Silver nanofiber assisted lipid extraction from biomass of a Louisiana Chlorella vulgaris/Leptolyngbya sp. co-culture

• Silver nanofibers (AgNF) enhance the lipid extraction from microalgal biomass.
• 1000 μg g−1 of silver nanofibers increased up to 136% the microwave lipid extraction.
• The fatty acid profile of the extracted lipids meets ASTM D 6751 biodiesel standard.
• Microwave heating at 70 °C for 5 min and 1000 μg g−1 AgNF extracted the most lipids.

The presence of bulk water and the resistant cell walls significantly limit the efficiency of lipid extraction from microalgal biomass paste. Current methods to rupture the cell walls (i.e. grinding after freeze-drying, osmotic shock, sonication) are energy intensive and time consuming. Due to their high surface energy concentration and high surface to volume ratio, silver nanoparticles can enhanced the cell wall rupture to increase the extraction efficiency of cell components. In this study, silver nanofibers were added as enhancers for the Folch’s extraction method and microwave assisted extraction of lipids from wet biomass paste (water content of 80.9%). Nanofibers concentrations of 0–1000 μg g−1 were tested. Two solvent:biomass ratios were tested in the Folch’s extraction method. Two temperatures (70 and 90 °C) and three treatment times (2, 5 and 10 min) were compared in the microwave assisted extraction. The results showed that the extraction efficiency increased with increased concentration of the nanofibers in the range tested. At concentrations of 1000 μg g−1 silver nanofibers (w/w based on the solvent and biomass solution) the efficiency of lipid extraction increased by ∼30% and 50% for the Folch’s and microwave assisted lipid extraction respectively. Treatment with AgNO3 in the same concentration as the nanofibers did not improve the extraction compared with no silver or nanofibers addition. The extraction method affected the lipid fatty acids profile. The Folch’s extraction with no silver nanofibers resulted in proportionally higher short chain saturated fatty acids, but lower lipid extraction. The microwave assisted lipid extraction provides the best results considering fatty acid profile, treatment time, solvent use and lipid extraction efficiency.