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Algae are being explored as a sustainable energy feedstock, having potential to reduce dependence on petrofuels and offset greenhouse gas emissions. Economic considerations and principles of green design suggest that if algae-to-fuel technology is to be successful, biofuels must be produced simultaneously with value-added co-products. At present, the algae industry is centered around a limited number of products, such as low-volume/high-value speciality nutrients. New products for medium- and high-volume markets will be needed as biomass production increases in scale. This Perspective highlights non-fuel applications of algal biomass that have received relatively little attention to date but are promising for future development. It is our goal to draw attention to some of the unique opportunities that algae present with respect to biochemical composition as compared to lignocellulosic energy crops. [ABSTRACT FROM AUTHOR]

Building an optical filtration function into a microfluidic chip is a promising way of simplifying the optical detection system of a microfluidic device. In this paper, a PDMS microfluidic chip filter that is capable of transmitting chlorophyll fluorescence and blocking interfering light in the visible wavelength range was developed for living algae detection with a smartphone. The chip was fabricated by sealing a layer of crystal violet solution in a PDMS layer on the top of the Sudan II-doped PDMS slab, which has a straight microchannel. Optimum dye concentrations and thicknesses for the crystal violet solution layer and Sudan II-doped PDMS slab were investigated and determined by spectrum measurements. It was found that the cut-on range of this integrated microfluidic chip is extended to about 625 nm and the transmittance in the chlorophyll fluorescence range (650 nm to 710 nm) is as high as 95%, when 25 mg L−1 Sudan II-doped PDMS slab (with a 3 mm thickness) and 2 mg L−1 crystal violet solution (with a 0.3 mm thickness) were used. Living algae detection using this chlorophyll-fluorescence-filtering PDMS microfluidic chip and a smartphone-based imaging platform was achieved, and the results compared favorably with those using a commercial filter. [ABSTRACT FROM AUTHOR]

Non-spherical flagellate algae play an increasingly significant role in handling problematic issues as versatile biological micro/nanorobots and resources of valuable bioproducts. However, the commensalism of flagellate algae with distinct structures and constituents causes considerable difficulties in their further biological utilization. Therefore, it is imperative to develop a novel method to realize high-efficiency selection of non-spherical flagellate algae in a non-invasive manner. Enthused by these, we proposed a novel method to accomplish the selection of flagellate algae based on the numerical and experimental investigation of dielectrophoretic characterizations of flagellate algae. Firstly, an arbitrary Lagrangian--Eulerian method was utilized to study the electro-orientation and dielectrophoretic assembly process of spindle-shaped and ellipsoid-shaped cells in a uniform electric field. Secondly, we studied the equilibrium state of spherical, ellipsoid-shaped, and spindle-shaped cells under positive DEP forces actuated by rightangle bipolar electrodes. Thirdly, we investigated the dielectrophoretic assembly and escape processes of the non-spherical flagellate algae in continuous flow to explore their influences on the selection. Fourthly, freshwater flagellate algae (Euglena, H. pluvialis, and C. reinhardtii) and marine ones (Euglena, Dunaliella salina, and Platymonas) were separated to validate the feasibility and adaptability of this method. Finally, this approach was engineered in the selection of Euglena cells with high viability and motility. This method presents immense prospects in the selection of pure non-spherical flagellate algae with high motility for chronic wound healing, bio-micromotor construction, and decontamination with advantages of no sheath, strong reliability, and shape-insensitivity. [ABSTRACT FROM AUTHOR]

A simple and potent chemosensor AFL has been successfully developed to recognize Sn2+ selectively in marine algae or, more precisely, seaweed, as they are at huge risk from marine contamination. The bioaccumulation of Sn2+, mainly by the algae community, poses a great threat to the entire environment as Sn2+ toxicity flows towards higher organisms through food chain. The chemosensor AFL shows high selectivity and sensitivity towards Sn2+ with an extremely low detection limit, i.e. 90 nM, and demonstrates turn-on fluorescence with a bright cyan blue colour. The interaction mechanism is well supported by absorption, fluorescence titration, NMR titration and mass spectrometry, as well as theoretical analysis. Moreover, tin accumulation in green algae has also been revealed efficiently through confocal microscopic imaging. The quantification studies demonstrate that the AFL probe can be used as a proficient fluorescent marker for detecting Sn2+ in aquatic plants to save the marine ecosystem. [ABSTRACT FROM AUTHOR]

