Algal Fatty Acids Research Articles

Enhancing biomass and fatty acid productivity of Tetraselmis sp. in bubble column photobioreactors by modifying light quality using light filters

Some artificial light sources able to emit photons at specific wavelengths, such as LEDs, are useful for studying the effects of light quality on microalgal growth and production of fatty acids; however, they should not be used for outdoor cultivation of microalgae to produce bioenergy. Instead, various light filters capable of selectively transmitting red, blue, and red+blue light regions in solar radiation were used to cover 0.4 L bubble column photobioreactors to cultivate Tetraselmis sp. KCTC12236BP and investigate the influence of light quality on microalgal growth and fatty acid production. Biomass and fatty acid productivities in red light (0.10 ± 0.05 g/L/day and 11.8 ± 0.5 mg/L/day, respectively) were 7 ~ 53% and 9 ~ 61% higher than other colored lights based on the same number of supplied photons, respectively. The composition of fatty acids did not change significantly in response to transmitted light qualities of the filter. The ratio of saturated to unsaturated fatty acids was 3:7, and their contents were 12% in all groups, which corresponds with the results of LEDs. Plotting biomass and fatty acid productivity over the red photon fraction in supplied light revealed that increased productivities were closely correlated with red photon fraction in the filtered light. Overall, the results presented herein indicate that enhanced production of algal fatty acid could be achieved by application of light filters in outdoor settings without artificial lights.

Tracing sea ice algae into various benthic feeding types on the Chukchi Sea shelf

Climate change in the Arctic is expected to have drastic effects on marine primary production sources by shifting ice-associated primary production to an overall greater contribution from pelagic primary production. This shift could influence the timing, amount, and quality of algal material reaching the benthos. We determined the contribution of sea ice particulate organic matter (iPOM) to benthic-feeding invertebrates by examining concentrations and stable carbon isotope values (expressed as δ13C values) of three fatty acids (FAs) prominent in diatoms: 16:4(n-1), 16:1(n-7), and 20:5(n-3). Our underlying assumption was that diatoms make up the majority in sea ice algal communities compared with phytoplankton communities. According to the FA concentrations, subsurface deposit feeders consumed the most iPOM and suspension feeders the least. Conversely, there were little differences in δ13C values of FAs between deposit and suspension feeders, but the higher δ13C values of 16:1(n-7) in omnivores indicated greater consumption of iPOM. We suggest that omnivores accumulate the ice algal FA biomarker from their benthic prey, which in turn may feed on ice algae from a deposited sediment pool. The dissimilar results between FA concentrations and isotope values suggest that the FAs used here may not be sufficiently source specific and that other unaccounted production sources, such as bacteria, may also contribute to the FA pool. We propose that FA isotope values are a more indicative biomarker than FA concentrations, with a further need for more specific ice algal biomarkers to resolve the question of ice algal contributions to the Arctic benthic food web.

Resource partitioning between Pacific walruses and bearded seals in the Alaska Arctic and sub-Arctic.

Climate-mediated changes in the phenology of Arctic sea ice and primary production may alter benthic food webs that sustain populations of Pacific walruses (Odobenus rosmarus divergens) and bearded seals (Erignathus barbatus). Interspecific resource competition could place an additional strain on ice-associated marine mammals already facing loss of sea ice habitat. Using fatty acid (FA) profiles, FA trophic markers, and FA stable carbon isotope analyses, we found that walruses and bearded seals partitioned food resources in 2009-2011. Interspecific differences in FA profiles were largely driven by variation in non-methylene FAs, which are markers of benthic invertebrate prey taxa, indicating varying consumption of specific benthic prey. We used Bayesian multi-source FA stable isotope mixing models to estimate the proportional contributions of particulate organic matter (POM) from sympagic (ice algal), pelagic, and benthic sources to these apex predators. Proportional contributions of FAs to walruses and bearded seals from benthic POM sources were high [44 (17-67)% and 62 (38-83)%, respectively] relative to other sources of POM. Walruses also obtained considerable contributions of FAs from pelagic POM sources [51 (32-73)%]. Comparison of δ13C values of algal FAs from walruses and bearded seals to those from benthic prey from different feeding groups from the Chukchi and Bering seas revealed that different trophic pathways sustained walruses and bearded seals. Our findings suggest that (1) resource partitioning may mitigate interspecific competition, and (2) climate change impacts on Arctic food webs may elicit species-specific responses in these high trophic level consumers.

