ISOLATION, MORPHOLOGICAL IDENTIFICATION AND CHARACTERIZATION OF INDIGENOUS MICROALGAE FROM DIFFERENT SOUTH-EASTERN FRESHWATER HABITAT OF BANGLADESH

Abstract

To utilize the enormous potentiality of indigenous microalgae, this study contains indices on isolation of some primordial freshwater microalgae and to determine their growth rate, pigments and proximate composition. For microalgae isolation, streak plating method in agar, serial dilution and capillary pipetting was performed and for the evaluation of growth performance, data were collected in terms of cell density and optical density. Selected microalgae (Nephrocytium sp., Nannochloropsis sp., Selenastrum sp., Sphaerocystis sp., Ankistrodesmus sp., Monoraphidium sp., Pectinodesmus sp. and Scenedesmus sp.) were mass cultured in commercial Bold Basal Medium (BBM), harvested at their stationary phases to determine the pigments content (chlorophyll-a, chlorophyll-b, carotenoid and phycobiliproteins) and proximate composition (protein, lipid and carbohydrate). Results showed that, onset of stationary phase (9–14 days) varied among the eight species where in the stationary phase; cell density was significantly higher (p˂0.05) in Nannochloropsis sp. All microalgae showed chlorophyll-a as the main pigment component, where Monoraphidium sp. showed significantly highest (p˂0.05) chlorophyll-a (11.264±0.065 μg/mL), b (2.082±0.067 μg/mL) and carotenoid content (8.05±0.07 μg/mL). Moreover, total phycobiliproteins was also significantly higher (p˂0.05) in Scenedesmus sp. (6.105±0.12 mg/g) and significantly lowest (p˂0.05) in Pectinodesmus sp. (1.152±0.012 mg/g) and Sphaerocystis sp. (1.296±0.007 mg/g). Significantly higher (p<0.05) amount of total protein was recorded in Nannochloropsis sp. (34.34±1.22 % dry weight) and significantly lower (p<0.05) in Scenedesmus sp. (21.77±2.17 % dry weight) and Ankistrodesmus sp. (24.26±0.78 % dry weight). Similarly, highest and lowest (p<0.05) amount of lipid content was recorded in Monoraphidium sp. (25.28±0.31 %dry weight) and Pectinodesmus sp. (11.79±0.27 %dry weight), respectively. In addition, carbohydrate content was highest (p < 0.05) in Pectinodesmus sp. These findings indicate that the microalgae assessed in this study have potential as multi-nutrient and pigments supplement, as well as can be manipulated for high protein, lipid and pigments production for the sustainable use of native species in aquaculture, pharmaceuticals and nutraceuticals industry