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The enzyme alkaline phosphatase (ALP) is gaining interest because it exerts bioactive properties and may be a potentially important therapeutic agent for many disorders and diseases. Microalgae are considered an important novel source for the production of diverse bio-compounds and are gaining momentum as functional foods/feeds supplements. So far, studies for the production of ALP are limited to mammalian and partly to some heterotrophic microbial sources after its extraction and/or purification. Methods:&nbsp, Arthrospira was cultivated under P-limitation bioprocess and the effect of the P-limitation degree on the ALP enrichment was studied. The aim of this work was to optimize the cultivation of the edible and generally-recognized-as-safe (GRAS) cyanobacterium Arthrospira platensis for the production of single-cell (SC) biomass enriched in ALP as a potential novel functional diet supplement. Results: The results revealed that the relationship between intracellular-P and single-cell alkaline phosphatase (SC-ALP) activity was inverse, SC-ALP activity was the highest (around 50 U g−1) when intracellular-P was the lowest possible (around 1.7 mg-P g−1) and decreased gradually as P availability increased reaching around 0.5 U g−1 in the control cultures. Under the strongest P-limited conditions, a more than 100-fold increase in SC-ALP activity was obtained, however, protein content of A. platensis decreased significantly (around 22–23% from 58%). Under a moderate P-limitation degree (at intracellular-P of 3.6 mg-P g−1), there was a relatively high SC-ALP activity (&gt, 28 U g−1) while simultaneously, a relative high protein content (46%) was attained, which reflects the possibility to produce A. platensis enriched in ALP retaining though its nutritional value as a protein rich biomass source. The paper presents also results on how several parameters of the ALP activity assay, such as pH, temperature etc., and post-harvest treatment (hydrothermal treatment and biomass drying), influence the SC-ALP activity.

(1) Background: Arthrospira (commonly known as Spirulina) is an edible cyanobacterium that is produced worldwide as a food supplement owing to its high nutritional value. Arthrospira displays strong potential as an important ingredient in the development of novel functional foods. Polysaccharides from Arthrospira are biologically active compounds and hence there is interest in producing biomass rich in carbohydrates. (2) Methods: A. platensis was cultivated under different degrees of phosphorus limitation in order to trigger the accumulation of carbohydrates. The biomass was then characterized in terms of its content of α- and β-glucans, total dietary fiber and monosaccharide profile. Fourier-transform infrared spectroscopy (FTIR) was used for the rapid analysis of the main biomass components. (3) Results: Phosphorus limitation resulted in an increase in carbohydrates (from 23% up to 65% dry biomass) of which 4–12% (in relation to the dry biomass) was α-glucans and 20–34% was 1.3:1.6 β-glucans, while 1.4:1.6 β-glucans were not detected. Total dietary fibers ranged from 20–32% (of dry biomass), whereas among the carbohydrates, the predominant monosaccharide was glucose (&gt, 95%). FTIR performed well when applied as a prediction tool for the main biomass components. (4) Conclusions: Since β-glucans are of particular interest as biologically active compounds, this study demonstrates that phosphorus-limited A. platensis could be a potential ingredient for the development of novel functional foods.

Brewers’ Spent Grain (BSG) represents the 85% of the total residue produced during the beer brewing process, with a global annual production volume exceeding the 30 Mtons. Study herein concerns the application of solid state fermentation (SSF) process for the efficient transformation of BSG into high nutritional value animal feed. The investigated SSF procedure was initiated by Pleurotus ostreatus, which constitutes a natural source of β-glucans and metabolites (vitamins, nutrients). Thus, it is possible to reduce the environmental impacts caused by BSG production and simultaneously contribute to the tackling of proteinaceous animal feed shortage observed during the last decade. The method developed resulted in a significant increase of protein content by 49.49%, a 10-fold increase of their 1,3 − 1,6 β-glucans content and a respective reduction of cellulose content by 11.42%. The application of this method is expected to provide a solid background for the utilization of BSG as substrate for fungi initiated SSF, a bioprocess allowing the significant reduction of the environmental impact caused by the beer brewing industry and simultaneously produce animal feed with high protein content and nutritional characteristics suitable for fulfilling animals’ nutritional needs and improving their welfare.

