Oil sorption behavior of acetylated nettle fiber

Abstract

In this work, acetylation of raw nettle fibers was performed to improve the oil sorption capacity. Raw nettle fibers were acetylated with acetic anhydride using N-Bromosuccinimide (NBS) as a catalyst. Box–Behnken experimental design was used to study the effect of some selected parameters such as reaction time, reaction temperature and catalyst concentration (%) on weight percent gain (WPG) and oil sorption behavior. Highest WPG and oil sorption were achieved at 90?min reaction time, 120?°C and 2% catalyst. The oil sorption of acetylated nettle was 23.21?g/g and 18.75?g/g against diesel engine oil and crude oil, respectively. Nettle fibers were also characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis and Scanning electron microscopy. Oil sorption capacity of acetylated nettle were higher than that of commercial polypropylene sorbent. Hence, these acetylated nettle fibers can be used in the place of synthetic sorbents for oil spill cleanup applications.     

壳聚糖固定化纤维素酶的条件优化

采用Plackett-Burman试验设计和正交试验设计对影响固定化纤维素酶活的因素进行了筛选和优化.探讨了纤维素酶、壳聚糖、乙酸、乙醇、戊二醛、氢氧化钠等试剂对固定化效果的影响,筛选出制备固定化纤维素酶过程中的主要影响因素.结果表明:壳聚糖、乙酸、乙醇浓度、酶浓度分别为15g/L、2.0%、40%、100%时,以壳聚糖为载体制备固定化纤维素酶的活力最高,成型效果最好.     

改性菠萝皮渣纤维素固定化菠萝蛋白酶研究

为了探究改性纤维素作为固定化酶载体的可行性,在离子液体中用L-丝氨酸对提取的菠萝皮渣纤维素进行均相改性,并将改性菠萝皮渣纤维素用于固定化菠萝蛋白酶。采用傅里叶变换红外光谱仪、热重分析仪以及X射线衍射光谱仪对菠萝皮渣纤维素、改性菠萝皮渣纤维素以及固定化酶进行了表征。结果表明,菠萝皮渣纤维素被成功改性,晶体结构从纤维素Ⅰ型转变为纤维素Ⅱ型;菠萝蛋白酶成功地固定在改性菠萝皮渣纤维素上,且固定化酶较改性菠萝皮渣纤维素的热稳定性得到提升。对酶的固定化工艺和酶学特性进行研究,结果表明,固定化酶的优化制备工艺为菠萝皮渣纤维素与离子液体的质量比为3∶100,L-丝氨酸与菠萝皮渣纤维素的质量比为1∶1,戊二醛溶液体积分数为1%,交联时间为1.0 h。与游离菠萝蛋白酶相比,固定化菠萝蛋白酶具有更好的温度稳定性和酸环境稳定性。     

低取代度乙酰化大米淀粉的性质研究

以大米淀粉为原料,乙酸酐为酯化剂,制备了5种取代度分别为0.056、0.079、0.091、0.098和0.124的乙酰化淀粉。结果表明乙酰化大米淀粉的透明度随着取代度的增大而增加。大米淀粉经酯化后,凝沉性明显减弱,不易回生。乙酰化大米淀粉的溶解度和膨润力随温度的升高而增加,且明显高于原大米淀粉;糊化温度显著降低,衰减值也降低。乙酰化大米淀粉凝胶的硬度比原淀粉明显降低,弹性和内聚性变化不大。通过乙酰化处理,大米淀粉的功能性质得到明显改善。     

Degradation of carbendazim and 2,4-dichlorophenoxyacetic acid by immobilized consortium on loofa sponge

