRACT FROM AUTHOR]

• SW treatment of Ulva biomass led to the production of hydrochar and phytochemicals. • SW treatment led to the extraction of 84.9% protein from the total Ulva protein. • Ethanol production was optimized with S. cerevisiae and E. coli , in a two-step. • 0.84% of Israel's EEZ can cover all national demand for protein by using Ulva. Marine seaweeds are promising biomass feedstock for the co-production of food, energy and chemicals in a biorefinery. In this study, subcritical water hydrolysis (SWH) was applied to the biomass of green seaweed Ulva sp., fast-growing cosmopolitan seaweed. The SWH was done with seawater at 180 °C and 10.5 bar during 40 min with 8% w/w solid load. This treatment resulted in 211 ± 7 mg of hydrochar g−1 dry weight (DW) of Ulva sp. with higher heating value (HHV) double that of the initial biomass. The liquid fraction content per gram of Ulva DW included 5.2 ± 1.15 mg of 5-HMF; 24.1 ± 2.84 mg total monosaccharides (composed of 14.3 ± 1.78 mg glucose, 5.1 ± 0.41 mg rhamnose, 2.3 ± 0.41 mg fructose, 1 ± 0.06 mg xylose, 0.9 ± 0.08 mg galactose and 0.6 ± 0.11 mg glucuronic acid); 58 ± 11.78 mg protein (corresponding to 84.9 ± 13.2% of the total protein); and free amino acids (3.64 ± 0.07 mg leucine, 2.08 ± 0.13 mg arginine, 1.54 ± 0.01 mg isoleucine and 1.06 ± 0.03 mg alanine). Two-step fermentation optimization was done with Saccharomyces cerevisiae and Escherichia coli in Ulva hydrolysate following the SWH, with ethanol yield of 4.67 ± 0.76 mg g−1 DW Ulva. Based on these process results, some economics and sustainability indicators were estimated for large-scale macroalgae-based biorefinery. The required offshore areas for Ulva cultivation to satisfy the entire national demand in Israel for plant-based protein, char for electricity production (20% blend co-firing with coal), or ethanol for transportation (10% blend in gasoline), are 0.8%, 3.1% and 34.3%, respectively of the Israeli exclusive economic zone in the Mediterranean sea. The total revenue expected for the co-products derived from Ulva sp. via SWH varies between $0.26 and $1.06 kg−1 DW. [ABSTRACT FROM AUTHOR]