This study examined the effects of monochromatic illumination (blue, red, green and yellow) employing light-emitting diodes (LEDs), trophic conditions (photoautotrophic and mixotrophic), and nitrogen availability (high and low peptone concentration) on the growth and biochemical composition of Auxenochlorella protothecoides. The results revealed that mixotrophic conditions did not favor A. protothecoides, giving lower growth rates compared to heterotrophy (dark conditions). However, mixotrophy gave significantly higher growth rates compared to photoautotrophy. The best light wavelengths for mixotrophic cultivation were that of white and red. In all cases investigated in this study, high peptone concentration (4 g/L) resulted in decreased growth rates. Regarding the biochemical composition of A. protothecoides, the strongest effect, irrespective of trophic conditions, was caused by nitrogen availability (peptone concentration). Specifically, at nitrogen replete conditions (4 g/L peptone), biomass was rich in proteins (32–67%), whereas under deplete conditions (0.5 g/L peptone), A. protothecoides accumulated mainly carbohydrates (up to 56%). Mixotrophic conditions generally favored higher carbohydrate content, whereas photoautotrophic conditions favored higher protein content. The different illumination spectra did not have any clear effect on the biochemical composition (metabolites content), except that, in all trophic conditions, the use of the green spectrum resulted in higher chlorophyll b content. Chlorophyll a fluorescence studies revealed that the trophic conditions and the high peptone concentrations impacted the photosystem II (PSII) performance, and also affected plastoquinone re-oxidation kinetics and the heterogeneity of the PSII reaction centers.

Microalgae (including cyanobacteria) have recently gained interest as a potential food and feed source due to their high nutritional value. Some microalgae and cyanobacteria have been traditionally consumed worldwide. Under the European Union’s legislation, they are considered, with only few exceptions, as novel foods, and therefore in order to enter the EU market it is required primarily to be authorized after risk assessment to ensure that they do not display any risk to public health. This chapter gives an overview of the current legislative situation of microalgae as food in the European Union and discusses the potential health risks associated with the consumption of microalgae and cyanobacteria.

Anaerobic Digestion (AD) is a process that is well-known and fast-developing in Europe. AD generates large amounts of digestate, especially in livestock-intensive areas. Digestate has potential environmental issues due to nutrients (such as nitrogen) lixiviation or volatilization. Using liquid digestate as a nutrient source for microalgae growth is considered beneficial because digestate could be valorized and upgraded by the production of an added value product. In this work, microalgal biomass produced using liquid digestate from an agricultural biogas plant was investigated as a slow-release fertilizer in tomatoes. Monoraphidium sp. was first cultivated at different dilutions (1:20, 1:30, 1:50), in indoor laboratory-scale trials. The optimum dilution factor was determined to be 1:50, with a specific growth rate of 0.13 d&minus, 1 and a complete nitrogen removal capacity in 25 days of culture. Then, outdoor experiments were conducted in a 110 dm3 vertical, closed photobioreactors (PBRs) in batch and semi-continuous mode with 1:50 diluted liquid digestate. During the batch mode, the microalgae were able to remove almost all NH4+ and 65 (&plusmn, 13) % of PO43&minus, while the microalgal growth rate reached 0.25 d&minus, 1. After the batch mode, the cultures were switched to operate under semi-continuously conditions. The cell densities were maintained at 1.3 &times, 107 cells mL&minus, 1 and a biomass productivity around 38.3 mg TSS L&minus, 1 d&minus, 1 during three weeks was achieved, where after that it started to decline due to unfavorable weather conditions. Microalgae biomass was further tested as a fertilizer for tomatoes growth, enhancing by 32% plant growth in terms of dry biomass compared with the control trials (without fertilization). Similar performances were achieved in tomato growth using synthetic fertilizer or digestate. Finally, the leaching effect in soils columns without plant was tested and after 25 days, only 7% of N was leached when microalgae were used, against 50% in the case of synthetic fertilizer.

