Effects Of NaOH-Catalyzed Organosolv Pretreatment And Surfactant On The Enzymatic Hydrolysis Of Sugarcane Bagasse

Energy shortage,environmental pollution,global warming and other issues have become great challenges for all countries in the world today.This series of problems are largely caused by excessive reliance on non-renewable energy sources such as coal and oil.Therefore,it is necessary for all countries in the world to find a new energy source that can replace fossil energy.Biomass energy is favored because of its renewability,low pollution,wide distribution and easy degradation.Sugarcane bagasse,composed of cellulose,hemicellulose and lignin,is the main by-product of sugar industry.Its low content of ash,concentrated source,high yield,stability,uniform properties make it to be a high-quality agricultural and forestry biomass.The cellulose and hemicellulose in sugarcane bagasse can be converted into sugar-based chemicals by biochemical methods and then into bioethanol or hydrocarbon fuel.However,the intact structure formed by cellulose,hemicellulose and lignin in raw material impedes the attack of cellulase,leading to the the low efficiency of enzymolysis.Therefore,it is necessary to carry out appropriate pretreatment to alter their structure and characteristics to improve enzymolysis efficiency.In this study,sugarcane bagasse was used as raw material to investigate the effects of several different alkali-catalyzed organic solvent pretreatment on the degradation of hemicellulose and lignin and their subsequent enzymolysis.Furtheremore,the effect of Tween 80 on the enzymolysis efficiency was also detected.Meanwhile,X-ray diffraction,scanning electron microscopy and thermogravimetric analysis of native and pretreated samples were carried out to explore the effects of different pretreatment methods on the content,composition and structure of cellulose,hemicellulose and lignin in sugarcane bagasse.When sugarcane bagasse was pretreated with 5%NaOH-enhanced ethanol at 180℃for 30 min,about 91.6%of glucose could be obtained after hydrolysis for 72 h.With the addittion of Tween 80,the glucose yield reached 93.0%after 24 h,representing 94.6%of glucose in the pretreated residue.With the addition of Tween 80,when the dosage of cellulase is reduced by half and the enzymolysis time is shortened to 24 h,similiar glucose yield could also be obtained,suggesting that Tween 80 could not only save 2/3 of the hydrolysis time,but also save the dosage of cellulase and further reduce the cost.When sugarcane bagasse was pretreated with different concentrations of NaOH-enhanced ethanol and two-step,hemicellulose and lignin were removed to expose more cellulose,thus improving the accessibility of enzymes to cellulose.The higher the NaOH loading in organic solvent pretreatment,the more glucose was liberated.Meanwhile,during two-step pretreatment,the synergistic enzymolysis performance of NaOH and ethanol is better than that of NaOH pretreatment and ethanol pretreatment alone.For the sample pretreated with NaOH-enhanced ethanol pretreatment,the glucose yield reached95.1%after hydrolysis for 24 h with Tween 80,which was similar to the glucose yield after enzymolysis for 72 h without adding Tween 80,indicating that adding Tween 80 could save2/3 of the enzymolysis time.When the enzymolysis time wasextended from 6 h to 24 h,the increased glucose yield by adding Tween 80 showed a downward trend.When sugarcane bagasse was pretreated with liquid hot water/sulfuric acid and ethanol/sodium hydroxide under mild conditions,the glucose yield of the sample pretreated with NaOH-enhanced ethanol was 41%and 205%higher than that of the sample pretreated with NaOH and ethanol alone.When dilute H₂SO₄pretreatment was used in the first stage,the NaOH-enhanced ethanol pretreatment was used in the second stage,the highest yield of glucose with Tween 80 was 76%,accounting for 84.5%of the glucose in the pretreated substrate.With the addition of Tween 80,when the enzyme dosage is reduced by half or the enzymatic hydrolysis time is shortened to 24 h,the glucose yield was similiar with that obtained after 72 h without Tween 80.