共查询到20条相似文献,搜索用时 15 毫秒
1.
Angela Martino Pier G. Pifferi Giovanni Spagna 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1994,61(3):255-260
This paper describes a new, simple and inexpensive procedure for separating pectinlyase (PL, EC 4.2.2.3) from β-glucosidase (β-glu, EC 3.2.1.21), both of which have potential for use in the beverage processing industry. The method described here, which entails the treatment of crude preparations with bentonite (4% (w/v)) and the acidification of the resulting supernatant to pH 3·5, leads to the production of two enzymic solutions which contain PL and β-glu, respectively. In both solutions the amount of brown pigment is considerably less than in the crude mixture, and partial purification from extraneous proteins is also achieved. 相似文献
2.
Natividad Ortega Maria D. Busto Manuel Perez-Mateos 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1998,73(1):7-12
β-D -Glucosidase was immobilised by entrapment in two different matrices (calcium alginate and polyacrylamide gels), in order to compare how the immobilisation could stabilise the enzyme towards thermal and proteolytic deactivation. While the enzyme trapped in polyacrylamide gel showed an optimum temperature for activity at 10°C lower than that of the free enzyme, the optimal temperature after immobilisation in alginate beads was not altered (60°C). The immobilisation of enzyme in alginate beads caused a larger increase in the thermal stability than the entrapment in polyacrylamide gels. The stabilisation factors obtained as 55, 60 and 65°C for β-glucosidase immobilised in alginate and polyacrylamide gels were 2·03, 3·06, 2·19 and 2·04, 0·35, 1·01, respectively. In contrast, the β-glucosidase immobilised in polyacrylamide gels was more resist-ant in proteolysis than that trapped in alginate beads. © 1998 Society of Chemical Industry 相似文献
3.
Rubn Cuervo Fernndez Beatriz Guilarte Maresma Antonio Jurez Josefina Martínez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(3):268-272
β‐fructofuranosidase (EC 3.2.1.26) from Aspergillus sp 27H isolated from soil was investigated for production of fructooligosaccharides (FOS) using whole cells. It possesses hydrolytic and transfructosylating activities that can be altered by modifying the reaction conditions. The optimal conditions for the transfructosylating activity occur in the pH range 5.5–6.0 and at 60 °C, while hydrolytic activity was highest at pH 4.0 and 55 °C. At low sucrose concentration (10 g dm?3) there was rapid conversion of sucrose to glucose and fructose and very low concentrations of FOS were obtained. However, at sucrose concentrations higher than 216 g dm?3 the concentrations of hydrolysis products were reduced. Under the following conditions: pH 5.5, temperature 40 °C, sucrose concentration 615 g dm?3 and enzyme concentration 20β‐fructofuranosidase units g?1 of sucrose, the FOS concentration reached a maximum value of 376 g dm?3 (234 g dm?3 1‐kestose and 142 g dm?3 nystose) and the proportion of FOS in the solids in the reaction mixture was 600–620 g kg?1 at 6 h. These results suggest that β‐fructofuranosidase from Aspergillus sp 27H could be an appropriate enzyme for the commercial production of FOS. Copyright © 2004 Society of Chemical Industry 相似文献
4.
Juan L. Lequerica Teresa Valds Caspar Prez-Martínez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,54(2):151-157
Activities of endo-β-4-glucanase and β-glucosidase from Clostridium papyrosolvens (CECT 747) were studied under different conditions. No indications were found for the presence of more than one β-glucosidase after ion exchange and ammonium sulphate fractionation. β-Glucosidase showed activity against p-nitrophenyl-β-D-glucopyranoside and cellobiose but was not inhibited by δ-gluconolactone. Independent cellobiose phosphorylase activity could also be detected. The β-glucosidase was essentially intracellular. By the use of stationary phase culture assays, enzyme induction at low concentrations of cellobiose was observed, whilst glucose had no effect. Regulation of endo-β-1,4-glucanase and β-glucosidase were compared. 相似文献
5.
