木聚糖酶最适pH值的研究

研究了以里氏木霉RutC - 3 0合成的木聚糖酶的最适pH值范围。结果表明 ,内切—木聚糖酶的最适pH值范围在 4.0～ 5 .0之间 ,β—木糖苷酶的最适pH值范围在 3 .0～ 4.0之间。研究还表明 ,与内切—木聚糖酶相比 ,pH值对β—木糖苷酶的影响更大。当pH值为 4.0时 ,酶水解总糖得率最高 ,适于制备木糖 ,而当pH值为 5 .0～ 6 .0时 ,较适于制备木低聚糖。     

两级超滤部分纯化里氏木霉纤维素酶

研究了里氏木霉纤维素酶超滤过程中pH值的影响,结果显示适宜的pH为7.0。在pH 7.0的条件下,依次用PVDF100超滤膜和PS30超滤膜对纤维素酶粗酶液进行恒体积洗滤方式超滤,以洗出其中的杂蛋白,纯化之后的里氏木霉纤维素酶系中内切葡聚糖酶、外切葡聚糖酶、β-葡萄糖苷酶分别被纯化了2.1、1.78和1.49倍,而且维持了里氏木霉纤维素酶系构成的稳定性。此时,相应酶组分的回收率分别为75.9%、81.8%和54.0%。     

Effect of purified Trichoderma reesei cellulases on formation of cotton powder from cotton fabric

The mode of action of monocomponent purified Trichoderma reesei cellobiohydrolases (CBHI and CBHII) and endoglucanases (EGI and EGII) on cotton fabrics was studied by analyzing the weight loss of the fabric, the reducing sugars, the soluble oligosaccharides and the molecular weight of the cotton powder formed. The impact of mechanical action on these factors was also evaluated. EGI and EGII released the highest amounts of reducing sugars and soluble oligosaccharides in both treatments with or without additional mechanical action. After cellulase treatment without additional mechanical action, all of the cellulases were found to have reduced the molecular weight of cotton poplin powder. When mechanical action was combined with enzyme treatments, only EGII reduced the molecular weight. The weight loss of EG‐treated fabrics was clearly higher than the weight loss of CBH‐treated fabrics with both low and high mechanical action levels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1917–1922, 2003     

外切-β-葡聚糖酶基因重组里氏木霉的筛选及其产酶性能

外切-b-葡聚糖酶是纤维素酶的重要组分之一,提高该组分的活力是增强纤维素酶协同降解性能、降低纤维素水解成本的关键。分别采用微晶纤维素琼脂平板法和滤纸崩解法,对已有的基因重组转化子进行筛选试验,获得了6个优良转化子,其滤纸崩解速率和微晶纤维素琼脂平板上的生长速率都较大。进一步在摇瓶条件下进行复筛试验,获得了外切-β-葡聚糖酶（C₁）高产转化子Trichoderma reesei ZU-101,液体培养48 h,其C₁酶活力可达18.24 U·ml^-1,是出发菌株的2.16倍;分析结果表明：重组转化子的纤维素酶体系中内切-b-葡聚糖酶和纤维二糖酶的活力与出发菌株相比变化不大,但由于外切-b-葡聚糖酶活力得到了大幅度提高,纤维素酶的总活力（滤纸酶活力FPA）也提高了61.9%。采用纤维素酶对碱预处理玉米秸秆进行酶解试验,当酶用量为20 FPIU·（g底物）^-1,水解48 h,重组转化子T.reesei ZU-101纤维素酶的酶解得率高达94.4%。本文的研究结果在可再生纤维素资源的生物转化与利用方面具有广阔的应用前景。     

