The Culture Ecology And Biochemical Compositions Of Sixteen Microalgae Strains

In this study, fifteen microalgae strains were isolated from freshwater, and aculture experiment was conducted to determine the optimum water temperature andlight intensity of the fifteen microalgae. The biochemical compositions of thesemicroalgae were also analyzed. Results indicated that the optimum water temperatureand light intensity for Selenastrum sp. SHOU-F1，Chlorococcum sp. SHOU-F3，O.solitaria SHOU-F5，Kirchneriella obesa SHOU-F9，Ankistrodesmus sp. SHOU-F29，Chlorococcum sp. SHOU-F30， Ankistrodesmus sp. SHOU-F33， Chlorella sp.SHOU-F44，Chlorella sp. SHOU-F46，Chlorococcum infusionum SHOU-F48，Chlorella sp. SHOU-F49，S. dimorphus SHOU-F4，C. sphaericum SHOU-F10，Tetrachlorella sp. SHOU-F24and Scenedesmus sp. SHOU-FX were30.8,29.8,39.8,29.7,34.2,34.6,23.5,26.2,31.4,29.2,30.5,29.4,34.4,24.6,24.7℃and21,16,60,23,23,15,119,206,42,8,18,12,82,109,106mol·m-2·s-1, respectively. Undersuitable culture conditions, Selenastrum sp. SHOU-F1，Chlorococcum sp. SHOU-F3,O. solitaria SHOU-F5， Chlorella sp. SHOU-F44，Chlorella sp. SHOU-F49cells hadthe hightest protein contents(27.61%~31.92%), Chlorococcum sp. SHOU-F3, C.sphaericum SHOU-F10, Chlorella sp. SHOU-F44had the hightest carbohydratecontents(34.21%~42.02). While Selenastrum sp. SHOU-F1， Chlorococcum sp.SHOU-F3, Ankistrodesmus sp. SHOU-F33Chlorella sp. SHOU-F44cells obtainedthe hightest total lipid contents(11.40%~15.69%). On the contrary, S. dimorphusSHOU-F4had the lowest protein contents(18.97%), Chlorococcum infusionumSHOU-F48had the lowest carbohydrate contents (8.45%) and O. solitaria SHOU-F5,C. sphaericum SHOU-F10, Chlorococcum infusionum SHOU-F48had the lowestlipid contents(3.65%~4.55%).We studied the effect of nitrogen limitation high iron concentration and salinitystress on lipid and fatty acid of two microalgae Selenastrum sp. SHOU-F1and O.solitaria SHOU-F5.The result showed, increase salinity and iron concentration canenhance intracellular lipid content. Limited nitrogen can raise lipid congtents of O. solitaria SHOU-F5, instead of Selenastrum sp. SHOU-F1. We also finded that thefatty acid of O. solitaria SHOU-F5was ΣPUFA>ΣSFA>ΣMUFA. In low salinity, thefatty acid of Selenastrum sp. SHOU-F1was ΣPUFA>ΣMUFA>ΣSFA, while salinityraised to10, it changed to ΣMUFA>ΣPUFA>ΣSFA. In high iron concentration, DHA,EPA and ARA of O. solitaria SHOU-F5raised, but DHA of Selenastrum sp.SHOU-F1down.A Chlorella stain (2003ZGH023) was cultured at the modes on photoautotrophic(light, basic nutrient formula)，mixotrophic with high carbon level(light, basic nutrientformula,8gram organic carbon per liter), mixotrophic with low carbon level (4gramorganic carbon per liter) and heterotrophic with low carbon level (darkness, basicnutrient formula,4gram organic carbon per liter) respectively. The effect of differenttrophic modes on growth performance and nutrtional composition of the Chlorellawere studied. The result indicated that adding organic carbon in culture mediumsignificantly increased the cell density and biomass of Chlorella2003ZGH023. Theheterotrophic group had a cell density as high as54.73×106cell/mL or biomass6.86g(dw)/L. The sizes of the Chlorella2003ZGH023cell in heterotrophic andmixotrophic groups were larger than that in autotrophic group. The assays on nutritionshowed that the protein content of Chlorella2003ZGH023cell declined significantlywhile the total fat content increased significanly in heterotrophic modes. The crudeprotein contents in photoautotrophic mode, mixotrophic mode with high carbon level,mixotrophic mode with low carbon level and heterotrophic mode were41.88%±0.14%,24.60%±0.07%,21.93%±0.13%and12.91%±0.35%respectively.The variation on amino acid content of cell in different trophic modes was consistentwith that on crude protein. The total lipids in the mixotrophic mode with high-carbongroup (15.32%±1.58%) and heterotrophic mode with low-carbon group (14.15%±0.93%) were significantly higher than those in mixotrophic mode with low-carbongroup (12.35%±0.25%) and photoautotrophic mode (10.04%±0.3%). There weresignificant differences in fatty acid compositions of cell whic h cultured in differenttrophic modes.18:3n3and14:1were the dominant fatty acids of Chlorella2003ZGH023in photoautotrophic mode.14:1and18:1n9were the major fatty acidsof Chlorella2003ZGH023in mixotrophic modes.18:1n9and16:0were the mostabundant fatty acids of Chlorella2003ZGH023in heterotrophic mode.