Phosphopantetheinylation in the green microalgae Chlamydomonas reinhardtii

Microalgal biofuel is a promising solution to the decline of fossil fuels. However, algal fatty acid metabolism, the machinery producing the raw material for biofuels, remains poorly understood. The central unit of the fatty acid synthase (FAS) is the acyl carrier protein (ACP), which is responsible for holding the product. Fatty acid biosynthesis is initiated through posttranslational modification of the ACP by the phosphopantetheinyl transferase (PPTase). We identified two PPTases, PptC1 and PptC2, in the model alga Chlamydomonas reinhardtii by genome analysis and phylogenetic and structural comparison. Both PPTases are of Sfp-type, the archetypical PPTase type for non-ribosomal peptide and polyketide biosynthetic pathways in bacteria and cyanobacteria. In vitro analysis revealed that PptC2 has a broader substrate range than PptC1. Both PPTases were able to activate the cognate ACP of the type II FAS, while PptC2 also recognized ACP of Escherichia coli type II FAS and actinorhodin type II polyketide synthase. Besides FAS as PPTase target, the C. reinhardtii genome encodes a single type I PKS, and we hypothesize that PptC2 is responsible for its activation. Screening of the currently available microalgal genome data revealed that most green microalgae appear to carry two PPTases forming clusters with each C. reinhardtii PPTase, while microalgae of other divisions carry one or two PPTases and do not cluster in the pattern of the green algal data. This new understanding on the PPTases in microalgae shows that microalgae are already primed for biotechnological applications in contrast to other organisms. Thus, microalgae have great potential for metabolic engineering efforts in the realm of biofuel and high-value products including direct engineering of the fatty acid or secondary metabolism using the natural genomic reservoir and as biotechnological platform for heterologous expression.

Chemically enhanced lipid production from microalgae under low sub-optimal temperature

Low sub-optimal temperatures are one of the major environmental factors that significantly affects growth and lipid production of microalgae. However, until now little research has been done to estimate and reduce the effects of low sub-optimal temperatures (typically 15°C–20°C) on productivity of algal lipids, which serve as feedstock for biodiesel. We addressed this issue by growing the microalga Chlorella sorokiniana under a low sub-optimal temperature (18°C) (the optimal temperature was 26°C, which was used as a control). Algal growth was inhibited at 18°C compared to 26°C, resulting in overall decreased lipid productivity; however, decreased temperature increased the total lipid content of the algal cell. Importantly, decreased lipid productivity under the low sub-optimal temperature was improved by an application of exogenous glycine betaine at 500mg/L compared to the control treatment of 26°C. Quantitative PCR analysis showed that exogenous glycine betaine enhanced expression of genes encoding Rubisco, one of the key enzymes involved in carbon fixation through photosynthesis. The expression of other key genes involved in the Calvin cycle was up-regulated by treatment with glycine betaine at both 18°C and 26°C. In addition, glycine betaine treatment had little influence on algal fatty acid profiling, hence it did not affect the cetane number that is a key parameter of biodiesel quality. Taken together, our evidence supports a chemically enhanced lipid production of microalgae under low sub-optimal temperatures whose lipid output was comparable to those at optimal temperatures. The novel application of glycine betaine could strengthen the algal biodiesel industry by extending the geographical range for cultivation into areas with cooler climates.

Dietary supplements: health from the ocean?

Dietary supplements: health from the ocean?

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids.

Essential fatty acids (EFA), which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid) concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting diatoms, cryptophytes and dinoflagellates as key sources of LCEFA. Moreover, the analyses indicate that future shifts towards cyanobacteria-dominated communities will result in lower LCEFA content in aquatic ecosystems.

Investigation of the Fatty Acid Profile in Some Macroalgae in Relation to the Environmental Conditions for Biodiesel Production

