微波诱变选育纤维素酶高产木霉

利用微波诱变的方法,对一株产纤维素酶的木霉进行了改造,提高了其对纤维素的降解能力。通过微波诱变筛选出5株纤维素酶高产菌株,其在摇瓶试验中的平均纤维素酶活力为野生型菌株的1.35倍,其中酶活力最高的菌株MW6,其纤维素酶产量为野生型菌株的1.4倍。固体发酵试验结果显示野生型菌株及诱变后的突变菌株在固体发酵中的酶活力均略低于摇瓶培养的酶活力,酶活力提高最快的菌株MW6,其固体培养的酶活力与液体摇瓶培养的差距最小。     

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。     

N~＋注入诱变选育纤维素酶高产菌株及发酵产酶营养因子优化研究

应用低能氮离子（N＋）注入技术对纤维素酶产生菌里氏木霉（Trichoderma reesei）进行诱变选育,在能量为10 keV,注量为150×10^14和200×10^14N＋/cm^2的条件下分别筛选得到3株纤维素酶高产菌株,连续5代遗传稳定性实验结果表明,所得到的高产菌株遗传稳定性较好,羧甲基纤维素酶活力均提高到3.300 IU/mL以上,较出发菌株（2.698 IU/mL）提高了20.0%以上。采用Plackett-Burman实验设计法和旋转中心组合设计法系统地研究高产菌株150-1-1发酵营养因子组成,得到了纤维素酶产量随葡萄糖、麸皮和微晶纤维素等营养因子的变化规律及相应的响应面分析图。实验结果表明,葡萄糖、麸皮和微晶纤维素浓度与纤维素酶活存在显著的相关性,当葡萄糖浓度为4.9 g/L,麸皮浓度为23.0 g/L,微晶纤维素浓度为7.7 g/L时,150-1-1纤维素酶滤纸酶活力达到2.439 IU/mL,较优化前（2.000 IU/mL）提高了22.0%。     

N+注入诱变选育纤维素酶高产菌株及发酵产酶营养因子优化研究

应用低能氮离子（N⁺）注入技术对纤维素酶产生菌里氏木霉（Trichoderma reesei）进行诱变选育,在能量为 10 keV,注量为150×10¹⁴和200×10¹⁴ N⁺/cm²的条件下分别筛选得到3株纤维素酶高产菌株,连续5代遗传稳定性实验结果表明,所得到的高产菌株遗传稳定性较好,羧甲基纤维素酶活力均提高到3.300 IU/mL 以上,较出发菌株 （2.698 IU/mL） 提高了20.0%以上。采用Plackett-Burman实验设计法和旋转中心组合设计法系统地研究高产菌株 150-1-1 发酵营养因子组成,得到了纤维素酶产量随葡萄糖、麸皮和微晶纤维素等营养因子的变化规律及相应的响应面分析图。实验结果表明,葡萄糖、麸皮和微晶纤维素浓度与纤维素酶活存在显著的相关性,当葡萄糖浓度为4.9 g/L,麸皮浓度为23.0 g/L,微晶纤维素浓度为7.7 g/L时,150-1-1纤维素酶滤纸酶活力达到2.439 IU/mL,较优化前 （2.000 IU/mL） 提高了22.0%。     

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-β-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-β-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-β-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。     

纤维素酶的液体发酵

用液体发酵对11株纤维素酶产生苗的产酶时间和水平进行了比较，两株里氏木霉、两株康氏木霉和一株土曲霉产纤维素酶活力较高，试验菌株的产酶高峰期除EBGA为8．5天少，其余酶均在11．5天以上。对产酶活力较高的两株菌进行了诱导底物和添加物试验，结果表明，未处理过的一些木质纤维素（稻草粉、麦秸粉和玉米芯粉等）对康氏木毒有明显的作用，稀土微肥在实验条件下没有明显的效果。     

湿地土壤产纤维素降解菌株的筛选及其性质研究

采用稀释涂平板法从宁夏湿地土壤样品中筛选出一株纤维素降解活力较高的菌株C6-2,经鉴定该菌株为烟曲霉菌(Aspergillus fumigates),对菌株C6-2发酵产酶条件及其所产酶的部分酶学性质进行了研究。结果表明,菌株C6-2的最适培养温度为30℃,该菌株能在以微晶纤维素或羧甲基纤维素钠或小麦秸秆为唯一碳源的培养基中生长,并可产生具有较好热稳定性的羧甲基纤维素酶、木聚糖酶和葡聚糖酶。     