Molecular Characterization of Xyloglucanase cel74a from Trichoderma reesei

Background: The filamentous fungus Trichoderma reesei is used on an industrial scale to produce enzymes of biotechnological interest. This fungus has a complex cellulolytic system involved in the degradation of lignocellulosic biomass. However, several aspects related to the regulation of the expression of holocellulolytic genes and the production of cellulases by this fungus are still understood. Methods: Here, we constructed a null mutant strain for the xyloglucanase cel74a gene and performed the characterization of the Δcel74a strain to evaluate the genetic regulation of the holocellulases during sugarcane bagasse (SCB) cultivation. Results: Our results demonstrate that the deletion of xyloglucanase cel74a may impact the regulation of holocellulase expression during SCB cultivation. The expression of cellulases cel7a, cel7b, and cel6a was reduced in Δcel74a strain, while the hemicellulases xyn1 and xyn2 were increased in the presence of SCB. The cel74a mutation also affected the xyloglucan hydrolysis patterns. In addition, CEL74A activity was modulated in the presence of calcium, suggesting that this ion may be required for efficient degradation of xyloglucan. Conclusions: CEL74A affects the regulation of holocellulolytic genes and the efficient degradation of SCB in T. reesei. This data makes a significant contribution to our understanding of the carbon utilization of fungal strains as a whole.     

Hydrolysis of carboxymethylcellulose with mixtures of cellulase and β‐1,4‐glucosidase

We studied the hydrolysis of carboxymethylcellulose at 50 °C and pH 4.9 with a commercial preparation of cellulase (Celluclast) supplemented with a commercial β‐1,4‐glucosidase product (Novozym). The initial concentration of carboxymethylcellulose was varied between 2 and 12.5 kg m^?3 for assays with Celluclast and two Novozym/Celluclast ratios (0.5 and 1). We determined the conversion to glucose and the overall conversion in terms of glucose equivalent. Conversion to glucose turned out to be directly proportional to the product of experimental time multiplied by the concentration of Celluclast and the constant of proportionality increased concomitantly with the concentration of Novozym. Overall conversion remained unaffected by the concentration of Novozym. © 2001 Society of Chemical Industry     

Biopolishing of cotton fabrics with total cellulases of Trichoderma reesei and optimization using Taguchi methods

Biopolishing of cotton fabrics enhances appearance and handle of the fabrics without compromising on essential properties. Process of biopolishing is influenced by concentration of cellulases, temperature, pH, and duration of treatment, besides the activity levels of enzymes, method of mechanical agitations and construction features of fabrics. Optimization of process parameters, including mechanical agitations and fabric construction features, has been carried out using Taguchi methods followed by analysis of variance and confirmation tests. All the design parameters, used in the study, have predominant influence on weight loss, fabric strength after biopolishing while thickness, bursting strength, abrasion losses, and flexural rigidity of the fabrics were significantly influenced by the concentration of cellulases together with duration of treatment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

里氏木酶利用预处理小麦秆生产纤维素酶的应用研究

为了降低里氏木霉生产纤维素酶的成本,研究了小麦秸秆经白腐菌和酸处理后主要成分如纤维素、木聚糖、木质素含量的变化,采用正交实验考察了里氏木霉菌发酵小麦秆生产纤维素酶的最佳条件,研究得到的最佳条件为:小麦秆∶麸皮=2∶3,培养温度30℃,起始pH 5.0,发酵时间48 h。通过对正交实验条件的优化,发酵液滤纸酶活(FPA)为6.11 IU.mL-1,羧甲基纤维素酶活(CMCase)为29.11 IU.mL-1,纤维二糖酶活(CBA)为16.11 IU.mL-1。和原工艺相比FPA、CMCase和CBA分别提高了30.78%、26.82%和37.11%。     

Partial purification and characterization of the cellulases from clostridium cellulolyticum h10

The extracellular cellulolytic complex from Clostridium cellulolyticum H10 has been isolated and partially characterized. Through application of gel filtration and ion exchange chromatography techniques it has been established that in its native state this complex essentially consists of highly stable macromolecular structures (M^r c. 20 000 kDa) (similar to those described for different cellulolytic bacteria and currently termed cellulosomes) exhibiting avicelase, carboxymethylcellulase (CMCase) and xylanase activities. Furthermore, immunoaffinity assays show that this extracellular cellutosomal form of the complex is immunochemically similar to the cell-associated form. Another feature of the C. cellulolyticum H10 complex is that the Avicel-adsorbed fraction consists essentially of three major components, two of them (those of 160–170 and 72 kDa) having no detectable activity and one (that of 95 kDa) being associated with strong CMCase activity.     

