Promoting Cell Growth And Lipid Synthesis Of Scenedesmus Obliquus By Mix-culturing With The Bacterium And Supplementing NaHCO₃

Microalgae are the major feed-stocks for biofuel production because of their excellent properties including high growth rate,easily cultivated and high lipid content.However,compared with fossil fuels,the production cost of biodiesel is still relatively high,and sustainable commercial production cannot be achieved.Therefore,how to increase algae yield and lipid content is a key issue in the production of biodiesel.S.obliquus has high lipid content that is generally about 50%of its dry weight,and it is an ideal raw material for biodiesel.Therefore,we use S.obliquus as the research object and the effects of alga-bacteria mixed culture(M),supplementation of NaHCO₃(C),and the combination of both(MC)on cell growth and lipid synthesis of S.obliquus were studied.The main result are show as follow.Alga-bacteria mixed culture(M):In this study,four microorganisms were isolated from S.obliquus:the bacteria of B₁,B₂,B₃,and fungus F₁ and the microorganism B1 that had the best effect on the promotion of S.obliquus was selected.The optimal cell concentration ratio of S.obliquus and bacteria B₁ was 4:1 and an optimal mixed culture system of S.obliquus and bacteria was constructed.Supplementation of NaHCO₃(C):Compared with the single culture of Scenedesmus(0.72 g/L,156.8 mg/g),the biomass and lipid content of S.obliquus at the concentration of0.3 g/L NaHCO₃ reached the maximum values of 1.38 g/L and 225.1 mg/g.Increased by91.7%and 43.5%respectively.Similarly,when the NaHCO₃ concentration was 0.3 g/L,the contents of chlorophyll a and chlorophyll b reached the maximum values of 11.7 g/L and4.1 g/L,which were increased by 265%,193%,compared with the absence of NaHCO₃ and the end of the p H culture reached the maximum value of 9.1,indicating that 0.3 g/L NaHCO₃ had the best effect on the promotion of S.obliquus.Mix-culturing with the bacterium and supplementing NaHCO₃:Results shown that comparing to the individual culture of S.obliquus(CK),the biomasses of M,C and MC increased 68%,98%,and 195%,their lipid contents increased 35.6%,41.6%,and 50.4%;and the proportion of C18-1 fatty acids increased 17%,30.8%and 47.4%respectively.These results suggest that MC is of potential application in biodiesel feedstock production.