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Soares Cleide M. F. De Castro Heizir F. Santana M. Helena A. Zanin Gisella M. 《Applied biochemistry and biotechnology》2002,98(1-9):863-874
In agreement with previous studies, promising results were obtained when lipase was immobilized on controlled pore silica
(CPS) in the presence of polyethylene glycol (PEG 1500). This methodology rendered immobilized derivatives with higher operational
stability than those lacking PEG 1500. This article extends the scope of this approach by evaluating the combined effects
of PEG concentration and lipase loading employing a multivariate statistical approach. A 22 factorial design with center point was adopted for a full understanding of these effects and their interactions. Conditions
that maximize the immobilization yield were different from those attained for the biocatalyst’s operational stability. Possible
reasons for the increase in both activity and stability of lipase immobilized on CPS in the presence of PEG 1500 are discussed
in light of the influence of surface hydrophilic/hydrophobic balance. 相似文献
125.
Tullia Gallina Toschi William W. Christie Lanfranco S. Conte 《Journal of separation science》1993,16(12):725-730
The triacylglycerol composition of olive oil samples has been determined by stereospecific analysis after partial hydrolysis with ethyl magnesium bromide, derivatization, preparative chiral HPLC, transesterification, and GC quantitation of fatty acid methyl esters. The data obtained for position sn-2 were compared with those from capillary GC analysis of monoacyl sn-2-glycerols after enzymatic lipolysis of triacylglycerols. The determination of triacylglycerols collected by silver ion HPLC and quantified (as fatty acid methyl esters) by GC, together with direct GC analysis on a polar column, have then furnished a comprehensive picture of the triacylglycerol content of olive oil. 相似文献
126.
Serebryakov E. P. Shcherbakov M. A. Gamalevich G. D. Struchkova M. I. 《Russian Chemical Bulletin》2003,52(3):734-739
Two new methods for the determinatuion of the absolute configuration of methyl 4-methyl-6-(2-methylprop-1-enyl)cyclohexa-1,3-dienecarboxylate are proposed, and the configurations attributed previously to its (+)- and (–)-enantiometers are confirmed. Chiral methyl carboxylate is converted into the corresponding alcohol whose configuration is deduced from either the rate of hydrolysis of the respective racemic acetate in the presence of pancreatic lipase (method 1) or from the difference between the Eu(fod)3-induced shifts of the MeO signals in the 1H NMR spectra of the diastereomeric esters of S- or R-Mosher"s acid (method 2). 相似文献
127.
L.?E.?RodgersEmail author P.?J.?Holden R.?B.?Knott K.?S.?Finnie J.?R.?Bartlett L.?J.?R.?Foster 《Journal of Sol-Gel Science and Technology》2005,33(1):65-69
The application of small angle neutron scattering (SANS) to the characterisation of sol–gel hosts containing biomolecules offers the opportunity to explore the relationship between gel structure and catalyst. A model system involving the immobilisation of Candida antarctica lipase B (CALB) was investigated.Gels were produced by fluoride-catalysed hydrolysis of fixed ratios of tetramethylorthosilicate (TMOS) and methyltrimethoxysilane (MTMS). Phase separation between the enzyme and the evolving sol–gel matrix was minimised by incorporating glycerol into the sol–gel precursor solution. The potential stabilising effect of the NaF catalyst upon the enzyme was also investigated. Scattering studies were conducted on both immobilised lipase, and lipase in free solution. Scattering studies on free enzyme provided evidence of multiple populations of enzyme aggregates and showed that choice of solvent affected the degree of aggregation. Both NaF and glycerol affected neutron scattering, indicating changes in lipase conformation. Increasing glycerol concentration increased the degree of aggregation and produced differences in solvent packing on the surface of protein molecules. Initial evidence from SANS data indicated that the presence of the enzyme during gel formation conferred structural changes on the gel matrix. Modelling the effect of sol–gel encapsulation on lipase requires comparison of data from free enzyme to the immobilised form. Removal of the enzyme from the sol–gel structure, post gelation, is necessary to better characterise the modified matrix. This methodological problem will be the subject of future investigations. 相似文献
128.
129.
Freire Denise M. Teles Elaine M. F. Bon Elba P. S. Anna Geraldo Lippel Sant’ 《Applied biochemistry and biotechnology》1997,(1):409-421
A preliminary screening work selectedPenicillium restrictum as a promising micro-organism for lipase production. The physiological response of the fungus towards cell growth and enzyme
production upon variable carbon and nitrogen nutrition, specific air flow rate (Qa) and agitation (N) was evaluated in a 5-L
bench-scale fermenter. In optimized conditions for lipase production meat peptone at 2% (w/v) and olive oil at 1% (w/v) were
used in a growth medium with a C/N ratio of 9.9. Higher C/N ratios favored cell growth in detriment of enzyme production.
Low extracellular lipase activities were observed using glucose as carbon source suggesting glucose regulation. Final lipase
accumulation of 13,000 U/L was obtained, using optimized specific air flow rate (Qa) of 0.5 wm and an impeller speed (N) of
200 rpm. Agitation showed to be an important parameter to ensure nutrient availability in a growth medium having olive oil
as carbon source. 相似文献
130.
Laura F. Solares 《Tetrahedron》2006,62(14):3284-3291
Enzymatic acetylations of N-substituted cis- and trans-3,4-dihydroxypiperidine and hydrolysis of their diacetylated derivatives have been studied. High enantioselectivities are obtained with Pseudomonas cepacia lipase and Candida antarctica lipase B for the hydrolysis of the trans-derivative, while the cis-derivatives are not adequate substrates in the same biocatalytic conditions. The enantiopreference of these processes can be rationalized by means of a molecular modelling study. 相似文献