Screening of cyanobacteria for phycobiliproteins and effect of different environmental stress on its yield

Comparative analysis of geotypic variations in the proteome of Nostoc commune

Cyanobacterium Nostoc commune is a filamentous terrestrial prokaryotic organism widely distributed, which suggest its high adaptive potential to environmental or abiotic stress. Physiological parameters and proteomic analysis were performed in two accession of N. commune with the aim to elucidate the differences of physiological trails between distant geotypes, namely Antarctic (AN) and central European (CE). The result obtained clearly showed that the AN geotype demonstrates elevated levels of total phenols, flavonoids, carotenoids, and phycobiliproteins, indicative of its adaptation to environmental stress as referred by comparison to CE sample. Additionally, we employed LC-MS analysis to investigate the proteomes of N. commune from AN and CE geotypes. In total, 1147 proteins were identified, among which 646 proteins expressed significant (up-regulation) changes in both accessions. In the AN geotype, 83 exclusive proteins were identified compared to 25 in the CE geotype. Functional classification of the significant proteins showed a large fraction involved in photosynthesis, amino acid metabolism, carbohydrate metabolism and protein biosynthesis. Further analysis revealed some defense-related proteins such as, superoxide dismutase (SOD) and glutathione reductase, which are rather explicitly expressed in the AN N. commune. The last two proteins suggest a more stressful condition in AN N. commune. In summary, our findings highlight biochemical processes that safeguard the AN geotype of N. commune from extreme environmental challenges, not recorded in CE accession, probably due to less stressful environment in Europe. This study brings the first ever proteomic analysis of N. commune, emphasizing the need for additional investigations into the climate adaptation of this species with rather plastic genome.

Chlorpyrifos enrichment enhances tolerance of Anabaena sp. PCC 7119 to dimethoate

Organophosphorus (OP) insecticides are widely used for on-field pest control, constituting about 38% of global pesticide consumption. Insecticide tolerance has been recorded in microorganisms isolated from the contaminated soil. However, the cross-tolerance of laboratory-enriched cultures remains poorly understood. A chlorpyrifos tolerant (T) strain of Anabaena sp. PCC 7119 was developed through continuous enrichment of the wild strain (W). The cross-tolerance of the T strain to the OP insecticide dimethoate was assessed by measuring photosynthetic performance, key enzyme activities and degradation potential. The presence of dimethoate led to a significant reduction in the growth and pigment content of the W strain. In contrast, the T strain demonstrated improved growth and metabolic performance. Chl a and carotenoids were degraded faster than phycobiliproteins in both strains. The T strain exhibited superior photosynthetic performance, metabolic efficiency and photosystem functions, than of W strain, at both the tested dimethoate concentrations (100 and 200 μM). The treated T strain had more or less a normal OJIP fluorescence transient and bioenergetic functions, while the W strain showed a greater fluorescence rise at ≤ 300 μs indicating the inhibition of electron donation to PS II, and at 2 ms due to reduced electron release beyond QA. The T strain had significantly higher levels of esterase and phosphatases, further enhanced by insecticide treatment. Dimethoate degradation efficiency of the T strain was significantly higher than of the W strain. T strain also removed chlorpyrifos more efficiently than W strain at both the tested concentrations. The BCFs of both chlorpyrifos and dimethoate were lower in the T strain compared to the W strain. These findings suggest that the enriched strain exhibits promising results in withstanding dimethoate toxicity and could be explored for its potential as a bioremediating organism for OP degradation.

Microalgae: A Promising Source of Bioactive Phycobiliproteins

Phycobiliproteins are photosynthetic light-harvesting pigments isolated from microalgae with fluorescent, colorimetric and biological properties, making them a potential commodity in the pharmaceutical, cosmetic and food industries. Hence, improving their metabolic yield is of great interest. In this regard, the present review aimed, first, to provide a detailed and thorough overview of the optimization of culture media elements, as well as various physical parameters, to improve the large-scale manufacturing of such bioactive molecules. The second section of the review offers systematic, deep and detailed data about the current main features of phycobiliproteins. In the ultimate section, the health and nutritional claims related to these bioactive pigments, explaining their noticeable potential for biotechnological uses in various fields, are examined.

Microalgae-Derived Pigments for the Food Industry

In the food industry, manufacturers and customers have paid more attention to natural pigments instead of the synthetic counterparts for their excellent coloring ability and healthy properties. Microalgae are proven as one of the major photosynthesizers of naturally derived commercial pigments, gaining higher value in the global food pigment market. Microalgae-derived pigments, especially chlorophylls, carotenoids and phycobiliproteins, have unique colors and molecular structures, respectively, and show different physiological activities and health effects in the human body. This review provides recent updates on characteristics, application fields, stability in production and extraction processes of chlorophylls, carotenoids and phycobiliproteins to standardize and analyze their commercial production from microalgae. Potential food commodities for the pigment as eco-friendly colorants, nutraceuticals, and antioxidants are summarized for the target products. Then, recent cultivation strategies, metabolic and genomic designs are presented for high pigment productivity. Technical bottlenecks of downstream processing are discussed for improved stability and bioaccessibility during production. The production strategies of microalgal pigments have been exploited to varying degrees, with some already being applied at scale while others remain at the laboratory level. Finally, some factors affecting their global market value and future prospects are proposed. The microalgae-derived pigments have great potential in the food industry due to their high nutritional value and competitive production cost.

Effects of Temperature, pH, and NaCl Concentration on Biomass and Bioactive Compound Production by Synechocystis salina

Synechocystis salina is a cyanobacterium that has biotechnological potential thanks to its ability to synthesize several bioactive compounds of interest. Therefore, this study aimed to find optimal conditions, in terms of temperature (15-25 °C), pH (6.5-9.5), and NaCl concentration (10-40 g·L^-1), using as objective functions the productivities of biomass, total carotenoids, total PBPs, phycocyanin (PC), allophycocyanin (APC), phycoerythrin (PE), and antioxidants (AOXs) capacity of Synechocystis salina (S. salina) strain LEGE 06155, based in factorial design resorting to Box-Behnken. The model predicted higher biomass productivities under a temperature of 25 °C, a pH of 7.5, and low NaCl concentrations (10 g·L^-1). Maximum productivities in terms of bioactive compounds were attained at lower NaCl concentrations (10 g·L^-1) (except for PE), with the best temperature and pH in terms of carotenoids and total and individual PBPs ranging from 23-25 °C to 7.5-9.5, respectively. PE was the only pigment for which the best productivity was reached at a lower temperature (15 °C) and pH (6.5) and a higher concentration of NaCl (≈25 g·L^-1). AOX productivities, determined in both ethanolic and aqueous extracts, were positively influenced by lower temperatures (15-19 °C) and higher salinities (≈15-25 g·L^-1). However, ethanolic AOXs were better recovered at a higher pH (pH ≈ 9.5), while aqueous AOXs were favored by a pH of 8. The model showed that biomass production can be enhanced by 175% (compared to non-optimized conditions), total carotenoids by 91%, PC by 13%, APC by 50%, PE by 130%, and total PBPs by 39%; for AOX productivities, only water extracts exhibited a (marginal) improvement of 1.4%. This study provided insightful information for the eventual upgrading of Synechocystis salina biomass in the biotechnological market.

