Abstract:
Spirulina, a blue-green microalgae is grown commercially throughout the world due to the high protein content and non-toxic features of the algal biomass. The Zarrouk’s medium which contains Na2CO3 and NaHCO3 as the carbon sources is known to be the standard medium for Spirulina cultivation. Higher purchasing cost of the carbon sources is recognised to be a limiting factor for largescale cultivation. Low-cost alternative sources of carbon which can replace Na2CO3 and NaHCO3 in the Zarrouk’s medium has a great economic impact on the commercial production. This study aimed at assessing the growth of Spirulina in different alternative sources of carbon under different concentrations. Table sugar, cassava flour, sweet potato flour and taro flour were used as alternative sources. The Zarrouk’s medium was substituted with different levels (25%, 50%, 75% and 100%) of the solutions prepared with the alternative carbon sources. The algae were cultured at room temperature for 16 days under illumination of 4,000 Lux. The growth was assessed as optical density (OD) using a spectrophotometer at 560 nm and then converted to dry weight (g L-1). According to the results, 100% carbon in the Zarrouk’s medium could be replaced by taro flour and 50% carbon could be replaced by cassava flour. A significantly higher dry weight (1.033 g L-1) was recorded from taro flour at 100% replacement level at the end of 16-day incubation. Therefore NaHCO3 and Na2CO3 in the Zarrouk’s medium could completely be replaced by taro flour solution which substantially reduces the cost of production as well. Cassava flour solution could also be used as an effective replacement while mixing with Zarrouk’s medium into the ratio 1:1. Table sugar and sweet potato flour are found to be poor sources of carbon to replace the NaHCO3 and Na2CO3 in the Zarrouk’s medium. The results could be further confirmed by assessing the growth of Spirulina under different supplementary levels of taro and cassava flour.