两种木质素对纤维素酶水解的影响机制

为探究木质素对纤维素酶水解效率的影响,将苦竹中提取的乙醇木质素（EOL-B）和磨木木质素（MWL-B）作为模型物添加到微晶纤维素中进行酶吸附和水解。结果表明：添加8 g/L MWL-B使得反应72 h的葡萄糖得率从51.34%降低到46.06%;添加8 g/L EOL-B使得反应72 h葡萄糖得率从51.34%增加到61.06%。与MWL-B相比,EOL-B与纤维素酶蛋白之间亲和力和结合力较低,故纤维素酶在EOL-B上的非特异吸附更少。FT-IR和¹³C NMR分析表明：经乙醇处理后,木质素分子中C-C凝缩单元减少,β-O-4'键断裂,导致木质素分子的亲水性增加,阻断了与纤维素酶蛋白疏水性氨基酸的结合,对纤维素酶蛋白吸附量减少,从而使得纤维底物周围的酶蛋白浓度增加,水解率提高。     

云芝木聚糖酶的培养和Tween80对其产酶的促进作用

本文研究了不同碳源和吐温80（Tween80）对云芝木聚糖酶产醇的影响，当以1％滤纸为碳源时，木聚精酶活最高可达11U／mL，用微晶纤维素为碳源时也能产生很高的木聚精酶．而以1％木聚糖为碳源时，只能产生很低的木聚精酶活．Tween80对木聚糖酶的产生具有明显的促进作用，分别可达3倍（微晶纤维素为碳原）和30％以上（滤纸为碳源），这主要由于Tween80能促进木糖耷醉的分泌，提高胞外木糖苷酶的活性。     

紫外线诱变提高细菌产纤维素酶活力的研究

从南京红山动物园土样及食草动物的粪便中分离出14种产纤维素酶菌株,其中F1表现出较高的酶活力.以F1为出发菌株,通过紫外线诱变处理,采用透明圈法初筛和摇瓶培养复筛,获得了10株高产纤维素酶的突变株Q1～Q10.经紫外线诱变处理的Q3突变株产酶活力最高,与出发菌株相比酶活力提高了15.8倍.     

Phospholipids of two strains of dermatophyte,Arthroderma uncinatum

The phospholipid composition of a mutant strain of the dermatophyteArthroderma uncinatum was compared with that of the wild type. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, diphosphatidylglycerol, phosphatidylinositol, and phosphatidic acid were present, and there was marked variation in the amounts of phosphatidylcholine, phosphatidylserine, and phosphatidic acid in the two strains. Thus, the ratio of phosphatidylcholine (wild type) to phosphatidylcholine (mutant) was 2∶1; the ratio of phosphatidylserine (wild type) to phosphatidylserine (mutant) was 3∶1 and the ratio of phosphatidic acid (wild type) to phosphatidic acid (mutant) was 1∶5. In both strains, the predominant fatty acid was 18∶2, with 54.0% in the wild type and 46.7% in the mutant. Qualitatively, the same fatty acids, with the exception of C_20∶0, were found in all of the phospholipid classes; C_20∶0, both in the mutant strain (5.79%) and the wild type (trace amounts), was associated with phosphatidylserine. There was a significant difference in the rates of growth of the two strains; the mutant strain grew more rapidly than, and produced three times as much mycelium as, the wild type. The mutant strain also produced larger proportions of total lipid and phospholipid than the wild type; there was 20.5% total lipid and ca. 5% phospholipid in the mutant compared with 15.5% total lipid and 2.6% phospholipid in the wild type.     

紫外和快中子结合诱变选育杆菌肽产生菌

在杆菌肽产生菌地衣芽孢杆菌的菌种选育中,利用紫外线照射和快中子辐射相结合的方法,获得突变株B-55,其摇瓶效价较出发菌株提高23%。经过5次传代实验,仍具有稳定的产抗生素特性。     

~(60)Co―γ射线诱变褐色高温单孢菌的研究

以褐色高温单孢菌(Thermomonospora fusca)为出发菌株,通过60Co―γ射线诱变孢子悬液,采用透明圈法初筛和摇瓶培养复筛的方法,获得了一株纤维素酶高产菌株AV5,与出发菌株相比,其产酶能力提高1.8倍。     

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%。     

Mutation of Cl.beijerinckii protoplasts by 60Co-γ irradiation

以产丁醇菌Cl.beijerinckii为出发菌株,将其原生质体化后进行⁶⁰Co-γ辐照诱变,筛选出了一株稳定高产的变异株。原生质体的最优制备条件为：将培养至15 h的细胞添加1 g.L^-1甘氨酸和0.3 U.L^-1青霉素培养2 h后,37℃下,2×10⁴ U.L^-1溶菌酶作用8 h脱壁。经平板计数,原生质体形成率可达99.82％,原生质体再生率达10.12％。采用⁶⁰Co-γ射线进行辐照诱变,当辐照剂量率5 Gy.min^-1,辐照剂量为500 Gy时,原生质体致死率可达99.3％。经反复筛选,获得一株丁醇高产菌株R₃,该菌具有较高的遗传稳定性。在P₂半合成液体培养基中,37℃下静置培养72 h,总溶剂产量较出发菌株提高81.46％,丁醇产量提高85.41％。     