Lucília Domingues Carla Oliveira Inês Castro Nelson Lima Jos A Teixeira 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(8):809-815
Improved productivity and costs reduction in fermentation processes may be attained by using flocculating cell cultures. The production of extracellular heterologous β‐galactosidase by recombinant flocculating Saccharomyces cerevisiae cells, expressing the lacA gene (coding for β‐galactosidase) of Aspergillus niger under the ADHI promotor and terminator in a bioreactor was studied. The effects of lactose concentration and yeast extract concentration on β‐galactosidase production in a semi‐synthetic medium were analysed. The extracellular β‐galactosidase activity increased linearly with increasing initial lactose concentrations (5–150 g dm?3). β‐Galactosidase production also increased with increased yeast extract concentration. During the entire fermentation, no accumulation of the hydrolysed sugars, glucose and galactose, was observed. The catabolic repression of the recombinant strain when cultured in a medium containing equal amounts of glucose and galactose was confirmed. In complete anaerobiosis, the fermentation of lactose resulted in a very slow fermentation pattern with lower levels of β‐galactosidase activity. The bioreactor operation together with optimisation of culture conditions (lactose and yeast extract concentration) led to a 21‐fold increase in the extracellular β‐galactosidase activity produced when compared with preliminary Erlenmeyer fermentations. Copyright © 2004 Society of Chemical Industry 相似文献
6.
Krishna Bahadur SomaiMagar Yong Rok Lee 《Advanced Synthesis \u0026amp; Catalysis》2014,356(16):3422-3432
Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.
7.
Dirk G. Derycke Erick J. Vandamme 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1984,34(1):45-51
An inulinase producing Aspergillus niger strain was isolated from Compositae rhizosphere soil samples. High inulinase levels were produced on a corn steep liquor (CSL)-maltose medium in the absence of inulin at 28°C within 110 h of fermentation. Media based on CSL-sucrose yielded high cell-bound inulinase activity; on inulin-based media the enzyme was mainly extracellularly produced. Both crude extra-and intracellular inulinase preparations displayed identical pH and temperature optima with maximal activity at pH 4.3–4.4 and at 55–56°C. These properties are favourable in view of large scale inulinase application for pure fructose production. High operation temperatures would avoid microbial contamination of reactors and would allow the use of high inulin-substrate concentrations, a limiting factor in obtaining high conversion ratios. The remarkably low pH optimum prevents colour formation and undesirable chemical side reactions. An advantageous low ratio of invertase to inulinase activity (S/I value) of 0.85 was found for the crude extracellular enzyme preparation. Crude inulin (chicory) extracts are hydrolysed faster than pure inulin. Apart from inulin (100% hydrolysis), sucrose (45%) and raffinose (20%) are also hydrolysed, and no liberation of oligomers or of sucrose from inulin was observed. These facts indicate that the A. niger enzyme is an exo-acting inulinase. The above characteristics make this A. niger inulinase an industrially attractive enzyme for the preparation of pure fructose from inulin-containing agricultural crops. 相似文献
8.
Vladimír Jirk 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,65(2):179-185
Aspergillus vesicolor mycelial cells were covalently immobilized on a glutaraldehyde-ε-amino-caproyl-NH2-Separon, and the constitutively-produced β-glucanase system and some properties of purified β-1,3-glucanase were compared with those of freely suspended cells. It was found that the mycelial immobilization modulates the composition of the β-glucanase system as well as stimulates the export of a functionally different β-1,3-glucanase. 相似文献
9.
