加压毛细管电色谱测定甘蔗中三种多酚类化合物

为建立加压毛细管电色谱(pCEC)分离检测甘蔗中多酚类化合物绿原酸、阿魏酸、表儿茶素的方法,采用C₁₈毛细管色谱柱,以NaH₂PO₄和甲醇为流动相,优化了流动相比例、缓冲盐pH、缓冲盐浓度、分离电压、流速等色谱条件。结果表明,在流动相为15.0 mmol/L NaH₂PO₄+12.5 mmol/L庚烷磺酸钠(pH5.0)/甲醇(50:50,V/V)、分离电压为1 kV、流动相总流速为0.06 mL/min、检测波长为220 nm的色谱条件下,绿原酸、阿魏酸、表儿茶素分离较好,在20~320 μg/mL线性关系良好,相关系数分别为0.9978、0.9922、0.9971,检出限分别为0.14、0.75、1.65 μg/mL,相对标准偏差分别为2.82%、2.69%、1.18%,平均回收率分别为96.79%、100.71%、99.01%。该方法快速、准确、重复性好,适用于甘蔗中多酚类化合物的分离检测。     

固相萃取-超高效液相色谱-三重四极杆质谱法测定甘蔗中3-硝基丙酸

目的建立固相萃取-超高效液相色谱-三重四极杆质谱联用技术(solidphaseextraction-ultra performanceliquidchromatographytandemmassspectrometry,SPE-UPLC-MS/MS)测定甘蔗中3-硝基丙酸(3-nitropropionic acid, 3-NPA)的分析方法。方法甘蔗汁和甘蔗渣经PSA固相萃取提取净化,以1%氨水甲醇溶液洗脱,氮吹吹干定容于0.5%甲酸水溶液中,以Waters HSS T3色谱柱(2.1 mm×50 mm, 1.8μm)在流动相乙腈-水(1:1,V:V)条件下进行分离,电喷雾负离子MRM模式下检测,以基质标准曲线定量。结果甘蔗汁中3-硝基丙酸的线性范围为5～1000μg/kg,检出限(S/N=3)为1.2μg/kg,甘蔗渣中线性范围为10～1000μg/kg,检出限(S/N=3)为2.7μg/kg。甘蔗汁和甘蔗渣3-NPA的加标回收率为96.5%～101.2%,相对标准偏差为1.54%～5.35%。结论该方法简单、灵敏、准确,可用于甘蔗中3-硝基丙酸检测。     

Etherification of Alkali-pretreated Sugarcane Bagasse Cellulose in Tetrahydrofuran

Sugarcane bagasse (SCB) is an important by-product in the sugar industry. It is a source of cellulose fibers or cellulose for paper mills and textiles factories. In this study, SCB was ethyl etherified in tetrahydrofuran (THF) after alkali pretreatment. The alkali concentration for the pre-treatment, the ratio of ethyl bromide (EtBr) to dried SCB in the reaction, reaction time, and temperature were investigated for the etherification of SCB. The ethoxyl content and characterization of the product were determined using headspace gas chromatography (HS-GC), Fourier Transform Infrared (FT-IR) and ¹³C-NMR spectroscopy, respectively. It was found that SCB was well-etherified with EtBr in alkali-THF. Upon ethylation of SCB, the ethoxyl content of the product was high when the alkali concentration and the ratio of EtBr to dried SCB were controlled from 50% to 75% and 4:1 (V/w) to 6:1 (V/w), respectively. The reaction occurred optimally when the temperature was controlled below 110℃; above this temperature, the degree of etherification decreased. The thermal stability of ethylated SCB was higher than that of SCB but slightly lower than that of commercial ethyl cellulose. Ethylated SCB has the potential to form composites with many materials because it is soluble in a wide variety of solvents.     

Agricultural by-products as granular activated carbons for adsorbing dissolved metals and organics

Surplus, low value agricultural by-products can be made into granular activated carbons (GACs) which are used in environmental remediation. This study characterized and evaluated GACs, made from these feedstocks, as effective removers of organics and metals from water. The by-products included soft lignocellulosics such as rice straw, soybean hull, sugarcane bagasse, peanut shell, and harder materials such as pecan and walnut shells. The softer materials were combined with a binder, molasses, to produce briquettes and pellets. The precursors were CO₂- or steam-activated, and subsequent treatments included oxidation to enhance metal adsorption. Many of the GACs had acceptable physical GAC attributes, such as durability, for commercial usage. GACs made from pecan and walnut shells adsorbed higher levels of benzene, toluene, methanol, acetonitrile, acetone, and 1,4-dioxane from an aqueous mixture than commercial GACs. Neither CO₂ nor steam activation was particularly advantageous in enhancing metal adsorption. Oxidation using O₂–N₂ gas increased metal adsorption while (NH₄)S₂O₈ solution did not. In a copper solution, oxidized GACs made from soybean hull had three to four times the Cu(II) adsorption capacity of metal-adsorbing, commercial GACs. Oxidized GACs made from soybean hull, sugarcane bagasse, peanut shell, and rice straw adsorbed from a mixture higher amounts of Pb(II), Cu(II), Ni(II), Cd(II) and Zn(II) than any commercial GACs. Commercial GACs adsorbed only Pb(II), Cu(II) and Cd(II). The GACs made from the agricultural by-products have considerable potential for adsorption of organics and metals of environmental concern. © 1998 SCI.     