Macroalgae are a valuable energy source that can be transformed into numerous products most notably fuels and chemicals due to their high content of carbohydrates, proteins, and vitamins. In order to use macroalgae on a commercial scale, it is essential to evaluate various potential pathways into value-added products as well as intermediate components and technologies. Furthermore, the prospective processes have to be economically competitive while simultaneously offering minimum environmental impact in terms of carbon and other waste emissions. This in turn presents a large decision-making problem with a significant combinatorial complexity. This study addresses this problem by utilizing a superstructure process design approach for a seaweed biorefinery which produces mixed alcohols and mixed organic acids via an anaerobic digestion/volatile fatty acid route. Seventeen design alternatives have been proposed to determine the optimal design and technical feasibility by maximizing the net present value in the most environmentally beneficial manner. The results indicate that biofuel production from macroalgae is economically viable at a minimum ethanol selling price of $1.17 gal−1. Furthermore, the optimal design enables a 90% reduction in carbon dioxide emissions. Results of the sensitivity analysis show that seaweed price is the most important parameter that can contribute in improving the economics, thereby confirming that the cost-effective and efficient large-scale seaweed cultivation is of utmost importance to the success of macroalgae-based biofuel production. [ABSTRACT FROM AUTHOR]

Fucoidans are sulfated polysaccharides mostly derived from algae and used in a number of applications (e.g. nutrition, cosmetics, pharmaceuticals and biomaterials). In this study, the electrochemical behaviour of fucoidans extracted from two algal species (Undaria pinnatifida and Fucus vesiculosus) was assessed using voltammetry at an array of micro-interfaces formed between two immiscible electrolyte solutions (μITIES) in which the organic electrolyte phase was gelled. Cyclic voltammetry revealed an adsorption process when scanning to negative potentials, followed by a desorption peak at ca.−0.50 V on the reverse scan, indicating the electroactivity of both fucoidans. U. pinnatifida fucoidan showed a more intense voltammetric signal compared to F. vesiculosus fucoidan. In addition, use of tridodecylmethylammonium (TDMA+) or tetradodecylammonium (TDDA+) as the organic phase electrolyte cation provided improved detection of both fucoidans relative to the use of bis(triphenylphosphoranylidene)ammonium (BTPPA+) cation. Application of adsorptive stripping voltammetry provided a linear response of current with fucoidan concentration in the range 2–20 μg mL−1 for U. pinnatifida fucoidan (with TDMA+) and 10–100 μg mL−1 for F. vesiculosus fucoidan (with TDDA+). The combination of TDMA+ in the organic phase and adsorptive pre-concentration for 180 s afforded a detection limit of 1.8 μg mL−1 fucoidan (U. pinnatifida) in aqueous phase of 10 mM NaOH and 2.3 μg mL−1 in synthetic urine (pH adjusted). These investigations demonstrate the electroactivity of fucoidans at the μITIES array and provide scope for their detection at low μg mL−1 concentrations using this approach. [ABSTRACT FROM AUTHOR]