Michael Lloyd Richard Lloyd Philip Keene Andrew Osborne 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(12):1099-1106
BACKGROUND: Pharmaceutical companies continue to evaluate β‐amino acids and β‐lactams in a range of drug candidates. The development of a highly efficient and selective bioresolution of cyclic β‐lactam substrates could yield enantiopure lactams and β‐amino acids with medicinal potential. The aim of this work was to discover and develop a biocatalyst capable of selectively hydrolysing β‐lactam substrates. RESULTS: Screening of our in‐house culture collection led to the discovery of a microorganism, Rhodococcus globerulus (NCIMB 41042) with β‐lactamase activity. Whole‐cell bioresolutions of the β‐lactams 1–4 were successfully carried out and in all cases enantiomeric excesses of the residual lactam and amino acid product were found to be greater than 98%. For one example, the bioresolution was optimised to operate at 60 g L?1 substrate concentration with a 20% wt/wt cell paste loading. CONCLUSION: A microorganism, Rhodococcus globerulus (NCIMB 41042), capable of selectively hydrolysing a range of cyclic β‐lactams, has been discovered. A scalable whole‐cell bioresolution process has been developed, leading to the synthesis of multigram quantities of enantiomerically pure β‐lactams and β‐amino acids. Copyright © 2007 Society of Chemical Industry 相似文献
10.
Gaetano Giammona Gennara Cavallaro Giovanna Pitarresi Elisa Pedone 《Polymer International》2000,49(1):93-98
In the present study the derivatization of two water‐soluble synthetic polymers, α,β‐poly(N‐2‐hydroxyethyl)‐DL ‐aspartamide (PHEA) and α,β‐polyasparthylhydrazide (PAHy), with glycidyltrimethylammonium chloride (GTA) is described. This reaction permits the introduction of positive charges in the macromolecular chains of PHEA and PAHy in order to make easier the electrostatic interaction with DNA. Different parameters affect the reaction of derivatization, such as GTA concentration and reaction time. PHEA reacts partially and slowly with GTA; on the contrary the reaction of PAHy with GTA is more rapid and extensive. The derivatization of PHEA and PAHy with GTA is a convenient method to introduce positive groups in their chains and it permits the preparation of interpolyelectrolyte complexes with DNA. © 2000 Society of Chemical Industry 相似文献
11.
Shuhong Mao Boyuan Hua Na Wang Xiaojie HU Zhijiang Ge Yanqing Li Sha Liu Fuping Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2013,88(2):287-292
BACKGROUND: The improved efficiency of steroid biotransformation using the biphasic system is generally attributed to the positive effect on the solubility of substrate in aqueous media. A promising alternative for the application of organic solvents in biphasic systems is the use of ionic liquids (ILs). This study aims to investigate the applicability of the biphasic ILs/water system for 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by Aspergillus ochraceus. RESULTS: Of the seven ILs tested, [C3mim][PF6] exhibited the best biocompatibility, with markedly improved biotransformation efficiency. In the [C3mim][PF6]‐based biphasic system, substrate conversion reached 90% under the condition in which buffer pH, volume ratio of buffer to ILs, cell concentration, and substrate concentration were 4.8, 10/1, 165 g L?1 and 20 g L?1, respectively. This is more efficient than that of the monophasic aqueous system. The effects of the cations and anions of these ILs on the 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus is also discussed. CONCLUSION: The above results showed that IL/water biphasic system improved the efficiency of 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus, thus suggesting the potential industrial application of ILs‐based biphasic systems for steroid biotransformation. © 2012 Society of Chemical Industry 相似文献
12.
Eleonora Gianolio Resmi Mohan Albrecht Berkessel 《Advanced Synthesis \u0026amp; Catalysis》2016,358(1):30-33
The dynamic kinetic resolution of α‐substituted racemic β‐lactams by alcoholytic ring‐opening, catalyzed by immobilized lipase B from Candida antarctica is described. With this process, a variety of racemic α‐substituted N‐Cbz‐azetidinones (Cbz=benzyloxycarbonyl) was transformed to the corresponding N‐Cbz‐protected β2‐amino acid allyl esters with high enantioselectivity (up to 99%) and high yields (up to quantitative) at room temperature.