蔗渣半纤维素的热裂解特性及动力学研究

利用热重分析(TG)在不同的升温速率和连续通氮的情况下对蔗渣半纤维素的热失重行为进行了研究.结果表明,蔗渣半纤维素的热解分为脱水、热解初期、主要热裂解和炭化四个阶段.其主要失重区间为200℃～315℃左右,并出现一个肩状峰,在700℃时焦炭残留物比例较高,大约在20wt%左右.利用Coats-Redfern积分法对得到的热失重曲线进行了模拟.     

酶解条件对蔗渣还原糖得率的影响及产物分析研究

研究了两种纤维素酶酶制剂(Ⅰ、Ⅱ)对蔗渣还原糖得率的影响.实验发现复酶的还原糖得率高于单酶的得率.在复酶法中,分步的还原糖得率(60%生物量)略高于一步法(59.0%生物量)得率.酶解液分析表明,蔗渣酶解产物主要有木糖、葡萄糖及少量的果糖和纤维二糖;红外分析表明酶解后残渣的纤维素吸收峰明显减弱,电镜观察得固体残渣表面出现孔洞,结构疏松,但基本框架无很大变化.     

蔗汁西瓜皮果酒发酵工艺研究

通过单因素试验初步确定了蔗汁～西瓜皮混合果浆酒精发酵的工艺条件;然后通过正交实验进一步优化了工艺参数,确定了蔗汁一西瓜皮果浆酒精发酵的最佳工艺组合为：PH为5．5,初始糖度为20％,发酵温度为27℃,酵母用量（m／m）为0．50％,发酵时间为48h。     

甘蔗渣的不同预处理方法比较及其酶水解的类分形动力学

分别采用NaOH（0.45 mol/L aq.）、HCl（0.034 mol/L aq.）和高温液态水（LHW）三种方法对甘蔗渣进行预处理,并对其组分变化和酶解效果进行了比较。NaOH预处理方法获得最高的木质素去除率,达91.1%,糖损失率达23.5%;HCl和LHW预处理结果类似,木聚糖溶解率分别为85.2%和79.7%,糖损失率均约为15%,木质素去除率均小于16%。三种方法处理的甘蔗渣经纤维素酶水解后得到总单糖（葡萄糖 + 木糖）浓度分别为38.7 g/L（NaOH）、16.1 g/L（HCl）和15.6 g/L（LHW）。综合比较预处理和酶水解工艺,NaOH水溶液预处理法的糖回收率最高,其次为HCl水溶液预处理法,LHW预处理法的糖回收率最低。作为描述纤维素酶反应动力学的有力工具,类分形理论的研究表明,各种预处理后底物的不规则性依次为：HCl＞LHW＞NaOH,其与酶的有效吸附大小依次为：NaOH＞HCl＞LHW。     

甘蔗尾中酵母菌的分离与鉴定

以0～90 d打包青贮发酵的甘蔗尾为试验材料,采用传统培养法和平板划线分离法得到7株酵母菌。对纯化后的酵母菌进行形态观察、API 20 C AUX生化鉴定试剂盒鉴定及内转录间隔区（ITS）序列核糖体脱氧核糖核酸（rDNA）分子生物学鉴定,并对其生长性能进行初步探索。结果显示：菌株X1、X7、X9和X10被鉴定为Kazachstania humilis,菌株X3、X4和X6被鉴定为扁平云假丝酵母（Candida humilis）。7个菌株在培养24 h后菌液OD660 nm值达到9.90～12.84,生长性能较好。     

压榨机榨蔗能力计算公式的探讨

对于压榨机榨蔗能力的计算公式,各国未能找出其规律,只能用经验公式来表示,因而各国计算公式都不相同。本文抓住影响压榨能力的关键所在,通过分析榨辊自身入辘的机理而推出新的公式,并用工厂实际数据进行对比而得出各种公式的优劣,进一步指出新公式的意义及各种因素影响压榨能力的规律。