Aquatic organisms, such as microalgae (Chlorella, Arthrospira (Spirulina), Tetrasselmis, Dunalliela etc.) and duckweed (Lemna spp., Wolffia spp. etc.) are a potential source for the production of protein-rich biomass and for numerous other high-value compounds (fatty acids, pigments, vitamins etc.). Their cultivation using agro-industrial wastes and wastewater (WaW) is of particular interest in the context of a circular economy, not only for recycling valuable nutrients but also for reducing the requirements for fresh water for the production of biomass. Recovery and recycling of nutrients is an unavoidable long-term approach for securing future food and feed production. Agro-industrial WaW are rich in nutrients and have been widely considered as a potential nutrient source for the cultivation of microalgae/duckweed. However, they commonly contain various hazardous contaminants, which could potentially taint the produced biomass, raising various concerns about the safety of their consumption. Herein, an overview of the most important contaminants, including heavy metals and metalloids, pathogens (bacteria, viruses, parasites etc.), and xenobiotics (hormones, antibiotics, parasiticides etc.) is given. It is concluded that pretreatment and processing of WaW is a requisite step for the removal of several contaminants. Among the various technologies, anaerobic digestion (AD) is widely used in practice and offers a technologically mature approach for WaW treatment. During AD, various organic and biological contaminants are significantly removed. Further removal of contaminants could be achieved by post-treatment and processing of digestates (solid/liquid separation, dilution etc.) to further decrease the concentration of contaminants. Moreover, during cultivation an additional removal may occur through various mechanisms, such as precipitation, degradation, and biotransformation. Since many jurisdictions regulate the presence of various contaminants in feed or food setting strict safety monitoring processes, it would be of particular interest to initiate a multi-disciplinary discussion whether agro-industrial WaW ought to be used to cultivate microalgae/duckweed for feed or food production and identify most feasible options for doing this safely. Based on the current body of knowledge it is estimated that AD and post-treatment of WaW can lower significantly the risks associated with heavy metals and pathogens, but it is yet unclear to what extent this is the case for certain persistent xenobiotics.

The detection of new pollutants, stricter environmental regulations, and advancements in treatment technologies are driving improvements in bioprocesses for treating wastewater. Specifically, special concern is being placed on phosphorus and nitrogen forms, which spur eutrophication of water bodies, and emerging micropollutants such as pharmaceuticals and person-care products. Algae and cyanobacteria cultivation requirements include water and nutrient sources that currently are supplied by fertilizers, which provide poor sustainability and economics. Using wastewater as a source of nitrogen and phosphorus represents an attractive option to cultivate microalgae simultaneous with contaminant removal. Phycoremediation refers to the assimilation or disintegration of organic and inorganic compounds (carbon, nitrogen, or phosphorus), metals, and emerging contaminants in wastewater by microalgae – algae and cyanobacteria. In addition, added value comes when the microalgae are harvested to become feedstock for biofuels such as biogas. Although promising studies have been published for algal growth in wastewater while simultaneously removing contaminants, limitations in the scale-up process still have to be addressed. In this work, we summarize biological mechanisms by which nutrients and contaminants are removed by microalgae. We specifically address the interactions that the microalgae have with other microorganisms and the production of extracellular polymeric substances, a mechanism well known in the literature, but hardly studied in microalgae. Finally, we discuss different strategies reported to improve the scale up of microalgae cultivation in wastewater.

In this study, Arthrospira platensis was grown in the presence of different glycerol concentrations (0.5&ndash, 9 g/L) under three light intensities (5, 10 and 15 Klux) in semi-continuous mode and under non-axenic conditions. The aim of this study was to investigate the growth performance, the biomass biochemical composition and any interactions between A. platensis and bacteria that would potentially grow as well on glycerol. The results here show that glycerol did not have any positive effect on biomass production of A. platensis. In contrast, it was observed that by increasing glycerol concentration the growth performance of A. platensis was restricted, while a gradual increase of bacteria population was observed, which apparently outcompeted and repressed A. platensis growth. Chlorophyll fluorescence measurements (Quantum Yields) revealed that glycerol was not an inhibiting factor per se of photosynthesis. On the other hand, cyanobacterial biomass grown on glycerol displayed a higher content in proteins and lipids. Especially, protein productivity was enhanced around 15&ndash, 35% with the addition of glycerol compared to the control. In distinction, carbohydrate and photosynthetic pigments (phycocyanin and chlorophyll-&alpha, ) content decreased with the increase of glycerol concentration. The results here suggest that A. platensis did not utilize glycerol for biomass production but most probably as metabolic energy carrier towards synthesis of proteins and lipids, which are more energy consuming metabolites compared to carbohydrates. The study revealed that the addition of glycerol at amounts of 0.5&ndash, 1.5 g/L could be a strategy to improve protein productivity by A. platensis.