A fungicide, carbendazim (methyl-2-benzimidazole carbamate; MBC), and a herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), could be simultaneously degraded by a microbial consortium obtained from several soil samples in Japanese paddy fields with enrichment continuous culture. The degradation ability of the consortium was increased by immobilization on loofa (Luffa cylindrica) sponge in comparison with that of free-living consortium. MBC and 2,4-D were completely degraded within 5.5 d and 1.5 d, respectively. The toxicity of these pesticides in culture medium to Daphnia magna was reduced by treatment with the consortium corresponding to their degradation. The degradation ability of the immobilized consortium at pHs in the range from 6 to 9, at temperatures from 15 degrees C to 37 degrees C, and at low NH(4)(+)-N concentrations (1-10 mg/l) was not very different from that under the basal condition (pH 7, 30 degrees C, 424 mg/l NH(4)(+)-N and 472 mg/l PO(4)(3)(-)-P). At low pHs 4 and 5, the ability was significantly lower than that of the basal condition. Moreover, incubation at low PO(4)(3)(-)-P concentrations (1-10 mg/l) caused a decrease in pH at which the degradation ability also became lower. However, the ability in this culture completely recovered when pH was adjusted to 7 or the phosphate concentration was increased to the basal level. Analysis by denaturing gradient gel electrophoresis (DGGE) showed the whole population of the consortium became faint at low pH or low phosphate concentrations but became distinct again as much as those under the basal conditions, indicating that the decrease in the degradation ability caused by low pH was due to that whole population of the consortium underwent serious damage but could survive and recover. These results suggest the immobilized consortium on loofa sponge is a promising material for bioremediation of polluted water with these pesticides in paddy fields.     

Effect of acetylation on the functional properties of lentil (Lens culinaris) globulin

The functional properties of native and acetylated (62.5, 84.1, 90.1 and 93.0%) globulins were evaluated. Acetylation caused a shift in isoelectric pH from 4.5 to 3.5. The solubility of acetylated globulins improved considerably above pH 4.0 but deteriorated below this pH. Increasing acetylation enhanced water absorption (from 1.08 to 1.67, 1.96, 2.29 and 2.33 ml g^?1) but reduced oil absorption capacity (from 2.61 to 2.17, 2.15, 2.05 and 1.76 ml g^?1). In comparison with native globulin the relative viscosity of acetylated globulins also increased, but with an increase in acetylation level there was a decrease in relative viscosity (2.13, 1.81, 1.65 and 1.62). The emulsifying activity of 62.5% acetylated globulin increased from 54.2% for native globulin to 56.0%, but above this level of acetylation the activity decreased. Emulsion stability followed a similar behaviour. The foaming capacity of native globulin was improved by 62.5% acetylation but reduced at higher acetylation levels. Maximum foam stability was observed for 90.1% acetylated globulin. © 2002 Society of Chemical Industry     

Effect of hydroxypropyl β-cyclodextrin on physical properties and transition parameters of amylose–lipid complexes of native and acetylated starches

The effect of hydroxpropyl β-cyclodextrin (HPβ-CD) on physical properties and digestibility of wheat, potato, waxy maize and high-amylose maize starches before and after acetylation was studied. Effect of HPβ-CD on amylose–lipid complexes in native and acetylated potato starches synthesized using α-lysophosphatidylcholine was also studied. Acetylation increased swelling factor, amylose leaching, peak viscosity and susceptibility to α-amylase hydrolysis, but decreased gelatinization temperature and enthalpy and gel hardness in all starches. HPβ-CD markedly increased swelling factor and amylose leaching in native and acetylated wheat starches but had little or no impact on other starches. Wheat starch gelatinization enthalpy decreased in the presence of HPβ-CD but gelatinization temperature of all the starches was slightly increased. HPβ-CD had no influence on enzymatic hydrolysis. Melting enthalpy of amylose–lipid complex in both native and acetylated wheat starches was decreased by HPβ-CD. Acetylation also decreased the melting enthalpy of amylose–lipid complex in wheat starch. Similar trend of thermal transitions was observed in the presence of HPβ-CD for the amylose–lipid complexes synthesized in potato starch. Acetylation reduces the complex formation ability of the amylose polymer. Similar to gelatinization, acetylation widened the melting temperature range of amylose–lipid complexes while shifting it to a lower temperature. Higher swelling and amylose leaching, and decreased gelatinization temperature and enthalpy resulting from acetylation of wheat starch is consistent with its influence on starch hydration. Similar effects resulting from the inclusion of HPβ-CD were consistent with the disruption of amylose–lipid complex by HPβ-CD which promotes granular hydration.     

