Thermosynechococcus sp. CL-1 applied to CO2 fixation, estrogen degradation and carotenoids production analysis

• Main Authors: Yu-LingChang, 張瑜玲
• Other Authors: Hsin Chu
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/vmp6z8

碩士 === 國立成功大學 === 環境工程學系 === 105 === Urbanization and industrialization possess a severe threat to the environment as it overloads the ecosystem by disposing millions tons of wastewater. The specific category of pollutants comprises the compounds that may affect the normal hormonal function or possess endocrine-related functions, known as endocrine disrupting chemicals (EDCs). Estrogens seems as unavoidable and major EDCs in domestic wastewater. The concentrations of estrogens in farm wastewaters typically vary from a few nanograms/liter to several microgram/liter. Especially, 17β-estradiol (E2) is known to be the primary causative agent for feminization of aquatic wildlife. Microalgae have recently gained huge attention worldwide because their sustainability and multifunctionality. Microalgae are highlighted due to their ability to capture carbon dioxide (CO2) and to convert it into oxygen and biomass. The molecular oxygen is used as an electron acceptor by bacteria to degrade organic matter. Thermosynechococcus sp. CL-1 (TCL-1) was chosen in this study in order to grow it in a high-temperature flue gas streams to investigate its performance of the CO2 fixation rate, estrogens degradation, and antioxidant response carotenoids production under various cultivation conditions. The results showed that the E2 concentration sharply dropped and E2 was readily transformed into estrone (E1). E1 was degraded by TCL-1 in the algal treatment system. The removal of estrogens was achieved mainly through biodegradation. The possible mechanisms of E2 degradation by TCL-1 are illustrated as following; Pathway 1: Firstly, TCL-1 accumulated E2 into biomass. Secondly, TCL-1 intracellular enzymes transformed E2 into E1. Finally, E1 was released to the liquid phase for further degradation. Pathway 2: TCL-1 extracellular enzymes transformed E2 into E1. It can be found that light intensity was critical factor on biomass productivity and CO2 fixation rate in this system. The highest total estrogens (including E1 and E2) removal efficiency appeared at lower initial E2 concentration, higher light intensity, and lower initial nitrate concentration. The higher carotenoids productivity appeared at higher light intensity and nitrate concentration above 1.2 mM with estrogens wastewater. In present study, the highest biomass productivity, carbon fixation rate, total estrogens degradation kinetics, zeaxanthin productivity and β-carotene productivity were 7.04 mg/L/h, 11.41 mg/L/h, 0.0227 h-1, 0.006 mg/L/h and 0.043 mg/L/h, respectively, under 200 μE m-2 s-1 light intensity. The maximum specific degradation rate was 0.1049 g estrogens/g biomass/h when initial E2 concentration was 20.0 mg/L.