Although ammoniacal nitrogen is the preferred nitrogen source for microalgae/cyanobacteria, at elevated concentrations and high pH values it may negatively impact photosynthesis and growth. Chlorophyll (Chl) fluorescence analysis is a useful tool to monitor the influence of various stress conditions on the photosynthetic activity of plants or microalgae/cyanobacteria. In this study, we investigated the effect of ammoniacal nitrogen on Chl fluorescence in microalgae/cyanobacteria. Chl fluorescence analysis revealed that the parameters related to flux ratios and specific energy fluxes of photochemistry were gradually inhibited as the free ammonia (FA) concentration increased. Photosynthetic electron transport activity was measured using artificial electron acceptors, donors or inhibitors. These analyses suggest that ammonia has multiple impacts on the photosynthetic apparatus; photosystems I (PSI) and II (PSII), the electron transport chain, the oxygen-evolution complex (OEC) as well the dark respiration were gradually inhibited by increasing FA concentration. At high FA concentration, the PSI/PSII activity increased, suggesting that PSI was more tolerant to FA than PSII. Non-photochemical quenching (NPQ) decreased to zero at elevated FA concentrations. The Chl fluorescence data obtained in the presence of DCMU (diuron) suggest that the decrease of NPQ under ammonia inhibition/toxicity is due to the increase of PSI/PSII activity. The rapid response of Chl fluorescence transients to increases in FA may allow one to use pulse amplitude modulation (PAM) fluorescence as a tool to monitor ammonia inhibition/toxicity in cultures of microalgae/cyanobacteria.

© 2019 Society of Chemical Industry BACKGROUND: The cyanobacterium Arthrospira contains proteins and the blue pigment phycocyanin that can be used as a natural colourant in the food industry. The aim of this study was to investigate a strategy for increasing the yield of phycocyanin and protein from Arthrospira cultures by shading the cultures with neutral density and red light filters. Experiments were conducted under three different irradiance conditions: (i) laboratory tests under relatively low light intensities (100 μmol m −2 s −1 ), (ii) laboratory tests under relatively high light intensities (516 μmol m −2 s −1 ) and (iii) scaled-up tests under natural conditions by cultivating Arthrospira in raceway ponds in a greenhouse. RESULTS: In all cases, shading of cultures with red filters resulted in biomass with increased phycocyanin content achieving a maximum of 134, 71 and 121 mg g −1 under low light intensity, high light intensity and natural conditions, respectively. Under high light intensity and natural conditions, shaded cultures displayed phycocyanin of higher purity and increased protein content, which reached up to 43 and 65%, respectively. CONCLUSIONS: Shading of Arthrospira cultures by low-cost polyester red light filters may be an effective way for enhancing phycocyanin production and improving its purity in outdoor ‘spirulina farms’. © 2019 Society of Chemical Industry. ispartof: JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY vol:94 issue:6 pages:2047-2054 status: published

International audience; Crude phycocyanin extract (PC-E) from a two-phase cultured Saharian Arthrospira sp. strain with a purity grade of 1.24 (reagent grade) was characterized regarding its stability, bio-functionality and bio-activity. PC-E showed higher solubility values above pH 6.0, while the maximum stability was achieved at pH 6.0. PC-E was stable only up to 50 degrees C, while the addition of stabilizing agents (PEG-4000 and sorbitol) significantly enhanced thermostability. FTIR and DSC analysis revealed that thermostabilization by PEG-4000 and sorbitol addition was achieved through hydrogen bound and amorphous glass formation. Emulsifying and foaming properties of PC-E were concentration-dependent. PC-E displayed antioxidant activity in a dose dependent manner, including beta-carotene bleaching inhibition, ferrous chelating effect, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 63%, 78% and 100% at 5 mg mL(-1), respectively. Moreover, PC-E exhibited great antibacterial activity at 5 mg mL(-1) against Staphylococcus aureus, Micrococcus luteus, Escherichia colt and Pseudomonas sp.

