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Journal ArticleDOI

An integrated salinity-driven workflow for rapid lipid enhancement in green microalgae for biodiesel application

24 Nov 2016-RSC Advances (The Royal Society of Chemistry)-Vol. 6, Iss: 113, pp 112340-112355

AbstractA laboratory based integrated approach was undertaken for improvement of lipid accumulation in green microalgae under sodium chloride (NaCl) stress. The maximum biomass yields (1.22 ± 0.04 g L−1 in Chlorella and 1.31 ± 0.04 g L−1 in Chlorococcum) were obtained in the media with initial NaCl concentrations at 2 g L−1 (for Chlorella) and 0.05 g L−1 (for Chlorococcum) after 14 days of culture. Interestingly, maximum lipid accumulation obtained was 45.8 ± 0.4% w/v for Chlorella (on day eight) and 36.33 ± 0.56% w/v for Chlorococcum (on day ten) at an exposure of 5 g L−1 and 1.5 g L−1 NaCl concentrations, respectively. Fatty acid profiles of methyl esters for neutral and polar lipid fractions showed the presence of myristic (C14:0), palmitic (C16:0), palmitoleic (C16:1), oleic (C18:1) and linoleic (C18:2) acids as major fatty acids. Fluorescence intensities (% positive Nile red stained cells) of neutral and polar lipid fractions were also higher in NaCl stress conditions. A significant correlation between polar lipid and neutral lipid was found in both Chlorella (r2 = 0.979) and Chlorococcum (r2 = 0.972). Flow cytometric study demonstrated a positive fluorescence signal for neutral and polar lipid bodies related to Nile red fluorescence. Associated biochemical changes, like those in total chlorophyll, carotenoid, carbohydrate and protein contents, were determined under variable NaCl concentrations. The elemental compositions (CHNS) and CO2 fixation rate were assessed using high lipid yielding cells under optimum NaCl concentrations. Biodiesel fuel properties were obtained from high lipid yielding cells of the test microalgae and compared with Indian and international diesel standards. Finally large-scale cultivation of Chlorella ellipsoidea was performed in a hybrid photobioreactor (800 L capacity) and the highest biomass and lipid content obtained was 1.66 ± 0.09 g L−1 (at 8 days) and 54.73 ± 1.78% w/v (at 10 days) at 5 g L−1 NaCl respectively. This optimized NaCl concentration makes it an economical substitute for biodiesel production on a large scale.

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Citations
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Journal ArticleDOI
Abstract: This study achieves a better understanding how Scenedesmus quadricauda microalgae participate in the phycoremediation of a reverse osmosis (RO) concentrate at a high salinity (8000 mg Cl− L− 1). Algal treatment of the RO concentrate under continuous illumination resulted in a notable increase in the biodegradability of dissolved organic matter, subsequent removal of biodegradable fractions, and simultaneous removal of nutrients (N and P). This is the first time that S. quadricauda is shown to induce the degradation of polymeric organic matter in the RO concentrate, which is typically refractory to microbial decomposition. In this study, the mechanisms for algae-induced degradation were investigated by measuring the hydrogen peroxide (H2O2) released out of algal cells and dispersed in the aqueous phase. The algae-induced biodegradation process has an advantage over typical electrochemical oxidation technologies in that photo-sensitive living organisms are capable of self-repair, reproduction, and nutrient uptake. Our results indicate that the use of algae-induced oxidation is highly feasible as a safe, inexpensive technology to pre-treat non- or slowly-biodegradable organic matter in wastewater prior to downstream biological processing.

