Nutrient Source For Cultivation Research Articles

Anaerobic digestion of lipid-extracted microalgae: Enhancing nutrient recovery towards a closed loop recycling

Nutrient recycling is essential to make microalgae cultivation sustainable at industrial scale. To this aim, lab-scale anaerobic digestion experiments of Chlorella vulgaris after lipid extraction were carried out to evaluate biogas yield and nutrients recovery in the liquid digestate. Then, this liquid fraction was used as source of nutrients for cultivation of a closely related C. vulgaris species, in order to assess the possibility of re-cultivating microalgae towards a closed-loop nutrient recycling process. The biological methane potential tests resulted in biogas production of about 347NmLgVS−1 with 43% v/v methane content. In re-growth experiments, the liquid digestate showed an insufficient amount of soluble sulfate and phosphorus. However, by amending these two nutrients, the specific growth rate and final biomass concentration increased to about 2 d−1 and 2gL−1, respectively, which were comparable to those obtained in a defined control medium. The low content of soluble phosphorus in liquid digestate was mainly due to precipitation and removal with the solid phase. Several techniques were hence tested to enhance phosphorus solubilisation, and highest recoveries of up to 41% were obtained when using NaHCO3. Finally, C. vulgaris was grown in such treated digestate, obtaining a final biomass production comparable to that of the control, without the need of external phosphorus supply.

BIOMASS PRODUCTION AND TREATMENT OF KITCHEN WASTE WATER WITH NOSTOC MUSCORUM-A POTENTIAL BIOFERTILIZER

Kitchen waste water emerging from Tirumala hills, a world famous piligrim centre was used as a source of nutrients for cultivation of Nostoc muscorum. A complete randomized design (CRD) was created for the experiment which was performed on BG-11 medium, 100% kitchen waste water (100% KW) and 75% kitchen waste water (75% KW). The physicochemical properties of kitchen waste water and the yield of biomass were determined from the cultures harvested every three days for a period of 15 days. After cultivation the kitchen waste water met the standards of safe discharge in India. The organisms could able to remove maximum of 98% of contaminants during its growth in waste water. The highest production of biomass was achieved in BG-11 medium followed by 100% KW and 75% KW.