Lipid Induction And Production Mechanism In Microalgae

Microalgal oil is regarded as third generation biofuels source.The research on the mechanism of metabolism regulation of lipid in microalgae can provide a theoretical basis for using biological methods to cultivate algae with high oil content and high growth rate.This is also a fundamental step to solve the problems which restrict the industrialization of microalgae biodiesel.Selecting Botrycoccus braunii,Platymanas subcordiformis and Chlamydomonas reinhardtii as research object,this research explored the regularity of lipid accumulation in microalgae under normal culture conditions.ROS inhibitors were applied to microalgae under nitrogen deficiency condition,and the lipid content and oxidative stress in microalgae cells were determined.Finally,different ROS inducers were applied and biomass and intracellular lipid content were determined.Based on the results,the function of ROS in the process of oil accumulation was discussed,and then to explore the mechanism of microalgae lipid synthesis.The quantitative determination methods of three kinds of microalgae were optimized,and the growth characteristics of three microalgae were explored.It was found that Botrycoccus braunii had high lipid content and low growth rate and longer reaction time for the external stimulus,the observation time should be extend in the stress experiment.The aerated culture unit could shorten the growth cycle of Platymanas subcordiformis and increase its lipid content.Chlamydomonas reinhardtii is a model creature that has been fully sequenced.It had short growth cycle and the physiological changes under the external stimulus could be observed within 24 h.The experimental cycle could be greatly shortened by using this algae.Under nitrogen deficiency stress,the lipid content increased in Chlamydomonas reinhardtii and Botrycoccus braunii,meanwhile the content of ROS and MDA in the cells also increased.After adding ROS inhibitors to nitrogen deficiency medium,the increasing range of ROS and MDA content had decreased.This indicated that ROS may be a mediator for lipid accumulation process in Chlamydomonas reinhardtii and Botrycoccus braunii.Through the experiment of adding ROS inducer,it was found that 1 mmol/L H₂O₂ did not inhibit the growth of Chlamydomonas reinhardtii and could increase its lipid content,which was a suitable condition to induce the increasing of lipid content in Chlamydomonas reinhardtii.Adding sodium copper chlorophyllin and sodium ascorbate at the same time can induce the lipid production of Chlamydomonas reinhardtii and shorten the lipid production time.The results suggest that ROS may be involved in the process of lipid production in microalgae.However,it is not necessary that all types of ROS can effectively promote the lipid content of Chlamydomonas reinhardtii,which may be closely related to the type of ROS and the induction conditions.These results provide a theoretical basis for further exploring the function of ROS in the process of lipid accumulation and the mechanism of lipid production in microalgae.