Optimized incorporation of hydrothermal liquefaction (HTL, reaction in water at elevated temperature and pressure) within an integrated biorefinery requires accurate models to predict the quantity and quality of all HTL products. Existing models primarily focus on biocrude product yields with limited consideration for biocrude quality and aqueous, gas, and biochar co-products, and have not been validated with an extensive collection of feedstocks. In this study, HTL experiments (300 °C, 30 min) were conducted using 24 different batches of microalgae feedstocks with distinctive feedstock properties, which resulted in a wide range of biocrude (21.3–54.3 dry weight basis, dw%), aqueous (4.6–31.2 dw%), gas (7.1–35.6 dw%), and biochar (1.3–35.0 dw%) yields. Based on these results, a multiphase component additivity (MCA) model was introduced to predict yields and characteristics of the HTL biocrude product and aqueous, gas, and biochar co-products, with only feedstock biochemical (lipid, protein, carbohydrate, and ash) and elemental (C/H/N) composition as model inputs. Biochemical components were determined to distribute across biocrude product/HTL co-products as follows: lipids to biocrude; proteins to biocrude ＞ aqueous ＞ gas; carbohydrates to gas ≈ biochar ＞ biocrude; and ash to aqueous ＞ biochar. Modeled quality indicators included biocrude C/H/N contents, higher heating value (HHV), and energy recovery (ER); aqueous total organic carbon (TOC) and total nitrogen (TN) contents; and biochar carbon content. The model was validated with HTL data from the literature, the potential to expand the application of this modeling framework to include waste biosolids (e.g., wastewater sludge, manure) was explored, and future research needs for industrial application were identified. Ultimately, the MCA model represents a critical step towards the integration of cultivation models with downstream HTL and biorefinery operations to enable system-level optimization, valorization of co-product streams (e.g., through catalytic hydrothermal gasification and nutrient recovery), and the navigation of tradeoffs across the value chain. [ABSTRACT FROM AUTHOR]

A new pathway to upgrade directly the biocrude derived from Nannochloropsis oceanica hydrothermal liquefaction (HTL) to kerosene-range biofuel was conducted without using a solvent. The influential factors including the catalyst/biocrude ratio (wt/wt%) and temperature were investigated to improve the biofuel's yield, physical properties and component characteristics. The biofuel was characterized at 44.5 MJ kg−1 higher heating value (HHV) with 1.95% N and 0.72% O by two-stage hydrotreated upgrading. The carbon distribution was analyzed and the transfer of components and elements were discussed for a better understanding of the mechanism of the upgrading process. The results of component analyses suggested that the heteroatoms in phenols, pyrroles and indoles were difficult to remove. In order to obtain a further reduction of oxygen and nitrogen contents, they need a specific upgrading. Higher reaction temperature had a facilitative effect on the generation of aromatic hydrocarbons. The two-stage upgrading also improved the aromatic hydrocarbon contents from 9.64% (stage-1) to 17.38% (stage-2). In addition, the content of kerosene-range biofuel with carbon numbers from 8 to 16 was 65.53% in stage-1 upgrading biofuel and 79.02% in stage-2 upgrading biofuel. [ABSTRACT FROM AUTHOR]

An algae-based biorefinery relies on the efficient use of algae biomass through its fractionation of several valuable/bioactive compounds that can be used in industry. If this biorefinery includes green platforms as downstream processing technologies able to fulfill the requirements of green chemistry, it will end-up with sustainable processes. In the present study, a downstream processing platform has been developed to extract bioactive compounds from the microalga Isochrysis galbana using various pressurized green solvents. Extractions were performed in four sequential steps using (1) supercritical CO2 (ScCO2), (2) ScCO2/ethanol (Gas Expanded Liquid, GXL), (3) pure ethanol, and (4) pure water as solvents, respectively. The residue of the extraction step was used as the raw material for the next extraction. Optimization of the ScCO2 extraction was performed by factorial design in order to maximize carotenoid extraction. During the second step, different percentages of ethanol were evaluated (15%, 45% and 75%) in order to maximize the extraction yield of fucoxanthin, the main carotenoid present in this alga; the extraction of polar lipids was also an aim. The third and fourth steps were performed with the objective of recovering fractions with high antioxidant activity, eventually rich in carbohydrates and proteins. The green downstream platform developed in this study produced different extracts with potential for application in the food, pharmaceutical and cosmetic industries. Therefore, a good approach for complete revalorization of the microalgae biomass is proposed, by using processes complying with the green chemistry principles. [ABSTRACT FROM AUTHOR]

