Outdoor Cultivation of Spirulina platensis for Mass Production

Abstract

In the present study, the blue-green alga Spirulina platensis (NRC) was used for mass production under outdoor cultivation in three open ponds with a final capacity of 75 m3 net cultivation volume. Subculturing was performed within sequences and gradual volumes till 1,200 L open plate photobioreactor. The first and second ponds (30 cm depth) were used for the actual continuous production, while the third pond (80 cm depth) was used as a continuous inoculum supplier. In spite of low turbulence of the third pond due to high depth, all ponds had the same mechanical specification concerning paddle wheel structure and turbulence rate (16 rpm). A final nutrient concentration was employed based on Zarrouk medium by commercial grade compounds with some modifications. The nutrition was performed for the third pond by extra supplementation of extra doses of macro and micro-nutrients during the production period and dilution took place when culture was transferred to production ponds (first and second). Each production pond was harvested every 48 hours and the remainder water was return again into the third pond. The harvested pond yielded about 40 kg per day of fresh algal weight containing about 85% moisture on a dry weight basis. The results proved that using urea as nitrogen and carbon source with corn steam liquor instead of sodium nitrate and low bicarbonate, reduces production cost and supports growth medium by an adequate amount of carbon dioxide on the expense of the luxury use of sodium bicarbonate (16.8 g.l-1). Chemical analysis of the produced biomass showed 58-62% crude protein, 6-8% of ether extract and 8-11% of total carbohydrates. S. platensis contained total essential amino acids (131.3 mg/g), with a predominance of arginine followed by glutamic acid, leucine and phenylalanine.