In the present paper, the use of raw poultry litter (PL) as a nutrient source for the cultivation of Arthrospira platensis and Chlorella vulgaris was investigated. PL was added to acid solution (62.5 mM H 2 SO 4 ) for the extraction of nutrients contained in PL. After settling, the supernatant, called PL leachate (PLL) was diluted 25 ×, 20 ×, 15 ×, and 10 × and used as a medium for the cultivation of A. platensis and C. vulgaris . A. platensis could not survive in 15 × and 10 × diluted leachate and while in 20 × and 25 × dilutions the biomass production was only half of that in a control medium (Zarrouk). The biomass composition had a high carbohydrate content (37–44%), which suggests that A. platensis was stressed due to nutrient limitation. C. vulgaris grew well in PLL-based media and the biomass production was higher than in the control medium (BG-11). Biomass composition of C. vulgaris in PLL-based media had lower protein content and higher carbohydrate and lipid content than in the control medium. The overall process for producing microalgal biomass from PL that we propose includes: (i) acid extraction of nutrients through the generation of PL leachate (PLL), (ii) indoor PL composting and recovery of stripped ammonia and CO 2 , and (iii) use of recovered ammonia and CO 2 along with the PLL for the cultivation of microalgae and cyanobacteria for the production of biomass.

In the present work the cyanobacterium Arthrospira platensis and the microalga Chlorella vulgaris were fed-batch cultivated in ammonia-rich wastewater derived from the anaerobic digestion of poultry litter. Aim of the study was to maximize the biomass production along with the nutrient removal aiming to wastewater treatment. Ammonia and phosphorus removals were very high (>95%) for all cultures investigated. Both microorganisms were able to remove volatile fatty acids to an extent of >90%, indicating that they were capable of mixotrophic growth. Chemical oxygen demand and proteins were also removed in various degrees. In contrast, in all cultures carbohydrate concentration was increased. The biochemical composition of the microorganisms varied greatly and was influenced by the indicate that the nutrient availability. A. platensis accumulated carbohydrates (≈ 40%), while C. vulgaris accumulated lipids (≈ 50%), rendering them interesting for biofuel production.

Flocculation of microalgae is a promising low-cost strategy to harvest microalgae for bulk biomass production. However, residual flocculants can interfere in further downstream processes or influence biomass quality. In this study, a new concept is demonstrated based on reversible magnesium hydroxide flocculation, using Chlorella vulgaris and Phaeodactylum tricornutum as respectively a freshwater and a marine model species. We show that flocculation was induced by precipitation of magnesium hydroxide at high pH (10 to 10.5). This resulted in a magnesium content of the microalgal biomass of 5% for Chlorella and 18% for Phaeodactylum. After pre-concentration of the microalgal biomass by gravity sedimentation, 95% of the precipitated magnesium hydroxide could be removed from the biomass by mild acidification (pH 7 to 8). The pH fluctuations experienced by the microalgae during flocculation/de-flocculation had no influence on biomass composition (FAME, total N and P, carbohydrates, proteins, mineral content) and on the viability of microalgal cells. Magnesium can thus be used as pH-dependent reversible flocculant for harvesting microalgae in both marine and freshwater medium. ispartof: BioEnergy Research vol:8 issue:2 pages:716-725 status: published