黑曲霉液体深层发酵产纤维二糖酶的研究

纤维二糖酶（cellobiase）是纤维素酶系中的重要组分之一,目前由里氏木霉（Trichoderma reesei）生产的纤维素酶制剂中纤维二糖酶的活力明显偏低,限制了纤维素的糖化效率。本文采用一个黑曲霉菌株（Aspergillus niger ZU-04）,在液态发酵条件下生产纤维二糖酶,对主要的发酵工艺参数进行了研究,结果表明,培养基中添加1.0%的麸皮对纤维二糖酶的形成有明显的促进作用;葡萄糖、玉米浆粉的适宜浓度分别为2.0%、0.3%;变温培养缩短了产酶周期,培养4d,酶活力达到最高,为6.23IU/mL。采用黑曲霉纤维二糖酶与里氏木霉纤维素酶协同水解酸预处理后的玉米芯,当纤维素酶用量为20IU/g底物时,纤维二糖酶活力和滤纸酶活力比例为0.43,2d酶解得率达到91.1%。     

Effect of reagent type on the acetylation of barley and maize starches

The objective of this work was to study the effect of reagent type on properties of acetylated barley starch (BS) and maize starch (MS) after modification with acetic anhydride (AA) and vinyl acetate (VA) at similar molar concentration for mole of glucose of both reagents. Degree of substitution (DS), morphological characteristics and granule size distribution, gelatinization and retrogradation, pasting properties, and X‐ray diffraction pattern were evaluated. Acetylation disturbs the short and long range order, and the effect was higher with AA than VA, and for BS than MS. This is due to the higher DS determined in AA–BS. In the pasting profile, acetylated starch showed the maximum peak viscosity at lower temperature, this effect was strongest for BS and anhydride acetic‐acetylation. Differential scanning calorimetry showed decrease in gelatinization parameters in acetylated starches (temperatures and enthalpy), and retrogradation was suppressed by acetylation. This effect was stronger in starches acetylated with AA despite their higher DS. This pattern can be explained from the occurrence of surface effects in acetylation with AA.     

杏鲍菇多糖的分离纯化、乙酰化修饰及其抗氧化活性

目的:分离纯化杏鲍菇多糖,对其进行乙酰化修饰,并研究修饰前后以及不同取代度对多糖抗氧化活性的影响。方法:水提醇沉法制备杏鲍菇多糖,经DEAE-Sepharose Fast Flow阴离子交换柱、Sephacryl-S400分子筛色谱柱分离纯化获得均一组分,采用乙酸酐法对其进行乙酰化修饰,制备三个不同取代度的乙酰化杏鲍菇多糖,采用体外抗氧化模型评价乙酰化杏鲍菇多糖的活性。结果:杏鲍菇多糖经分离纯化得到组分PEP-I-1,乙酰化修饰得到三个乙酰化产物Ac-PEP-I-1-a、Ac-PEP-I-1-b和Ac-PEP-I-1-c,取代度分别为0.132、0.406和0.537。杏鲍菇多糖修饰前后对自由基均具有清除作用,且呈现一定的剂量关系。结论:乙酰化修饰提高了杏鲍菇多糖对羟自由基和超氧阴离子自由基的清除能力,取代度越大,清除能力越强;乙酰化修饰减弱了对DPPH自由基的清除作用,且取代度越大,清除能力越弱。     

响应面法优化固定化酿酒酵母细胞制备工艺研究

酿酒酵母的固定化细胞技术能够实现可连续与重复再利用性强、并且能够实现酿酒酵母细胞的高密度培养.本研究利用海藻酸锰代替海藻酸钙作为固定化酿酒酵母的载体,采用响应面方法优化固定化工艺,为了降低海藻酸锰凝胶球的传质阻力,在凝胶球中添加适量的经过酶解的秸秆纤维素.结果表明,最佳工艺条件为海藻酸钠(SA)初始浓度为2.18％,秸秆纤维素(CS)添加量为0.21％,CaC12初始浓度为5.21％,在此BBD响应面模型优化条件下,制备固定化酿酒酵母细胞的包埋率理论值可达到88.02％.包埋率从48％提高为88.02％.表明了BBD响应面模型对于制备固定化细胞的工艺流程具有很高的的应用价值.     

