CrCl_(3)预处理和表面活性剂对杨木酶解效率的影响

Effects of CrCl_(3) pretreatment and surfactant on improving enzymatic hydrolysis of poplar

为了探究预处理和表面活性剂对纤维素酶水解效率的影响,该研究以杨木为研究对象,探究了温度对CrCl_(3)预处理的影响,同时从表面活性剂种类、用量和酶添加量3个方面分析表面活性剂对CrCl_(3)预处理后样品酶解的促进作用。结果表明:CrCl_(3)预处理对杨木组分分离有良好的促进效果,经160℃预处理后葡萄糖得率达到65.9%。通过结构表征发现预处理后杨木结构完整度降低,提高了纤维素的可接触面,进而提高了酶解效率。在酶解段加入木质素磺酸钙可显著缩短酶解时间,提高酶解效率,同时有效降低纤维素酶用量,最终酶解72h后葡萄糖得率达85.5%,当酶用量为5 FPU/g时,葡萄糖得率(68%)已经达到其在不添加时的葡萄糖得率,该研究为提升木质纤维原料预处理效率和降低酶解成本提供了一定的理论支持。

Biomass energy has the advantages of recyclability and environmental friendliness.Poplar grows rapidly and has a relatively high cellulose content,making it an excellent raw material for the production of biomass energy.However,the cellulose,hemicellulose and lignin of poplar are intertwined to form a dense structure,making it difficult to be hydrolyzed in normal cases.In this work,poplar was pretreated by CrCl_(3)as catalyst,the effect of different temperatures was compared,and the optimal pretreatment temperature was determined.Results showed that under the conditions of 0.05 mol/L CrCl_(3),solidliquid ratio of 1/10,pretreatment time of 20min,stirring speed of 300 r/min and pretreatment temperature of 160°C,the components of poplar were effectively separated after pretreatment with CrCl_(3),while 10.4%lignin and 90.0%hemicellulose removal,and cellulose content increased by 35.6%,hemicellulose and lignin content decreased by 85.5%and 29.9%,respectively.The yield of glucose increased by 568.1%after 72h.In addition,the structure and physical properties of the raw and pretreated poplar were characterized by scanning electron microscope(SEM)、diffraction of X-rays(XRD)and Fourier transform infrared spectrometer(FT-IR).Experimental results indicated that the structure of poplar became loose after CrCl_(3)pretreatment,improving the contact surface of cellulose.The crystallinity(CrI)of poplar raw material was 63.84%,then increased to 71.07%after CrCl_(3)pretreatment,which was due to the removal of amorphous hemicellulose during pretreatment.In the FT-IR test,the characteristic absorption peak of acetyl groups in hemicellulose was significantly weakened after CrCl_(3)pretreatment compared with the raw material,a strong benzene ring characteristic absorption peak was retained at 1510 cm−1,and the characteristic peak ofβ-glycosidic bonds still appeared around 898 cm−1.It is further demonstrated that CrCl_(3)pretreatment removed most of hemicellulose and retained the majority of cellulose,which promoted the subsequent enzymatic hydrolysis process,but had less effect on lignin.The enzymatic hydrolysis of pretreated poplar was conducted under the conditions of pH value is 4.8,enzymatic hydrolysis temperature of 50°C,shaker speed of 150 r/min,enzyme addition of 20 FPU/g substrate,surfactant dosage of 150mg/g substrate,exploring the promotion effect of surfactant type,dosage and enzyme addition on enzymatic hydrolysis.It was found that the glucose yield of 69.7%was obtained after 24 h with calcium lignosulfonate,which was higher than that after 72 h without additive.Further extending the hydrolysis time to 72 h,the glucose yield reached 85.5%.When the cellulase loading was 5 FPU/g substrate,the glucose yield with calcium lignosulfonate(68.0%)was constant with that when the enzyme dosage was 20 FPU/g substrate without additive.That the addition of calcium lignosulfonate could reduce the hydrolysis time,decrease the dosage of cellulase,and enhance the efficiency of enzymatic hydrolysis.Consequently,the CrCl_(3)pretreatment effectively removed the lignin and hemicellulose,while remained cellulose to promote hydrolysis efficiency.Furthermore,the addition of calcium lignosulfonate as a surfactant in the enzymatic hydrolysis also improve hydrolysis efficiency.This study provides some theoretical support for the improvement of pretreatment and the reduction of enzymatic hydrolysis cost.