共查询到17条相似文献,搜索用时 97 毫秒
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产氨基酰化酶米曲霉高产菌株的选育 总被引:4,自引:0,他引:4
采用亚硝基瓜抑菌圈法对米曲霉菌株3042,AF92011,AF93018,AF93020,AF93022,AF93332进行诱变处理,从诱变菌株中筛选到几个高产氨基酰化酶菌株(3042-5,AF93020-2,AF93020-6和AF93022-5),对DL-蛋氨酸的拆分活力分别比出发菌株提高34.1%、157.6%、152.4%和145.4%,其中米曲霉菌株3042的诱变菌株3042-5最高酶活力达203.1U/ml 相似文献
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通过在不同的反应时间,反应温度,缓冲液种类及pH条件下测定氨基酰化酶的活力,得出氨基酰化酶的最佳活力条件。试验结果表明,氨基酰化酶在反应温度为37℃、磷酸缓冲液pH为7.5、与底物反应30 m in时,活力最高。 相似文献
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用荧光光谱法、截流荧光法和酶活力测定法研究了在盐酸胍溶液中米曲霉氨基酰化酶变性动力学。我们发现在4.8mol/L盐酸胍溶液作用下(0.05mol/L磷酸缓冲溶液,pH7.4,25℃),氨基酰化酶二聚体解离成单亚基过程是一个十分快速的过程,反应速率常数k为3361l/s,即约需3ms时间完成;而单亚基分子的构象变化需要约20min方能到达平衡态,这是一个逐渐变化的缓慢过程。酶分子在胍作用下的失活现象同酶分子的结构变化紧密相关,在胍浓度大于4mol/L时酶完全失活。在高浓度盐酸胍下酶失活主要是因为酶二聚体迅速解离成单亚基的过程和单亚基构象逐渐变化的缓慢过程。双亚基解离常数大小标志着酶分子亚基间作用力的强弱。 相似文献
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Water Concentration and Activity Effects on Aminoacylase in Aqueous/Organic One-Liquid-Phase Systems
Aminoacylase has been employed as a model system to study its catalytic properties at low water concentrations/water activities with different water-miscible organic cosolvents. Cosolvents assayed were alcohols and polyols with pure logarithm of the partition coefficient (log P) values, on the standard water/octanol system, ranging between -5.2 and 0.24.
Experimental hydrolysis equilibrium constants (Kapp), at a constant water concentration, decreased with the fall in log P of the cosolvent, as well as with reduction of the water concentration/water activity, as would be expected. The enzyme hydrolytic and synthetic activities, measured at a constant water concentration/water activity value, followed a sigmoidal dependence on log P of the cosolvent employed when the water concentration or water activity values were lower than 50% (w/w) or 0.66, respectively. This became a hyperbolic relationship at higher water concentration/water activity values. A linear relationship between the logarithm of the limiting water activity necessary to maintain enzyme activity and log P was obtained. Both hydrolytic and synthetic activities were suppressed for water activities higher than 0.66 and cosolvents with log P lower than -1.6. 相似文献
Experimental hydrolysis equilibrium constants (Kapp), at a constant water concentration, decreased with the fall in log P of the cosolvent, as well as with reduction of the water concentration/water activity, as would be expected. The enzyme hydrolytic and synthetic activities, measured at a constant water concentration/water activity value, followed a sigmoidal dependence on log P of the cosolvent employed when the water concentration or water activity values were lower than 50% (w/w) or 0.66, respectively. This became a hyperbolic relationship at higher water concentration/water activity values. A linear relationship between the logarithm of the limiting water activity necessary to maintain enzyme activity and log P was obtained. Both hydrolytic and synthetic activities were suppressed for water activities higher than 0.66 and cosolvents with log P lower than -1.6. 相似文献
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在双水相系统中生物转化丙烯腈为丙烯酰胺的研究 总被引:2,自引:0,他引:2
本文研究了以产腈水合酶的恶臭假单胞菌JP-1,在聚乙二醇/磷酸盐双水相系统中转化丙烯腈为丙烯酰胺的条件.双水相系统的组成为:聚乙二醇6000浓度0.05g/ml,磷酸氢二钾浓度0.20g/ml,丙烯腈浓度0.30mol/L,含酶细胞浓度0.10g/ml,pH9.0.25℃时转化率最高;pH10.0时酶最稳定;温度越低,酶的稳定性越好.还研究了在反应过程中间歇补充丙烯腈生成丙烯酰胺,以及从反应液中提纯丙烯酰胺的方法. 相似文献
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以竹叶黄酮水提溶液为原料,采用PEG(聚乙二醇)/(NH4)2SO4双水相体系对竹叶黄酮进行萃取,考察了PEG平均相对分子质量、PEG质量分数、(NH4)2SO4质量分数、pH值、NaCl质量分数、原液质量分数、萃取温度等对双水相及竹叶黄酮萃取效果的影响。双水相萃取法提取竹叶黄酮的最优条件为:PEG 400 31%,(NH4)2SO411%,pH 3.9,NaCl 0.7%,原液51.5%,萃取温度20℃,在此条件下得到的竹叶黄酮萃取率为97.8%。结果说明,双水相萃取法操作简单方便,成本低,不会引起生物质失活或变性,适合于黄酮类化合物的萃取分离。 相似文献
