The defatted algal biomass (100 g) was added to 100 mL of 97%
H2SO4 in a fume cupboard. The resultant mixture was kept for 24 h
at room temperature, and was subsequently refluxed in the fume
hood for 4 h. The mixture was allowed to cool to room temperature.
The acid layer was removed, and the biomass thus treated
was washed several times with deionized water. The resultant
treated biomass was further soaked in 2% NaHCO3 solution to
remove any remaining acid and the pH was adjusted to 7. The
biomass was dried in an oven at 150 C for 46 h under nitrogen
flow