粗糙脉孢菌固态发酵产纤维素酶工艺优化

从青储饲料中分离得到一株产纤维素酶能力较强的丝状真菌,经形态学和26SrDNA D1/D2区序列比对分析,确认该菌株属粗糙脉孢菌(Neurospora crassa)。通过单因素实验和正交实验探讨了碳源、氮源、无机盐、料水比、培养温度、培养时间对菌株固态发酵产纤维素酶的影响。确定最适产酶工艺为:碳源麸皮与稻草秆的质量比6∶4、氮源3%(NH4)2SO4、料水比1∶1.5(g∶mL)、培养温度30℃、培养时间60h,无机盐KH_2PO_4和MgSO_4对产酶影响不显著,在最适产酶工艺下,固态发酵产纤维素酶酶活达到251.27U·g-1以上。     

高产纤维素酶菌株的筛选及产酶条件的研究

植物纤维是自然界最丰富的资源,筛选高产纤维素酶菌株,降低纤维素酶的生产成本,让植物纤维变废为宝一直是研究热点。从腐烂植物叶片中分离到一株高产纤维酶菌株CXYJ-1。对CXYJ-1菌株进行发酵培养条件的研究,结果表明,以豆饼粉为碳源,(NH_4)_2SO_4为氮源,培养温度为35～37℃,初始pH=5,培养96 h,产酶活力最高,CMC酶活为4.8 U/mL,FP酶活为4.5 IU/mL。     

一株产纤维素酶镰刀菌的筛选、鉴定与酶学性质

根据菌株菌落、菌丝体、孢子等形态特征及其生理特性,初步鉴定高产纤维素酶的丝状真菌为尖孢镰刀菌(Fusarium oxysporum),命名为XA-1。考察了不同碳源及氮源、培养温度、初始pH等因素对XA-1产酶的影响,并研究了该菌所产纤维素酶酶学性质及酶解性能。该菌的最适产酶条件为:分别以水葫芦和硫酸铵为碳、氮源,30℃,pH 5.0,培养6 d后,内切葡聚糖酶(CMCase)、β-葡萄糖苷酶(β-Gluase)和滤纸酶活力(FPA)分别达到4 083.2、3 258.8 U/g和773.2 U/g(成熟曲)。CMCase、β-Gluase最适反应温度为45℃,FPA则为55℃;CMCase、β-Gluase和FPA的最适反应pH分别为5.0、4.5和5.0。菌株XA-1纤维素酶酶解香蕉秆或水葫芦32 h后,酶解得率分别达到27.3%和29.8%。菌株XA-1在纤维素酶开发及转化秸秆类纤维素为可发酵糖方面显示出较好的应用前景。     

复合诱变选育纤维素酶高产菌株

以绿色木霉为原始菌株,以纤维素酶酶活为考察指标,进行纤维素酶高产菌株的筛选。首先进行紫外诱变,筛选得到一株纤维素酶高产菌株A4,其羧甲基纤维素酶酶活和滤纸酶活为35.36 U/mL和25.30 U/mL,较出发菌株提高了26.37%和16.00%。继续用A4进行亚硝酸钠诱变,得到纤维素酶高产菌株F1,其羧甲基纤维素酶酶活和滤纸酶活为44.29 U/mL和29.00 U/mL,较出发菌株提高了24.90%和14.62%。     

镰刀菌发酵培养液中纤维素酶的分离纯化

选用镰刀菌菌株液体培养产纤维素酶。将菌株在30℃、120 r.min-1摇床培养108 h,5000 r.min-1离心20 min,取上清液经硫酸铵分级沉淀、Sephadex G-100凝胶过滤层析和DEAE-Sephadex A-50离子交换层析进行纤维素酶的分离纯化,并用SDS-PAGE进行纯度检验。结果表明,分离纯化后的纤维素酶酶活为35.25 U.mL-1,比活力提高到19.56倍。为进一步研究纤维素酶的组分、结构奠定了基础。     

产纤维素酶细菌的筛选及其产酶优化

利用刚果红染色法筛选产纤维素酶菌株,采用分子生物学技术和形态学观察作为鉴定手段,通过滤纸条崩解实验测定实际降解能力.以葡聚糖内切酶活(CMCase)和滤纸酶活(FPase)为指标,进行单因素和响应面试验优化.结果表明,获得一株产纤维素酶细菌(Xh-12),鉴定为不动杆菌属,发酵培养7 d后对滤纸条的减重率可达54.4％...     