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白地霉Cryytococcus neoformans脂肪酶的双水相萃取 总被引:2,自引:0,他引:2
本文研究了不同无机盐的双水相体系对白地霉脂肪酶的萃取分离效果,对PEG/(NH4)2SO4成相系统进行了系统的研究,通过考察体系PEG分子量、不同的无机盐、PEG浓度、(NH4)2SO4浓度、离子强度、pH值及(NH4)2SO4浓度对反萃取的影响,并通过正交实验进一步优化了实验条件,初步确定在PEG浓度15%,(NH4)2SO4浓度22.5%,pH8.0,不加NaCl的条件下进行双水相萃取,脂肪酶分离系数和纯化倍数分别为6.8和7.5,比活力达到40.3 U/mg蛋白。 相似文献
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Amanda Reges de Sena Flávio Manoel Barros Oliveira Tonny Cley Campos Leite Talita Camila Evaristo da Silva Nascimento Keila Aparecida Moreira 《Preparative biochemistry & biotechnology》2017,47(9):945-951
The aims of the current study are to assess the influence of polyethylene glycol (PEG) concentration, molar mass, pH, and citrate concentrations on aqueous biphasic systems based on 24 factorial designs, as well as to check their capacity to purify tannase secreted by Aspergillus tamarii URM 7115. Tannase was produced through submerged fermentation at 26°C for 67?h in Czapeck-Dox modified broth and added with yeast extract and tannic acid. The factorial design was followed to assess the influence of PEG molar mass (MPEG 600; 4,000 and 8,000?g/?mol), and PEG (CPEG 20.0; 22.0 and 24.0% w/w) and citrate concentrations (CCIT 15.0, 17.5, and 20.0%, w/w), as well as of pH (6.0, 7.0, and 8.0) on the response variables; moreover, partition coefficient (K), yield (Y), and purification factor (PF) were analyzed. The most suitable parameters to purify tannase secreted by A. tamarii URM 7115 through a biphasic system were 600 (g/mol) MPEG, 24% (w/w) CPEG, 15% (w/w) CCIT at pH 6.0 and they resulted in 6.33 enzyme partition, 131.25% yield, 19.80 purification factor and 195.08 selectivity. Tannase secreted by A. tamarii URM 7115 purified through aqueous biphasic systems composed of PEG/citrate can be used for industrial purposes, since it presents suitable purification factor and yield. 相似文献
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复合诱变对米曲霉产曲酸的影响 总被引:4,自引:0,他引:4
发酵法生产曲酸还未实现大规模工业化生产的原因之一是曲酸菌种产酸率较低,本文以平展米曲霉(Aspergillus oryzae effusus)AS32为出现菌株,经UV和^60Co诱变处理,筛选获得一株高产曲酸变异株AUR163,以葡萄糖为碳源,酵母膏为氮源,32℃摇瓶和30L罐发酵培养4天,产酸达6.8g/100mL。平均生产效率为17.0g/L.d最高可达30.5g/L.d比出发菌AS32提高190%以上,这表明UV和^60Co作诱剂,可以大幅度提高米曲霉的曲酸生产效率。 相似文献
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Aqueous two-phase systems 总被引:6,自引:0,他引:6
Dr. Rajni Hatti-Kaul 《Molecular biotechnology》2001,19(3):269-277
Biphasic systems formed by mixing of two polymers or a polymer and a salt in water can be used for separation of cells, membranes,
viruses, proteins, nucleic acids, and other biomolecules. The partitioning between the two phases is dependent on the surface
properties and conformation of the materials, and also on the composition of the two-phase system. The mechanism of partitioning
is, however, complex and not easily predicted. Aqueous two-phase systems (ATPS) have proven to be a useful tool for analysis
of biomolecular and cellular surfaces and their interactions, fractionation of cell populations, product recovery in biotechnology,
and so forth. Potential for environmental remediation has also been suggested. Because ATPS are easily scalable and are also
able to hold high biomass load in comparison with other separation techniques, the application that has attracted most interest
so far has been the large-scale recovery of proteins from crude feedstocks. As chemicals constitute the major cost factor
for large-scale systems, use of easily recyclable phase components and the phase systems generated by a single-phase chemical
in water are being studied. 相似文献