Saccharides Separation from Phaeodactylum Tricornutum Through Low-Frequency Ultrasound (LF-USN) and Ultrafiltration (UF) Technology

In this study, low-frequency ultrasound (LF-USN, 24 kHz) was firstly used to recover biomolecules from Phaeodactylum tricornutum (P. tricornutum), and then ultrafiltration (UF) technology was used to separate the saccharides. The results showed that LF-USN greatly increased the yield of bioactive compounds (p < 0.05). Scanning electron microscopy (SEM) results showed that USN disrupted P. tricornutum cellular structures during extraction, as confirmed by particle size distribution tests. Different molecular weight cut-offs (MWCOs) membranes (4, 10, 50, 100, 150, 300, 500 kDa) were used to separate saccharides. The permeate flux decreased with the UF process, and the membrane fouling index (MFI) was related to MWCOs. The conductivity and bioactive compounds concentration of the permeate increased with the UF process. Most of the protein and polyphenols and almost all pigments were retained during USN-UF process, promoting the saccharides concentration of permeate. The saccharides purity was affected by membrane MWCOs in USN-UF process, with a saccharides purity of ~78% by 4~150 kDa membrane and ~70% by 300~500 kDa membrane.