Oil Microalgae’s Response To Environmental Factors And Fed-batch Culture

Microalgae were regareded as alternative energy resources and a promising feedstock for biodiesel production. This study aimed to increase microalgae lipid accumulation through optimizing a variety of environmental factors and using different cultivation modes. Moreover, the removal efficiency of heavy metals by microalgae was also studied so as to use wastewater as medium to reduce the microalgae biodiesel production cost.The optimized environmental factors for lipid production were:a carbon content accounting for a quarter of of OM medium,43.69g L-1of NaCl,0.11mmol L-1of Fe3+, pH6,20℃,12h:12h of light and dark cycle and nitrogen starvation for3days. The biomass yield was102.33times higher than the initial yield and the lipid content was22.84%. Chlorella minutissima UTEX2341growth entered the logarithmic phase on the1st day, and the highest biomass yield of3.07g L-1d-1was achieved on the2nd day. Under the condition of environmental stress, the content of C16-C18in total fatty acid was96%-97%, indicating that Chlorella minutissima UTEX2341could meet the requirements of biodiesel production.The highest adsorption rate of Chlorella minutissima UTEX2341fresh cells of different concentrations of Cd2+,Cu2+,Mn2+and Zn2+in artificially simulated wasterwater were98.12%,100%,80.15%and85.07%respectively and the lipid contents were slightly higher than those in control. The adsorption rate of dry cells of Cd2+, Cu2+, Mn2+and Zn2+were93.7%,93.1%,95.17%and100%. The adsorption process of Cd2+, Cu2+and Mn2+conformed to the Langmuir model and Freundlich model. Also, the ratio ofadsorpted Cd2+amount by cell wall and protoplast was about1:2.2, indicating that Chlorella minutissima UTEX2341’s aborsoprtion of heavy metal was mainly intracellular adsorption.This study laid foundation for heavy metal wastewater treatment, at the same time, greatly reduce the microalgae biodiesel production cost.In7L fermentation tank, the highest biomass yield, lipid content and lipid yield of batch culture were7.32g L-1,19%, and0.97g L-1respectively. In the fed-batch culture, the highest biomass yield and lipid yield were17.01g L-1and2.55g L-1, respectively2.32times and2.63times as much as in batch cultivation. It laid foundation for further high-density cultivation of Chlorella minutissima UTEX2341.