Culture of the green microalga, Haematococcus pluvialis, in low-cost vegetable-based media prepared using rotten wax gourd (Benincasa hispida)

The microalga Haematococcus pluvialis has diversified uses including formulation of fish foods. This microalga containing fish feed produces pigment in the flesh and enhances the growth and survival rate of the aquaculture organisms. The mass culture of H. pluvialis using commercial inorganic medium is expensive; therefore, in the present study, an alternate low-cost vegetable waste-based medium, the supernatant of the digested rotten wax gourd (Benincasa hispida), was used to culture the microalga. To assess the growth performance, H. pluvialis was cultured in 25% (T₁), 50% (T₂), and 75% (T₃) of the digested rotten wax gourd supernatant (DRWGS) and in commercial Kosaric Medium (KM) (T₄). The proximate composition of the rotten wax gourd, the physicochemical characteristics of the DRWGS, and the measured physicochemical parameters of the cultured media prepared using the DRWGS revealed the suitability of the rotten wax gourd for the growth of H. pluvialis. The growth of H. pluvialis in terms of cell density, mean daily division rate, optical density, dry cell weight, and chlorophyll-a was found highest in T₄, followed by T₃, T₂, and T₁, respectively. Importantly, the growth parameters and the protein and lipid content of the microalga H. pluvialis exhibited no significant (p > 0.05) difference between T₄ (KM) and T₃ (75% DRWGS). The findings of the present study revealed that the digested rotten wax gourd supernatant can be utilized for the mass culture of the microalga H. pluvialis, and the higher concentration up to a certain level of the supernatant is good for the culture. The cost of production of a certain amount of the commercial medium KM is about two times higher than the production of the same amount of the 75% DRWGS medium. This low-cost DRWGS can be used in mass production of the microalga H. pluvialis which has a high potential in rearing zooplankton and fish larvae in hatcheries. Fish larvae grown on live feeds (microalgae and zooplankton) normally have high growth and survival rate. Adequate supply of high-quality fish larvae to the farmers in due time is the prerequisite for sustainable enhanced aquaculture.