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.