Salinity pretreatment synergies heat shock toxicity in cyanobacterium Anabaena PCC7120

This study was undertaken to bridge the knowledge gap pertaining to cyanobacteria's response to pretreatment. The result elucidates the synergistic effect of pretreatment toxicity in cyanobacterium Anabaena PCC7120 on morphological and biochemical attributes. Chemical (salt) and physical (heat) stress-pretreated cells exhibited significant and reproducible changes in terms of growth pattern, morphology, pigments, lipid peroxidation, and antioxidant activity. Salinity pretreatment showed more than a five-fold decrease in the phycocyanin content but a six-fold and five-fold increase in carotenoid, lipid peroxidation (MDA content), and antioxidant activity (SOD and CAT) at 1 h and on 3rd day of treatment, respectively, giving the impression of stress-induced free radicals that are scavenged by antioxidants when compared to heat shock pretreatment. Furthermore, quantitative analysis of transcript (qRT-PCR) for FeSOD and MnSOD displayed a 3.6- and 1.8-fold increase in salt-pretreated (S-H) samples. The upregulation of transcript corresponding to salt pretreatment suggests a toxic role of salinity in synergizing heat shock. However, heat pretreatment suggests a protective role in mitigating salt toxicity. It could be inferred that pretreatment enhances the deleterious effect. However, it further showed that salinity (chemical stress) augments the damaging effect of heat shock (physical stress) more profoundly than physical stress on chemical stress possibly by modulating redox balance via activation of antioxidant responses. Our study reveals that upon pretreatment of heat, the negative effect of salt can be mitigated in filamentous cyanobacteria, thus providing a foundation for improved cyanobacterial tolerance to salt stress.

A Review on a Hidden Gem: Phycoerythrin from Blue-Green Algae

Phycoerythrin (PE) is a pink/red-colored pigment found in rhodophytes, cryptophytes, and blue-green algae (cyanobacteria). The interest in PE is emerging from its role in delivering health benefits. Unfortunately, the current cyanobacterial-PE (C-PE) knowledge is still in the infant stage. It is essential to acquire a more comprehensive understanding of C-PE. This study aimed to review the C-PE structure, up and downstream processes of C-PE, application of C-PE, and strategies to enhance its stability and market value. In addition, this study also presented a strengths, weaknesses, opportunities, and threats (SWOT) analysis on C-PE. Cyanobacteria appeared to be the more promising PE producers compared to rhodophytes, cryptophytes, and macroalgae. Green/blue light is preferred to accumulate higher PE content in cyanobacteria. Currently, the prominent C-PE extraction method is repeated freezing-thawing. A combination of precipitation and chromatography approaches is proposed to obtain greater purity of C-PE. C-PE has been widely exploited in various fields, such as nutraceuticals, pharmaceuticals, therapeutics, cosmetics, biotechnology, food, and feed, owing to its bioactivities and fluorescent properties. This review provides insight into the state-of-art nature of C-PE and advances a step further in commercializing this prospective pigment.

Characterization of cyanobacterial isolates from freshwater and saline subtropical desert lakes

Characterization of Cyanobacteria in lakes with different physicochemical properties provides insights into the diversity of this phylum and knowledge of their features that are relevant to biotechnology applications. Six Cyanobacterial isolates were recovered from freshwater Lake Nasser and saline Lake Qarun, Egypt. The isolates were identified based on both morphology and molecular markers, 16S rRNA, and RuBisCO cbbL genes. The isolates SN1, SN2, SN3, SN4, Q1, and Q2 showed homologies with Merismopedia, Oscillatoria, Limnothrix, Persinema, and Jacksonvillea, respectively. The cbbL sequences for isolates SN1, Q1, and Q2 represented the first records for candidates relating to the genera Merismopedia and Persinema, and Jacksonvillea, respectively. Biochemical contents, carbohydrates, proteins, lipids, pigments, and ash-free dry weight were measured for each isolate. Isolate SN2 had the highest content of allophycocyanin, 71 ± 4.8 mg/g DW, and phycoerythrin, 98 ± 6.7 mg/g DW, while the isolate SN4 had the highest composition of total protein, lipid, carotenoid, and chlorophyll a, recording 364.7 ± 6.4 mg/g DW, 67.6 ± 0.2 mg/g DW, 0.261 ± 0.01 mg/g DW, and 10 ± 0.6 mg/g DW, respectively. Isolate Q1 recorded the maximum amount of phycocyanin, 114 ± 20.7 mg/g DW among isolates. The isolate Q2 was observed to have the highest carbohydrate content, 274 ± 14.5 (mg/g DW), and ash-free dry weight, 891.8 ± 2.8 mg/g DW. Thus, the study indicated that the current isolates may represent promising resources for biotechnological applications.

