Enhanced biomass and phycocyanin production of Arthrospira (Spirulina) platensis by a cultivation management strategy: Light intensity and cell concentration.

This work investigated the cultivation of Arthrospira (Spirulina) platensis BP in a photobioreactor under light intensities of 635, 980, 1300, and 2300 µmol m-2 s-1, using a semi-continuous mode to keep cell concentration at optical densities (OD) of 0.4, 0.6, and 0.8. The highest productivity of biomass (0.62 g L-1 d-1) and phycocyanin (123 mg L-1 d-1) were obtained when cells were grown under a light intensity of 2300 µmol m-2 s-1 at OD 0.6. At this concentration, the efficiency of energy consumption to the biomass of algae was around 2.26-2.31 g (kW h)-1 d-1, while, a maximum photosynthetic efficiency of 8.02% was obtained under a light intensity of 635 µmol m-2 s-1 at OD 0.8. This indicates how light intensity, cell concentration, and light-dark conditions can enhance biomass and phycocyanin production, if well manipulated.

The potential of polysaccharide extracts from Caulerpa lentillifera waste.

Caulerpa is a marine macroalgae and is rich in polysaccharides, which have the potential for immunostimulatory and anticoagulant activity. The objective of this work was to increase the value of C. lentillifera waste by polysaccharide extraction. A polysaccharide yield of about 25% of dry weight was obtained under the following optimized conditions: two-stage extraction (60 min/stage) using a ratio of 1:15 (w/v) at 90 °C, and 2× precipitation by the final concentration of 75% ethanol. The polysaccharide extracts contained a non-reducing sugar that accounted for 44% of weight extracts as a major sugar and consisted of four neutral sugars: mannose (33.3%), galactose (31.9%,), glucose (27.0%) and xylose (7.6%). In addition, it contained sulfate, which is approximately 8.37% of weight extracts and had a phenolic content of around 1.27 mg GAE/g sample. Moreover, it demonstrated α-glucosidase inhibitory activity with an IC50 value of 13.59 mg/mL. This result suggests that the polysaccharide extracts could potentially be used for preventing diabetes disease. The economic analysis also showed an economic feasibility for producing polysaccharide extracts from C. lentillifera waste. This is an alternative for farmers in order to increase the value of C. lentillifera waste.

Stepwise extraction of high-value chemicals from Arthrospira (Spirulina) and an economic feasibility study.

Arthrospira (Spirulina) consists of diverse high-value chemicals, such as phycocyanin, lipids/total fatty acids (TFA), and polysaccharides, which have been used for food, cosmetic and pharmacological applications. This study compared various stepwise extraction processes for these high-value chemicals. Considering the yield and properties of extracts, the most suitable extraction order was phycocyanin, lipid/TFA and polysaccharides. The yield of the main product (food-grade phycocyanin) was 8.66% of the biomass dry weight, whereas the yields of the subsequent lipid/TFA and polysaccharide coproducts were 3.55% and 0.72%, respectively. The economic analysis showed that producing phycocyanin alone was economically feasible, but producing coproducts (lipid/TFA and polysaccharides) was not. The production cost of phycocyanin was US$ 249.70 kg-1, which is an encouraging figure for large-scale production. Moreover, the phycocyanin content of Arthrospira materials utilized for extraction should not be lower than 15% of dry weight to ensure positive the net present value (NPV) of investment.

Biomass and lipid enhancement in Ankistrodesmus sp. cultured with reused and minimal nutrients media.

Microalgae are a promising feedstock for biofuel production. Lipid content in microalgae could be enhanced under nutrient depletion. This work investigated the effect of the nutrient on lipid accumulation in Ankistrodesmus sp. culture. Batch cultures were carried out using fresh BG11 medium, and after the harvest, the medium was reused for the next culture; this method was repeated two times. The maximum lipid productivity of 29.75 mg L(-1) day(-1) was obtained from the culture with the second reuse medium. In continuous cultures, Ankistrodesmus sp. was cultured in both fresh and modified BG11 mediums. The modified BG11 medium was adjusted to resemble the content of the first reuse medium. As a comparison between batch and continuous cultures, it was proven that the productivity in the continuous culture was better than in the batch, where the achievable maximum biomass and lipid were 188.30 and 38.32 mg L(-1) day(-1). The maximum lipid content of 34.22% was obtained from the continuous culture at a dilution rate of 0.08 day(-1), whereas the maximum saturated and unsaturated fatty acid productivities of 79.96 and 104.54 mg L(-1) day(-1) were obtained at a dilution rate of 0.16 day(-1.)

Polysaccharide extraction from Spirulina sp. and its antioxidant capacity.

To optimize polysaccharide extraction from Spirulina sp., the effect of solid-to-liquid ratio, extraction temperature and time were investigated using Box-Behnken experimental design and response surface methodology. The results showed that extraction temperature and solid-to-liquid ratio had a significant impact on the yield of polysaccharides. A polysaccharides yield of around 8.3% dry weight was obtained under the following optimized conditions: solid-to-liquid ratio of 1:45, temperature of 90°C, and time of 120 min. The polysaccharide extracts contained rhamnose, which accounted for 53% of the total sugars, with a phenolic content of 45 mg GAE/g sample.

Separation and purification of phycocyanin from Spirulina sp. using a membrane process.

