After 48 h of pretreatment, solubilisation (being standardised as the increase of SCOD/TCOD relative to control experiments) increased from 7.9% to 15.6%. The result indicates that some soluble intracellular components were released into the liquor and some large molecules or cell structures such as flagella were severely disrupted to small molecules, smaller than the pore size of filter membrane (0.22 lm). The extent of solubilisation is somewhat higher than that reported by Sheng et al. (2011), who applied pulsed-electric-field pretreatment to cyanobacteria, indicating that FNA pretreatment is a relatively severe pretreatment technology.