Desmodesmus sp. from biowaste to produce electrospinning membranes: Effect of ultrasounds and ozone pre-treatments

Abstract

Desmodesmus sp. microalgae previously employed in wastewater management was reused as a raw material for producing green nanofibrous membranes through electrospinning. The reduction of biowastes as well as the replacement of common non-degradable plastics would benefit the process sustainability. In this work, different amounts of microalgae (1.25%, 2.5% and 5% wt) were dispersed in an acetic acid/water solution (80/20) and then electrospun at 0.3 mL/h, 25 kV. The presence of acetate cellulose (17%) was required to obtain nanofibres since the microalgae solutions were not sufficiently viscous for electrospinning processing. For the first time, the effect of ultrasound (50 and 125 kWh/kg), and ozone (9 mg/kg) on microalgae before the electrospinning process was evaluated. Ultrasound prompted cell rupture, which allowed both a greater release and higher exposure of the protein, which eventually enabled the formation of nanofibers from the microalgae waste. However, when the intensity of ultrasounds increased from 50 to 125 kWh/kg, a higher presence of aggregates and defects in the fibres could be observed, probably due to protein aggregation. Thus, nanofibrous mats with c.a. 50 nm fibre diameter were obtained when ultrasound pre-treatment at 50 kWh/kg was applied. Protein unfolding was also inferred from the rheological measurements, as higher viscosity values were obtained (∼ 4.1 Vs. 2.5 Pa·s for 50 and 125 kWh/kg ultrasounds, respectively). The present work highlights the potential that Desmodesmus sp. microalgae have in the production of green electrospun mats, still quite unexplored. These bio-based mats possess great potential in different applications that can range from filtering to scaffolds.