In this study, fatty acids profile was determined in four algal species; namely Ulva fasciata (Chlorophyta), Corallina mediterranea, Corallina officinalis and Pterocladiella capillacea (Rhodophyta) which were collected from two sites (Abu-Qir Bay and Eastern Harbor) located on the Egyptian Mediterranean Sea during the four seasons in the period (2011-2012). In addition, nutrient content in the algal species (total nitrogen and phosphorus) and the environmental conditions of the ambient sea water were measured to find out their effect on the algal fatty acids content. The nitrogen content in algal species was almost equal in both sites. In contrast, the phosphorus content was higher in Abu-Qir (0.33-1.71%) than in Eastern Harbor (0.21-0.74%). The fatty acids profile showed different correlations with water’s physico-chemical properties. The fatty acids profile of the four algal species revealed high content of SFAs against MUFA and PUFA in both sites. Consequently, the algae were screened to define the suitable site, season and species for the highest quality and quantity of biodiesel production. Biodiesel physical properties; the Degree of Unsaturation (DU), Long Chain Saturation Factor (LCSF), Cold Filter Plugging Point (CFPP), Iodine Value (IV), Saponification Value (SV), the Cetane Number (CN), Kinematic viscosity (υ), density (ρ), the Higher Heating Value (HHV), C18:3% (wt%) and double bond Db ≥4(wt%) were calculated. All the investigated algae showed biodiesel properties that follow the standard values set for optimum biodiesel, with the green alga U. faciata collected from Abu-Qir during winter, as the best choice for producing biodiesel; whereas, the extracted fatty acids from Corallina officinalis is more suitable to be used for production of blenders, which can be added to the petroleum diesel in order to increase its quality, oxidative stability and octane number.

Comparison of pigment and proximate compositions of Tisochrysis lutea in phototrophic and mixotrophic cultures

Pigment contents and proximate compositions are important traits to evaluate the nutritional value of microalgae. The environmental condition and nutrient availability in the culture medium are hypothesised to regulate algal colour, nutritional composition and production. This study aimed to compare the pigment and proximate compositions in Tisochrysis lutea under phototrophic and mixotrophic conditions in an attempt to improve algal product quality. Algae were grown in the phototrophic and mixotrophic conditions at 50 μmol photons m−2 s−1 for 12 h daily, but 50 mM glycerol was added as a carbon source in the mixotrophic culture. The pigment contents in algae significantly increased in the mixotrophic condition, and the contents of chlorophylls a and c and carotenoids increased nearly 60 % compared with those in the phototrophic condition. The contents of saturated and polyunsaturated fatty acids in algae were significantly higher while the content of monounsaturated fatty acids was significantly lower in the mixotrophic condition than those in the phototrophic condition. Although the contents of protein, lipid and carbohydrate in T. lutea were not different, their overall production was significantly enhanced in the mixotrophic condition compared to the phototrophic condition. This study indicates that mixotrophic culture promotes pigment and proximate production and the change of fatty acid profile in algae depends on the addition of organic carbon to the culture medium.

Predominance and sources of alkane and fatty acid biomarkers in the surface sediments of Chitrapuzha River (South India).

Surface sediment samples were collected from Chitrapuzha (Cochin) estuarine system to identify the natural and anthropogenic origin of organic matter. The distribution and sources of organic matter were assessed with the help of fatty acid and alkane biomarkers. Fatty acids ranging from C12 to C28 were identified and C16:0 was the most abundant fatty acid, which contributed between 23.5 % and 52.4 % to total fatty acids. The low levels of polyunsaturated fatty acids indicate the effective bacterial recycling of algal fatty acids during the whole settling and depositing process. Aliphatic hydrocarbons ranging from C12 to C33 were identified and the total concentration ranged from 7876 to 43,357 ng g(-1). The presence of unresolved complex mixtures and lower pristane to phytane ratios indicates the petroleum contamination in the study area.

Taxonomy and growth conditions concur to determine the energetic suitability of algal fatty acid complements

We hypothesize that, in algae, carbon allocation to lipids depends on the combined effects of the metabolic constraints imposed by the genotype (i.e., species-specific differences in composition) and on the acclimation responses (phenotype) to changes in the stoichiometry of available inorganic carbon (for photosynthesis) and nitrogen (primarily for amino acids, protein, and nucleic acid synthesis). We thus cultured three taxonomically distinct algae, the green alga Dunaliella salina, the diatom Thalassiosira pseudonana, and the dinoflagellate Protoceratium reticulatum, at four nitrate concentrations and constant inorganic carbon. Since energy availability also directly impacts carbon partitioning, we studied the effect of irradiance on the oil quality of P. reticulatum. We used Fourier transform infrared (FTIR) spectroscopy to study carbon allocation and biomass reduction level and gas chromatography for fatty acid analysis. The fatty acid complements of the three species were different; within each species, growth conditions substantially altered oil quality. We ranked the oils in terms of their suitability as biodiesels, using international standards as reference. We believe that this approach may help to identify the appropriate combination of taxa and culture conditions for algal biodiesel production and in general offers insight on carbon allocation to fatty acids.

