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Subject: Biochemistry × Author: Amanpreet Kaur × End date: 2021 × Type: Thesis ×
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    ThesisItemOpen Access
    Enhancing carbohydrate and starch accumulation in microalgae for bioethanol production
    (Punjab Agricultural University, Ludhiana, 2019) Amanpreet Kaur; Taggar, Monica Sachdeva
    The present study was carried out to optimize the culture conditions for enhancing carbohydrate and starch accumulation in Chlorella sorokiniana for the bioethanol production. The growth and biomass of microalgae was studied with the sparging of carbon dioxide into the culture medium. The mean growth (0.70), fresh biomass (7983.33 mg l-1), dry biomass (1516.67 mg l-1) and biomass productivity (163.33 mg l-1 day-1) of microalgae was higher with the sparging of carbon dioxide into the culture medium. The effect of different concentrations of potassium nitrate, i.e. 4, 2 and 1 g l-1 in the culture medium revealed high growth (0.98), fresh (8053.33 mg l-1) and dry biomass (1556.67 mg l-1) of microalgae at 4 g l-1 potassium nitrate in the culture medium. The maximum accumulation of total carbohydrate (50.28%) and starch (34.06%) in the microalgae was observed at 1 g l-1 potassium nitrate concentration in the culture medium at 2 days after culturing (DAC) while the total soluble protein content (18.24%) was observed to be maximum at 4 g l-1 potassium nitrate concentration in the culture medium at 8 DAC. The maximum chlorophyll a, b and total chlorophyll content of 403.22 μg g-1 fw, 346.66 μg g-1 fw and 749.88 μg g-1 fw of microalgae was observed at 4 g l-1 potassium nitrate level in the culture medium, respectively. Morphological characterization of C. sorokiniana revealed dense starch granules in the cells under nitrogen limiting conditions. Chitosan, at a concentration of 200 ppm, showed maximum flocculation (90.94%) of microalgal suspension after 60 min. Pre-treatment of microalgal biomass with 1 N sulphuric acid revealed maximum production of total (487.41 mg g-1) and reducing sugars (277.56 mg g-1). The fermentation of microalgal hydrolysate by Saccharomyces cerevisiae resulted in maximum ethanol content and yield of 0.52 g and 0.052 g g-1 biomass at 96 h of fermentation.