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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Agricultural and Biosystems Engineering

First Advisor

Gary A. Anderson


Anabaena sp, Synechocystis sp, Chlorella sp, Nannochloropsis sp, Growth media, Limiting nutrient, Nitrate, Phosphorus, Sulfate, flocculation, photocatalysis, tetracycline, phenol


In this study the elemental composition of media and algae both were compared and the required elements to get a unit biomass are studied. The limiting and critical factors for algae growth are culture medium, pH, light, aeration, temperature, Etc. Nutrients in the right proportions are essential to harvest high density algal biomass in order to get more end product. Every element in the growth medium plays a significant role in the production of a single algal cell. The culture medium includes major and minor nutrients to be added to the growing biomass in sufficient quantities to get higher biomass concentration. In this study the elemental composition of media and algae both were compared and the required elements to get a unit biomass are studied. For Anabaena sp, phosphorus is found to be the limiting nutrient. For Synechocytis sp, Nitrogen is the limiting nutrient and for Chlorella sp, sulphur is limiting. Nannochloropsis sp growth was limited by sulphur as the major nutrient and copper as the minor nutrient. Different nutrients are supplied in different quantities based on the requirement of the cells. The limiting nutrient is the one which is completely used up by the cells first and thereby limiting cell growth and cell division. The wild strain Anabaena 7120 is grown in a BG-11 medium. Three major nutrients (nitrate, phosphorus, and sulfate) are measured in the medium to determine the decrease in quantity of the nutrient. The change in quantity is assumed to be taken up by the cell. These nutrients are quantified using a spectrophotometer. The relationship between biomass dry weight and optical density was also obtained. The results show that the nutrient nitrate was consumed by the cell up to certain level and then it increased in the media. Sulfate concentration remained the same and the amount of phosphorus gradually decreased to zero. Thus the nutrient phosphorus is the limiting nutrient for the strain Anabaena 7120 wild type grown in the BG-11 medium. Harvesting of algae is the most expensive process in the manufacturing of biofuel. In this study the efficiency of pH induced flocculation is analyzed. The pH of the media with culture is increased to 8, 9, 10, 11, and 12. The efficiency is calculated by measuring the OD value of the supernatant at 700nm after one hour and after 12 hours. The result suggests that high pH for short time gives better results. The flocculation efficiency of the sample at pH 12 after one hour gives 88% recovery and after 12 hours 90% efficiency is achieved. Photocatalysis is an emerging method to degrade organic compounds in the environment without any byproduct production. In this study two organic compounds (tetracycline and phenol) were used. These two compounds were treated with TiO2 in the presence of UV light to degrade them. The cell viability was observed at different time intervals after the 6th, 12th, 18th, 30th and 42nd hours. Photocatalytic experiments conducted in this study indicate that there is little increase in the percent cell viability of treated and untreated samples. The culture provided with air and temperature may degrade the antibiotic, thus reducing the lethal effect of it. The phenol also shows similar results like tetracycline. Phenol is a volatile organic compound and may volatilize when air is fed into the culture flask. This may be the reason for increasing cell viability in the culture sample. The nutrient rich culture media, light, and air make the cyanobacteria resistant to the antibiotic. Thereby having less effect on culture.

Library of Congress Subject Headings

Cyanobacteria Flocculation Photocatalysis


Includes bibliograp[hical references (pages 87-108)


application/ pdf

Number of Pages



South Dakota State University


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