Seasonal variation of Fatty acids and stable carbon isotopes in sponges as indicators for nutrition: biomarkers in sponges identified.

To get a better understanding of sponge feeding biology and efficiencies, the fatty acid (FA) composition and (13)C natural abundance of sponges and of suspended particulate matter (SPM) from surrounding seawater was studied in different seasons at three locations. Haliclona oculata and Haliclona xena from the Oosterschelde, the Netherlands, Halichondria panicea and H. xena from Lake Veere, the Netherlands, and Aplysina aerophoba and Dysidea avara from the Mediterranean, Spain, were studied. Several FA biomarkers for different algal groups, bacteria and sponge biomass were identified in all sponges. The FA concentration variation in sponges was related to changes in fatty acid concentration in SPM. Stable carbon isotopic ratios (δ(13)C) in sponge specific FAs showed very limited seasonal variation at all sites. Algal FAs in sponges were mainly acquired from the SPM through active filtration in all seasons. At the two sites in the Netherlands only in May (spring), the sponge specific FAs had similar δ(13)C ratios as algal FAs, suggesting that sponges were mainly growing during spring and probably summer. During autumn and winter, they were still actively filtering, but the food collected during this period had little effect on sponge δ(13)C values suggesting limited incorporation of filtered material into the sponge body. The sponge A. aerophoba relied mostly on the symbiotic bacteria. In conclusion, fatty acid composition in combination with stable carbon isotope analysis can be used to analyze the food source of sponges.

Forest harvest effects on mercury in streams and biota in Norwegian boreal catchments

Forest harvesting practices can potentially increase mercury run-off from catchments. A paired catchment experiment was conducted in a boreal forest in southern Norway, to test effects of forest harvest operations on (i) concentrations and fluxes of methylmercury (MeHg), total mercury (HgT), nutrients and dissolved organic matter (TOC), and on (ii) MeHg bioaccumulation in stream foodwebs.Thirty percent of a catchment was harvested in winter time with snow cover but no soil frost, resulting in wheel tracks and soil compaction. Pre-harvest differences included higher streamwater MeHg, HgT and TOC, and lower pH in the treated catchment compared to the reference.No significant treatment effects on concentrations of MeHg, HgT and TOC were detected, whereas concentrations of nutrients (ammonium, nitrate, phosphorus (P)) increased significantly. Estimated catchment export of nitrate and ammonium increased fourfold, as a combined effect of changed discharge and concentrations. Export of MeHg and HgT increased weakly, primarily because of an increase in discharge.Levels of MeHg in stream invertebrates mirrored differences in aquatic MeHg between the two streams, resulting in higher MeHg in biota in the harvest catchment in pre-harvest conditions. After harvest, MeHg levels in primary consumers (herbivorous stoneflies) were no longer different between the two streams, despite continued exposure to higher aqueous MeHg in the harvested catchment. Simultaneously, dietary biomarkers (δ15N signature, lipid- and algal fatty acid content) in the stoneflies had changed significantly, consistent with higher nutrient loadings and associated higher diet availability in the harvested stream.The results of our experiment do not support that forest management has a strong impact on catchment MeHg production. Catchment disturbance through forest harvesting may decrease MeHg in aquatic biota, because of higher stream productivity and associated higher quality of dietary sources, at least in the short-term. Other studies on catchment MeHg production to disturbance have shown a range in responses, from strong to none. So far, no factor has emerged to explain such range in responses. Predictions of forest management effects on MeHg in streamwater and aquatic food webs are hampered by limited understanding of catchment controls on MeHg production.

Optimization of Medium Using Response Surface Methodology for Lipid Production by Scenedesmus sp.

Lipid production is an important indicator for assessing microalgal species for biodiesel production. In this work, the effects of medium composition on lipid production by Scenedesmus sp. were investigated using the response surface methodology. The results of a Plackett–Burman design experiment revealed that NaHCO3, NaH2PO4·2H2O and NaNO3 were three factors significantly influencing lipid production, which were further optimized by a Box–Behnken design. The optimal medium was found to contain 3.07 g L−1 NaHCO3, 15.49 mg L−1 NaH2PO4·2H2O and 803.21 mg L−1 NaNO3. Using the optimal conditions previously determined, the lipid production (304.02 mg·L−1) increased 54.64% more than that using the initial medium, which agreed well with the predicted value 309.50 mg L−1. Additionally, lipid analysis found that palmitic acid (C16:0) and oleic acid (C18:1) dominantly constituted the algal fatty acids (about 60% of the total fatty acids) and a much higher content of neutral lipid accounted for 82.32% of total lipids, which strongly proved that Scenedesmus sp. is a very promising feedstock for biodiesel production.

