Enhanced enzymatic hydrolysis of rice straw via pretreatment with deep eutectic solvents-based microemulsions

In this study, four deep eutectic solvents (DESs) were used as cheaper and “greener” alternatives to ionic liquids (ILs) to create novel microemulsions . Compared with 1-ethyl-3-methyl imidazolium acetate ([Emim]Ac), the DESs of lactic acid:glucose:water and lactic acid:fructose:water (molar ratio = 5:1:3) comprising acid hydrogen-bond donor (p K a = 3.86) showed stronger capability to form the microemulsions with Tween 20 , methanol and cyclohexane . After the pretreatment of rice straw at 70 °C for 12 h by using the microemulsions (mass ratio of DES, Tween 20/methanol, cyclohexane = 0.1:0.8:0.1), 54.3% of lignin was removed, and the crystalline structure was significantly disrupted. When the content of DES (lactic acid:glucose:water) increased to 50%, the sugar yield of the residues was increased to 88.1%, which was 3 times than that of untreated one. Moreover, the enzymatic hydrolysis of the residues is linearly and positively correlated with the delignification abilities of the DES microemulsion.