液氨预处理对农作物秸秆化学结构及酶解效果的影响

  目的  探索液氨预处理(liquid ammonia treatment，LAT)对生物质原料水解顽抗性和纤维素类生物质酶解效率的影响。  方法  采用LAT法对小麦Triticum aestivum秸秆(以下称麦秸秆)、高粱Sorghum bicolor秸秆、苜蓿Lotus corniculatus草及三者混合物(质量比为1∶1∶1)进行预处理，利用热重分析仪、傅里叶变化红外光谱仪、X-射线衍射仪和扫描电镜等对其预处理前后的化学结构变化进行表征，研究预处理温度和酶解时间对4种原料中葡聚糖和木聚糖的酶解转化率的影响。  结果  LAT预处理对生物质原料的化学结构影响显著。经LAT预处理后，葡聚糖、木聚糖和阿拉伯糖等化学组分的相对含量降低；氧(O)和氢(H)元素的相对含量降低，部分含氢(H)、氧(O)元素的官能团发生脱落；结晶度出现小幅下降，生物质表面孔隙结构增多，酶在生物质化学结构上的可及度增加。麦秸秆和混合物的最佳预处理温度为90 ℃，苜蓿草和高粱秸秆的最佳预处理温度为110 ℃；随酶解时间延长，4种原料中葡聚糖和木聚糖的酶解率都增加；葡聚糖的最大酶解率从大到小为麦秸秆、混合物、高粱秸秆、苜蓿草，木聚糖的最大酶解率从大到小依次为高粱秸秆、麦秸秆、混合物、苜蓿草。  结论  LAT预处理可以提高木质纤维素生物质尤其是麦秸秆和高粱秸秆的酶解效率。图8表2参24

Effects of LAT on chemical structure and enzymatic hydrolysis of crop straw

  Objective  This study aims to investigate the effects of liquid ammonia treatment (LAT) pretreatment on the hydrolysis resistance of biomass and the enzymatic hydrolysis rate of lignocellulosic biomass.  Method  Four different types of lignocelluloses biomass, namely wheat straw (Triticum aestivum), alfalfa (Lotus corniculatus), sorghum straw (Sorghum bicolor), and their mixture (mass ratio 1∶1∶1), were pretreated by LAT method, and the effect of LAT on their chemical structure changes was studied by using thermo gravimetric analysis (TGA), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), and scanning electron microscope (SEM). Then, the effect of pretreatment temperature and enzymatic hydrolysis time on the enzymatic hydrolysis conversion rates of glucan and xylan in the four raw materials was investigated.  Result  LAT had a significant effect on the chemical structure of biomass materials. After this pretreatment, the relative content of glucan, xylan, and arabinan in four types of lignocelluloses biomass slightly decreased. The relative content of O and H decreased because some functional groups containing O and H dropped off. The crystallinity decreased slightly, while the surface pore structure significantly increased, and the availability of enzymes in the chemical structure of biomass increased. The optimum pretreatment temperature of wheat straw and mixture was 90 ℃, while that of alfalfa and sorghum straw was 110 ℃. The enzymatic hydrolysis rates of glucan and xylan increased with the increase of enzymatic hydrolysis time. Among the four types of lignocelluloses biomass, the highest enzymatic hydrolysis rate of glucan obtained at the optimal enzymatic hydrolysis condition was wheat straw, followed by the mixture, sorghum straw, and alfalfa. The enzymatic hydrolysis rate of xylan ranging from large to small was sorghum straw, wheat straw, the mixture, and alfalfa.  Conclusion  LAT can improve the enzymatic hydrolysis efficiency of lignocellulosic biomass, especially that of wheat straw and sorghum straw. Ch, 8 fig. 2 tab. 24 ref.]