28 citations

Journal ArticleDOI
TL;DR: Indole-3-acetic acid (IAA), the most common naturally occurring plant hormone, can exert stimulatory at low concentrations and inhibitory effects at high concentrations on the growth of the green alga Desmodesmus, and it is discovered that lipid droplets accumulated in algal cells grown at a high IAA concentration.
Abstract: Phenotypic plasticity is the ability of a single genotype of an organism to exhibit variable phenotypes in response to fluctuating environments. It plays a crucial role in their evolutionary success. In natural environments, the importance of interactions between microalgae and other microorganisms is generally well appreciated, but the effects of these interactions on algal phenotypic plasticity has not been investigated. In this study, it revealed that indole-3-acetic acid (IAA), the most common naturally occurring plant hormone, can exert stimulatory at low concentrations and inhibitory effects at high concentrations on the growth of the green alga Desmodesmus. The morphological characteristics of Desmodesmus changed drastically under exposure to IAA compared with the algae in the control environment. The proportion of Desmodesmus unicells in monocultures increased with the IAA concentration, and these unicells exhibited less possibility of sedimentation than large cells. Furthermore, we discovered that lipid droplets accumulated in algal cells grown at a high IAA concentration. Results also demonstrated that the presence of algal competitor further stimulated inducible morphological changes in Desmodesmus populations. The relative abundance of competitors influenced the proportion of induced morphological changes. The results indicate that phenotypic plasticity in microalgae can be a response to fluctuating environments, in which algae optimize the cost–benefit ratio.

12 citations

Journal ArticleDOI
TL;DR: Spectroscopic analysis on fatty acids and Fatty Acid Methyl Esters derived from diatom exhibited similarities in specific functional groups between algal oil and biodiesel, exhibiting potential scope for large scale application of environment friendly biocatalysts to enhance the conversion performances of the transesterification process.
Abstract: Fatty acid methyl ester (biodiesel) has been derived from oil present in algae through transesterification using catalysts of acids, base, supercritical fluids, etc. These catalysts are corrosive and have been posing challenges of contaminating the environment necessitating environmentally friendly and biodegradable catalysts such as enzyme (lipase) based biocatalysts. In this study, fungal strains (endophytic/free spores) were isolated from an estuarine ecosystem and screened for extracellular lipase activities. A novel fungal strain Cladosporium tenuissimum, identified through molecular technique exhibited higher lipolytic activity among the isolates. The crude lipase extracted from fungus was subjected to ammonium sulphate precipitation and purification using Superdex 200 gel filtration chromatographic system. The molecular weight of purified lipase was found to be ∼46 KDa and a specific activity of 37.2 U/mg. Lipase activities attained stability and reached maximum at 60 °C temperature and pH of 6. The purified enzyme was used as a biological catalyst for enzymatic transesterification of oil obtained from an indigenously isolated salt tolerant diatom Nitzschia punctata. Spectroscopic analysis on fatty acids and Fatty Acid Methyl Esters derived from diatom exhibited similarities in specific functional groups between algal oil and biodiesel. Comparisons on biodiesel yield estimation and FAME compositions of enzyme catalyzed, acid catalyzed biodiesel assessed through gas chromatographic techniques revealed a higher efficiency (87.2 ± 0.47%) of biocatalysts compared to conventional acid catalyst (83.02 ± 0.35%) exhibiting potential scope for large scale application of environment friendly biocatalysts to enhance the conversion performances of the transesterification process.

12 citations

Journal ArticleDOI
Abstract: Anthropogenic CO2 emissions are the main contributors to climate change. Among the various efforts to reduce atmospheric CO2 levels, cultivation of microalgae is the most promising approach owing to its high photosynthetic rates and CO2 fixation efficiencies than terrestrial counterparts. However, the accurate quantification method of CO2 fixation during the cultivation of microalgae in photobioreactors (PBRs) is lacking. Present methods for the determination of CO2 fixation during microalgae cultivation include direct and indirect methods, where 79% of direct method studies of the bibliometric analysis compared to 21% of indirect method studies. Direct methods evaluate the carbon content in microalgae biomass using assumptive values, though it results in significant errors as high as 50% in quantifying the CO2 fixation. This can be improved by measuring the carbon contents using elemental and total organic carbon analysis. On the other hand, indirect methods quantify CO2 concentration at inlet and outlet of PBRs by using gas chromatography or infrared sensors. It is rather difficult to validate the accuracy of direct and indirect methods due to the lack of comparative works and analysis among the methods. Additionally, there are no current studies that provide in-depth discussion and perspectives on the CO2 fixation methods. Therefore, the main aim of this critical review is to analyse, contrast and discuss the differences as well as inaccuracies of direct and indirect microalgae CO2 fixation quantifications in PBRs. This is followed by the recommendations for further improvements, and standard guidance for future studies in applying appropriate CO2 fixation quantification methods.

