Invivo detection of triacylglycerols through Nile red staining and quantification of fatty acids in hyper lipid producer Nannochloropsis sp. cultured under adequate nitrogen and deficient nitrogen condition

The green alga Nannochloropsis sp. was grown in a medium containing adequate (1.5 g/L sodium nitrate) and absence of nitrogen (0 g/L sodium nitrate) for improving the triacylglycerols (TAGs) level and fatty acid content for sustainable biodiesel production. Initially, the biomass yield of Nannochloropsis sp. was determined from the day of inoculation till 18th day and it is observed that on 14th day higher biomass yield at about 1.4 g/L was obtained. The Nile red stained cells from nitrogen sufficient and nitrogen starvation conditions observed under confocal microscopy revealed that neutral lipids exist as oil bodies were higher in nitrogen starved condition and also, the TAG content was 13.31% dryweight in nitrogen starved cells than nitrogen amended (10.46%) Nannochloropsis cells. The extracted lipids subjected for FTIR study showed the presence of TAG functional group in both condition and similarly, the FAME obtained from both condition showed the vibration at 1743 cm-1 for ester functional group. The fatty acid composition of nitrogen deplete condition revealed oleic acid methyl ester (28.7%), Behenic acid methyl ester (14.2%), cis-11, 14, 17-Eicosatrienoic acid methyl ester (8.8%) as predominant fatty acids than nitrogen supplied condition. The TAG content and FAME composition reported in this study makes Nannochloropsis sp. as plausible candidate for pilot scale biodiesel production.

Automated summary

This study investigates the growth and lipid composition of the green alga Nannochloropsis sp. under nitrogen sufficient and nitrogen starvation conditions. It found that nitrogen starvation led to higher biomass yield, increased neutral lipids as oil bodies, and higher triacylglycerols (TAGs) content. Analysis also showed a different fatty acid composition, with oleic acid methyl ester, behenic acid methyl ester, and cis-11, 14, 17-eicosatrienoic acid methyl ester being the predominant fatty acids under nitrogen depletion. These findings suggest that Nannochloropsis sp. is a promising candidate for pilot scale biodiesel production.