Screen Of High-lipid Content Marine Microalgae Strains Based On Preparation Of Biodiesel

The development and utilization of bio-energy is an important way to relieve the pressure of global energy shortage.Biodiesel can be a focus of the bio-energy, beacause it is a cleaner-burning and renewable fuel.Microalgae have been considered to be a ideal source of biodiesel for its high growth rate and high lipid content.The purpose of this paper is getting high-lipid microalgae strains with high growth rate by screen and random mutagenesis.After that,culture conditions and cultivation methods are optimized for large-scale production.The main results were shown as follow:1) Six species of high-lipid content microaigae were selected,as candidates of source of microalgal biodiesel,by algal species collection in field and determination of lipid contents of strains preserve in Diatom Lab,Xiamen University.These six species and their lipid contents were:Pheaodactylum tricomutum,34.4%; Chaetoceros muelleri,25.1%;Chaetoceros curvisetus,24.2%;Thalassiosira pseudonana,24.3%;Navicula halophila,39.1%;Nitzschia frustulum var.Symbiotica, 35.7%.Among the microalgae determined,benthic diatoms are very high in lipid content2) Evaluate neutral lipid content in Thalassiosira pseudonana using Nile Red fluorescence method.After optimization,0.5μg/mL was selected as the optimum dye concentration,10 min and 40℃was selected as the optimum staining time and temperature,respectively.The optimum concentration range of microalgae was between OD₆₈₀ 0.1-0.4.The method and a conventional gravimetric determination method provided similar results on replicate samples of Thalassiosira pseudonana and Chaetoceros muelleri.But this method has been unsuccessful in Pheaodactylum tricomutum3) Seven mutant strains of Thalassiosira pseudonana were isolated for their high lipid content after ultraviolet radiation.Lipid contents were determinated by Nile Red fluorescence method and conventional gravimetric determination method in the first round and second screen,respectively.HL-1,which has the highest lipid content among seven mutants,has 19.3%more lipid content than starting strain.However,the growth rate of HL-1 was lower than starting strain while biomass of HL-1 was higher than starting strain4) Orthogonal test was designed to find out the optimum conditions for growth and lipid accumulation of Pheaodactylum tricornutum and Chaetoceros curvisetus. The results show,light tensity 4500 lx,17℃,NO₃^- concentration 2mmol/L,EDTA-Fe concentration 10^-4mmol/L is the best condition for growth of P.tricornutum,when the best condition for lipid accumulation is light tensity 3000lx,22℃,NO₃^- concentration 0.5mmol/L,10^-6mmol/L.And the best conditions for growth of C.curvisetus is light tensity 6000lx,27℃,NO₃^- concentration 2mmol/L,EDTA-Fe concentration 10^-6mmol/L,when the best condition for lipid accumulation is light tensity 3000lx, 17℃,NO₃^- concentration 1mmol/L,EDTA-Fe concentration 10^-5mmol/L5) Biodiesel was produced with oil extract from different microalgae species,the biodiesel yield is 5.6-15.3%(dry weight ).Two benthic diatom can yield more biodiesel than other species.The yield of biodiesel can reach 15.3%and 14.3%in Navicula halophila and Nitzschia frustulum var.symbiotica,respectively...