13.
Guoqiang Zheng Songwei Li Xiaoli Zhang Chuntai Liu Kun Dai Jingbo Chen Qian Li Xiangfang Peng Changyu Shen 《Polymer International》2011,60(7):1016-1023
On the premise that shear in the slit die of an extruder was minimized as far as possible, β‐nucleated isotactic polypropylene (iPP) was extruded. Simultaneously, once the extrudate (in the melt state) left the die exit, it was stretched at various stretching rates (SRs). For iPP with a low content of β‐nucleating agent (β‐NA), the crystallinity of β‐phase (Xβ) initially increases with increasing SR, and then decreases slightly with further increase in SR. However, for iPP containing a higher content of β‐NA, with increasing SR, Xβ decreases monotonically, indicating a negative effect of SR on β‐phase formation. Small‐angle X‐ray scattering and polarized optical microscopy experiments reveal that, when SR is less than 30 cm min?1, the increasing amount of row nuclei induced by increasing SR is mainly responsible for the increase of Xβ. In contrast, when SR exceeds 30 cm min?1, the overgrowth of shish structures unexpectedly restrains the development of β‐phase, and spatial confinement is considered as a better explanation for the suppression of β‐phase. Copyright © 2011 Society of Chemical Industry 相似文献
14.
Modification of isotactic polypropylene (iPP) with two nucleation agents, namely 1,3:24‐bis(3,4‐dimethylobenzylideno) sorbitol (DMDBS) (α‐nucleator) and N, N′‐dicyclohexylo‐2,6‐naphthaleno dicarboxy amide (NJ) (β‐nucleator), leads to significant changes of the structure, morphology and properties. Both nucleating agents cause an increase in the crystallization temperature. The efficiency determined in a self‐nucleation test is 73.4 % for DMDBS and 55.9 % for NJ. The modification with NJ induces the creation of the hexagonal β‐form of iPP. The addition of DMDBS lowers the haze of iPP while the presence of NJ increases the haze. Copyright © 2004 Society of Chemical Industry 相似文献
15.
Shengwei Chen Qinxin Lou Yuyang Ding Shasha Zhang Wenhui Hu Junling Zhao 《Advanced Synthesis \u0026amp; Catalysis》2015,357(11):2437-2441
We have developed and optimized an enantioselective Michael reaction of malononitrile with β,β‐disubstituted nitroalkenes. This reaction was catalyzed by a cinchona alkaloid derived thiourea catalyst, producing products of high yields (up to 98 %) and stereoselectivities (up to 93 % ee). One of the adducts was used as an intermediate for the synthesis of dihydropyrrole derivative bearing a synthetically valuable quaternary chiral center.
16.
Xiaoting Wu Fang Xie Zheng Ling Liang Tang Wanbin Zhang 《Advanced Synthesis \u0026amp; Catalysis》2016,358(15):2510-2518
A regio‐ and enantioselective copper‐catalyzed 1,4‐conjugate addition of trimethylaluminium to linear δ‐aryl‐substituted α,β,γ,δ‐unsaturated alkyl ketones was developed. A series of γ,δ‐unsaturated alkyl ketones were obtained in good yields with high regio‐ and enantioselectivity (up to 88% ee and 96:4 dr). Expansion of the reaction scope to substrates containing aromatic heterocycles also afforded good yields and enantioselectivities (up to 91% ee) with very high regioselectivities, exclusively providing the single 1,4‐products.
17.
Xing‐Kuan Chen Chang‐Wu Zheng Sheng‐Li Zhao Zhuo Chai Ying‐Quan Yang Gang Zhao Wei‐Guo Cao 《Advanced Synthesis \u0026amp; Catalysis》2010,352(10):1648-1652
A highly enantioselective Michael addition of cyclic 1,3‐dicarbonyl compounds to β,γ‐unsaturated α‐keto esters catalyzed by amino acid‐derived thiourea‐tertiary‐amine catalysts is presented. Using 5 mol% of a novel tyrosine‐derived thiourea catalyst, a series of chiral coumarin derivatives were obtained in excellent yields (up to 99%) and with up to 96% ee under very mild conditions within a short reaction time. 相似文献
18.