降解水葫芦中纤维素的优良菌株的筛选

在腐烂的水葫芦中利用刚果红平板染色法分离筛选具有产纤维素酶活性的四株菌株,通过考察其产纤维素酶活力及降解水葫芦的水平,从而筛选出一株产纤维素酶活较高同时能高效降解水葫芦的优良菌株D1。在降解水葫芦的过程中,CMC酶活最高为2.262μmol/min.mL,滤纸酶活最高为1.592μmol/min.mL。D1菌株发酵液中10天左右的还原糖质量浓度达到2.273 g/L,14天降解水葫芦达到39.13%。经初步鉴定该菌株为绿色木霉。     

响应面法和变温培养优化海洋黑曲霉产纤维素酶发酵条件

选用响应面法和变温培养相结合的方法,优化了一种海洋黑曲霉生产耐盐性纤维素酶的液体发酵条件。首先通过单因素实验初步确定碳源、氮源、温度、表面活性剂、接种量、装液量以及初始pH;随后选择Plackett-Burman(PB)设计挑选出影响滤纸酶活(FPA)的主要成分:麸皮和吐温-80(Tween-80);再通过爬坡实验,使麸皮和吐温-80浓度接近最大酶活区域;接着选择响应面分析快速有效地求得该菌株产耐盐性纤维素酶的最佳培养基配方;最后进行了变温培养实验确定适宜的稳定期培养温度。得到的优化发酵条件为:麸皮5.53%(w),玉米浆0.5%(w),磷酸二氢钾0.2%(w),Tween-80 0.197%(w),初始pH 5.0,接种量8%(mol),装液量40 m L,180 r/min,37℃培养2 d后继续28℃培养2 d。优化后的滤纸酶活为0.566 U/m L,与未优化时的酶活(0.283 U/m L)相比增加了94.5%。     

酸/碱预处理对两株木霉降解玉米秸秆效果的影响

研究了木霉菌(Trichoderma jw-1)、木霉菌(Trichoderma jw-2)及曲霉(Aspergillus xm.)在相同培养条件下,以纤维素为碳源产葡聚糖内切酶活力(CMC酶活)及滤纸酶活力(FPA酶活)的情况,并将其进行混合培养发酵,研究了不同菌系配比对CMC酶活及FPA酶活的影响。并以CMC酶活及FPA酶活作为指标,利用不同化学法处理玉米秸秆,对预处理条件进行了优化。结果表明:Trichoderma jw-1与Trichoderma jw-2组合产纤维素酶量最高,CMC酶活可达2.76 U/mL,FPA酶活可达1.52 U/mL;经10%NaOH预处理后,Trichoderma jw-1与Trichoderma jw-2的复合菌系降解秸秆效率最好,秸秆干粉失重率可达76.8%。     

产纤维素酶增效蛋白菌株的筛选及培养条件优化

为了寻找高效的产纤维素酶增效蛋白菌株,建立一种筛选方法从土壤中筛选得到一株产纤维素酶增效蛋白的细菌POEP1,其所产增效蛋白对纤维素酶(来源于黑曲霉Aspergillus niger)的滤纸酶活有明显的增效作用,通过对其进行16SrDNA分类鉴定,确定该菌株为栖稻假单胞菌(Pseudomonas oryzihabitans)。为进一步提高POEP1产纤维素酶增效蛋白的水平,对其培养条件进行优化。采用单因子试验筛选出最佳碳源为麦麸,最佳氮源为黄豆粉。再通过Plackett-Burman设计对与发酵相关的11个因子进行试验,筛选出麦麸、黄豆粉和KH2PO4为3个主要显著因子;由Box-Behnken实验结合响应面分析确定主要因子的最优水平为:麦麸质量浓度32.3 g L 1,黄豆粉质量浓度24.7 g L 1,KH2PO4质量浓度4.36 g L 1。优化后纤维素酶增效蛋白的产量提高1.7倍,增效活力由15.79 U mL 1增至43.31 U mL 1。     

Preparation of microcrystalline cellulose from rice straw under microwave irradiation

Crude cellulose was isolated from rice straw and then converted into microcrystalline cellulose (MCC) via partial hydrolysis. Both the isolation and partial hydrolysis were carried out under microwave. Rice straw was successively pretreated with alkaline and acid solutions before hydrolysis. Lignin and silica were almost removed but partial removal of hemicellulose in dilute alkali solution, and the residual hemicellulose was further removed in dilute acid solution. The total removal rates of hemicellulose, lignin and silica reached up 92.0%, 98.5%, and 96.8%, respectively. The cellulose content of 93.6 wt % in MCC was given by partial hydrolysis of crude cellulose isolated from rice straw. The comparison between microwave irradiation and traditional heating method was also investigated. Compared to traditional heating method, similar results were obtained while milder conditions, including shorter time and lower temperature, were required. An effective microwave‐assisted and energy‐efficient methodology using rice straw as the alternative source of cellulose fiber was developed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44901.     