Platform chemicals can be readily converted into various value-added chemicals and fuels. Photosynthetic production of platform chemicals directly from CO2 by cyanobacteria, in the presence of sunlight, holds promise for addressing global energy and environmental concerns. Herein, we report the photosynthetic production of C3 platform chemicals using engineered Synechococcus elongatus PCC7942 as the kernel. The engineered S. elongatus strain YW1 expressing glycerol-3-phosphatase produced a C3 intermediate, glycerol, with a high concentration of 1.17 g L−1 and a maximum production rate of 7733 μg L−1 H−1. Strain YW1 could serve as the kernel for the production of various C3 chemicals. By extending heterologous pathways in the cyanobacterial kernel, the carbon flux was further channelled to produce two platform chemicals: dihydroxyacetone by introducing glycerol dehydrogenase and 3-hydroxypropionic acid by introducing glycerol dehydratase and aldehyde dehydrogenase. Co-cultivation of the cyanobacterial kernel and another microbe, Klebsiella pneumoniae, was also performed to convert the C3 intermediate produced from CO2 to 1,3-propanediol, an important monomer for biodegradable material production. Besides direct photosynthetic production and co-cultivation, we demonstrated that glycerol produced by the cyanobacterial kernel can be used as a fermentation feedstock after simple concentration. The production processes presented here display great potential for carbon capture and storage and for sustainable production of chemicals and fuels. [ABSTRACT FROM AUTHOR]

This paper reports on a detailed study of the influence of salinity on the biological activity of 1-alkyl-3-methylimidazolium chlorides on two green algae Oocystis submarinaand Chlorella vulgaris, one diatom Cyclotella meneghinianaand one blue-green alga Geitlerinema amphibium. All these organisms inhabit the Baltic Sea, an environment naturally varying greatly in salinity. The toxicity effects of ILs towards cyanobacterial and algal organisms were tested in fresh water and in water of four different salinities—8, 16, 24 and 32 PSU—reflecting the whole range encountered in the Baltic Sea. Increasing the salinity was found to exert a significant influence on ionic liquid toxicity in all cases. The lower toxicity is probably due to the reduced permeability of ionic liquid cations through the algal cell walls. Higher chloride concentrations offer a good ion-pairing environment for imidazolium cations, which therefore compete with hydroxyl or silanol functional groups in cell-wall structures. The results of this work indicate that at higher salinities algal growth is inhibited to a significantly lesser extent. With the same IL concentration, the toxicity decreases by eight–ten times in the algae or about three times in the cyanobacterium in the 0–32 PSU salinity range. [ABSTRACT FROM AUTHOR]

Biomass materials are abundant, low-cost, non-hazardous, disposable, environmentally friendly, and renewable organic materials that are considered an appropriate solution for environmental contamination. Algae are renewable living organisms that grow throughout the world. More than one million algal species grow around the world. Algae have several important applications in materials science. One of the important applications of algae is preparing electrochemical energy storage (EES) devices. EES-devices are considered as an appropriate solution for industries to reduce environmental pollution. EES-device preparation from renewable organic materials is a significant issue which has been extensively examined by scientists in recent years. Tremendous effort has been applied to prepare EES-devices from algae as a renewable resource. The four main parts of EES-devices are the electrode, binder, electrolyte, and membrane, and can be prepared from algae. The purpose of this review is to provide an overview of the progress in the preparation of EES-devices from algae, examine algae-EES electrochemical properties in the last few decades, and also present an appropriate perspective for future research on algae-based EES-devices. [ABSTRACT FROM AUTHOR]

Covering: 1957 to 2017 Algae constitute a heterogeneous group of eukaryotic photosynthetic organisms, mainly found in the marine environment. Algae produce numerous metabolites that help them cope with the harsh conditions of the marine environment. Because of their structural diversity and uniqueness, these molecules have recently gained a lot of interest for the identification of medicinally useful agents, including those with potential anticancer activities. In the current review, which is not a catalogue-based one, we first highlight the major biological events that lead to various types of cancer, including metastatic ones, to chemoresistance, thus to any types of current anticancer treatment relating to the use of chemotherapeutics. We then review algal metabolites for which scientific literature reports anticancer activity. Lastly, we focus on algal metabolites with promising anticancer activity based on their ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. Thus, we highlight compounds that have, among others, one or more of the following characteristics: selectivity in reducing the proliferation of cancer cells over normal ones, potential for killing cancer cells through non-apoptotic signaling pathways, ability to circumvent MDR-related efflux pumps, and activity in vivo in relevant pre-clinical models. [ABSTRACT FROM AUTHOR]

