Breaking open hard nuts. Cell wall disruption, nutrient release and stabilization of Phaeodactylum tricornutum biomass

Phaeodactylum triconrutum (P. tricornutum) biomass has been called a microalgal cell factory, having the potential to contribute multiple nutrients and functional compounds to the blue-green economy in the future. To succeed, efficient production methods must be established, including cell wall disruption, biorefinery and stabilisation technologies. In our recent studies, cell wall disruption up to 93% was achieved in P. tricornutum biomass processed by bead milling using larger (0.75-2.0 mm) glass beads. Lower disruption degree levels were achieved using smaller glass (0.25-0.4mm) or Zr (0.3mm) beads, (75% vs 88%, respectively). Increased disruption degree gave a maximum of 25% increase in the analysed EPA levels, a moderate and not statistically significant increase in the analysed total lipid extract using glass, and decreased lipid extract levels using Zr beads. Soluble protein release increased using the more efficient larger beads and was not significantly affected by processing with smaller beads. Total and specific phenolic compound release and total antioxidant capacity of the P. tricornutum biomass increased by more efficient cell wall disruption, accompanied however by increased losses of natural antioxidant compounds such as vitamin C in a storage trial. Accompanying microorganisms were eliminated up to nearly 100% by bead milling, however following different disruption patterns as compared to microalgal cells. Bead milling and cell wall disruption significantly affected the rheological properties, namely the viscosity of processed P. tricornutum biomass, which was highest in the biomass of the highest disruption degree compared to non-disrupted biomass of higher dry matter level.