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.

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.