Preparation of hybridizing zeolitic imidazolate frameworks with carboxymethylcellulose for adsorption separation of n-hexane/3-methylpentane

A novel ZIF-8-CMC hybrid material was fabricated from the hybridization of ZIF-8 and carboxymethylcellulose (CMC) by impregnation method for n-hexane/3-methylpentane separation. The surface properties of ZIF-8 were tailored by introducing CMC into ZIF-8 nanoparticles. In this work, adsorption separation of n-hexane (nHEX) and 3-methylpentane (3MP) on ZIF-8-CMC were investigated by batch vapor-phase adsorption and liquid-phase breakthrough adsorption. The adsorption selectivity of nHEX/3MP reversed from preferable adsorption of nHEX to preferable adsorption of 3MP upon the increasing of CMC containing in the hybrid materials. As the temperature increases, the adsorption amounts of nHEX and 3MP decrease. With the increasing of CMC contents, the nHEX uptake decreased, the uptake capacity of 3MP increased gradually. For liquid-phase breakthrough adsorption, the dynamic adsorption capacity of nHEX also decreased with the increasing of temperature.     

厌氧水解的新解读：快速水解和慢速水解

挥发性脂肪酸（VFA）具有可生化性好、附加价值高等优点而得到广泛应用,厌氧消化产VFA是目前学术界的研究热点,但对有机物经过水解后的生物降解性能则少有论及,厌氧发酵过程中的水解产物存在“数量”和“质量”之间的权衡问题。为了进一步提高厌氧发酵过程中微生物对有机物的利用效率,突破水解对厌氧消化的限制性作用,从基质碳源释放快慢及厌氧发酵过程中碳源降解性能不同,本文将厌氧水解分为快速水解和慢速水解,分别阐述了两种水解方式的含义、分类以及优缺点,指出细胞内外碳源的释放速率和释放方式的不同是影响厌氧产酸和生物降解性能的决定性因素。最后指出快速水解与慢速水解相结合的分阶段联合处理方式,是今后厌氧消化产VFA的主要研究方向。     

Morphology,crystallization and enzymatic hydrolysis of poly(L‐lactide) nucleated using layered metal phosphonates

Poly(L ‐lactide) (PLLA) was prepared via melt blending and nucleated using three layered metal phosphonates, i.e. zinc phenylphosphonate (PPZn), calcium phenylphosphonate (PPCa) and barium phenylphosphonate (PPBa). The morphology, crystallization and enzymatic hydrolysis of PLLA nucleated using PPZn, PPCa and PPBa were investigated. The results of both wide‐angle X‐ray diffraction and transmission electron microscopy observations show that the layers of PPZn, PPCa or PPBa are barely exfoliated or intercalated by PLLA chains in the melt‐blending process. PPZn, PPCa and PPBa serve as effective nucleating agents, accelerating both non‐isothermal and isothermal crystallization and enzymatic hydrolysis of PLLA. An interesting aspect is that the nucleating ability of PLLA incorporating PPZn, PPCa and PPBa decreases in the order PPZn > PPCa > PPBa, whereas the enzymatic hydrolysis of PLLA incorporating PPZn, PPCa and PPBa decreases in the reverse order, which is due to the different dispersion and interfacial interactions of PPZn, PPCa and PPBa throughout the PLLA matrix. Copyright © 2010 Society of Chemical Industry     

袋式除尘器滤饼固定化研究

为研究滤饼微观结构,对滤饼固定化方法进行了研究。首先介绍了传统的树脂包埋法,分析了该方法的优缺点。提出了一种新型的滤饼固定化方法——羧甲基纤维素钠(CMC)黏合法。经检测证明,CMC黏合法固定过程耗时短,方法简单,可真实反映滤饼结构。     

聚琥珀酰亚胺的水解动力学过程

合成聚天门冬氨酸阻垢剂时,都要经历中间产物聚琥珀酰亚胺(PSI)水解生成聚天冬氨酸钠盐这一步骤。研究探讨水解温度、反应时间、NaOH浓度和NaOH用量对聚琥珀酰亚胺水解产物聚天冬氨酸阻垢率的影响。通过正交试验,发现反应时间对水解产物聚天冬氨酸的阻垢率影响最大,水解温度影响较小;得到最佳水解条件为:水浴温度60℃,时间30 m in,NaOH浓度为2 mol/L,NaOH用量为20 mmol,即在此条件下制备的聚天冬氨酸阻垢率最高。根据实验数据,推测聚琥珀酰亚胺的水解动力学过程属于连串反应。     

