杨木废弃物湿氧化预处理提高酶解效率的工艺研究

Pretreatment of Poplar Wood Residues Using Wet Oxidation to Enhance Enzymatic Digestibility

对杨木废弃物制生物燃料的湿氧化预处理条件进行优化实验。研究表明,湿氧化预处理杨木废弃物的最佳工艺为:初始p H值10,温度195℃,最佳保温时间15 min,氧压1.2 MPa。所得物料得率为51.7%。酶解优化工艺条件为:酶解温度49℃,酶解时间56 h,酶用量38 FPU/g。其他条件为:p H值4.8,固液比1∶50,酶解纤维素转化率为96.4%。湿氧化预处理过程使原料中的半纤维素含量由18.7%降到1.43%,Klasson木素含量由23.6%降到13.5%;木素溶出率为43%,半纤维素溶出率为92%。X射线衍射分析显示原料的结晶度从57.4%降到了54.8%;扫描电镜显示湿氧化预处理后纤维的细纤维化程度增强;高效液相色谱显示预处理分离液中木糖含量较高,并含有单糖降解产物如乙酸、甲酸和糠醛等单糖降解产物。湿氧化预处理可以较大幅度地降解或脱除原料中的木素和半纤维素,改变原料的结晶结构,增加了可酶解性,提高了物料中纤维素转化率。

Nowadays production of renewable fuels,especially boil-oil or bio-ethanol,is the main way for efficient utilization of lingo cellulosic biomass in the world. This paper carried out the study to optimize wet oxidation pretreatment conditions for utilizing poplar residues from the preparation sector of paper mill,to produce bioethanol. The research results showed that the optimal conditions of wet oxidation pretreatment for poplar residues were as follows： initial pH value 10,temperature 195℃,time at 195℃ 15 min,oxygen pressure 1. 2 MPa. The yield of the obtained material of wet oxidation pretreatment was 51. 7%. The optimal enzymatic hydrolysis conditions were： temperature 49℃,time56 h,enzyme charges 38 FPU / g at the pH of 4. 8 and the ratio of substance to liquor was 1∶ 50. The cellulose conversion rate was 96. 4% on the pretreated substance. After wet oxidation pretreatment,hemicelluloses content of the substance decreased from 18. 7% to 1. 43%,Klasson lignin content decreased from 23. 6% % to 13. 5%,which mean that almost 43% of lignin and 92% hemicelluloses were degraded and solved from the raw material. XRD analysis indicated that the crystallinity decreased from 57. 4% to 54. 8%. The obvious fibrilization of the pretreated fiber was found by SEM. HPLC analysis results showed that pretreatment liquid contained higher content of xylose,and monosaccharide degradation products,such as acetic acid,formic acid and furfural. Wet oxidation pretreatment was able to greatly degrade or remove lignin and hemicellulose significantly,reduce the crystallinity ofthe lingo cellulosic material, which could improve enzymatic degradability and increase reduce sugar yield and cellulose conversion rate.