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排序方式: 共有404条查询结果,搜索用时 15 毫秒
1.
Sirirung Wongsakul Poonsuk Prasertsan Uwe T. Bornscheuer Aran H‐Kittikun 《European Journal of Lipid Science and Technology》2003,105(2):68-73
Commercial immobilized lipases were used for the synthesis of 2‐monoglycerides (2‐MG) by alcoholysis of palm and tuna oils with ethanol in organic solvents. Several parameters were studied, i.e., the type of immobilized lipases, water activity, type of solvents and temperatures. The optimum conditions for alcoholysis of tuna oil were at a water activity of 0.43 and a temperature of 60 °C in methyl‐tert‐butyl ether for ~12 h. Although immobilized lipase preparations from Pseudomonas sp. and Candida antarctica fraction B are not 1, 3‐regiospecific enzymes, they were considered to be more suitable for the production of 2‐MG by the alcoholysis of tuna oil than the 1, 3‐regiospecific lipases (Lipozyme RM IM from Rhizomucor miehei and lipase D from Rhizopus delemar). With Pseudomonas sp. lipase a yield of up to 81% 2‐MG containing 80% PUFA (poly‐unsaturated fatty acids) from tuna oil was achieved. The optimum conditions for alcoholysis of palm oil were similar as these of tuna oil alcoholysis. However, lipase D immobilized on Accurel EP100 was used as catalyst at 40 °C with shorter reaction times (<12 h). This lead to a yield of ~60% 2‐MG containing 55.0‐55.7% oleic acid and 18.7‐21.0% linoleic acid. 相似文献
2.
Guan-Chiun?Lee Dong-Lin?Wang Yi-Fang?Ho Jei-Fu?ShawEmail author 《Journal of the American Oil Chemists' Society》2004,81(6):533-536
Lipase from Pseudomonas fluorescens efficiently catalyzed the alcoholysis of various TG in dry alcohols. For TG with short-chain FA, more MG were accumulated.
The yields of MG were affected by the alcohols used. The maximum yields of MG were as follows: 85% for monoacetin in n-butanol, 96% for monobutyrin in ethanol or n-butanol, 50% for monocaprylin in n-butanol, 48% for monolaurin in isopropanol, and 45% for monopalmitin in isopropanol. The MG produced were judged to be 2-MG
by TLC analysis. The presence of organic cosolvent affected the reaction rate of the lipase-catalyzed alcoholysis of TG. For
the alcoholysis of various TG in ethanol and cosolvent (1∶1, vol/vol), the rates had the following orders: (i) for tributyrin,
hexane > toluene > acetone > ethyl acetate > chloroform > acetonitrile > pyridine; (ii) for tricaprylin, hexane > acetone
> toluene > acetonitrile > ethyl acetate > pyridine > chloroform; and (iii) for trialurin, hexane > acetonitrile=acetone >
ethyl acetate > pyridine=chloroform > toluene. 相似文献
3.
生物地耕法降解含油污泥的研究 总被引:3,自引:0,他引:3
对含油质量分数为9.0%和10.2%的油泥进行生物地耕法的研究。结果表明,生物降解120d后,油泥残油质量分数分别由9.0%和10.2%降至3.1%和4.0%,石油降解率分别为65.6%和60.8%;同时利用气相色谱-质谱分析生物降解前后含油污泥中饱和烃的组分和质量分数变化,含油质量分数为9.0%和10.2%油泥中的长链烷烃分别减少39.8%和42.2%。 相似文献
4.
Xiaoyang Gu 《Theoretical computer science》2011,412(48):6696-6711
Consider the problem of calculating the fractal dimension of a set X consisting of all infinite sequences S over a finite alphabet Σ that satisfy some given condition P on the asymptotic frequencies with which various symbols from Σ appear in S. Solutions to this problem are known in cases where
- (i)
- the fractal dimension is classical Hausdorff or packing dimension (by work of Volkmann and Olsen), or
- (ii)
- the fractal dimension is effective (even finite-state) and the condition Pcompletely specifies an empirical distribution π over Σ, i.e., a limiting frequency of occurrence for every symbol in Σ.