半纤维素酶添加对碱处理甘蔗渣结构及酶解的影响

半纤维素作为木质纤维素的重要组分之一,通过氢键与纤维素的微纤丝结合,严重阻碍了纤维素表面与纤维素酶的接触,降低了酶解的效率。该试验以碱处理甘蔗渣作为底物,通过添加不同量的半纤维素酶去除不同比例的半纤维素。通过成分分析、X射线衍射(XRD)和扫描电镜(SEM)等手段分析添加半纤维素酶前后残渣的结构和酶解特性变化,发现随着半纤维素酶添加量的增大,残渣中木质素所占的比例逐渐增大,结晶指数逐渐增大,电镜表面沟壑逐渐加深,纤维束之间结构变得疏松。以半纤维素酶处理过的甘蔗渣作为底物,按照5FPU/g底物加入纤维素酶水解72h,与不添加半纤维素酶对照组相比,添加1600U/g半纤维素酶处理的试验组木聚糖的转化率提高了74.24%,葡聚糖转化率提高了35.30%。通过半纤维素酶添加可以有效促进纤维素酶解过程的进行,节约反应时间提高酶解转化率。     

Co-Cultivation of Aspergillus niger and Trichoderma reesei Enables Efficient Production of Enzymes for the Hydrolysis of Wheat Bran

Agro-residues like wheat bran may be a useful carbon source for fermentation processes. However, due to their composition, hydrolysis appears complex. A co-cultivation process was established with the two fungi A. niger and T. reesei for the production of an adapted mixture of enzymes for hydrolysis. This enzyme solution reached a higher space-time yield of sugars during the hydrolysis of wheat bran compared to enzymes from respective monocultures, demonstrating the potential of this co-culture for the production of complementary enzyme mixtures for the hydrolysis of wheat bran.     

酶解木质素的分离与结构研究

采用两种方法从酶解玉米秸秆制备能源酒精的残渣中分离得到酶解木质素。根据不同的分离条件,酶解木质素的得率为20%～35%。应用UV、FT-IR、GPC和13C-NMR研究了不同分离方法的酶解木质素的结构特性。结果表明,所分离的酶解木质素分子量较小,在结构上较好地保留了各种活性基团。与木质素磺酸钙相比,酶解木质素的红外图谱中多了1700cm-1和1328cm-1峰,说明酶解木质素存在非共轭羰基作用。紫外图谱在210nm,280nm和310nm附近有峰值出现,说明其具有木质素的基本结构特征,且结构上有很大的不饱和性。由13C-NMR图谱解析可知,所提取酶解木质素为GSH型木质素,主要以β-O-4、β-5、β-1的结构存在。以氢氧化钠作为萃取剂的酶解木质素提取率比有机溶剂高。酶解木质素的有效利用将提高酶解玉米秸秆制备能源酒精的经济效益。     

Preparation of fast pH‐responsive ferric carboxymethylcellulose/poly(vinyl alcohol) double‐network microparticles

BACKGROUND: Carboxymethylcellulose (CMC) and poly(vinyl alcohol) (PVA) are biocompatible, and their complex hydrogel shows pH responsiveness. Thus, they are chosen as starting materials to prepare physically dual‐crosslinked Fe‐CMC/PVA microparticles with improved properties. RESULTS: Fe‐CMC/PVA double‐network microparticles were obtained via a facile process under mild conditions. Sodium carboxymethylcellulose was crosslinked with ferric ions to form particles that contained aqueous PVA solution in an emulsion system. The hydrogel particles were then subjected to a freezing–thawing cycle to achieve further crosslinking; the size of the particles formed was in the range 0.2–1.2 µm. The microparticles were capable of maintaining the stability of proteins such as hemoglobin in an acidic environment and exhibited pH‐responsive release behavior. CONCLUSION: The pH responsivity of the Fe‐CMC/PVA physical double‐network microparticles is fast, which is helpful for effectively protecting a loaded bioactive substance. Thus, they may be potential candidates for pH‐sensitive applications. Copyright © 2008 Society of Chemical Industry