Dear Aly,

Regards.

I don´t know if is possible to modify the lipid abundance profile in algae using techniques as radiation or electromagnetic fields. Nevertheless, best method ever depends on specific algae species that you are studying. 

Algae is algae, but remember that is an incredible diverse microbial group. Review in published literature the response of your genus to diverse common stimulus, these responses will provide to you an idea to start evaluations or, probably, the answer.

Gustavo G.  

Dear Gustavo,

Thanks so much for this clearance and for your help. Actually, we are dealing with Chlorella sp. 

Aly

Lipid will get produce in stress conditions. The new strategies you are talking about will work if they cause stress to Algal cells. I think electric current or radiation should work.

Stress is actually the best way to improve lipid, may be I will try to find out the best Intensity/Voltage of the electric current and try it.

Thanks Jayant

I agree that stress is the best approach to get algae that are already capable of making lipid to accumulate excess lipid. A lot of Chlorella are able to accumulate lipid but some accumulate starch on stress - so you have to be careful of the Chlorella strain you are using. We used two different strains (Identified as Chlorella vulgaris) and one on stress accumulated more lipid and one more starch. The classical way is nitrogen stress - grow up you algae to maximum density and add no more nitrogen - might take a week for them  to start accumlation but they start making a lot of lipid if they are accumulators. For heterotrophic growth just adding a large amount of sugar will eventually force nitrogen starvation and lipid accumulation (like in Chlorella protothecoides).

Feng P, Deng Z, Fan L, Hu Z. Lipid accumulation and growth characteristics of Chlorella zofingiensis under different nitrate and phosphate concentrations. J Biosci Bioeng 2012; 114(4): 405-10

Espinosa-Gonzalez I, Parashar A, Bressler DC. Heterotrophic growth and lipid accumulation of Chlorella protothecoides in whey permeate, a dairy by-product stream, for biofuel production. Bioresource Technology 2013; 155C: 170-76

Gao C, Wang Y, Shen Y, et al. Oil accumulation mechanisms of the oleaginous microalga Chlorella protothecoides revealed through its genome, transcriptomes, and proteomes. BMC Genomics 2014; 15: 582

May be the following links usful:

https://www.researchgate.net/publication/289527945_Effect_of_light_intensity_on_biofuel_production_fro

https://www.researchgate.net/publication/275965908_Enhancement_of_Biodiesel_Production_from_Local_Isolates_of_Microalgae?ev=prf_pub

https://www.researchgate.net/publication/257341920_SStimulation_of_biodiesel_production_from_two_algae_Chlorella_vulgarisBerjerinckandNitzschiapalea_Kutz_Smithand_study_their_some_growth_parameters_under_different_light_intensitytimulation_of_biodiese

https://www.researchgate.net/publication/275521444_An_attempt_to_Stimulate_lipids_for_Biodiesel_Production_from_locally_Isolated_Microalgae_in_Iraq?ev=prf_pub

https://www.researchgate.net/publication/275965908_Enhancement_of_Biodiesel_Production_from_Local_Isolates_of_Microalgae

.Regard

Article Effect of Light Intensity on Biofuel Production from Green A...

Article Enhancement of Biodiesel Production from Local Isolates of Microalgae

Article Stimulation of biodiesel production from two algae: Chlorell...

Article An attempt to Stimulate lipids for Biodiesel Production from...

I have observed the Euglena blooms during rainy season  in some  lakes and  color of those cells is  green  but during the winter entire lake color changed to pink due accumulation of pigments by Euglena. Like that Chlamydomonas nivalis accumualte red pigment and cells color  turn into red. Azolla also accumulates the anthocyanin pigment and its color also changed . Extreme conditions may favors the   accumulation of  the pigments 

I would like to thanks so much Mr. Allnut, Hassan and Rao for your greatest answer, It is very helpful for my understanding and help for my project work. 

Also, I don't know much on the limit of those techniques because high-stress conditions will lead also to the cell membrane damage and the microalgae could die.