包埋类脂的吸附剂制备及吸附POPs性能

用丙酮作溶剂将三油酸甘油酯分散到醋酸纤维(CA)基体中,采用悬浮聚合的方法制备出了一种兼具亲水性,又能高倍富集持久性有机污染物的球形复合吸附剂。通过对分散剂的种类及其用量、悬浮介质的种类及其用量的研究,获得了球形复合吸附剂的最佳合成路线与工艺.球形吸附剂粒径为1～2mm。通过荧光分析和电镜扫描分析,表明三油酸甘油酯已被包埋到醋酸纤维基体中,并得到了均匀分散。采用七氯、狄氏剂、异狄氏剂、灭蚁灵为代表性的持久性有机污染物(POPs)。动力学吸附实验表明,当初始浓度为1μg/L时,在快速吸附阶段,溶液中80%的氯、狄氏剂、异狄氏剂可得到有效去除,但并没有达到吸附平衡。快速吸附完后,还在持续地进行慢速吸附。而对于灭蚁灵,吸附速度远远低于其他几种POPs。实验证明了吸附速度不仅与辛醇/水系数有关,而且还与有机污染物的分子结构有关。     

Tween 80和鼠李糖脂对稻草酶解的影响

采用纤维素酶促水解的方法,以稻草为底物,探讨了添加化学表面活性剂Tween 80和生物表面活性剂鼠李糖脂对酶解过程的糖产率、酶稳定性、纤维素转化率的作用以及对酶动力学特征和酶在纤维素上吸附的影响.结果表明,不同浓度的Tween 80和鼠李糖脂对稻草酶解有不同程度的促进,添加0.016%和0.048%Tween 80使糖产率分别提高18.07%和11.98%,而添加0.01%和0.03%鼠李糖脂使糖产率分别增加了23.01%和22.16%,相比较鼠李糖脂的效果更好.表面活性剂能有效增强酶的稳定性,添加高浓度表面活性剂的酶稳定性优于添加低浓度表面活性剂,添加浓度为0.048%的Tween 80得到最高相对CMCA(羧甲基纤维素酶活)108.06%和最高相对FPA(滤纸酶活)80.26%.表面活性剂能提高酶解反应的纤维素转化率,而且添加鼠李糖脂的转化率明显高于Tween 80.表面活性剂不仅能够提高最大反应速度并使米氏常数变大,而且显著地降低了纤维素酶在纤维素上的吸附.     

Combination effect of pH and acetate on enzymatic cellulose hydrolysis

The productivity and efficiency of cellulase are significant in cellulose hydrolysis. With the accumulation of volatile fatty acids (VFAs), the pH value in anaerobic digestion system is reduced. Therefore, this study will find out how the pH and the amount of acetate influence the enzymatic hydrolysis of cellulose. The effects of pH and acetate on cellulase produced from Bacillus coagulans were studied at various pH 5-8, and acetate concentrations (0-60 mmol/L). A batch kinetic model for enzymatic cellulose hydrolysis was constructed from experimental data and performed. The base hypothesis was as follows: the rates of enzymatic cellulose hydrolysis rely on pH and acetate concentration. The results showed that the suitable pH range for cellulase production and cellulose hydrolysis (represents efficiency of cellulase) was 2.6-7.5, and 5.3-8.3, respectively. Moreover, acetate in the culture medium had an effect on cellulase production (K1= 49.50 mmol/L, n=1.7) less than cellulose hydrolysis (K1=37.85 mmol/L, n=2.0). The results indicated that both the pH of suspension and acidogenic products influence the enzymatic hydrolysis of cellulose in an anaerobic environment. To enhance the cellulose hydrolysis rate, the accumulated acetate concentration should be lower than 25 mmol/L, and pH should be maintained at 7.     

巴氏醋酸杆菌发酵处理甲醇废水合成细菌纤维素的研究

介绍了巴氏醋酸杆菌以甲醇为唯一碳源、以酵母膏或蛋白胨为氮源合成细菌纤维素,同时净化甲醇废水的方法,并对合成细菌纤维素的培养条件进行了研究。试验得出巴氏醋酸杆菌的适宜发酵条件为：发酵培养基中甲醇质量分数为3．5％左右,发酵培养基初始pH为5．0～6．0。接种量为5％,发酵培养温度为30℃,振荡器转速为100r／min。     

