Effect of nutrient limitation and light in the production of polyhydroxybutyrates and glycogen by cyanobacteria cultivated in wastewater
Tutor / directorGarcía Serrano, Joan
Document typeBachelor thesis
Rights accessOpen Access
Non-degradable plastics are a serious environmental problem. The use of living resources to produce biodegradable plastics could be a possible solution. Polyhydroxybutyrates (PHB), which are polymers with similar properties to polypropylene, and glycogen, which can be converted into bioethanol, are produced by cyanobacteria and other microorganisms. Cyanobacteria have the advantage of accumulating these substances using only CO2 and solar energy. Wastewater treatment could be used as a culture medium for cyanobacteria to reduce the bioplastics production costs. The main objectives of this work are to study the use of cyanobacteria as tertiary wastewater treatment, the effect of nutrient limitations and light hours on the accumulation of PHB and glycogen, and the best way to operate a reactor to select cyanobacteria against green algae. It has been possible to eliminate 64,8% of the nitrogen and 70,5% of the phosphorus coming from the secondary treatment and the digestate. Proving the ability of cyanobacteria to remove contaminants. A maximum glycogen concentration of 838 mg / L was obtained under nitrogen limitation and 12 h light conditions and a PHB of 104,2 mg / L under phosphorus limitation and 24 h light conditions. Therefore, it can be deduced that nitrogen limitation has more effect on glycogen accumulation, and phosphor on PHB. However, according to the defined economical Key performance indicator (KPI) the product benefits do not justify the lighting expenses. Finally, it can be said that the optimal cultivation conditions are limitation of phosphor and 12h light per day.