乙酰化马铃薯微晶淀粉的制备及性能

为改善马铃薯淀粉性能,拓宽其应用领域,对马铃薯淀粉进行微晶化和乙酰化复合改性。本文以马铃薯淀粉为原料、盐酸为酸解剂、醋酸酐为乙酰化试剂、氢氧化钠为催化剂对乙酰化马铃薯微晶淀粉的制备和性能进行了研究。结果表明:马铃薯淀粉经微晶化及乙酰化后,其抗酸性、抗碱性和冷热黏度稳定性增强,但其凝沉性、冻融稳定性、蓝值和起始分解温度降低。马铃薯微晶淀粉结构为B型,乙酰化对马铃薯淀粉微晶结构有影响。     

磁性固定化纤维素酶的制备及其磁响应性

本研究以磁性壳聚糖微球为载体,采用吸附法制备磁性固定化纤维素酶。以酶活力为考察指标,研究了不同工艺条件对制备固定化酶的影响,及其在外加磁场下的磁响应性的变化。实验结果表明,制备磁性固定化纤维素酶最适条件为:吸附时间10h,pH5.0,离子浓度0.05mol/L,酶用量为150mg。在外加磁场作用下,比较磁性固定化纤维素酶与游离纤维素酶酶活力的变化发现:当磁场强度<500mT与曝磁时间<60min时,游离纤维素酶的酶活随着磁场强度与曝磁时间的增加而增加,但超出此范围,酶活就明显下降;而当磁场强度<300mT与曝磁时间<60min时,磁性固定化纤维素酶酶活与游离纤维素酶的变化趋势相似。     

Expression of two Trichoderma reesei xylanases in the fission yeast Schizosaccharomyces pombe

Two xylanase genes (xyn1 and xyn2) were amplified by the polymerase chain reaction (PCR) technique from first-strand cDNA prepared from mRNA of Trichoderma reesei QM9414. The genes were located under the human cytomegalovirus gene promoter (CMVp) on copy-number-controlled plasmids (pTLxyn1 and pTLxyn2). When both plasmids were introduced into Schizosaccharomyces pombe, functional xylanases (XYN I and XYN II) were secreted by the recombinant yeasts. The secreted XYN I protein had a molecular mass of 21 kDa whereas XYN II was produced as two molecular forms with sizes of 21 and 28 kDa, the former being not glycosylated and the latter N-glycosylated. XYN I was secreted in the culture medium at a level of about 25 microg/ml and XYN II at about 170 microg/ml. The recombinant xylanases had the same characteristics with respect to the effects of temperature and pH on the enzyme activity as the native ones.     

产纤维素酶里氏木霉的研究进展

里氏木霉在生产纤维素酶方面具有很多优点,如生长环境粗放、稳定性好、产酶效率高、纤维素酶的各组分结构较为合理等。主要介绍了里氏木霉产纤维素酶高产菌株的筛选方法,包括自然育种、诱变育种、原生质体融合、基因工程和酶分子改造等。并对里氏木霉生产的纤维素酶在食品、动物饲料和医药等领域中的应用和前景展望进行了简单阐述。     

可高效降解甜高粱秸秆产糖的纤维素酶研究

为评价实验室自制的纤维素酶对甜高粱秸秆纤维素的降解效果,以5种不同发酵工艺所产的5组纤维素酶和商品纤维素酶为研究对象,通过对各纤维素酶的滤纸酶活、分解微晶纤维素所产的还原糖量及对甜高粱秸秆中纤维素转化率的检测可知,在5组自制的纤维素酶中,纤维素酶Ⅱ的滤纸酶活最高（1 364.84 U/mL）,但纤维素酶Ⅴ对微晶纤维素的分解能力最强,并在50 ℃,48 h时其对甜高粱秸秆纤维素的转化率最高,达到11.69%,表明纤维素酶Ⅴ可高效分解甜高粱生物质材料转化成可发酵的糖,在发酵生物乙醇和高附加值的化工产品方面极具潜力。     