10 citations

Journal ArticleDOI
Abstract: Antioxidant properties of four common green algal genera viz. Cladophora glomerata, Chaetomorpha aerea, Rhizoclonium crassipellitum, and Pithophora cleveana collected from Sunderban areas of Eastern India were tested in controlled and nutrient stress conditions. Experimental algae were exposed to growth media with variations in nitrate and NaCl salt concentrations from 0 to 1500 ppm level for a period of 21 days. A dose-dependent upregulation in total phenols, flavonoids, pigment, and antioxidant property in relation to % DPPH activity and % ferrous ion chelating activity was observed. Maximum phenol content was observed for algal biomass exposed to 1500 ppm nitrate stress conditions (52.55 ± 0.01 mg GAE/g DW-16.48 ± 0.041 mg GAE/g DW) with Rhizoclonium showing the maximum contents. In the case of total flavonoid content, maximum upregulation was noted in the hypersaline conditions and Pithophora showed the highest contents amongst all (71.8 ± 0.21 mg QE/g DW). The highest carotenoid contents were observed in 750 ppm stress condition. Optimally stressed algal biomass having maximum carotenoid levels and high antioxidant levels were selected as fish feed ingredients, based on dose- and time-dependent two-way Anova and Tukeys test (750 ppm nitrate, 7 days). The processed biomass was included as fish feed ingredient to study the nutritive effects on goldfish (Carassius auratus). Algal feed (AF) was prepared from algal biomass only, which was further mixed with the commercial feed (CF) in varying proportions to formulate three different types of value-added feed (VAF). The experimental feed (25% VAF, 50% VAF, 75%VAF and AF) were tested against commercial feed (control) for 30 days in artificially aerated static aquaria system. The feed type formulated as 50% VAF was found to be most effective in terms of skin pigmentation, growth, and antioxidant activities of experimental fishes showing almost (1.44–4-folds increase) compared to the control setup. Statistically significant results were obtained regarding nutritive properties of experimental feed and fishes using PCA and Tukeys test respectively. Body weight gain and specific growth rate also changed significantly in experimental fishes.

6 citations


References
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Journal Article
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
Abstract: Since 1922 when Wu proposed the use of the Folin phenol reagent for the measurement of proteins, a number of modified analytical procedures utilizing this reagent have been reported for the determination of proteins in serum, in antigen-antibody precipitates, and in insulin. Although the reagent would seem to be recommended by its great sensitivity and the simplicity of procedure possible with its use, it has not found great favor for general biochemical purposes. In the belief that this reagent, nevertheless, has considerable merit for certain application, but that its peculiarities and limitations need to be understood for its fullest exploitation, it has been studied with regard to effects of variations in pH, time of reaction, and concentration of reactants, permissible levels of reagents commonly used in handling proteins, and interfering substances. Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.

285,427 citations

Journal ArticleDOI
TL;DR: Evidence that a copper enzyme, polyphenoloxidase (otherwise known as tyrosinase or catecholase), is localized in the chloroplasts of spinach beet (chard), Beta vu?garis is presented.
Abstract: The chloroplast, as the seat of chlorophyll pigments in plants, occupies a unique position in the economy of the green cell. In recent years there has been a renewed interest in the reactions and properties of chloroplasts as a result of the work of Hill (11, 12) and Hill and Scarisbrick (13, 14) who demonstrated that the reaction characteristic of photosynthesis in green plants, the evolution of oxygen, occurs in appreciable quantities in isolated chloroplasts under the influence of light and in the presence of suitable oxidants (2, 7, 8, 26). In the course of an investigation of oxygen evolution by isolated chloroplasts it was deemed important to explore their enzymatic composition. Of special interest were considered enzymes capable of participating in oxidation-reduction reactions, and more particularly, those localized principally, if not entirely, in the chloroplasts. This paper presents evidence that a copper enzyme, polyphenoloxidase (otherwise known as tyrosinase or catecholase), is localized in the chloroplasts of spinach beet (chard), Beta vu?garis.