Microalgae and cyanobacteria are a promising new source of biomass that may complement agricultural crops to meet the increasing global demand for food, feed, biofuels and chemical production. Microalgae and cyanobacteria cultivation does not interfere directly with food production, but care should be taken to avoid indirect competition for nutrient (fertilizer) supply. Microalgae and cyanobacteria production requires high concentrations of essential nutrients (C,N,P,S,K,Fe, etc.). In the present paper the application of nutrients and their uptake by microalgae and cyanobacteria is reviewed. The main focus is on the three most significant nutrients, i.e. carbon, nitrogen and phosphorus; however other nutrients are also reviewed. Nutrients are generally taken up in the inorganic form, but several organic forms of them are also assimilable. Some nutrients do not display any inhibition effect on microalgal or cyanobacterial growth, while others, such as NO2 or NH3 have detrimental effects when present in high concentrations. Nutrients in the gaseous form, such as CO2 and NO face a major limitation which is related mainly to their mass transfer from the gaseous to the liquid state. Since the cultivation of microalgae and cyanobacteria consumes considerable quantities of nutrients, strategies to improve the nutrient application efficiency are needed. Additionally, a promising strategy to improve microalgal and cyanobacterial production sustainability is the utilization of waste streams by recycling and waste nutrients. However, major constraints of using waste streams are the reduction of the range of the biomass applications due to production of contaminated biomass and the possible low bio-availability of some nutrients. publisher: Elsevier articletitle: Microalgal and cyanobacterial cultivation: The supply of nutrients journaltitle: Water Research articlelink: http://dx.doi.org/10.1016/j.watres.2014.07.025 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved. ispartof: Water Research vol:65 pages:186-202 ispartof: location:England status: published

Herein a new approach for the application of wastewater nutrients for the cultivation of cyanobacteria or microalgae is described. Natural zeolite was used as medium for the sorption of ammonia from wastewater and subsequently as nitrogen releaser in cultures of Arthrospira. platensis. The main scope of the present approach was to isolate ammonia from the wastewater and to transfer it into the culture medium excluding thus the suspended solids, the dissolved colored compounds or any other possible contaminant of the wastewater. The results demonstrate that the indirect use of ammonia derived from wastewater using zeolite as sorption and releasing medium for the cultivation of A. platensis is promising. This is the first time that a medium was used for indirect application of wastewater nutrient for the production of cyanobacterial or microalgal biomass. publisher: Elsevier articletitle: Using natural zeolite for ammonia sorption from wastewater and as nitrogen releaser for the cultivation of Arthrospira platensis journaltitle: Bioresource Technology articlelink: http://dx.doi.org/10.1016/j.biortech.2013.12.122 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved. ispartof: Bioresource Technology vol:155 pages:373-378 ispartof: location:England status: published

In the present study the potential of bioethanol production using carbohydrate-enriched biomass of the cyanobacterium Arthrospira platensis was studied. For the saccharification of the carbohydrate-enriched biomass, four acids (H2SO4, HNO3, HCl and H3PO4) were investigated. Each acid were used at four concentrations, 2.5 N, 1 N, 0.5 N and 0.25 N, and for each acid concentration the saccharification was conducted under four temperatures (40 °C, 60 °C, 80 °C and 100 °C). Higher acid concentrations gave in general higher reducing sugars (RS) yields (%, gRS/gTotal sugars) with higher rates, while the increase in temperature lead to higher rates at lower acid concentration. The hydrolysates then were used as substrate for ethanolic fermentation by a salt stress-adapted Saccharomyces cerevisiae strain. The bioethanol yield (%, gEtOH/gBiomass) was significantly affected by the acid concentration used for the saccharification of the carbohydrates. The highest bioethanol yields of 16.32% ± 0.90% (gEtOH/gBiomass) and 16.27% ± 0.97% (gEtOH/gBiomass) were obtained in hydrolysates produced with HNO3 0.5 N and H2SO4 0.5 N, respectively.

Herein the effect of increasing light intensity on the degree of ammonia toxicity and its impact on the photosynthetic performance of Arthrospira and Chlorella was investigated using Chl fluorescence as a technique to characterize their photosystem II (PSII) activity. The results revealed that the increase of light intensity amplifies the ammonia toxicity on PSII. Chl fluorescence transients shown that at a given free ammonia (FA) concentration (100mg-N/L), the photochemistry potential decreased by increasing light intensity. The inhibition of the PSII was not reversible either by re-incubating the cells under dark or under decreased FA concentration. Moreover, the decrease of photochemical and non-photochemical quenching (NPQ) of fluorescence suggest that ammonia toxicity decreases the open available PSII centers, as well the inability of PSII to transfer the generated electrons beyond QA. The collapse of NPQ suggests that ammonia toxicity inhibits the photoprotection mechanism(s) and hence renders PSII more sensitive to photoinhibition.

