Application of magnesium sulfate and its nanoparticles for enhanced lipid production by mixotrophic cultivation of algae using biodiesel waste

CG (Crude glycerol) is one of the major wastes of biodiesel production process. It can be used as a substrate for lipid production by algae and the produced lipid can be recycled as a feedstock for biodiesel production. In order to avoid substrate inhibition, lipid production media are prepared by diluting the CG with distilled water. However, CG contains only a small amount of Mg (57.41 ± 18 ppm) and its concentration is further decreased to around 0.57 ppm during the dilution process. Apart from having a number of roles in algal physiology, Mg is the central atom of chlorophyll. Therefore, MgSO4 was evaluated as a Mg source to supplement the CG based media used for lipid production by Chlorella vulgaris. By supplementing the process with 1 g/L of MgSO4, nearly 185.29 ± 4.53% improvement in lipid production has been achieved. Further, application of MgSO4 nanoparticles was found to improve the lipid production by 118.23 ± 5.67%. Interestingly, unlike MgSO4, its nanoparticles were found to enhance the lipid production at the expense of only a small amount of glycerol. Thus, application of MgSO4 nanoparticles could be a potential strategy for enhanced lipid yield.