高产谷胱甘肽酵母菌株的选育和培养条件的初探

以Saccharomyces cerevisiaeG796-2为出发菌株,通过紫外线照射结合乙硫氨酸平板筛选,连续两代诱变筛选分离得到高产突变株Saccharomyces cerevisiae SE-2;摇瓶试验胞内谷胱甘肽含量达到2.2%,较出发菌株G796-2提高62.9%,传代试验表明其遗传性能稳定。对SE-2的培养条件进行了研究。采用正交化实验和双碳源实验对培养基进行优化,结果表明,最佳初糖浓度6%,葡萄糖/糖蜜=3.5:1,半胱氨酸的添加浓度5mmoL?L?1较为适宜。在优化的培养条件下培养39h,SE-2谷胱甘肽总量达180mg?L?1以上,较G796-2提高81.2%。     

Ni2+-Fe3+-CO2-3-LDHs亲油改性及其除油性能研究

尿素作为沉淀剂,采用均相沉淀技术制备了Ni2+-Fe3+-CO2-3-LDHs层状材料.以Ni2+-Fe3+-CO2-3-LDHs作为前驱体,分别与NaCl、十二烷基磺酸钠(CH3(CH2)11SO3Na)进行离子交换反应得到Ni2+-Fe3+-CH3(CH2)11SO-3-LDHs新型吸附剂材料,成功实现了将CH3(CH2)11SO-3负载到Ni2+-Fe3+-LDHs层状材料,对Ni2+-Fe3+-CO2-3-LDHs进行亲油改性,研究表明该改性后的材料为介孔材料,其比表面积为196.2m2/g,平均孔径为18.3nm.利用Ni2+-Fe3+-CH3(CH2)11SO-3-LDHs复合材料对含油污水进行处理,实验表明十二烷基磺酸根离子插层Ni2+-Fe3+-LDHs后的产物增强了LDHs的亲油吸附性能,其饱和吸附量为6.57μL/g.     

Carob Fruit Polyphenols Reduce Tocopherol Loss,Triacylglycerol Polymerization and Oxidation in Heated Sunflower Oil

Heated oils may contain potentially toxic altered compounds. A denatured carob fiber, very rich in non-extractable tannins (Exxenterol^®), exhibits antioxidant activities in in vitro experiments. The present study was designed to evaluate in sunflower oil (SO) heated to frying temperature, the protective effect on oil thermal oxidation and polymerization of adding 10 mg Exxenterol/kg oil (SO-10) and 50 mg Exxenterol/kg oil (SO-50). After 2, 8 and 16 h at 180 °C, SO displayed a relevant increase in triacylglycerol-derived polar material (PM) and polymer contents and a decrease in α-tocopherol concentrations. Thermal oxidation changes were significantly checked in SO-50 throughout the 16-h heating, while SO-10 only displayed protection from thermal oxidation during the first 2 h of heating. Oil frying-life was doubled because formation of PM and polymers was inhibited by more than 50%. Results clearly show that this non-extractable tannin-rich fiber can be successfully employed as an additive to significantly prolong sunflower oil frying-life, and thus decrease the potential toxicity of the heated oil.     

Mechanical and fracture behavior of an artificially ultraviolet‐irradiated poly(ethylene‐carbon monoxide) copolymer

In this work, 1 wt % carbon monoxide (CO) poly(ethylene‐carbon monoxide) (ECO) copolymer sheets were artificially exposed to ultraviolet (UV) light with a power density of 3 mW/cm² for up to 130 h. A thorough mechanical characterization of the irradiated material was conducted, in which both the stress–strain data and the values of the quasistatic crack initiation and growth toughness were measured and correlated with companion uniaxial tensile tests and single‐edge‐notched fracture tests. Average values of the elastic modulus, failure strain, and failure stress were determined from the tensile tests. The full‐field optical technique of digital image correlation was used to quantify in‐plane deformation (displacements and displacement gradients) during the fracture experiments and to extract values of the crack initiation and growth fracture toughness. The elastic modulus increased monotonically with UV irradiation for the exposure times used in this investigation. In addition, for low irradiation times of less than 5 h, both the failure strain and failure stress of ECO decreased, and this caused a corresponding decrease in the crack initiation and growth toughness. However, for longer irradiation times, the failure strain remained almost invariable, whereas the failure stress increased by about 25% over that of unirradiated ECO. As a result, for longer irradiation times (>5 h), 1 wt % CO ECO became not only stiffer but also stronger and tougher, as quantified by companion fracture experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 139–148, 2004