Cosmetic Application of Cyanobacteria Extracts with a Sustainable Vision to Skincare: Role in the Antioxidant and Antiaging Process

Nature-based and sustainably sourced cosmetics have been dominating the area of skincare products worldwide. Due to their antioxidant and antiaging properties, compounds from cyanobacteria, such as carotenoids and phycobiliproteins, may replace synthetic ingredients in cosmetic formulations and may be used in products such as sunscreens, skincare creams, and makeup. In this study, we evaluated the potential of acetonic and aqueous extracts from cyanobacteria strains of the genera Cyanobium and Leptothoe and from strains within Synechococcales and Oscillatoriales orders, for use in cosmetics. Extractions were sequentially performed with acetone and water. Extracts were firstly analyzed for their toxicity to keratinocytes, fibroblasts, and endothelial cells (HaCAT, 3T3L1 and hCMEC/D3, respectively). The non-cytotoxic extracts were characterized in terms of total proteins, carotenoids, chlorophyll, phenols, phycobiliproteins, and analyzed for their antioxidant potential against the superoxide anion radical (O2•−), and for their ability to inhibit key enzymes associated with the skin aging process. Aqueous extracts were richer in total proteins and phycobiliproteins. The aqueous extracts of Synechococcales cyanobacterium LEGE 181157 and Synechococcales cyanobacterium LEGE 181150 showed the highest value for total proteins (760.81 and 695.25 μg BSA mL−1dry extract, respectively) and the best values regarding O2•− scavenging (IC50 = 63.24 and 112.18 μg mL−1dry extract, respectively) with a significant negative correlation observed (p < 0.01). Moreover, aqueous extracts of Synechococcales cyanobacterium LEGE 181150 and Synechococcales cyanobacterium LEGE 181157 inhibited hyaluronidase, (IC50 of 483.86 and 645.06 μg mL−1dry extract, respectively), with a significant negative correlation with total proteins (p < 0.05), pointing out the contribution of these compounds to the biological activities observed. Acetonic extracts were richer in carotenoids and phenols. Zeaxanthin and β-carotene were predominant among all strains, being present in higher amount in Cyanobium sp. LEGE 07175 (53.08 μg mg−1) and Leptothoe sp. LEGE 181156 (47.89 μg mg−1), respectively. The same strains also showed the highest values for collagenase inhibition at 750 μg mL−1dry extract (32.88 and 36.61%, respectively). Furthermore, Leptothoe sp. LEGE 181156 exhibited the lowest IC50 value for tyrosinase inhibition (465.92 μg mL−1dry extract) and Synechococcales cyanobacterium LEGE 181157 presented the best values for elastase inhibition (IC50 of 380.50 and IC25 of 51.43 μg mL−1dry extract). In general, cyanobacteria extracts demonstrated potential for being used for antiaging purposes, with aqueous extracts being more efficient at free radicals scavenging and acetonic ones at avoiding degradation of dermal matrix components.

The Effect of Colored and White Light on Growth and Phycobiliproteins, Chlorophyll and Carotenoids Content of the Marine Cyanobacteria Phormidium sp. and Cyanothece sp. in Batch Cultures

Two local marine cyanobacteria, Phormidium sp. and Cyanothece sp., were batch-cultured under 18-19.5 °C, at 40 ppt salinity, using white LED light of low (40 μmol photons/m2/s) and high (160 μmol/m2/s) intensity and, additionally, blue, green and red LED light. Yield was highest in high white light in both species (2.15 g dw/L in Phormidium, 1.47 g/L in Cyanothece), followed by green light (1.25 g/L) in Cyanothece and low white and green (1.26-1.33 g/L) in Phormidium. Green light maximized phycocyanin in Phormidium (0.45 mg/mL), while phycoerythrin was enhanced (0.17 mg/mL) by blue light and allophycocyanin by all colors (~0.80 mg/mL). All colors maximized phycocyanin in Cyanothece (~0.32 mg/mL), while phycoerythrin and allophycocyanin peaked under green light (~0.138 and 0.38 mg/mL, respectively). In Phormidium, maximization of chlorophyll-a (9.3 μg/mL) was induced by green light, while total carotenoids and b-carotene (3.05 and 0.89 μg/mL, respectively) by high white light. In Cyanothece, both white light intensities along with green maximized chlorophyll-a (~9 μg/mL) while high white light and green maximized total carotenoids (2.6-3.0 μg/mL). This study strongly indicates that these cyanobacteria can be cultured at the first stage under white light to accumulate sufficient biomass and, subsequently, under colored light for enhancing phycobiliproteins.

Health benefits of microalgae and their microbiomes

Microalgae comprise a phylogenetically very diverse group of photosynthetic unicellular pro‐ and eukaryotic organisms growing in marine and other aquatic environments. While they are well explored for the generation of biofuels, their potential as a source of antimicrobial and prebiotic substances have recently received increasing interest. Within this framework, microalgae may offer solutions to the societal challenge we face, concerning the lack of antibiotics treating the growing level of antimicrobial resistant bacteria and fungi in clinical settings. While the vast majority of microalgae and their associated microbiota remain unstudied, they may be a fascinating and rewarding source for novel and more sustainable antimicrobials and alternative molecules and compounds. In this review, we present an overview of the current knowledge on health benefits of microalgae and their associated microbiota. Finally, we describe remaining issues and limitation, and suggest several promising research potentials that should be given attention.

Commercial Potential of the Cyanobacterium Arthrospira maxima: Physiological and Biochemical Traits and the Purification of Phycocyanin

Simple Summary

Arthrospira maxima is an unbranched, filamentous cyanobacterium rich in important cellular products such as vitamins, minerals, iron, essential amino acids, essential fatty acids, and protein, which has made it one of the most important commercial photoautotrophs. To optimize the growth conditions for the production of target compounds and to ensure profitability in commercial applications, the effects of pH and temperature were investigated. A. maxima has been shown to be tolerant to a range of pH conditions and to exhibit hyper-accumulation of phycoerythrin and allophycocyanin at low temperatures. These traits may offer significant advantages for future exploitation, especially in outdoor cultivation with fluctuating pH and temperature. Our study also demonstrated a new method for the purification of phycocyanin from A. maxima by using by ultrafiltration, ion-exchange chromatography, and gel filtration, producing PC at 1.0 mg·mL⁻¹ with 97.6% purity.

Abstract

Arthrospira maxima is a natural source of fine chemicals for multiple biotechnological applications. We determined the optimal environmental conditions for A. maxima by measuring its relative growth rate (RGR), pigment yield, and photosynthetic performance under different pH and temperature conditions. RGR was highest at pH 7–9 and 30 °C. Chlorophyll a, phycocyanin, maximal quantum yield (F_v/F_m), relative maximal electron transport rate (rETR_max), and effective quantum yield (Φ_PSII) were highest at pH 7–8 and 25 °C. Interestingly, phycoerythrin and allophycocyanin content was highest at 15 °C, which may be the lowest optimum temperature reported for phycobiliprotein production in the Arthrospira species. A threestep purification of phycocyanin (PC) by ultrafiltration, ion-exchange chromatography, and gel filtration resulted in a 97.6% purity of PC.