Biotechnological applications of halophilic lipases and thioesterases

Lipases and esterases are enzymes which hydrolyze ester bonds between a fatty acid moiety and an esterified conjugate, such as a glycerol or phosphate. These enzymes have a wide spectrum of use in industrial applications where their high activity, broad substrate specificity, and stability under harsh conditions have made them integral in biofuel production, textile processing, waste treatment, and as detergent additives. To date, these industrial applications have mainly leveraged enzymes from mesophilic and thermophilic organisms. However, increasingly, attention has turned to halophilic enzymes as catalysts in environments where high salt stability is desired. This review provides a brief overview of lipases and esterases and examines specific structural motifs and evolutionary adaptations of halophilic lipases. Finally, we examine the state of research involving these enzymes and provide an in-depth look at an exciting algal-based biofuel production system. This system uses a recombinant halophilic lipase to increase oil production efficiency by cleaving algal fatty acids from the acyl carrier protein, which eliminates feedback inhibition of fatty acid synthesis.

Microphytobenthos and benthic macroalgae determine sediment organic matter composition in shallow photic sediments

Abstract. Microphytobenthos and benthic macroalgae play an important role in system metabolism within shallow coastal bays. However, their independent and interactive influences on sediment organic matter (SOM) are not well understood. We investigated the influence of macroalgae and microphytobenthos on SOM quantity and quality in an experimental mesocosm system using bulk and molecular level (total hydrolyzable amino acids, THAA; phospholipid linked fatty acids, PLFA; pigment) analyses. Our experiment used an incomplete factorial design made up of two factors, each with two levels: (1) light (ambient vs. dark) and (2) macroalgae (presence vs. absence of live macroalgae). Over the course of the 42-day experiment, total organic carbon (TOC) and total nitrogen (TN) increased under ambient light by 173 ± 14 and 141 ± 7%, respectively, compared to in the dark (78 ± 29 and 39 ± 22%). THAA comprised a substantial fraction of SOM (~ 16% of TOC, 35% of TN) and followed TOC and TN accumulation patterns. Mole percent composition of the THAA pool indicated that SOM was composed of more labile organic material (e.g., L-glutamic acid, phenylalanine) under ambient light conditions while SOM in dark treatments was more degraded, with higher proportions of glycine and D-alanine. PLFA content, which represents viable biomass, made up ~ 1% of TOC and contained high levels of algal fatty acids in the light, particularly PLFA derived from diatoms. In the presence of microphytobenthos (i.e., light and macroalgae treatments), SOM lability increased, resulting in the observed increases in bacterial PLFA concentrations. Macroalgae, which were added to half of the light treatments, decreased SOM accumulation compared to light treatments without macroalgae, with TOC and TN increasing by only 130 ± 32 and 94 ± 24%, respectively. This decrease likely resulted from shading by macroalgae, which reduced production of microphytobenthos. The presence of macroalgae decreased SOM lability as well, which resulted in diminished buildup of bacterial biomass. By the final day of the experiment, principal component analysis revealed that sediment composition in treatments with macroalgae was more similar to dark treatments and less similar to light treatments without macroalgae. Overall, microphytobenthos and benthic macroalgae fundamentally altered SOM quality and quantity, which may have notable ecological consequences for shallow-water systems such as increased hypoxia/anoxia, sulfide accumulation, enhanced mineralization and/or stimulated denitrification.

Chrysochromulina sp.: A proposed lipid standard for the algal biofuel industry and its application to diverse taxa for screening lipid content