The highest purity ratio of phycocyanin extract was obtained when fresh biomass was used as raw material. The crude extract was purified by membrane process using microfiltration and ultrafiltration. Membrane of pore sizes 5 µm, at feed flow rate of 150 mL min(-1), permeate flux of 58.5 L h(-1)m(-2) was selected for coarse filtration and membrane with pore size 0.8/0.2 µm at the flow rate of 100 mL min(-1), permeate flux of 336 L h(-1)m(-2) was selected for fine filtration, giving phycocyanin recovery of 88.6% and 82.9%, respectively. For ultrafiltration, membrane with MWCO at 50 kDa, 69 kPa and 75 mL min(-1) of flow rate with a mean permeate flux 26.8 L h(-1)m(-2) and a retention rate of 99% was found to be optimal. Under these filtration conditions, food grade phycocyanin with the purity around 1.0 containing c-phycocyanin as the major component was obtained.

Cultivation of Spirulina platensis using pig wastewater in a semi-continuous process.

The effluent from anaerobic digestion contains organic nitrogen and phosphorus, which are both required for growth of Spirulina platensis. Effluent (20%) from the upflow anaerobic sludge blanket (UASB) from a pig farm, supplemented with 4.5 g/l sodium bicarbonate (NaHCO(3)) and 0.2 g/l urea fertilizer (46:0:0, N:P:K), was found to be not only a suitable medium for the growth of Spirulina platensis but also a low-cost alternative. Cost calculation showed that this medium is 4.4 times cheaper than modifized Zarrouk's medium. The average productivities of a semi-continuous culture grown under outdoor conditions in a 6-l scale and a 100-l pilot scale were 19.9 g/m2/d and 12 g/m(2)/d, respectively. In addition, the biomass of organisms grown in UASB effluent contained approximately 57.9% protein, 1.12% gamma-linolenic acid, and 19.5% phycocyanin. The average rates of bicarbonate, total nitrogen, and phosphorus removal were 380 mg/l/d, 34 mg/l/d, and 4 mg/l/d, respectively.

Removal of lead (Pb(2+)) by the cyanobacterium Gloeocapsa sp.

Pb(2+) removal ability of the viable-freshwater cyanobacterium Gloeocapsa sp. was studied in batch experiments. Gloeocapsa sp. was cultured in the Medium 18 with pH adjusted to 3, 4, 5, 6 and 7. Growth was subsequently determined based on the increase of chlorophyll-a content. Gloeocapsa sp. was able to grow at all pH levels tested, except at pH 3. Removal of Pb(2+) was then further studied under pH 4. The results showed that Pb(2+) concentration in the range of 0-20 mg L(-1) was not inhibitory to Gloeocapsa sp. growth but reduced its Pb(2+) removal efficiency (by 4.5% when Pb(2+) concentration increased from 2.5 to 20 mg L(-1)). Pb(2+) removal characteristics followed the Langmuir adsorption isotherm with the maximum removal capacity (q(max)) of 232.56 mg g(-1). Adsorption of Pb(2+) by this cyanobacterium followed the second order rate reaction and intraparticle diffusion was likely the rate-determining step. The initial rate of Pb(2+)adsorption during intraparticle diffusion was slower under light than under dark conditions, indicating that light probably slowed down the initial rate of intraparticle diffusion through the repulsion effects on cell membrane.

Revealing differentially expressed proteins in two morphological forms of Spirulina platensis by proteomic analysis.

Spirulina is distinguished from other cyanobacteria by its spiral morphology; however, this cyanobacterium has frequently been observed with a linear morphology in laboratory and industrial conditions. In our laboratory conditions, the simultaneously presence of the linear and spiral forms has also been observed. In the present study, the two forms of S. platensis C1 were separated and grown as axenic cultures in order to study the proteins that were differentially expressed in the soluble and insoluble protein fractions of the spiral and the linear forms. Two dimensional-differential gel electrophoresis (2D-DIGE) was performed to separate differentially expressed proteins that were subsequently identified by mass spectrometry. The differentially expressed proteins suggested two points. First, the morphological change is possibly induced by various environmental stresses such as oxygen level, carbon dioxide level, nutrient availability, and light. Second, the change of cell-shape might be a result of the change in a cell shape determination mechanism. Thus, this study is the first to show evidence at the protein level that may explain this morphological transformation in Spirulina.

Production, composition and Pb2+ adsorption characteristics of capsular polysaccharides extracted from a cyanobacterium Gloeocapsa gelatinosa.

Pb2+ adsorption by the living cells of the cyanobacterium Gloeocapsa gelatinosa was studied. Cyanobacterial cells with intact capsular polysaccharide (CPS) showed 5.7 times higher Pb adsorption capacity than that of cells without CPS. The adsorbed Pb was desorbed by EDTA, indicating that Pb2+ adsorption occurred mainly on cell surface. Production, sugar content and ability of CPS to remove Pb2+ were then studied in details. CPS production by G. gelatinosa increased when culture time was prolonged. The maximum CPS production was 35.43 mg g(-1) dry weight after 30-day cultivation. Xylose, arabinose, ribose, rhamnose, galactose, glucose, mannose and fructose were the neutral sugars presented in CPS of G. gelatinosa. Acidic sugars including galacturonic and glucuronic acids were also found in CPS. The amount and composition of G. gelatinosa's CPS varied according to its growth phase and culture conditions. The highest amount of acidic sugars was produced when cultured under low light intensity. The extracted CPS rapidly removed Pb2+ from the solution (82.22+/-4.82 mg Pb2+ per g CPS), directly demonstrating its roles in binding Pb2+ ions. Its ability to remove Pb2+ rapidly and efficiently, to grow under sub-optimal conditions (such as low pH and low light intensity), and to produce high amount of CPS with acidic sugars, leads us to conclude that G. gelatinosa is a potential viable bioadsorber for mildly acidic water contaminated with Pb2+.