18,362 citations

Journal ArticleDOI
Yusuf Chisti1
TL;DR: As demonstrated here, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels.
Abstract: Continued use of petroleum sourced fuels is now widely recognized as unsustainable because of depleting supplies and the contribution of these fuels to the accumulation of carbon dioxide in the environment. Renewable, carbon neutral, transport fuels are necessary for environmental and economic sustainability. Biodiesel derived from oil crops is a potential renewable and carbon neutral alternative to petroleum fuels. Unfortunately, biodiesel from oil crops, waste cooking oil and animal fat cannot realistically satisfy even a small fraction of the existing demand for transport fuels. As demonstrated here, microalgae appear to be the only source of renewable biodiesel that is capable of meeting the global demand for transport fuels. Like plants, microalgae use sunlight to produce oils but they do so more efficiently than crop plants. Oil productivity of many microalgae greatly exceeds the oil productivity of the best producing oil crops. Approaches for making microalgal biodiesel economically competitive with petrodiesel are discussed.

8,281 citations

Journal ArticleDOI
TL;DR: Although all the transesterification reactions were quite rapid and the biodiesel layers achieved nearly 100% methyl ester concentrations, the reactions using sodium hydroxide turned out the fastest.
Abstract: The most common catalysts for biodiesel production are homogeneous basic catalysts. In the present paper, a comparison is made of different basic catalysts (sodium methoxide, potassium methoxide, sodium hydroxide and potassium hydroxide) for methanolysis of sunflower oil. All the reactions were carried out under the same experimental conditions in a batch stirred reactor and the subsequent separation and purification stages in a decanter. The analytical methods included gas chromatography and the determination of fat and oil conventional parameters. The biodiesel purity was near 100 wt.% for all catalysts. However, near 100 wt.% biodiesel yields were only obtained with the methoxide catalysts. According to the material balance of the process, yield losses were due to triglyceride saponification and methyl ester dissolution in glycerol. Obtained biodiesel met the measured specifications, except for the iodine value, according to the German and EU draft standards. Although all the transesterification reactions were quite rapid and the biodiesel layers achieved nearly 100% methyl ester concentrations, the reactions using sodium hydroxide turned out the fastest.

1,139 citations

Journal ArticleDOI
01 May 2012-Energies
TL;DR: The potential of lipid induction techniques in microalgae and their application at commercial scale for the production of biodiesel are discussed and several genetic strategies for increased triacylglycerides production and inducibility are developed.
Abstract: Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. High lipid productivity of dominant, fast-growing algae is a major prerequisite for commercial production of microalgal oil-derived biodiesel. However, under optimal growth conditions, large amounts of algal biomass are produced, but with relatively low lipid contents, while species with high lipid contents are typically slow growing. Major advances in this area can be made through the induction of lipid biosynthesis, e.g., by environmental stresses. Lipids, in the form of triacylglycerides typically provide a storage function in the cell that enables microalgae to endure adverse environmental conditions. Essentially algal biomass and triacylglycerides compete for photosynthetic assimilate and a reprogramming of physiological pathways is required to stimulate lipid biosynthesis. There has been a wide range of studies carried out to identify and develop efficient lipid induction techniques in microalgae such as nutrients stress (e.g., nitrogen and/or phosphorus starvation), osmotic stress, radiation, pH, temperature, heavy metals and other chemicals. In addition, several genetic strategies for increased triacylglycerides production and inducibility are currently being developed. In this review, we discuss the potential of lipid induction techniques in microalgae and also their application at commercial scale for the production of biodiesel.

683 citations