纤维素分解菌的筛选及其紫外诱变

利用羧甲基纤维素钠为唯一碳源培养基从朽木、腐烂的竹叶与稻草中分离得到8株纤维素分解菌,测定了其产酶活性。对其中产酶活性较高的2#菌株进行紫外线诱变,进一步筛选得到突变株M10,其相对酶活较出发菌株提高了89.1%。     

纳米微晶纤维素热稳定性的研究进展

纳米微晶纤维素来自天然高分子聚合物,具有成本低、强度高、轻便等特点,并可循环利用或者生物降解。纳米微晶纤维素研究倍受关注,但纳米微晶纤维素存在一些实用方面的困难。制备过程复杂、热稳定性差等是限制纳米微晶纤维素大规模商业化应用的主要的因素。本文综述了纳米微晶纤维素的热降解机理及其热稳定性影响因素,探讨了提高其热稳定性的途径。     

Studies on the production of lipids in fungi XIII. Changes of amount and composition of lipids in fungi in species of the genusPellicularia from cellulose by cultural conditions

The influence of growth temperature, carbon to nitrogen (C/N) ratio of the medium and the nitrogen source on the cell and lipid formation from cellulose by the speciesfilamentosa andpraticola of the genusPellicularia were investigated. The strains of thePellicularia genus fungi can be grown well utilizing powdery cellulose and sugar cane bagasse as the carbon source. The amount of lipids accumulated in the mycelium varied considerably depending on the difference in the cell growth associated with the cultivation condition, and the difference in the strain, C/N ratio and nitrogen source. The maximum accumulation of lipids in the mycelium (256 mg/400 ml of the medium) from cellulose was observed at 20 C with a C/N ratio of 5.7 using potassium nitrate as the nitrogen source forPellicularia filamentosa var.solani IFO 5879. Protein formation in the liquid medium is at its peak when the cell growth is at its maximum. The fatty acid compositions of the neutral and polar lipid fractions also were determined. Linoleic acid is the major fatty acid component of both fractions. The change in the total lipid content is less than 10% under any cuitivation condition.     

碱性纤维素酶基因在巴氏毕赤酵母中的表达及重组酵母菌发酵工艺的优化

目的克隆碱性纤维素酶基因,构建酵母整合型表达质粒,在巴氏毕赤酵母中表达,并对重组菌的发酵工艺进行优化。方法应用PCR技术从嗜碱性芽孢杆菌ATCC21833中扩增碱性纤维素酶基因,克隆至酵母整合型表达载体pGAPZαA中,构建重组表达质粒pGAPZαA-ATCC21833,并转化至巴氏毕赤酵母GS115。通过单因素实验及正交实验,确定重组酵母的最佳发酵培养基。在20L发酵罐中进行高密度发酵,观察碳源对批式发酵的影响,并检测在4种流加方式(连续恒速流加、间歇匀速流加、间歇递减流加、维持底物浓度流加)下的菌体干重及发酵液中的酶活性。结果重组表达质粒pGAPZαA-ATCC21833经酶切及DNA测序证明构建正确,其基因序列与嗜碱性芽孢杆菌KSM-635的碱性纤维素酶基因序列一致。最佳发酵培养基组成为6%葡萄糖、2%硫酸铵、12g/L磷酸二氢钾。碳源浓度对于重组酵母菌体生长及产酶至关重要。SDS-PAGE表明表达产物的相对分子质量约为103000。维持底物浓度的流加方式可获得最高的菌体干重(29.8g/L)及酶活力(24U/ml)。结论已成功构建了表达碱性纤维素酶的巴氏毕赤酵母工程菌,并确定了维持底物浓度的流加方式为最佳发酵方式。     

Isolation of highly purity cellulose from wheat straw using a modified aqueous biphasic system

Cellulose samples with molecular weights ranging from 8.39 × 10⁴ to 11.00 × 10⁴ g/mol were obtained from wheat straw. The dewaxed wheat straw was pretreated with aqueous hydrochloric acid followed by delignification using an environmentally benign poly(ethyleneglycol)/salt aqueous biphasic system. The yield of cellulose was in the range of 48.9%–55.5% and the cellulose contained 1.2%–3.2% hemicelluloses, and 0.97%–3.47% lignin. All the isolated cellulose samples could be directly dissolved in a 6 wt-% NaOH/4 wt-% urea aqueous solution through a precooling-thawing process to form a homogenous solution. The separation process was investigated and the obtained cellulose and its solution were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray apparatus, and X-ray diffraction. The results revealed that aqueous soluble cellulose can be directly prepared from wheat straw by this method and this study opens a novel pathway to prepare cellulosic materials from agricultural waste.     

