Enhancing Cell Growth And Lipid Production Of Green Alage DX01 By Co-culturing With The Fungus Simplicillium Lanosoniveu

Algae are the major feed-stocks for biofuel production,while some fungi and bacteria can establish symbiotic relationships with algae and promote their productivities.Hence,co-culture of algae with fungi or bacteria become the research hotspot worldwide.In this paper,the effects of symbiotic fungi on the growth of green algae cells and lipid synthesis were studied by the mixed culture of cyanobacterial symbiotic fungi Simplicillium lanosoniveum and green algae DX01.The aseptic species of green algae DX01 were obtained by the combination of dilution coating,centrifugal washing and antibiotic treatment.The experiment showed that the proportion of gentamicin and kanamycin sulfate was 1:1,and the sodium hypochlorite solution with mass fraction of 0.2%had a good inhibition effect on the mixed bacteria in green algae by treating 10 min in the solution of sodium hypochlorite.The effect of antibiotics was eliminated by multiple passages,and no other bacteria were found in dilution coating.The preliminary identification of the heterozygous bacteria in DX01mainly included four kinds of bacteria,which were N1 pink circular,N2 yellow circular,N3 yellow irregular fold,and N4 white circular.By colony count,the highest density of N1bacteria in the DX01 was 2.25×10⁷/mL,and the lowest N3 biomass density was0.1×10⁷/mL.Compared to DX01 monoculture,the specific growth rate(0.20 d^-1),cell productivity?0.17 g/?L·d??and biomass?2.85 g/L?of DX01 in co-culture increased 10.3%,51.3%and55.7%respectively;while the specific lipid synthetic rate?0.68 mg/?g·d??,lipid productivity?1.95 mg/?L·d??and lipid content?220.4 mg/g?increased 33.3%,107.5%and32.0%respectively,and also,the proportions of saturated fatty acids and monounsaturated fatty acids C18-1 and C18-2 in the lipid elevated,which is suitable for biofuel production.The fungus Simplicillium lanosoniveum promotes cell growth and lipid synthesis of green algae,and thus algae-fungi co-cultivation can be applied in biofuel feedstock production.Finally,we studied the relationship between carotenoids and lipids in DX01.The BBM medium was used as the nutrient of green algae,placed under the light condition.The carotenoid in the algae cells was obtained by acetone as the extractor,and the liquid chromatography was carried out.The main types of carotenoids in green algae are?-carotene,lutein and zeaxanthin.The main fatty acids in DX01 were C16-0,C18-2 and C18-3,accounting for 15.87%,20.46%and 19.33%respectively.The total lipid content of green algae DX01 accumulated at the mature stage,which was 169.3 mg/g.The carotenoid content reached the maximum value of 16.984 mg/g at sixteenth days.The trend of carotenoid content was basically the same as that of total lipid,and the carotenoid content increased with the accumulation of total lipid.