Effect of Acetylation on Some Properties of Corn and Potato Starches

Corn starch and starches separated from different potato cultivars were acetylated to evaluate the effect of plant source on the physicochemical, morphological, thermal, rheological, textural and retrogradation properties of the starches. Corn starch showed a lower degree of acetylation than potato starches under similar experimental conditions. The degree of acetylation for different potato starches also differed significantly. Morphological examination revealed that the granules of acetylated Kufri Chandermukhi and Kufri Sindhuri starches tended to appear as fused and less smooth than native starch granules. Acetylation of corn and potato starches decreased the transition temperatures and enthalpy of gelatinization and increased swelling power and light transmittance. However, the change in these was greater in the potato starches with higher percentage of small sized granules. Acetylated starches showed higher peak G', G'' and lower tan δ than their counterpart native starches during heating. Among the starches from different cultivars, the change in the rheological parameters after acetylation differed to a significant extent. The retrogradation was observed to be negligible in the acetylated cooked starch pastes. Results implied that the change in functional properties of starches with acetylation depends on source and granule morphology of native starch.     

里氏木霉RL-P37尿嘧啶营养缺陷型菌株的构建

里氏木霉（Trichoderma reesei） RL-P37作为纤维素酶高产菌,被广泛地应用在工业蛋白的生产过程.从基因水平对工业菌株进行分子改造已经成为提升工业菌株生产性状的重要手段.因此,亟需构建适用于基因敲除以及外源蛋白表达的营养缺陷型菌株,特别是可用于基因无痕敲除的尿嘧啶营养缺陷型菌株.本研究以潮霉素为标记,成功构建了里氏木霉RL-P37尿嘧啶营养缺陷型菌株,并得到Southern验证.该菌株在含有1.5 mg/mL 5-氟乳清酸、2 mg/mL尿苷的MM培养基中可以正常生长,并且在不含有尿苷的MM培养基上不能生长.此外,利用粗糙脉孢菌（Neurospora crassa）的pyr4基因对该突变体进行了回补.里氏木霉RL-P37尿嘧啶营养缺陷型菌株的构建为该菌纤维素酶表达和分泌的机理研究以及后续产酶性能分子改造奠定了物质基础.     

KINETIC MEASUREMENTS OF CELLULASE ACTIVITY ON INSOLUBLE SUBSTRATES USING DISODIUM 2,2' BICINCHONINATE

Determinations of cellulase activity using insoluble substrates have typically required long incubation times and significant amounts of enzyme. Utilizing disodium 2,2′-bicinchoninate, an assay has been developed to measure the initial production of reducing groups released during cellulase hydrolysis of insoluble, regenerated cellulose. The procedure permits the determination of total, soluble and insoluble reducing groups from a single reaction mixture under initial velocity conditions (< 3% hydrolysis). We report the applicability of this method to determinations of enzyme activity and for average molecular weight calculations of substrates. The K _m values for Trichoderma reesei EG I, EG II, CBH I and CBH II are reported using phosphoric acid swollen cellulose (average DP 166) as a substrate. Procedures for preparation of uniform cellulose suspensions are described.     

海藻酸钠与羧甲基纤维素钠固定化高温碱性脂肪酶

以海藻酸钠和羧甲基纤维素钠为复合载体,研究包埋法固定化毕赤酵母高温碱性脂肪酶。通过单因素试验考察了不同载体、载体浓度、酶与载体配比等因子对脂肪酶固定化的影响,并采用正交试验对脂肪酶固定化条件进行了优化。结果表明,包埋法固定化脂肪酶的最优条件为海藻酸钠含量1.0%、羧甲基纤维素钠含量0.25%、加酶量50 U/(g载体)、CaCl2浓度0.4 mol/L,固定化时间40 min。在最优固定化条件下,固定化脂肪酶酶活收率达99.50%。