Microscopic algae occupies every photic niche on Earth and provides an efficient and inherently scalable sunlight energy capture and chemical storage mechanism. However, fuel production from algae remains outside economic viability due to limitations in biomass cultivation and feedstock extraction. In particular, extraction strategies require prohibitive energy inputs to breach the cell wall and separate lipids, while underutilizing polysaccharide- and protein-rich leftovers. Also due to focus on lipids, cultivars become either unstable or unproductive. Meanwhile, recent advances have demonstrated the synthesis of a variety of fuels and other chemicals from sugars and proteins. Here, the energy-efficient deconstruction of algae cell walls, resulting in release of cell contents, is reported. This occurs by dissolution and hydrolysis of wet algae biomass in ionic liquids without acids, bases or other catalysts. Deconstruction reached completion in ＜50 min regardless of algae species, at 100 to 140 °C and atmospheric pressure. Based on this finding, a simple process that converts wet algae biomass into constituent fractions is proposed and modeled. These results show it is possible to eliminate intensive energy demand currently hindering the economic viability of algae while co-producing sugar and protein feedstocks that tie into emerging fuel and chemical conversion paths. [ABSTRACT FROM AUTHOR]

Room temperature ionic liquids (ILs) are non-volatile organic solvents that are considered environmentally-friendly alternatives to traditional industrial solvents. However, the evidence of IL toxicity is mounting, while the mechanisms of toxicity to freshwater organisms remain poorly understood. ILs have been shown to have a wide-ranging toxicity to different taxa of freshwater algae, and differences in algal cell wall composition have been posed as one possible explanation for this variation. The cell wall is known to play a critical role in mediating the transport of materials into and out of algal cells, including potential toxins. The objective of our study was to determine the role of the cell wall in the toxicity of ILs to the freshwater phytoplanktor Chlamydomonas reinhardtii. We exposed wild-type (having a cell wall) and mutant (lacking a cell wall) strains of C. reinhardtiito a range of concentrations of five structurally-different ILs in 96-h standard toxicity bioassays. Our results suggest that the cell wall is involved in determining the susceptibility of C. reinhardtiito some but not all ILs, indicating that other factors, such as the base cation of the IL, are also involved. The alkyl chain length of an IL, a key factor in previous IL toxicity bioassays, does not appear to influence the ability of the cell wall to mitigate IL toxicity. The results of this study have important implications for predicting the effects of ILs in aquatic ecosystems and for extrapolating the effects of ILs across organisms. [ABSTRACT FROM AUTHOR]

Many studies done so far on the aquatic ecotoxicity of ionic liquids have dealt with phytoplankton organisms. Nonetheless, benthic organisms are just as important if we are to fully understand the prospective fate and effects of ionic liquids in the aquatic environment. An investigation was therefore undertaken into the toxicity of 1-alkyl-3-methylimidazolium ionic liquids towards the diatom Bacillaria paxilliferand the cyanobacterium Geitlerinema amphibium, species characteristic of the benthic environment. As in the first part of this study (A. Lataa, M. Ndzi and P. Stepnowski, Green Chem., 2009, 11, 580–588), five 1-alkyl-3-methylimidazolium chlorides (from ethyl to decyl) were chosen as the test kit compounds for examining the expected alkyl chain length effect, together with 1-butyl-3-methylimidazolium tetrafluoroborate, dicyanamide, trifluoromethanesulfonate and methyl sulfate and α-methyl[poly(oxy-1,2-ethanediyl)]sulfate for investigating the influence of anions on the toxicity of ionic liquids towards the algal species under investigation. A pronounced alkyl chain effect was found with both organisms. The results indicate that P. amphibiumis more sensitive than B. paxillifer.It was also found that the use of trifluoromethanesulfonate and dicyanamide as counteranions in the IL structure gave rise to the most pronounced toxic effects in comparison with the other anions tested. It is assumed that the greater toxicities of long alkyl chain ILs will most probably not pose a greater threat to benthic organisms, since these compounds will undergo rapid and very strong adsorption to sedimentary matter. Short-chain compounds, which are known to be reversibly bound to sediments, may still pose a significant risk to benthic ecosystems, however. [ABSTRACT FROM AUTHOR]