Biodiesel production from oleaginous yeasts using livestock wastewater as nutrient source after phosphate struvite recovery

- Livestock wastewater (LW) was suggested for using feedstock for oleaginous yeast.
- Hydrodynamic cavitation (HC) showed the best performance in recovering struvite.
- Pretreated LW was nutritious enough for cultivating oleaginous yeasts.
- The quality of lipid extracted from the yeasts were suited for utilizing biodiesel.

Microbial oils, which can be converted to biodiesel, could be produced by oleaginous yeast. To reduce the overall cost, which is a limitation of heterotrophic cultivation, the livestock wastewater (LW) was examined as a feedstock. It was found that the LW needed pretreatment, and hydrodynamic cavitation (HC) was effective, surpassing sonication and shaking. The nature of HC made it possible to disintegrate cells and release nutrients like phosphorus; it also rendered ammonia stripping and struvite formation, when MgO was added. The pretreated LW with the HC supported the growth of the two yeasts: C. pseudolambica had 3.6 h of doubling time, 2.19 g/L of DCW, and 35.3% lipid per dry mass; and I. occidentalis had 2.9 h of doubling time with 6.54 g/L of final DCW, and 28.9% lipid per dry mass. All this showed the LW could turn into a valuable resource, as long as a suitable pretreatment.