Blended ionic liquid systems for macroalgae pretreatment

A novel ionic liquid (IL) blend system, consisted of a solvent IL for biomass dissolution and an acidic IL for acid-catalyzed hydrolysis of the released polysaccharides into simple sugars, was developed for the pretreatment of macroalgae Gelidium amansii. Acidic ILs with varying Hammett acidities were screened; among which, 1-n-butyl-3-methylimidazolium hydrogen sulfate was found most suitable as it provided the highest sugar yields with lowest propensity to degrade the produced sugars. On the other hand, 1-n-butyl-3-methylimidazolium chloride was found the most effective solvent IL for G. amansii. A compositional balance between the solvent IL and AIL was found critical to achieve the highest sugar yields. Interestingly, it was notable that the macroalgae was more efficiently dissolved in the selected IL blend than in the most effective pure solvent IL. Pretreatments can be accomplished under atmospheric environment but temperature control and timely reaction termination were both important in order to maximize the sugar yields and minimize the subsequent sugar degradation. Overall, the developed IL blend system proved to be viable for the pretreatment of macroalgae, an abundant renewable resource of fermentable sugars as valuable precursors for biofuel or biochemical production.