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l(-1) K(2)HPO(4)) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m(-2) s(-1)). The maximum biomass production was 3,592 ± 392 mg l(-1) and this was observed in 250 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1) light intensity after 32 days of cultivation. A maximum specific growth rate (μ(max)) of 0.55 d(-1) was obtained in 500 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1). The protein, lipid and chlorophyll contents of the biomass varied from 33.59 to 60.57 %, 5.34 to 13.33 % and 0.78 to 2.00 %, respectively. The most significant finding was that phosphorus limitation (10 mg l(-1) K(2)HPO(4)) caused a drastic increase of the carbohydrate content (59.64 %). The effect of phosphorus limitation on the carbohydrate content was independent of the light intensity. The accumulated carbohydrates are proposed to be used as substrate for biofuel generation via one of the appropriate biomass energy conversion technologies. Also, it was observed that phosphorus removal is a function of biomass density, phosphorus concentration and light intensity.

Carbohydrates are a desirable biomass compound for the generation of several biofuels. Phosphorus nutrient limitation causes a significant increase in the carbohydrate content of the cyanobacterium Arthrospira (Spirulina) platensis. Carbohydrates accumulated up to a content of 63.09 ± 3.43 % (±SD) in both batch and semi-continuous cultures. In order the production of carbohydrate-rich biomass through nutrient limitation to be maximized, it is suggested that the limited nutrients have to be supplied in amounts that they on one hand can support the biomass production while on the other hand they alter the composition of the biomass. In this study, phosphorus of 1.82 ± 0.16 mg g−1 of dry biomass was the optimized amount for the maximization of carbohydrates production by A. platensis. Regarding the need to decrease the application amounts of nutrients for biomass production, this study demonstrates that the phosphorus supply could be decreased an order of magnitude with no significant decrease in biomass production. In addition, it was observed that biomass rich in carbohydrates bio-flocculates, during settling without the addition of any flocculation agent or any other intervention. The bio-flocculation efficiency appears to be related with the carbohydrate content of the biomass. In maximum carbohydrate content (60 %), the biomass bio-flocculated at 68.49 ± 7.73 % the first 15 min and reached 80.25 ± 5.58 % 60 min after settling. The produced carbohydrates might be used as feedstock for biofuel generation, while the bio-flocculation and the overall settling characteristics of the carbohydrate-rich biomass could make its harvesting process much easier.

Recently research interest has focused on the production of biofuel from microalgae. Microalgae are photosynthetic microorganisms that grow utilizing solar energy, nevertheless, the quantities of fertilizers that should be used for their production are enormous. One alternative to the use of synthetic fertilizers is to employ wastes and wastewaters (W&WWs), especially from the agro-industrial sector which are rich in inorganic pollutants such as nitrogen and phosphorus, which can be recovered. Simultaneously with the cultivation of microalgae using wastes and wastewaters for biomass production, treatment of the wastes and wastewaters occur through removal of the pollutants. Filamentous cyanobacteria appear to be suitable candidates for cultivation in wastes and wastewaters because they produce biomass in satisfactory quantity and can be harvested relatively easily due to their size and structure. In addition their biomass composition can be manipulated by several environmental and operational factors in order to produce biomass with concrete characteristics. Herein we review the factors that affect the biomass composition of cyanobacteria and present several studies that discuss the culture of filamentous cyanobacteria in agro-industrial wastes and wastewaters, with special emphasis on Spirulina.

A study was conducted to investigate the effect of light intensity (21, 42, and 63 μmol photons m(-2) s(-1)) and photoperiod (8:16, 12:12, and 16:8 h light/dark) on the biomass production and its biochemical composition (total carotenoids, chlorophyll a, phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC), total protein, and carbohydrates) of a local isolate of Nostoc calcicola. The results revealed that N. calcicola prefers dim light; however, the most of the levels of light intensity and photoperiod investigated did not have a significant impact on biomass production. Increasing light intensity biomass content of chlorophyll a, PE, PC, APC, and total protein decreased, while total carotenoids and carbohydrate increased. The same behavior was observed also when light duration (photoperiod) increased. The interaction effect of increasing light intensity and photoperiod resulted in an increase of carbohydrate and total carotenoids, and to the decrease of chlorophyll a, PE, PC, APC, and total protein content. The results indicate that varying the light regime, it is capable to manipulate the biochemical composition of the local isolate of N. calcicola, producing either valuable phycobiliproteins or proteins under low light intensity and shorter photoperiods, or producing carbohydrates and carotenoids under higher light intensities and longer photoperiods.