ZsuzsannaCs. Gyarmati Arto Liljeblad Gyula Argay Alajos Klmn Gbor Bernth LiisaT. Kanerva 《Advanced Synthesis \u0026amp; Catalysis》2004,346(5):566-572
Racemic cis‐10‐azatetracyclo[7.2.0.12,6.14,8]tridecan‐11‐one was prepared from homoadamant‐4‐ene by chlorosulfonyl isocyanate addition. The transformation of the β‐lactam to the corresponding β‐amino ester followed by Candida antarctica lipase A‐catalyzed enantioselective (E>>200) N‐acylation with 2,2,2‐trifluoroethyl butanoate afforded methyl (1R,4R,5S,8S)‐5‐aminotricyclo[4.3.1.13,8]undecane‐4‐carboxylate and the (1S,4S,5R,8R)‐butanamide with>99% ee at 50% conversion. Alternatively, transformation of the β‐lactam to the corresponding N‐hydroxymethyl‐β‐lactam and the following Pseudomonas cepacia (currently Burkholderia cepacia) lipase‐catalyzed enantioseletive O‐acylation provided the (1S,4S,6R,9R)‐alcohol (ee=87%) and the corresponding (1R,4R,6S,9S)‐butanoate (ee>99%). In the latter method, competition for the enzyme between the (1R,4R,6S,9S)‐butanoate, 2,2,2‐trifluoroethyl butanoate and the hydrolysis product, butanoic acid, tended to stop the reaction at about 45% conversion and finally gave racemization in the (1S,4S,6R,9R)‐alcohol with time. 相似文献
19.
Luca Deiana Gui‐Ling Zhao Shuangzheng Lin Pawel Dziedzic Qiong Zhang Hans Leijonmarck Armando Crdova 《Advanced Synthesis \u0026amp; Catalysis》2010,352(18):3201-3207
The first example of a highly enantioselective organocatalytic aziridination of α‐substituted α,β‐unsaturated aldehydes is presented. The reaction is catalyzed by simple chiral amines and gives access to highly functional terminal azirdines containing an α‐tertiary amine stereocenter in high yields and enantiomeric ratios (95.5:4.5–98:2). 相似文献
20.
Synthesis and Pharmacological Evaluation of α4β2 Nicotinic Ligands with a 3‐Fluoropyrrolidine Nucleus 下载免费PDF全文
Dr. Lucia Tamborini Dr. Andrea Pinto Dr. Roberta Ettari Dr. Cecilia Gotti Dr. Francesca Fasoli Prof. Paola Conti Prof. Carlo De Micheli 《ChemMedChem》2015,10(6):1071-1078
Nicotinic acetylcholine receptors (nAChRs) play an important role in many central nervous system disorders such as Alzheimer’s and Parkinson’s diseases, schizophrenia, and mood disorders. The α4β2 subtype has emerged as an important target for the early diagnosis and amelioration of Alzheimer’s disease symptoms. Herein we report a new class of α4β2 receptor ligands characterized by a basic pyrrolidine nucleus, the basicity of which was properly decreased through the insertion of a fluorine atom at the 3‐position, and a pyridine ring carrying at the 3‐position substituents known to positively affect affinity and selectivity toward the α4β2 subtype. Derivatives 3‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)‐5‐(phenylethynyl)pyridine ( 11 ) and 3‐((4‐fluorophenyl)ethynyl)‐5‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)pyridine ( 12 ) were found to be the most promising ligands identified in this study, showing good affinity and selectivity for the α4β2 subtype and physicochemical properties predictive of a relevant central nervous system penetration. 相似文献