5.
张鉴 《安徽工业大学学报》1997,(3)
根据含化合物金属熔体结构的共存理论、相图和Fe-C系亚稳态化合物的有关热力学数据制定了Fe-Si-C熔体的作用浓度计算模型,计算结果符合实际,从而证明所推导的计算模型可以反映本熔体的结构实际.就碳而言,就碳而言,以饱和为标准态的碳作用浓度Nc′可以通过考虑纯物质到饱和标准态的转换系数Lc来求得. 相似文献
6.
采用直流电弧等离子体法 ,分别在 1个大气压的H2 +Ar和CH4+He混和气氛中制备了Fe、Ni、Fe-Ni合金磁性超微粒子 (UFP)。利用Fe、Ni、Fe-Ni合金超微粒子 ,选择适当的表面活性剂和载液 ,制备了高粘度磁性液体(ML) ,常温 (2 5℃ )粘度为 (2 6~ 6 0 )× 10 5mPa·s,高温 (85℃ )粘度为 (1 0~ 3 2 )× 10 5mPa·s,室温下饱和磁化强度为FeML 2 4 0 8~ 6 8 0 0Am2 /kg,NiML 10 19~ 17 83Am2 /kg,Fe-NiML 2 6 2 1~ 75 13Am2 /kg 相似文献
7.
This paper deals with the problem of global stabilization of linear discrete time systems by means of bounded feedback laws. The main result proved is an analog of one proved for the continuous time case by the authors, and shows that such stabilization is possible if and only if the system is stabilizable with arbitrary controls and the transition matrix has spectral radius less than or equal to one. The proof provides in principle an algorithm for the construction of such feedback laws, which can be implemented either as cascades or as parallel connections (“single hidden layer neural networks”) of simple saturation functions. 相似文献
8.
9.
Effects of feeding conjugated linoleic acid (CLA) to hens on progeny chick development and composition at hatch (NHC) and
three weeks of age (TWC) were assessed. CLA (0 or 0.5%, composed of mixed isomers of cis-9,trans-11 or trans-10,cis-12-CLA) was fed to hens with either safflower (SO) or olive oil (OO) (3 or 3.5%) to assure successful hatch for 2 weeks prior
to collection for incubation. Maternal CLA feeding had no effect on hatchability, but improved egg fertility (p < 0.05). Maternal feeding of CLA with SO increased 21 day-old progeny growth, while CLA with OO decreased growth (oil*CLA,
p < 0.05). In 25 day-old chicks (TWC), but not NHC, maternal CLA decreased the proportion of total body water (p < 0.05) and increased body ash (p < 0.05). While monounsaturated fatty acids were decreased and saturated fatty acids increased in eggs and NHC from hens fed
CLA, no differences in fatty acid composition were observed in chicks at 25 days of age from hens fed CLA. Maternal CLA feeding
resulted in the presence of c9,t11 and t10,c12-CLA in NHC, but only c9,t11 in the TWC. In conclusion, hens fed CLA led to improved fertility and altered body composition at 3 weeks of age. 相似文献
10.
Leila M. Guimarães Aguiar Rogério Matheus Vargas 《Journal of the American Oil Chemists' Society》1998,75(6):755-756
Glycerolysis of methyl stearate and tristearin has been carried out in the presence of alkylguanidines—strong nonionic bases—as
catalysts. When applied at 10 mol%, 1,5,7-triazabicyclo [4.4.0]dec-5-ene, 1,2,3-tricyclohexylguanidine, and 1,3-dicyclohexyl-2-n-octylguanidine give monoglycerides in more than 90% selectivity, in a maximum of 6 h reaction time. 相似文献