In this study, zeolite was employed for the separation and recovery of P from synthetic wastewater and its use as phosphorus (P) source for the cultivation of the green microalga Chlorella vulgaris and the cyanobacterium Arthrospira (Spirulina) platensis. At P-loaded zeolite concentration of 0.15–1 g/L, in which P was limited, the two species displayed quite different behavior regarding their growth and biomass composition. C. vulgaris preferred to increase the intracellular P and did not synthesize biomass, while A. platensis synthesized biomass keeping the intracellular P as low as possible. In addition under P limitation, C. vulgaris did display some little alteration of the biomass composition, while A. platensis did it significantly, accumulating carbohydrates around 70% from about 15%–20% (control). Both species could desorb P from zeolite biologically. A. platensis could recover over 65% and C. vulgaris 25% of the P bounded onto zeolite. When P-loaded zeolite concentration increased to 5 g/L, P was adequate to support growth for both species. Especially in the case of C. vulgaris, growth was stimulated from the presence of P-loaded zeolite and produced more biomass compared to the control. ispartof: International Journal of Molecular Sciences vol:16 issue:2 pages:4250-4264 ispartof: location:Switzerland status: published

In this study the biomass composition alteration of the cyanobacterium Arthrospira (Spirulina) platensis under various amounts of limited phosphorus is studied. It was observed that the alteration of the compounds of the biomass occurred gradually as the phosphorus became limited. Carbohydrates and lipids increased from about 9% up to 65% and from about 4.9% up to 7.5%, respectively, while proteins decreased from about 46.5% to 25% as the phosphorus became limited. The increasing of carbohydrates and lipids in addition to the decrease of proteins resulted to an increase of the carbon to nitrogen (C/N) ratio from about 4.6 to 12.2.

The filamentous cyanobacterium Arthrospira platensis is an attractive feedstock for carbohydrate-based biofuels because it accumulated up to 74% of carbohydrates when nitrogen stressed. Nitrogen stressed A. platensis also settled spontaneously, and this occurred simultaneously with carbohydrates accumulation, suggesting a link between both phenomena. The increased settling velocity was neither due to production of extracellular carbohydrates, nor due to degradation of gas vacuoles, but was caused by an increase in the specific density of the filaments as a result of accumulation of carbohydrates under the form of glycogen. Settling velocities of carbohydrate-rich A. platensis reached 0.64mh(-1), which allowed the biomass to be harvested using a lamella separator. The biomass could be concentrated at least 15 times, allowing removal of 94% of the water using gravity settling, thus offering a potential application as a low-cost and high-throughput method for primary dewatering of carbohydrate-rich A. platensis. publisher: Elsevier articletitle: Harvesting carbohydrate-rich Arthrospira platensis by spontaneous settling journaltitle: Bioresource Technology articlelink: http://dx.doi.org/10.1016/j.biortech.2014.12.084 content_type: article copyright: Copyright © 2014 Elsevier Ltd. All rights reserved. ispartof: Bioresource Technology vol:180 pages:16-21 ispartof: location:England status: published

The subject of this paper is the cultivation of the cyanobacterium Arthrospira (Sprirulina) platensis in olive-oil mill wastewater (OMWW) treated with sodium hypochlorite (NaOCl). The main positive effect of NaOCl on the OMWW characteristics is the decrease of the phenol concentration and turbidity, rendering the OMWW suitable for A. platensis growth. Maximum biomass production (1696 mg/l) was obtained when the concentration of OMWW in the cultivation medium was 10% with the supplementation of 1 g/l NaNO3 and 5 g/l NaHCO3. However, the addition of NaHCO3 has no significant effect, indicating that the only limited nutrient in this wastewater is nitrogen, while carbon is provided by the organic compounds of the wastewater. The maximum of the removals of chemical oxygen demand (COD) and carbohydrates was 73.18% and 91.19%, respectively, while phenols, phosphorus and nitrates in some runs was completely removed.