Experimental and theoretical investigation of the effects of iron on growth and lipid synthesis of microalgae in view of their use to produce biofuels

The effects of iron concentration on the growth and lipid synthesis of three microalgae strains were investigated to assess their potential to produce biofuels and/or other chemicals. The obtained results have shown that, except for Monodus subterraneus, augmentation of iron concentration led to a biomass productivity increase. However, such effect could be observed only when iron concentration overcame a specific threshold that depended on the specific strain. The augmentation of iron concentration from 0 to 100 mg L-1 determined the increase of lipid content of Chlorella vulgaris from 9% to 13%wt. Reductions from 27% to 22%wt and from 13% to 11%wt of lipid content were correspondingly observed Pseudochloris wilhelmii and Monodus subterraneus respectively. The effect of iron increase on lipid productivity was monotonic only for Chlorella vulgaris. For the other strains, specific ranges of iron concentration existed wherein lipid productivity was minimized or maximized. Moreover, it was observed that by modulating iron concentration different compositions of fatty acid methyl esters (FAMEs) of C. vulgaris could be obtained. An increase of the saturation degree of FAMEs could be obtained as a result of the increase of iron. A novel mathematical model that improves the only one available so far in the literature about the effect of iron on lipid synthesis is also proposed. Model results were successfully compared with experimental data thus somehow corroborating the assumptions underlying its formulation, i.e. that iron affects the intracellular storage of excess carbon, the response to oxidizing environment and the lipid peroxidation.

Automated summary

Increasing iron concentration can enhance biomass productivity of microalgae, but the specific threshold and effect varies among different strains. Different microalgae strains exhibit distinct responses in lipid synthesis to changes in iron concentration, leading to variations in fatty acid methyl esters (FAMEs) composition.