Cyanobacterial biorefinery: Towards economic feasibility through the maximum valorization of biomass

Cyanobacteria are well known for their plethora of applications in the fields of food industry, pharmaceuticals and bioenergy. Their simple growth requirements, remarkable growth rate and the ability to produce a wide range of bio-active compounds enable them to act as an efficient biorefinery for the production of valuable metabolites. Most of the cyanobacteria based biorefineries are targeting single products and thus fails to meet the efficient valorization of biomass. On the other hand, multiple products recovering cyanobacterial biorefineries can efficiently valorize the biomass with minimum to zero waste generation. But there are plenty of bottlenecks and challenges allied with cyanobacterial biorefineries. Most of them are being associated with the production processes and downstream strategies, which are difficult to manage economically. There is a need to propose new solutions to eliminate these tailbacks so on to elevate the cyanobacterial biorefinery to be an economically feasible, minimum waste generating multiproduct biorefinery. Cost-effective approaches implemented from production to downstream processing without affecting the quality of products will be beneficial for attaining economic viability. The integrated approaches in cultivation systems as well as downstream processing, by simplifying individual processes to unit operation systems can obviously increase the economic feasibility to a certain extent. Low cost approaches for biomass production, multiparameter optimization and successive sequential retrieval of multiple value-added products according to their high to low market value from a biorefinery is possible. The nanotechnological approaches in cyanobacterial biorefineries make it one step closer to the goal. The current review gives an overview of strategies used for constructing self-sustainable- economically feasible- minimum waste generating; multiple products based cyanobacterial biorefineries by the efficient valorization of biomass. Also the possibility of uplifting new cyanobacterial strains for biorefineries is discussed.

Cyanobacteria Secondary Metabolites as Biotechnological Ingredients in Natural Anti-Aging Cosmetics: Potential to Overcome Hyperpigmentation, Loss of Skin Density and UV Radiation-Deleterious Effects

The loss of density and elasticity, the appearance of wrinkles and hyperpigmentation are among the first noticeable signs of skin aging. Beyond UV radiation and oxidative stress, matrix metalloproteinases (MMPs) assume a preponderant role in the process, since their deregulation results in the degradation of most extracellular matrix components. In this survey, four cyanobacteria strains were explored for their capacity to produce secondary metabolites with biotechnological potential for use in anti-aging formulations. Leptolyngbya boryana LEGE 15486 and Cephalothrix lacustris LEGE 15493 from freshwater ecosystems, and Leptolyngbya cf. ectocarpi LEGE 11479 and Nodosilinea nodulosa LEGE 06104 from marine habitats were sequentially extracted with acetone and water, and extracts were analyzed for their toxicity in cell lines with key roles in the skin context (HaCAT, 3T3L1, and hCMEC). The non-toxic extracts were chemically characterized in terms of proteins, carotenoids, phenols, and chlorophyll a, and their anti-aging potential was explored through their ability to scavenge the physiological free radical superoxide anion radical (O2•−), to reduce the activity of the MMPs elastase and hyaluronidase, to inhibit tyrosinase and thus avoid melanin production, and to block UV-B radiation (sun protection factor, SPF). Leptolyngbya species stood out for anti-aging purposes: L. boryana LEGE 15486 presented a remarkable SPF of 19 (at 200 µg/mL), being among the best species regarding O2•− scavenging, (IC50 = 99.50 µg/mL) and also being able to inhibit tyrosinase (IC25 = 784 µg/mL), proving to be promising against UV-induced skin-aging; L. ectocarpi LEGE 11479 was more efficient in inhibiting MMPs (hyaluronidase, IC50 = 863 µg/mL; elastase, IC50 = 391 µg/mL), thus being the choice to retard dermal density loss. Principal component analysis (PCA) of the data allowed the grouping of extracts into three groups, according to their chemical composition; the correlation of carotenoids and chlorophyll a with MMPs activity (p < 0.01), O2•− scavenging with phenolic compounds (p < 0.01), and phycocyanin and allophycocyanin with SPF, pointing to these compounds in particular as responsible for UV-B blockage. This original survey explores, for the first time, the biotechnological potential of these cyanobacteria strains in the field of skin aging, demonstrating the promising, innovative, and multifactorial nature of these microorganisms.

Acclimation and Characterization of Marine Cyanobacterial Strains Euryhalinema and Desertifilum for C-Phycocyanin Production

This study involves evaluation of two native cyanobacterial strains Euryhalinema and Desertifilum isolated from a mangrove pond in Haikou (China) for their possible phycocyanin (C-PC) production. Maximal growth rate with highest chlorophyll and C-PC accumulation were observed at 28°C and 60 μmol photons m^-2 s^-1 photon flux density for Euryhalinema sp., while for Desertifilum sp. at 32°C and 80 μmol photons m^-2 s^-1. Nitrogen and iron concentration trails revealed that double strength concentration of sodium nitrate and ferric ammonium citrate in original BG11 media increased growth rate and accumulation of C-PC for both strains. Three different C-PC extraction methods were tested. The combined extraction protocol of freeze-thaw and ultrasonication markedly increased the C-PC extraction efficiency and attained the food grade purity (A ₆₂₀/A ₂₈₀ ratio >0.7), whereas a higher C-PC yield was found with Na-phosphate buffer. Furthermore, the clarified crude extract was used to purify C-PC by fractional ammonium sulfate [(NH₄)₂SO₄] precipitation, Sephadex G-25 gel filtration chromatography, and DEAE-sephadex ion exchange chromatography and attained analytical grade purity (A ₆₂₀/A ₂₈₀ ratio >3.9). Taken together, both strains showed their potential to be domesticated for valuable phycocyanin production.

Potential Antioxidant and Anticancer Activities of Secondary Metabolites of Nostoc linckia Cultivated under Zn and Cu Stress Conditions

The objective of the present study is to determine the antioxidant and anticancer activities of Nostoc linckia extracts cultivated under heavy metal stress conditions (0.44, 0.88, and 1.76 mg/L for zinc and 0.158, 0.316, 0.632 mg/L for copper). Phycobiliprotein, phenolic compounds, flavonoids, and tannins were measured. Active ingredients of extracts were evaluated by GC-mass spectroscopy. The obtained results revealed that higher zinc and copper concentrations showed growth inhibition while 0.22 mg/L (Zn) and 0.079 mg/L (Cu) enhanced growth, reaching its maximum on the 25th day. Increases in catalase, lipids peroxidation, and antioxidants, as well as tannins and flavonoids, have been induced by integration of 0.88 mg/L (Zn) and 0.316 mg/L (Cu). Elevation of Zn concentration induced augmentation of antioxidant activity of crude extract (DPPH or ABTS), with superior activity at 0.44 mg/L zinc concentration (81.22%). The anticancer activity of Nostoc linckia extract (0.44 mg/L Zn) tested against four cancer cell lines: A549, Hela, HCT 116, and MCF-7. The extract at 500 µg/mL appeared the lowest cell viability of tested cell lines. The promising extract (0.44 mg/L Zn) recorded the lowest cell viability of 25.57% in cervical cell line, 29.74% in breast cell line, 33.10% in lung cell line and 34.53% in the colon cell line. The antioxidant active extract showed significant stability against pH with attributed increase in antioxidant activity in the range between 8–12. The extract can be used effectively as a natural antioxidant and anticancer after progressive testing.

