作者机构：
[王克勤; 赵彩凤; 邓明; 齐慧; 武小芬; 陈亮] Hunan Institute of Nuclear Agricultural Science and Space Mutation Breeding, Hunan Academy of Agricultural Sciences, Changsha, 410125, China;[雷舒婷; 储奕; 苏小军] College of Food Science and Technology, Hunan Agricultural University, Changsha, 410125, China
通讯机构：
[Su, X.] C;[Wang, K.] H;Hunan Institute of Nuclear Agricultural Science and Space Mutation Breeding, China;College of Food Science and Technology, China
通讯机构：
Hunan Engineering Laboratory for Alcohol Fuels from Biomass, College of Food Science and Technology, Hunan Agricultural University, Changsha, China
摘要：
Radiation pretreatment of lignocellulosics has been widely applied for the breakdown of the stubborn cellulose structure to enable the cellulose to be more accessible to cellulolytic enzymes. However, the effects of gamma irradiation on the lignocellulosics structure changes and the composition of pretreatment degradation products are not well understood. In this study, the influences of irradiation dose on the microstructure and irradiated-degradation components of cellulose under Co-6 gamma-irradiation (0-1200 kGy) was comprehensively investigated using giant reed and Chinese silvergrass as model substrate. The microstructure of biomass was examined with Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Additionally, composition determination and degradation products were analyzed. FT-IR analysis show that irradiation destroyed the glycosidic bond and inter- and intramolecular hydrogen bond of cellulose. XRD and SEM analyses confirm that irradiation could damage the crystalline microstructure and surface morphology of lignocellulosics. Ion chromatography analysis demonstrates that there exist fermentation sugars such as glucose, xylose, arabinose, galactose and cellobiose. Moreover, some potential inhibitors, such as glucuronic acid, galacturonic acid, methanoic acid, acetic acid, furfuraldehyde and p-coumaric acid, were detected in the irradiation-derived degradation products. Irradiation dose exhibited obvious influences on the production of these products. These investigations would be helpful for further understanding the applications and fundamentals of gamma irradiation pretreatment for bioethanol production from lignocellulosics. (c) 2016 Elsevier B.V. All rights reserved.
摘要：
In this study, rapeseed straw was pretreated with Co-60-gamma radiation and digested with cellulase to improve sugar production. The compositions of straw were analyzed. Results showed that there were remarkable changes in total reducing sugar and an increase in the degradation of cellulose, hemicellulose and lignin. At a dose of 1200 kGy, 39.3 times more reducing sugar from the irradiated straw was released, as compared to the control (not irradiated) straw (35.34 vs. 0.90 mg/g). Furthermore, both the total content and the number of species of sugar compounds increased. Enzymatic digestion of the irradiated straw resulted in the degradation of 79.21% and 75.59% of cellulose and hemicellulose, respectively. The total reducing sugar increased by a factor of 4.6 to 392.50 mg/g in the irradiated straw from 86.18 mg/g in the control, with greater total content and more species of sugar compounds. Analyses with X-ray diffraction, infrared spectroscopy, and scanning electron microscopy showed that the microstructure of the irradiated straw was destroyed.
关键词：
Chinese silvergrass;Co-60 gamma-ray irradiation pretreatment;GC-MS;ion chromatography;degradation products
摘要：
After Co-60 gamma-ray irradiation pretreatment of Chinese silvergrass, a variety of products were identified by ion chromatography (IC) and gas chromatography-mass spectrometry (GC-MS). According to IC analysis, the degradation products included arabinose, galactose, glucose, xylose, D-galacturonic acid and D-glucuronic acid. The GC-MS analysis identified 22 carboxylic acids, 19 aromatic compounds and 3 furan compounds. The irradiation degradation mechanism was also discussed.
摘要：
为了解辐照改性马铃薯淀粉的酶解特性, 用α-淀粉酶和糖化酶同时作用于马铃薯原淀粉和经400 kGy剂量辐照处理后淀粉, 考察了pH值、酶解温度、α-淀粉酶用量、糖化酶用量对反应速率的影响。以米氏方程为基础, 用Lineweaver-Burk法求解动力学参数。结果表明, 辐照后马铃薯淀粉的酶解反应速率明显高于马铃薯原淀粉。在单一水解体系中, α-淀粉酶和糖化酶对辐照前后马铃薯淀粉的降解都遵循Michaelis-Menten方程, α-淀粉酶的Km分别为11.343 mg·mL-1和9.386 mg·mL-1, Vmax分别为0.406 mg(mL·min)-1和1.079 mg(mL·min)-1; 糖化酶的Km分别为10.307 mg·mL-1和8.905 mg·mL-1, Vmax分别为0.338 mg(mL·min)-1和0.821 mg(mL·min)-1; 水解产物葡萄糖对反应体系具有竞争性抑制剂的作用, 其抑制常数Ki分别为1.298 mg·mL-1和0.934 mg·mL-1。研究结果表明辐照有效提高了马铃薯淀粉的酶解反应活性。 In order to understand the enzymatic hydrolysis characteristics of irradiated potato starch, potato native starch and potato starch treated with 60Co-γ ray at dosage of 400 kGy were hydrolyzed by α-amylase and glucoamylase. The effects of pH, hydrolysis temperature and enzyme dosage on hydrolysis rate were investigated. Based on the Michaelis-Menten equation, the kinetic parameters were obtained by the Lineweaver-Burk method. The results indicated that hydrolysis rate of irradiated potato starch was obviously higher than that of native starch. Individual enzymatic hydrolysis processes obeyed the Michaelis-Menten model, and the Michaeli constant (Km) of α-amylase were 11.343 mg·mL-1 (native starch) and 9.386 mg·mL-1 (irradiated starch), and maximum reaction velocity (Vmax)of α-amylase were 0.406 mg(mL·min)-1 (native starch) and 1.079 mg(mL·min)-1 (irradiated starch), respectively. The Michaeli constant (Km)of glucoamylase were 10.307 mg·mL-1 (native starch) and 8.905mg·mL-1 (irradiated starch), and maximum reaction velocity (Vmax) of glucoamylase were 0.338 mg(mL·min)-1 (native starch) and 0.821 mg(mL·min)-1 (irradiated starch), respectively. The hydrolysis product glucose was a competitive inhibitor against the enzymes with an inhibitory constant (Ki) of 1.298 mg·mL-1 (native starch) and 0.934 mg·mL-1 (irradiated starch). It indicated that irradiation greatly increased enzymatic hydrolysis activity of potato starch.
