Effects Of Different Carbon Sources And Cultivation Methods On Lipid Production Of Scenedesmus Quadricauda

In this paper, the effects of different carbon sources and cultivation methods on lipid production of Scenedesmus quadricauda were studied. S. quadricauda could grow autotrophically using inorganic carbon sources, such as CO2 and NaHCO3. S. quadricauda utilized NaHCO3 weakly, but the algae fixed capacity of 5% CO2 was the strongest and CO2 concentration of 2% was most conducive to algae growth and lipid accumulation. Therefore, the high lipid productivity could be obtained with 2% CO2 aeration. S. quadricauda conducted heterotrophic metabolism using glucose, and 5g/L glucose was most favorable to algae biomass and lipid productivity which were much higher than that of Og/L glucose. S. quadricauda also could utilize CO2 and glucose at the same time to conduct facultative metabolism, with the highest lipid content of 32.9% and the highest lipid yield of 0.88g/L.Three cultivation methods, photosynthetic autotrophic culture, heterotrophic culture and facultative metabolism, were compared in this study. In photosynthetic autotrophic culture, algae grew very slowly and lipid content was much low. However, the highest biomass of algae was obtained in heterotrophic culture, and lipid content and total lipid reached highest in facultative culture. Therefore, facultative culture method was most beneficial for lipid production of S. quadricauda.S. quadricauda could grow in starch wastewater containing 3g/L glucose, and high biomass and microbial oil were obtained. Additionally, the degradation rate of wastewater COD reached 58.4%. Therefore, COD and production cost could be reduced by culturing S. quadricauda to produce microbial oil in starch wastewater containing sugar.Total biomass and lipid production could be increased by mix-cultivating of S. quadricauda and Rhodotorula glutinis. The total biomass of mix-culture was 5.97 times and 1.67 times of that of S. quadricauda single culture and R. glutinis monoculture, respectively. And lipid productivity of mix-culture was 3.6 times and 1.51 times of that of S. quadricauda single culture and R. glutinis monoculture, respectively. The optimal conditions of mix-cultivation were aeration rate of 1.4vvm and inoculation quantity of 10% yeast and 20% alga. Mix-culture medium was optimized through orthogonal experiment, and the optimal carbon and nitrogen sources were as follows (L):glucose 40g, urea 2.5g, yeast extracts 2.0g, soybean peptone 6.0g, NaNO32.0g, (NH4)2SO4 4.0g. After optimization, total biomass reached 22.28g/L with the highest lipid yield of 4.55g/L in 5L stirred fermentor, and the biomass and lipid yield increased by 77.6% and 135% than that of before optimization. The carbon and nitrogen source of mix-culture medium was further simplified and the highest lipid yield was obtained at the C/N of 20:1.