Synergy of production of value-added bioplastic, astaxanthin and phycobilin co-products and Direct Green 6 textile dye remediation in Spirulina platensis

Phyco-remediation of dyestuffs in textile wastewaters is of economic, industrial, and environmental importance. We evaluated the remediation of the textile dye, Direct Green 6 (DG6), by Spirulina platensis, and investigated the novel possibility that DG6 treatment enhances production of the biopolymer, polyhydroxybutyrate (PHB). We showed that both live and dead cells of Spirulina were capable of DG6 remediation, but live cells could be re-used with no loss of remediation efficiency. Furthermore, DG6 remediation by live cells resulted in increased algal biomass and trichome lengths, and stimulated production of valuable metabolites, including PHB, antioxidants, carbohydrates and pigments (phycobilins and astaxanthin). We determined the optimal conditions for DG6 remediation and an artificial neural network (ANN) accurately modeled the experimental data and predicted the concentration of dye as the most and algal turbidity as the least important parameters for DG6 removal efficiency. A DG6 concentration of 60 mg L^-1 resulted in the highest simultaneous co-production of PHB (12.7 ± 1.7% DW) and increase of astaxanthin (194%), carotenoids (50%), phenol (51%), carbohydrates (27%) total phycobilin (43%), together with the enhancement of biomass and trichome lengths (95%). Oxidative stress indices and enzyme activities such as peroxidases and laccase (involved in dye removal/antioxidant functions) were also increased by dye dosage. On the basis of our results, we propose that S. platensis may use DG6 dye as a nitrogen/carbon source for co-accumulation of valuable bioplastic and metabolites.

Valorization of microalgae biomass into bioproducts promoting circular bioeconomy: a holistic approach of bioremediation and biorefinery

The need for alternative source of fuel has demanded the cultivation of 3rd generation feedstock which includes microalgae, seaweed and cyanobacteria. These phototrophic organisms are unique in a sense that they utilise natural sources like sunlight, water and CO₂ for their growth and metabolism thereby producing diverse products that can be processed to produce biofuel, biochemical, nutraceuticals, feed, biofertilizer and other value added products. But due to low biomass productivity and high harvesting cost, microalgae-based production have not received much attention. Therefore, this review provides the state of the art of the microalgae based biorefinery approach to define an economical and sustainable process. The three major segments that need to be considered for economic microalgae biorefinery is low cost nutrient source, efficient harvesting methods and production of by-products with high market value. This review has outlined the use of various wastewater as nutrient source for simultaneous biomass production and bioremediation. Further, it has highlighted the common harvesting methods used for microalgae and also described various products from both raw biomass and delipidified microalgae residues in order to establish a sustainable, economical microalgae biorefinery with a touch of circular bioeconomy. This review has also discussed various challenges to be considered followed by a techno-economic analysis of the microalgae based biorefinery model.

A multi-objective hybrid machine learning approach-based optimization for enhanced biomass and bioactive phycobiliproteins production in Nostoc sp. CCC-403

The cyanobacterial phycobiliproteins (PBPs) are an important natural colorant for nutraceutical industries. Here, a multi-objective hybrid machine learning-based optimization approach was used for enhanced cell biomass and PBPs production simultaneously in Nostoc sp. CCC-403. A central composite design (CCD) was employed to design an experimental setup for four input parameters, including three BG-11 medium components and pH. We achieved a 61.76% increase in total PBPs production and an almost 90% increase in cell biomass by our prediction model. We also established a test genome-scale metabolic network (GSMN) for Nostoc sp. and identified potential metabolic fluxes contributing to PBPs enhanced production. This study highlights the advantage of the hybrid machine learning approach and GSMN to achieve optimization for more than one objective and serves as the foundation for future efforts to convert cyanobacteria as an economically viable source for biofuels and natural products.

Effects of fires on vascular plant and microalgae communities of steppe ecosystems

The article is focused on a hypothesis verification: the higher plants, microalgae and cyanobacteria may be used in bioindication of steppe ecosystem restoration dynamics after fires. On the territory of the Askania Nova biosphere reserve (Ukraine) 4 stationary polygons were investigated: SP1 – steppe area which had not been exposed to fire for 20 years preceding our study, as well as areas where single fires occurred in 2001 (SP2), 2005 (SP3), and a site where fires occurred in 2001 and 2004 (SP4). The investigation revealed the dynamics of height and projected area of the higher vegetation according to seasons during two years (2010 and 2011), as well as abundance and biomass of microalgae and cyanoprokaryotes in the soil layer by the layer of the depth to 15 cm. It was found that the effects of pyrogenic load remain evident for several years after the fires, manifesting in decrease of the height and projected area of herbage, the number and biomass of algae and cyanobacteria in the soil, especially to the depth of 5 cm. Multivariate general linear models were used to test the significance of the dependence of quantitative characteristics of vegetation, microalgae, and cyanoprokaryotes on environmental predictors (season, year, soil layer, and fire). In the model, 75.2% of the grass height variability and 91.6% of the grass projected area variability could be explained by the predictors under consideration. In the series SP1 → SP2 → SP3 → SP4 the grass height and projected area decreased. The differences in the projected area of the grass stand were most evident in spring. The model explained 89.1% of the variation in abundance and 91.6% of the variation in biomass of Bacillariophyceae. The abundance of Bacillariophyceae was greater in the upper soil layer than in the lower layer and decreased with depth. The abundance of this group of algae decreased in the series SP1 → SP2 → SP3 → SP4 at depths of 0–5 and 5–10 cm. Changes in abundances of Chlorophyta, Streptophyta, Heterokontophyta (Xanthophyceae and Eustigmatophyceae) equaling 47.6% could also be explained by the model. The abundance of this group of algae was greatest in the upper soil layer. In the upper soil layer, the maximum abundance of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was recorded for Polygon SP1 and the minimum for Polygon SP3. Within the model, 48.0% of the variation in biomass of Chlorophyta, Streptophyta, and Heterokontophyta (Xanthophyceae and Eustigmatophyceae) was explained by the environmental predictors. The biomass trend was coherent with the population trend. A special feature was that there was a significant increase in biomass at 10–15 cm depth at Polygon SP3 compared to other polygons at this depth. The model was able to explain 61.8% of the variation in abundance and 66.7% of the variation in cyanobacteria biomass. The highest abundance of cyanobacteria was found in the upper soil layer of polygon SP1. Somewhat lower numbers of cyanobacteria were at polygons SP2 and SP4, and the lowest were found in the upper soil layer at polygon SP3. In turn, the highest number of cyanobacteria was found particularly at this polygon in the 5–10 cm layer. The biomass in the 0–5 cm layer was coherent with the abundance pattern of this group. The research results confirmed that the quantitative characteristics of the higher vegetation (height and projected area) as well as of microalgae and cyanobacteria (abundance and biomass) may be used in bioindication of the dynamics of post-pyrogenic processes in steppe ecosystems.

