Effects Of Residual Ionic Liquid From Lignocellulose Pretreatment Process On The Biodiesel Downstream Biotransformation

Lignocellulosic biomass for its plentiful and renewable has recently received more attention as a potential feedstock to provide fermentable sugars which can be converted into biofuels by microorganisms.However,lignocellulose is a highly ordered and rigid polymer and the crystalline structure embarrass biodegradation by celluloytic enzymes.Therefore,lignocellulose typically needs a thermo-chemical treatment before hydrolysis to increase the entryway of cellulolytic enzymes.Traditional pretreatment methods seldom can achieve the pretreatment effect,but also take into account the cost and environmental security.Recently,ionic liquids(ILs),have been applied in pretreatment of lignocellulosic materials and good results have been achieved.Many rqports are committed to looking for ILs with good biocompatibility to achieve in situ saccharification and fermentation.However,this is bound to increase the reaction system for dilution,the difficulty of IL recovery and the cost.Therefore after pretreatment,low-cost recycling of ionic liquids is the key issues that should be resolved before the industrialization of the ionic liquid.Compared with water,low boiling point of ethanol and acetone used as the precipitant and the detergent can significantly reduce the cost of ILs recovery,but will lead to about 30 mM-60 mM residues.But the effects of residual ILs on the downstream biotransformation remain largely unknown.In this study,three representative ionic liquids,[Emim]Cl,[Emim][OAc]and[Emim][DEP],were chosen to examine their effects on cellulase activity and lipid production by the oleaginous yeast Rhodosporidium toruloides AS 2.1389.We found that they had some inhibition on enzymatic saccharification of a-cellulose but showed no significantly inhibition on the growth of R.toruloides in the nutrient-rich medium at the given concentrations.[Emim]C1 and[Emim][DEP]did not gave serious inhibition on R.toruloides lipid production and the distribution of fatty acids either.However,[Emim][OAc]gave a sharp reduction of lipid yield,lipid content,lipid coefficient and the distribution of fatty acids on R.toruloides.Further studies showed that the inhibition of[Emim][OAc]was mainly due to[OAc]"hydrolyzed to acetic acid whose assimilated resulted in the medium pH increased to 8.0 in a short time.This paper provided the basis for ionic liquids application in the lignocellulose pretreatment and its low cost recovery.