Research Of The Cultivation And Lipid Accumulation Of A Marine Microalgae Chlorella Sp. LPF

Microalgae biodiesel is an important biofuel of the third-generation energy.Considerable studies have been devoted to improve the lipid production from algal cells.Bicarbonate is an inorganic carbon source;its application not only promotes the microalgal growth,but also is suitable for the development of outdoor cultivation.In this study,we used bicarbonate as an external carbon source to cultivate microalgae for the production of microalgae lipid.At the same time,we evaluated the tolerances of microalgae strain to high salinity and high concentrations of bicarbonate,and investigated the effect of high salinity and high concentrations of bicarbonate on limiting bacterial growth in the outdoor cultivation.Besides,a microalgal cultivation method that coupling with bicarbonate and diluent urine was designed to expolore the possibility of low-cost outdoor cultivation of microalgae.The main contents and results of this study are as follows:1.A microalgae strain LPF was isolated and purified from the purchased Nannochloropsis sp.GY-H14.The results of 18S r DNA identification and phylogenetic analysis suggested that this microalgae strain is closely related to the genus Chlorella.Chlorella sp.LPF is a marine microalgae strain,which has a good growth in the f/2 medium.After the optimization,the best growth condition for Chlorella sp.LPF was as follows:temperature at 25~°C,salinity at 20‰,and the pH at 8.0.2.Addition of bicarbonate extremely enhanced microalgal lipid accumulation.Under the concentration of 100mM bicarbonate and 1mM nitrogen source,microalgal cells that used ammonium,nitrate or urea as nitrogen source had maximum lipid contents,which were55.0%,41.9%and 42.1%,respectively,at this point,maximum lipid productions reached to284,249 and 270 mg/L,respectively;Fatty acid composition analysis indicated that Chlorella sp.LPF produced very different fatty acid compositions when using different nitrogen sources;Time-course studies of biomass contents(include starch,protein,lipid,chlorophyll),lipid observation,and genes expression of functional enzymes(include carbon fixation,nitrogen assimilation and lipid synthesis)in response to bicarbonate proved the effect of bicarbonate on improving microalgal lipid production.3.Chlorella sp.LPF was able to tolerate 40‰of salinity and 900mM NaHCO3.When the microalgae was cultivated in the Pearl River water,tap water,or natural lake under the salinity of 40‰and 900mM NaHCO3,the cultivation were able to carried out without bacteria contamination.4.The utilization of urine as culture medium significantly promoted the production of microalgal biomass,but can not effectively promote the accumulation of lipid.The addition of bicarbonate further improved the microalgal growth and lipid accumulation.In both cases,the lipid production of algal cells was low.