不同天然大分子在膨胀型阻燃TPV复合材料中的作用

选择了纤维素、壳聚糖、淀粉三种天然大分子作为碳源,聚磷酸铵(APP)作为酸源和气源,按1∶2的质量比复配成三种不同的膨胀型阻燃剂。然后将三种膨胀阻燃剂添加到热塑性动态硫化橡胶(TPV)材料中,通过熔融共混的加工方法,制备得到阻燃TPV复合材料。力学性能测试实验显示,不同碳源的阻燃TPV复合材料的力学性能依次为:纤维素>壳聚糖>淀粉。极限氧指数和垂直燃烧实验结果表明:当阻燃剂质量分数达到30%时,以纤维素作为碳源的TPV复合材料的阻燃性能最好,其氧指数最高为25%,相对于纯TPV的19%,提高了6%,而且能达到V-1等级;壳聚糖和淀粉为碳源TPV复合材料的氧指数分别达到了23%和22%,且都能达到V-2等级。通过TGA和SEM研究了阻燃机理,结果表明,与其他两种碳源相比,纤维素为碳源的TPV复合材料的热稳定性最高,且在燃烧时能形成更加致密的炭层。     

Hydroxypropylation of cellulose isolated from bamboo (Dendrocalamus strictus) with respect to hydroxypropoxyl content and rheological behavior of the hydroxypropyl cellulose

Bamboo, a lignocellulosic material, is a renewable source of interest as feedstock for production of cellulose derivatives by chemical functionalization. Optimization of hydroxypropylation of cellulosic material (average DP 816), isolated from bamboo (Dendrocalamus strictus) was, therefore, performed with respect to maximum percent hydroxylpropoxyl (% HP) contents under varying reaction conditions and studying their effect on the % HP. The optimized reaction conditions were aqueous NaOH concentration 22%, propylene oxide concentration 17.4 mol/AGU, temperature 50°C, duration of hydroxypropylation 4 h to yield hydroxypropyl cellulose of % HP 65.89. The η_app of 1 and 2% solutions of the optimized product showed it to be non‐Newtonian pseudoplastic. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

利用纤维素水解液中的纤维二糖发酵制备丁二酸

纤维素水解液中通常含有纤维二糖。本文考察了Actinobacillus succinogenes NJ113利用纤维二糖厌氧发酵生产丁二酸的能力,并利用蔗渣纤维素制备纤维二糖作为碳源用于厌氧发酵生产丁二酸。3 L发酵罐厌氧发酵结果显示：以35 g/L纤维二糖作为碳源发酵制备丁二酸,其产量为23.51 g/L,产率达到67.17%;用含有18 g/L纤维二糖和17 g/L其它糖类的蔗渣纤维素水解液作为碳源发酵制备丁二酸,丁二酸的产量和产率分别为20.00 g/L和64.73%。因此,Actinobacillus succinogenes NJ113具有较强的利用纤维二糖生产丁二酸的能力,而且利用废弃的纤维素制备纤维二糖作为碳源高效、经济地发酵制备丁二酸具有可行性。     

Fabrication of a model cellulose surface from straw with an aqueous sodium hydroxide/thiourea solution

Model cellulose surfaces were prepared with both microcrystalline cellulose and cellulose isolated from wheat straw with different molecular weights. A sodium hydroxide/thiourea aqueous solution, instead of any organic solvents, worked as the solvent for dissolving cellulose, and model cellulose films were prepared by a two‐step method: first, the cellulose solution was deposited onto the surface of the substrate with the spin‐coating method, and second, the as‐prepared film was washed with deionized water to remove the impurities and was formed with a flattened surface. Atomic force microscopy was used to measure the morphology, surface roughness, and thickness of the cellulose thin films. X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectrometry were used to characterize the surface chemical information of the films. The results revealed that model cellulose surfaces could form from both kinds of cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008