Enhancement of Biological Pretreatment on Rice Straw by an Ionic Liquid or Surfactant

Fungal delignification can be a feasible process to pretreat biomass for bioethanol production if its performance is improved in terms of efficiency through a few modifications. The aim of this study was to enhance the biodelignification pretreatment of rice straw using laccase in the presence of ionic liquid (1-Allyl-3-methylimidazolium chloride, [AMIM]Cl) or surfactant (TritonX-100). Addition of 750 mg/L [AMIM]Cl and 500 mg/L TritonX-100 increases the lignin removal to 18.49% and 31.79%, which is higher than that of laccase only (11.97%). The enzymatic saccharification process was carried out based on different strategies. The highest cellulose conversion, 40.96%, 38.24%, and 37.91%, was obtained after 72 h of enzymatic saccharification when the substrate was washed with distilled water after pretreatment of rice straw with laccase + TritonX-100, laccase + [AMIM]Cl, and laccase only, respectively. In addition, the morphology and structure changes of pretreated and untreated rice straw were studied. Both surface area and cellulose crystallinity are substantially altered after laccase + [AMIM]Cl and laccase + TritonX-100 pretreatment. Enhanced saccharification efficiency of rice straw was achieved by laccase pretreatment with ionic liquid or surfactant in a single system.