Inquiry into the potential use of ionic liquids instead of inorganic acids in hydrothermal hydrolysis of macroalgae

Macroalgae represent a worldwide spread renewable source of valuable
biopolymers, polysaccharides and proteins that after pretreatment constitute an
intermediate platform for microbial and chemical production. In the present study
the potential of some ionic liquids (ILs) to extract and hydrolyze the algal
carbohydrates derived from Ulva sp. is examined and compared to the conventional
inorganic acid catalysts, H2SO4 and HCl. The experimental results reveal that the IL,
1 -butyl-3-methylimidazolium acetate, is superior to both acid auxiliaries in
extracting carbohydrates. The capacity of this IL for splitting reducing sugars under
the conditions of hydrothermal hydrolysis is comparable with the power of HCl, but
higher than HCl in terms of monosugar fraction and protein released. The highest
yields of reducing and monosugars and of protein are obtained by using the strong
dibasic acid, H2SO4. It could, however, produce dehydration by–products which
would incur inhibition of enzymatic and microbial processes fed by the algal liquor.