Cyanobacteria and Red Macroalgae as Potential Sources of Antioxidants and UV Radiation-Absorbing Compounds for Cosmeceutical Applications

In recent years, research on natural products has gained considerable attention, particularly in the cosmetic industry, which is looking for new bio-active and biodegradable molecules. In this study, cosmetic properties of cyanobacteria and red macroalgae were analyzed. The extractions were conducted in different solvents (water, ethanol and two combinations of water:ethanol). The main molecules with antioxidant and photoprotective capacity were mycosporine-like amino acids (MAAs), scytonemin and phenolic compounds. The highest contents of scytonemin (only present in cyanobacteria) were observed in Scytonema sp. (BEA 1603B) and Lyngbya sp. (BEA 1328B). The highest concentrations of MAAs were found in the red macroalgae Porphyra umbilicalis, Gelidium corneum and Osmundea pinnatifida and in the cyanobacterium Lyngbya sp. Scytonema sp. was the unique species that presented an MAA with maximum absorption in the UV-B band, being identified as mycosporine-glutaminol for the first time in this species. The highest content of polyphenols was observed in Scytonema sp. and P. umbilicalis. Water was the best extraction solvent for MAAs and phenols, whereas scytonemin was better extracted in a less polar solvent such as ethanol:_dH₂O (4:1). Cyanobacterium extracts presented higher antioxidant activity than those of red macroalgae. Positive correlations of antioxidant activity with different molecules, especially polyphenols, biliproteins and MAAs, were observed. Hydroethanolic extracts of some species incorporated in creams showed an increase in the photoprotection capacity in comparison with the base cream. Extracts of these organisms could be used as natural photoprotectors improving the diversity of sunscreens. The combination of different extracts enriched in scytonemin and MAAs could be useful to design broad-band natural UV-screen cosmeceutical products.

Cytokinin alleviates cypermethrin toxicity in Nostoc muscorum by involving nitric oxide: Regulation of exopolysaccharides secretion, PS II photochemistry and reactive oxygen species homeostasis

Growth of the most important nitrogen fixing cyanobacterium Nostoc muscorum is reported to be badly affected by the application of insecticides. To overcome their damaging effects, several strategies are being used. Out of these, some works on kinetin (KN, a synthetic cytokinin) has been recognized that it can overcome toxicity of insecticides in cyanobacteria. Besides this, it is now known that every hormone needs certain second messengers such as nitric oxide (NO) for its action. But implication of NO in KN-mediated regulation of insecticide toxicity is yet to be investigated. Hence in the current study, we have investigated the possible involvement of NO in KN-mediated regulation of cypermethrin toxicity in the cyanobacterium Nostoc muscorum. Cypermethrin decreased growth of Nostoc muscorum which was accompanied by decreased pigment contents and altered photosystem II (PS II) photochemistry that resulted in inhibition of photosynthetic process but KN significantly ameliorated cypermethrin toxicity. Cypermethrin induced production of free radicals (in-vivo and in-vitro) and weakened defensive mechanism (enzymatic and non-enzymatic defense system) which was restored by KN. Further, the results revealed that NG-nitro-l-arginine methyl ester (l-NAME, an inhibitor of nitric oxide synthase) worsened the effect of cypermethrin toxicity even in the presence of KN while 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (c-PTIO, a scavenger of NO) reversed KN-mediated amelioration even in the presence of sodium nitroprusside (SNP, an NO donor), suggesting that endogenous NO is required for mitigation of cypermethrin toxicity. Overall, our results first time show that endogenous NO is essential for KN-mediated mitigation of cypermethrin toxicity in the Nostoc muscorum.

Demarcating antioxidant response against aluminum induced oxidative stress in Westiellopsis prolifica Janet 1941

Aluminum metal pollution is considered as a primary limiting factor that reduced crop yield in South Asian subtropical country like India. In national context, Odisha contributes around more than 40% of total ore availability. Moreover, industrial mining and smelting aid are major concern for aluminum metal toxicity in territorial vicinity affecting the soil fertility, ecosystem and human health through food chain. The aluminum metal accumulation limits the soil fertility by antagonistic regulation of photosynthetic and nitrogen fixing microbiota. The increasing concern regarding aluminum pollution enterprise critical investigations for their bioremediation in contamination sites. In this notion, the current study was hypothesized to decrypt the rate limiting factors, their explicit mode of action and intracellular detoxification in a cyanobacterium, i.e., Westiellopsis prolifica isolated from ash pond of NALCO (National Aluminum Company Limited), Angul, Odisha. In the experimental setup, treatment with different concentrations of AlCl₃ (0-0.1 mM) was marked a decline in the growth of the strain due to the adverse regulation of photosynthetic pigments. However, the enforcement of catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD), guaiacol peroxidase (GPX) and glutathione reductase (GR) was critical for sustaining strain viability under oxidative imbalance. The observation of an increase in the antioxidant enzyme and MDA content was evident to sustain strain viability under such oxidative imbalance. The outcome of the anticipated study was apparent to demonstrate a colossal interlink between Al mediated induction of oxidative stress and their cellular detoxification via intracellular antioxidant enzymes and removal of H₂O₂ accumulation in cyanobacterium, W. prolifica. Statement of novelty Aluminum metal toxicity renders growth of Westiellopsis prolifica via affecting photosynthesis associated pigments. Westiellopsis prolifica deploys antioxidant defense enzymes to combat against aluminum mediated oxidative upset. Intracellular antioxidant enzymes provoke cellular survival of Westiellopsis prolifica under excessive uptake of aluminum in contaminated habitats.

