Salinity Treatment as Bacterial Control and Its Impact on Growth and Nutritional Value of Spirulina (Arthrospira platensis) Culture in Open Pond System

Cultivation of Spirulina in open ponds is always problematic due to microbial contamination, which results in reduced growth and productivity. Efficient methods are needed, for example changing the salinity of culture media because salinity can act as a limiting factor for many organisms. One simple and low-cost solution may be to to change the salinity of the culture environment, as salinity can act as a limiting factor for many organsims. The purpose of this study was to examine the impact of salinity (10‰–40‰, with salinity of 5‰ as a control) on bacterial contamination, growth and nutritional values of Spirulina cultured in an open pond. Bacterial contaminants measured using total plate count method revealed significant reduction of bacteria for the 10‰ treatment at day 5, but by day 10 the bacteria grew back because they were tolerant to the increase in salinity. Growth of Spirulina was enhanced at 10‰ and 20‰ in terms of density, while dry biomass was increased only at 20‰. Protein content was unchanged or even decreased at 20‰–40‰, while lipid content increased with salinity. Chlorophyll a, total chlorophyll and phycocyanin tended to decrease with increased salinity. Chlorophyll b tended to decrease when salinity increased to 10‰ and 20‰ (but without statistical support), and remained unchanged (relative to 5‰) at 30‰ and 40‰. Carotenoid was increased at levels of 10‰–30‰ but was not different from the control at 40‰. In conclusion, the present study showed that modification of salinity level may not be useful to prevent microbial contamination of Spirulina culture in open pond systems.