再生纤维素膜的微生物降解

采用田间掩埋、平皿培养和ＣＯ２释放试验分别测试了再生纤维素膜的生物降解性。试验结果表明：膜的失重随掩埋时间而增加;不同试验菌株对膜有不贩降解活性,其顺序为木霉Ｔ－３１１〉黑曲霉Ａ－３０５〉青霉Ｐ－３０７;掩埋或用菌株Ｔ－３１１接种４２ｄ后,膜的生物降解率可超过７０％;在膜的微生物降解过程中,失重、菌株在膜表面的可见生长和ＣＯ２释放分别是膜不同降解程度的表征,彼此既相关又有区别。     

一株发酵纤维素产丁酸菌及其代谢动力学特性

为开发降解纤维素产丁酸菌的种子资源,从牛粪、猪粪堆肥、玉米地土壤和腐木混合物的富集样品中分离得到一株厌氧降解纤维素产丁酸菌.该菌株细胞呈杆状,长7.1~9.1μm,直径1.2μm左右,经鉴定为丁酸梭菌(Clostridium butyricum),命名为C. Butyricum DCB.在35℃条件下,菌株DCB在纤维二糖液体培养基中的最大比生长速率为0.6536h^-1,世代时间为1.06h,纤维二糖降解速率为0.1g/(L·h),丁酸生成速率为0.06g/(L·h).该菌株利用纤维素发酵产丁酸的转化率高达0.23g/g,具有良好的开发前景.     

Effects of molecular weight and concentration of carboxymethyl cellulose on morphology of hydroxyapatite nanoparticles as prepared with one-step wet chemical method

Nano-sized apatite particles (nAP) synthesized with carboxymethyl cellulose (CMC) have shown great application potentials in in situ heavy metal remediation. However, differences in CMC’s properties effects on the size of nAP produced are not well understood. In this paper, two types of CMC, with respective molecular weights (MW) of ～120000 and ～240000 Dalton or respective polymerization degrees of 500 (CMC-500) and 1050 (CMC-1050), were studied in a concentration range of 0.05%–0.5% (w/w) for nAP synthesis. Morphology of the particles was characterized with transmission electron microscopy (TEM). Results showed that 0.05% CMC-500 solution gave an average particle size of 148.7±134.9 nm, 0.25% CMC-500 solution produced particles of 21.8±20.4 nm, and, 0.5% CMC-500 solution contained particles of 15.8±7.7 nm. In comparison, 0.05% CMC-1050 solution produced nanoparticles of 6.8±3.2 nm, 0.25% CMC-1050 produced smaller nAP of 4.3±3.2 nm, and 0.5% CMC-1050 synthesized the smallest nanoparticles in this study, with an average diameter of 3.0±2.1 nm. Chemical composition of the products was identified with X-ray diffraction (XRD) as pure hydroxyapatite. Interactions between nAP and CMC were discussed with help of attenuated total reflection Fourier transform infrared (ATRFTIR) spectroscopic data. This study showed that CMC at higher concentration as well as higher MW facilitated to produce finer nanoparticles, showing that nAP size could be manipulated by selecting appropriate CMC MW and/or applying appropriate CMC concentration.     

改性纤维素负载零价铁去除三氯甲烷的研究

以接枝改性后的纤维素SCB为载体,采用液相还原法制备改性纤维素负载零价铁吸附剂ZVI-SCB,利用XRD、ESEM进行表征,并研究其对三氯甲烷(TCM)的去除性能.系统探讨了不同材料、ZVI-SCB投加量、TCM的初始质量浓度、pH值和氯离子质量浓度对TCM去除性能的影响.在ZVI-SCB投加量为5g/L,TCM的初始质量浓度为36.7mg/L,pH值为3.1时,TCM的去除率高达84.4%.采用准一级方程和准二级方程对ZVI-SCB去除TCM的过程进行拟合,准二级动力学方程相关系数R的范围为0.996~0.999,证明ZVI-SCB对TCM的去除过程符合二级动力学模型.     

纤维素胺基树脂的制备及脱色性能评价

用氯化亚砜改性微晶纤维素,利用二乙烯三胺对氯化纤维素进行胺基取代制得纤维素胺基树脂。通过正交试验确定纤维素胺基树脂的最佳制备条件;红外分析以及X-衍射可知:氯化纤维素改性取代胺基得到纤维素胺基树脂。纤维素胺基树脂有较好的脱色功能。对甲基橙脱色条件为:吸附时间6 h,吸附温度为30℃,甲基橙初始浓度取为20 mg/L,树脂投加量为0.02 g。     

On Assessing Decomposition Rates of Plant Debris and Standard Cellulose Samples in Tundra Communities

Russian Journal of Ecology -