Two-stage cultivation strategy for the improvement of pigment productivity from high-density heterotrophic algal cultures

Herein, a two-stage cultivation process was devised to overcome low pigment content of algal biomass grown in heterotrophy. Post-treatment conditions (i.e., light intensity, temperature, pH and salinity) were initially tested for dense heterotrophically-grown Chlorella sp. HS2 cultures in a multi-channel photobioreactor (mcPBR), and the results clearly indicated the influence of each abiotic factor on algal pigment production. Subsequently, the optimal post-treatment conditions (i.e., 455 μmol m^-2 s^-1, 34.8℃, pH 8.23 and 0.7% (w/v) salinity), in which highest accumulation of algal pigments is expected, were identified using Response Surface Methodology (RSM). Compared to the control cultures grown in mixotrophy for the same duration of entire two-stage process, the results indicated a significantly higher pigment productivity (i.e., 167.5 mg L^-1 day^-1) in a 5-L fermenter following the post-treatment at optimal conditions. Collectively, these results suggest that the post-treatment of heterotrophic cultures can be successfully deployed to harness the nascent algae-based bioeconomy.

Spirulina cultivated under different light emitting diodes: Enhanced cell growth and phycocyanin production

This study evaluated light emitting diodes (LEDs) as a light source in Spirulina sp. LEB 18 cultures in terms of growth parameters and biomass composition. Different photoperiods (partial and integral) and colors (blue, green, red and white) were assessed. Blue, green, red and white LEDs increased biomass productivity and maximum specific growth rate of such cultivations. The maximum biomass concentration (1.77 ± 0.02 g L^-1) was obtained when red LEDs in integral light photoperiod were applied to cultivations. The biomass composition showed around 12.8% carbohydrates (w w^-1), 57.4% proteins (w w^-1) and 12.7% lipids (w w^-1). The major fatty acids produced during cultivations were palmitic, linoleic and γ-linolenic. Green LEDs in partial light photoperiod promoted a higher concentration of phycocyanin (126.39 mg g_biomass^-1). The potential of LEDs as an energy source in Spirulina sp. LEB 18 cultures was demonstrated by the biomass and bioproducts photostimulation.

Identification and antioxidant activity of synthetic peptides from phycobiliproteins of Pyropia yezoensis

The objective of the present study was to identify peptides, based on active components of the red algae seaweed Pyropia yezoensis, able to inhibit the generation of reactive oxygen species (ROS), which is associated with aging and oxidative activities. Phycobilin, specific to red algae, covalently binds with water-soluble proteins. There are three types of pigment bound proteins, known as phycobiliproteins (PBPs): Phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC). In the present study, PBPs reported previously to have antioxidant activities in P. yezoensis were identified and, based on these data, several peptides were synthesized (PBP 1-13) and their inhibition of ROS generation was examined. The existence of PBPs of each type, PE, PC and APC, was established in P. yezoensis and all were analyzed. In addition, PBP 1-2 and 7-9 peptides from PE were synthesized and showed antioxidant activities in HepG2 cells. In HepG2 cells, treatment with PBP2 reduced hydrogen peroxide-mediated oxidative stress and restored the expression of superoxide dismutase (SOD). Furthermore, phosphorylated nuclear factor erythroid-derived 2-like 2 (Nrf2) was elevated by PBP2 treatment. Overall, these results suggested that Nrf2-SOD pathways may be involved in the PBP2-mediated antioxidant effects. Therefore, from the investigations of P. yezoensis, several candidate peptides were identified with promising antioxidant and, potentially, anti-aging properties.

Effects of different light source and media on growth and production of phycobiliprotein from freshwater cyanobacteria

The aim of this study was to determine the effect of different light sources and media (wastewater and BBM) on the growth of Pseudanabaena mucicola and its phycobiliprotein production. Results showed that P. mucicola grown in white light using wastewater as medium attributed higher biomass (0.55 g L^-1) and when extracted with water, also showed significantly higher (P < .05) production (237.01 mg g^-1) and purity (1.14) of phycobiliprotein. This study validated that phycobiliprotein extracted from P. mucicola using water can be food grade natural blue pigment. Moreover, cyanobacteria grown in wastewater could cut down the production cost of phycobiliprotein.

Combining light strategies with recycled medium to enhance the economic feasibility of phycocyanin production with Spirulina platensis

C-phycocyanin (C-PC) produced from Spirulina platensis is of great commercial interest due to its healthcare properties. In this study, light sources and light-dark frequency were manipulated to enhance C-PC productivity of S. platensis. Using white LED resulted in higher C-PC production efficiency when compared to using fluorescent lamps and monochromatic LEDs. Proper adjustment of light-dark efficiency further increased C-PC production efficiency with relatively lower power consumption. In addition, using recycled medium in place of fresh medium proved to be an environmental-friendly and economic strategy for C-PC production with S. platensis. Optimal nitrate supplementation was also employed to improve the C-PC productivity. When grown under optimal culture conditions (i.e., light source, white LED; light-dark frequency, 30:30; recycled medium replacement, 50%; nitrate supplement, 45mM), S. platensis could obtain the highest C-PC content (14.9%) and C-PC productivity (101.1mg/L/d). This performance appears to be superior to that obtained from most related studies.

Availability and Utilization of Pigments from Microalgae

Microalgae are the major photosynthesizers on earth and produce important pigments that include chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins. Presently, synthetic colorants are used in food, cosmetic, nutraceutical, and pharmaceutical industries. However, due to problems associated with the harmful effects of synthetic colorants, exploitation of microalgal pigments as a source of natural colors becomes an attractive option. There are various factors such as nutrient availability, salinity, pH, temperature, light wavelength, and light intensity that affect pigment production in microalgae. This paper reviews the availability and characteristics of microalgal pigments, factors affecting pigment production, and the application of pigments produced from microalgae. The potential of microalgal pigments as a source of natural colors is enormous as an alternative to synthetic coloring agents, which has limited applications due to regulatory practice for health reasons.