BackgroundThe production of algal-derived oil has been recognized as an expanding new industry. Algal oil recovery and quality are impacted by both biological (algal cell type, growth physiology) and technical (recovery and extraction methodologies) constraints. Unfortunately, and unlike other well-established food and oil commodities, presently no universal reference standard exists for use in the algal oil industry. ResultsA laboratory-optimized strain of Chrysochromulina sp. is proposed as a natural matrix reference standard for algal fatty acid analysis. The alga is amenable to this purpose because: (a) as a soft-bodied organism, it is susceptible to many disruption and fatty acid extraction techniques; (b) it has a high fatty acid content (~40% dry weight); (c) the growth response and lipid profiles of this organism are highly reproducible; (d) unlike many algae that have limited fatty acid distributions, Chrysochromulina sp. cells contain a broad representation of both saturated and unsaturated fatty acids ranging from C:14 to C:22. As a proof of concept, Chrysochromulina sp. was used as a reference standard for comparing 20 taxonomically diverse algal cultures, grown under identical physiological conditions and analyzed for fatty acid content using a micro-GC/MS analytical technique. ConclusionsExpanding efforts in both commercial and research facilities will require the screening and monitoring of candidate algal strains for lipid synthesis. Universal adoption of a reference standard will provide a common platform to compare the fatty acid compositions of different algal strains grown under diverse environmental conditions and subjected to different oil recovery methods. A reproducibly generated natural matrix standard will have two distinct advantages: (a) as a reproducibly generated standard, it can supplant reference products that vary markedly among suppliers; and (b) the use of a natural matrix standard will help in the identification and elimination of errors in lipid extraction, derivatization and analysis.

Engineering fatty acid biosynthesis in microalgae for sustainable biodiesel

Microalgae are a promising feedstock for biodiesel and other liquid fuels due to their fast growth rate, high lipid yields, and ability to grow in a broad range of environments. However, many microalgae achieve maximal lipid yields only under stress conditions hindering growth and providing compositions not ideal for biofuel applications. Metabolic engineering of algal fatty acid biosynthesis promises to create strains capable of economically producing fungible and sustainable biofuels. The algal fatty acid biosynthetic pathway has been deduced by homology to bacterial and plant systems, and much of our understanding is gleaned from basic studies in these systems. However, successful engineering of lipid metabolism in algae will necessitate a thorough characterization of the algal fatty acid synthase (FAS) including protein-protein interactions and regulation. This review describes recent efforts to engineer fatty acid biosynthesis toward optimizing microalgae as a biodiesel feedstock.

Nutritional mode influences lipid accumulation in microalgae with the function of carbon sequestration and nutrient supplementation

Effect of nutritional mode viz., photoautotrophic, photoheterotrophic and photomixotrophic on the biomass growth and lipid productivity of microalgae was studied. Experiments were designed and operated in biphasic mode i.e., growth phase (GP) followed by stress induced starvation phase (SP). Nutritional mode documented marked influence on biomass growth and subsequent lipid productivity. Mixotrophic mode of operation showed higher biomass growth (4.45 mg/ml) during growth phase while higher lipid productivity was observed with nitrogen deprived autotrophic mode (28.2%) followed by heterotrophic (26.1%) and mixotrophic (19.6%) operations. Relative increments in lipid productivities were noticed in SP operation from GP in mixotrophic operation (2.45) followed by autotrophic (2.2) and heterotrophic (2.14) mode of operations. Higher concentrations of chlorophyll b and presence of lipid accumulating species supported the lipid biosynthesis. Algal fatty acid composition varied with function of nutritional modes and depicted eighteen types of saturated (SFA) and unsaturated fatty acids (USFA) with wide fuel and food characteristics.

Production of bio-diesel from macro-algae of the Orbetello lagoon by various extraction methods

In the last few years, there has been a significant increase in finding alternative energy sources to fossil fuel. Bio-diesel derived from vegetable oils has been shown to be a potential alternative. Presently, most of the available bio-diesel is made from edible oils, but it is believed that with a large-scale production of bio-diesel these stocks may cause an imbalance to the food supply. Algae and aquatic bio-mass have the potential to provide a new range of third generation bio-fuels. Recently, there has been substantial increase in attention to the possibility of using aquatic bio-mass. The aim of this study was to evaluate the macro-algae oil yield and lipid composition in order to produce bio-diesel from waste bio-mass. The algal bio-mass comes from the Orbetello lagoon (Southern Tuscany, Italy), where macro-algae grow naturally due to eutrophication and are harvested and stored in a landfill as a special waste product. Lipid extraction was carried out according to the Bligh and Dyer method and also by using a Dionex ASE200 (accelerated solvent extractor). The total lipid content was determined by micro-gravimetry and the fatty acids (FAs) by GC-FID and GC-MS after acid transesterification. Chaetomorpha linum was the most abundant species and had the highest lipid content. Lipid concentrations and profiles of the Orbetello lagoon's macro-algae were comparable with those reported in the literature for the same species or genus. Algal FAs corresponded to those that normally constitute bio-diesel. Thus, the results indicate that bio-diesel could be produced from the harvested algal bio-mass.