Study On The Suitable Cultural Conditions For Biodiesel Production By Microalgae Based On Multi-factor Control And Their Tolerance To Stress Parameters

Currently, using the microalgae for biodiesel production and couple with CO2emissions has become a hot issue. However, the increase in lipid yield of microalgaecan lead to a relative decrease in industrial production cost. The lipid content andbiomass are two major factors affecting lipid production of microalgae, and both ofthem are contradictions exist, while by changing only a single factor of cultureconditions is often difficult to obtain a high lipid yield. Therefore, in the present study,four species of microalgae were screened, which include two freshwater microalgaeand two marine algae, and based on single factor optimization experiments, bymultivariate joint research, aimed to obtain an effective culture program to promoteboth biomass and fat content, then further investigated the tolerance of microalgae tothe flue gas environment (low pH, high temperature, high CO2concentration), themain results are as follows:(1) In the research of phosphorus, iron, manganese, indole acetic effect onbiomass and lipid accumulation of four strains, result showed the impact of fourfactors on biomass of microalgae in order was phosphorus＞indole acetic acid＞iron＞manganese, while lipid was impacted greater by phosphorus, and followed byindole acetic acid and iron. Under the influence of four factors, in freshwatermicroalgae, the biomass and lipid content of Nannochloropsis limnetica were higherthan Chlorella vulgaris, while in marine algae, the biomass of Nannochloropsisoceanic closed with Dunaliella salina, but its fat content was significantly higher thanD. salina. Then, to chose N. limnetica and N.oceanic as the dominant algal, and thephosphorus and indole acetic acid as excellent factors.(2) Orthogonal designed based on factors and algae that have been screened. Theinformation obtained from the orthogonal test design for screening the most effectivecombinational measurement as follows: the combined of NaNO30.5g·L-1, K2HPO440mg·L-1, IAA0.1mg·L-1was the best measurement for improving the biomass of N.limnetica; and lipid accumulation under NaNO31.0g·L-1, K2HPO440mg·L-1, IAA 0.05mg·L-1condition would reach its maximum value; then under the combinedeffect of NaNO30.5g·L-1, K2HPO440mg·L-1, IAA0.05mg·L-1, N. limneticadisplayed the highest lipid production. The combination of NaNO340mg·L-1,NaH2PO44.4mg·L-1, IAA0.5mg·L-1was the most effective for N. oceanic toproduce lipid while the combined treatment of NaNO375mg·L-1, NaH2PO44.4mg·L-1, IAA0.05mg·L-1was the most effective for improving biomass and oil yieldsof the microalgae.N. limnetica displays the highest biomass(0.65g·L-1), the highest total lipidcontent(37.39%), the highest lipid yield (274.74mg·L-1) under different combinedconditions, and the maximum biomass, fat content and fat yield of N. oceanic are0.66g·L-1,44.35%,232.50mg·L-1. Moreover, the results in this study were apparentlyhigher than those of the microalgae treated with single factor.(3) In the condition of orthogonal optimized for maximum oil production toculture N. limnetica and N. oceanic, to test their tolerance in flue gas environment(low pH, high temperature, high concentrations of CO2). The results showed that N.limnetica can tolerate pH4,35℃,15%CO2, and the tolerance of N. oceanic was pH4,30℃,15%CO2, however, the growth of N.limnetic was not inhibited at35℃and15%CO2conditions, and the lipid yield reached782.67mg·L-1under the conditions of5%CO2. Thus, the tolerance of N.limnetic was better than N. oceanic.(4) Fatty acid composition analysis in GC-MS showed that the degree ofsaturation, chain length and branching of the fatty compounds of this two microalgaewere meet to the standard of biodiesel, however, both the tolerance and lipid yield ofN.limnetic were better than N. oceanic, results obtained in this work can further beapplied to industrial flue gas removal and biodiesel production was N.limnetic.