Impacts of varying light regimes on phycobiliproteins of Nostoc sp. HKAR-2 and Nostoc sp. HKAR-11 isolated from diverse habitats

The adaptability of cyanobacteria in diverse habitats is an important factor to withstand harsh conditions. In the present investigation, the impacts of photosynthetically active radiation (PAR; 400-700 nm), ultraviolet-B (UV-B; 280-315 nm), and PAR + UV-B radiations on two cyanobacteria viz., Nostoc sp. HKAR-2 and Nostoc sp. HKAR-11 inhabiting diverse habitats such as hot springs and rice fields, respectively, were studied. Cell viability was about 14 % in Nostoc sp. HKAR-2 and <10 % in Nostoc sp. HKAR-11 after 48 h of UV-B exposure. PAR had negligible negative impact on the survival of both cyanobacteria. The continuous exposure of UV-B and PAR + UV-B showed rapid uncoupling, bleaching, fragmentation, and degradation in both phycocyanin (C-PC) and phycoerythrin (C-PE) subunits of phycobiliproteins (PBPs). Remarkable bleaching effect of C-PE and C-PC was not only observed with UV-B or PAR + UV-B radiation, but longer period (24-48 h) of exposure with PAR alone also showed noticeable negative impact. The C-PE and C-PC subunits of the rice field isolate Nostoc sp. HKAR-11 were severely damaged in comparison to the hot spring isolate Nostoc sp. HKAR-2 with rapid wavelength shifting toward shorter wavelengths denoting the bleaching of both the accessory light harvesting pigments. The results indicate that PBPs of the hot spring isolate Nostoc sp. HKAR-2 were more stable under various light regimes in comparison to the rice field isolate Nostoc sp. HKAR-11 that could serve as a good source of valuable pigments to be used in various biomedical and biotechnological applications.

Effects of the naturally-occurring contaminant microcystins on the Azolla filiculoides-Anabaena azollae symbiosis

Harmful algal blooms (HABs) contaminate aquatic ecosystems and are responsible for animal poisoning worldwide. We conducted a toxicity test with the aquatic fern and the biofertilizer, Azolla filiculoides. The sporophytes were exposed to three concentrations (0.01, 0.1 and 1μgmL(-1)) of a microcystin (MC) cyanobacterial crude extract and purified MC-LR. The growth of A. filiculoides decreased only at 1μgmL(-1) crude extract concentration while with MC-LR it decreased at all the tested concentrations, indicating that the presence of other compounds in the crude extract altered toxicity and stimulated the fern growth at lower concentrations (0.01 and 0.1μgmL(-1)). Both phycoerythrocyanin and allophycocyanin levels decreased in all the concentrations of crude extract and MC-LR. The phycocyanin had a marked increase at 0.1μgmL(-1) crude extract concentration and a marked decrease at 1μgmL(-1) MC-LR concentration. These changes in the phycobiliprotein content indicate a shift in the antenna pigments of the cyanobionts of A. filiculoides. The changes in two oxidative stress enzymes, glutathione reductase for the crude extract assay and glutathione peroxidase for MC-LR assay, points towards the induction of stress defense responses. The low bioconcentration factor in both crude extract and MC-LR treatments can suggest the low uptake of microcystins, and indicates that the aquatic fern can be used as a biofertilizer and as animal feed but is not suitable for MC phytoremediation.

Marine Algae: a Source of Biomass for Biotechnological Applications

Biomass derived from marine microalgae and macroalgae is globally recognized as a source of valuable chemical constituents with applications in the agri-horticultural sector (including animal feeds and health and plant stimulants), as human food and food ingredients as well as in the nutraceutical, cosmeceutical, and pharmaceutical industries. Algal biomass supply of sufficient quality and quantity however remains a concern with increasing environmental pressures conflicting with the growing demand. Recent attempts in supplying consistent, safe and environmentally acceptable biomass through cultivation of (macro- and micro-) algal biomass have concentrated on characterizing natural variability in bioactives, and optimizing cultivated materials through strain selection and hybridization, as well as breeding and, more recently, genetic improvements of biomass. Biotechnological tools including metabolomics, transcriptomics, and genomics have recently been extended to algae but, in comparison to microbial or plant biomass, still remain underdeveloped. Current progress in algal biotechnology is driven by an increased demand for new sources of biomass due to several global challenges, new discoveries and technologies available as well as an increased global awareness of the many applications of algae. Algal diversity and complexity provides significant potential provided that shortages in suitable and safe biomass can be met, and consumer demands are matched by commercial investment in product development.

Physicochemical parameters optimization, and purification of phycobiliproteins from the isolated Nostoc sp

The present study investigated the effects of several physicochemical parameters on the improvement of phycobiliproteins (especially phycocyanin) synthesis in a newly isolated species of Nostoc sp. Standard BG11₀ medium was modified to enhance the biomass productivity in different photobioreactors. The initial pH of 8, light intensity of 40 μmol m(-2)s(-1), temperature of 35 °C, diurnal cycle of 16:8 h (light:dark regime), 75.48 μM Na₂CO₃ and 17.65 mM NaNO₃ were found most suitable for the phycobiliproteins synthesis. Cyanobacteria exhibited chromatic adaptation, causing overexpression of phycocyanin in red and phycoerythrin in green light. The maximum phycobiliproteins yield of 0.13 gg(-1) dry cell weight was obtained in green light. Phycocyanin was further purified using thin layer chromatography (TLC), anion exchange chromatography and SDS-PAGE (denaturing gel) electrophoresis.

Engineering strategies for simultaneous enhancement of C-phycocyanin production and CO2 fixation with Spirulina platensis

Spirulina platensis produces nutraceutical product C-phycocyanin (C-PC) and simultaneously mitigates CO2 emissions during its growth. Using a designed flat-type photobioreactor, the S. platensis biomass production was markedly enhanced, leading to a CO2 removal rate and a biomass concentration of 0.23 g/L/d and 2.25 g/L, respectively. The cell growth, CO2 fixation rate and C-PC production of S. platensis were investigated when it was cultivated under different irradiation conditions. As the light intensity increased from 100 to 700 μmol/m(2)/s, the overall biomass productivity, CO2 consumption rate and maximal C-PC productivity increased significantly to 0.74, 1.53 and 0.11 g/L/d, respectively. After determining the suitable light intensity, the nitrogen concentration was also adjusted to further enhance the performance of CO2 fixation and C-PC production. The results show that with an optimal nitrogen concentration of 0.045 M, the CO2 consumption rate and maximal C-PC productivity were further increased to 1.58 and 0.13 g/L/d, respectively.