Growth and quality of Chlorella vulgaris and Chaetoceros calcitrans in photobioreactors using low cost media formulated from fertiliser

Microalgae are gaining interest by numerous industries such as the aquaculture, health sciences and pharmaceutical. However, microalgae cultivation is constantly linked to high investment due to the cost of culture media. Therefore, formulation of low-cost media for high quality microalgae cultivation would increase the interest of microalgae usage in many industries. The current study aims to formulate a simple and cost-effective media for the cultivation of Chlorella vulgaris and Chaetoceros calcitrans. Locally available common fertiliser ‘Serbajadi 63’ containing 21:21:21 of nitrogen: phosphorus: potassium and ‘Serbajadi 46’ containing 46% of urea were used as the base formulae for the study. Twelve media were formulated for C. vulgaris and C. calcitrans with various concentrations and elements. The formulations were tested in two phases. In the first phase, C. vulgaris and C. calcitrans were cultured in 2 L flasks and were compared with the conventional media, i.e., Bold’s basal medium (BBM) and Conway, respectively. Formulations that showed comparable or better results were selected for phase two where the microalgae were mass cultured in 70 L photobioreactors (PBR) and analysed. During phase one, NPKFM which was formulated from 0.8 g/L of ‘Serbajadi 63’ with addition of MgSO4 (0.317 g/L) and acidified FeSO4.7H2O (0.02 g/L) produced favourable results for C. vulgaris culture. The formulation produced similar amounts (p > 0.05) of biomass and proteins as the control. Significantly higher amounts (p < 0.05) of chlorophyll-b (chl-b), carotenoids and carbohydrates were produced in NPKFM compared to BBM. Thus, NPKFM was used to mass culture C. vulgaris. Mass cultivation of C. vulgaris in NPKFM produced similar amounts (p > 0.05) of biomass, proteins and carbohydrates compared to BBM. Higher amount (p < 0.05) of lipids and polyunsaturated fatty acids (PUFA) were produced in NPKFM as well. In the case of C. calcitrans, the cultivation in 2 L flask revealed that NCFM produced the most favourable results compared to other formulations. NCFM was formulated from 0.476 g/L of ‘Serbajadi 63’ added with FeCl3.H2O (0.0013 g/L), MnCl2.4H2O (0.00036 g/L) and NaSiO3 (0.02 g/L) produced comparable (p > 0.05) optical density (OD) and cell density (CD) to Conway. Higher amounts (p < 0.05) of proteins and lipids were also produced in NCFM, while not significantly different (p > 0.05) amount of chlorophyll-a (chl-a) and chl-b were produced in both media. Thus, NCFM was selected for phase two. In the mass cultivation of C. calcitrans, NCFM produced significantly higher (p < 0.05) CD, proteins and lipids compared to the Conway medium. Additionally, similar (p > 0.05) amounts of carbohydrates, chl-a, chl-b, carotenoids and omega-6 were produced in both media as well. Economically, producing 1 L of NPKFM and 1 kg of C. vulgaris in NPKFM was found to be 59.09% and 49.93% cheaper respectively compared to BBM. Likewise, producing 1 L of NCFM and 1 kg of C. calcitrans in NCFM was 71.67% and 24.09% cheaper compared to Conway, respectively. Thus, both NPKFM and NCFM were suitable formulations for cost-effective mass cultivation of C. vulgaris and C. calcitrans, respectively.

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