Optimization On Culture Conditions Of Genetically Engineered Energy Microalgae Under Different Carbon Sources

With the development of global economy,the massive exploitation and utilization of fossil fuels has brought environmental pollution,significant greenhouse gas emission,sea level rise,and fossil resources depletion,which inversely threat the sustainable development of mankind.Thus,the pursuit of clean and sustainable alternative energy has become an urgent task.Due to the rapid growth and reproduction,strong survivability and low land demand,energy microalgae,a third generation of biofuels,have become an important feedstock for biodiesel production and other related energy products.Therefore,based on the current research of energy microalgae and its biodiesel production,this study is to start from upstream microalgae strains selection and focus on the midstream culture process of genetically engineered energy microalgae,to optimize the conditions for its biomass and oil accumulation,and finally to analyze the quality of downstream microalgae biodiesel,so as to provide technical support for the commercialization of energy microalgae.On the basis of the previous research in our laboratory,the genetically engineered Chlorella protothecoides was selected as the research object,which could improve biomass by 25.26%and lipid productivity by 36.28%in comparison to the original Chlorella protothecoides strain.Optimized the Selenite Enrichment Solution(SE)original heterotrophic medium through the response surface methodology,the biomass for SE optimized heterotrophic culture could reach 1.40±0.02 g/L and the oil yield could attain 32.23±0.24 mg/L/d,which was enhaced by 35.48%and by 56.43%than those of the SE original culture,respectively.In order to achieve high lipid production at low cultivation cost,waste molasses generated from sugar industry,which has low price and high sugar content,has been chosen to conduct a feasibility study on alternative substrate for refined glucose.After evaluation on Glucose Complete(GC),Molasses Hydrolysate Complete(MHC),Molasses Hydrolysate with Nitrogen Lack(MHNL),Molasses Hydrolysate Direct(MHD)and Molasses Direct(MD)heterotrophic cultures,MHNL heterotrophic medium could achieve the biggest biomass and the highest lipid productivity,which may provide an effective replacement of the refined glucose.Through further optimization by response surface methodlogy,the genetically engineered Chlorella protothecoides could achieve a biomass of 2.34±0.06 g/L,and a lipid productivity of 59.34±1.13 mg/L/d in MHNL optimized medium,which was enhanced by 58.98%than original MHNL medium,and by 132.81%than GC control medium,and by 78.60%than the previously optimized SE medium.Therefore,the optimized MHNL heterotrophic medium can be applied as an optimal economical and effective alternative cultivation medium for microalgae biodiesel production.