Contribution of Response Surface Design to the Synthesis of Monoacylglycerols Catalyzed by Rhizopus sp. lipase

The partially purified lipase from Rhizopus sp was tested as a biocatalyst for the synthesis of monolaurin from lauric acid and glycerol. A central composite rotatable design was applied to optimize the substrate molar ratio and the percentage of molecular sieve for achieving maximum monolaurin yield. The best results were obtained when the molar ratio of substrates was 1:1, the medium contained 100% (w/w) molecular sieve, and the reaction was conducted at 50 °C and 200 rpm applying 2 mg of the partially purified lipase. The maximum yield in monolaurin (17.52%) was achieved after a 72‐h reaction.     

Milling and Processing of Wheat and other Cereals Affect Their Capacity to Inhibit Pancreatic Lipase in Vitro

The inhibition of pancreatic lipase activity by extracts of raw, milled or processed cereals was measured in vitro. The inhibitory activity was high in durum wheat, soft wheat and millet, moderate in barley and white sorghum and very low in red sorghum. Milling whole-grain into flours markedly decreased the lipase inhibitory activity in all species. In durum wheat, the germ and the aleurone-layer fraction exhibited the highest inhibitory activity. Processing of soft wheat by bread making, popping, flaking, drum-drying and extrusion-cooking, or durum wheat by making pasta markedly decreased the lipase inhibitory capacity. Extractible proteins were implicated in the inhibition process. These effects also had some nutritional implications.     

Fluorometric detection of interaction between lipase and glyceride

Previously, we devised the efficient modification of lipase, which can be dissolved and still maintain its activity in organic solvents. In this work, the fluorescence of the modified lipase could be detected in chloroform. When glycerides were added to the modified lipase solution, the intrinsic tryptophan fluorescence of the modified lipase decreased, which suggests that the environment of the tryptophan residue was affected by the substrate. The interaction between the modified lipase and glyceride was studied kinetically in terms of fluorescence intensity of the tryptophan residue. Because glyceride is not subject to hydrolysis in nonaqueous solution, the dissociation constant of the enzyme-substrate complex could be determined. Thus, insight into the direct interaction between enzyme and substrate provided some structural information regarding the active site of lipase.     

Lipase production in continuous culture of Candida rugosa

The yeast Candida rugosa produces multiple extracellular lipases. The production of extra‐ and intracellular lipases was investigated in continuous cultures using a sole or different mixtures of carbon sources. Also, the effect of different C:N ratios was tested. Lipase productivity in continuous cultures increased by 50% compared with data obtained from batch fermentations and depended on the dilution rate applied. Maximum yields relative to consumed substrate were obtained with oleic acid at low dilution rate. It was found that during nitrogen limitation, lipase activity was suppressed. All carbon source mixtures tested allowed both cell growth and lipase production, but extra‐ and intracellular lipase activities were affected by the combination of substrates used. Maximum extracellular lipolytic productivity was attained with lactic and oleic acid mixtures, probably due to the non‐repressor effect of these carbon sources. The chemical composition of the biomass also depended on the type of substrate used and was related to the accumulation of lipidic compounds as intracellular inclusions, which were observed when oleic acid was used as the carbon source. The results obtained were compared with previous data from batch and fed‐batch cultures in order to select the best process strategies for the lipase production with C rugosa. The best lipase yields were obtained in fed‐batch fermentations using oleic acid. Copyright © 2003 Society of Chemical Industry     

酶法合成甘油二酯的研究进展

介绍了脂肪酶催化合成甘油二酯的工艺及其所用固定化酶反应器的研究进展。     

Lipase-catalysed acidolysis of lard with caprylic acid to produce structured lipid

Enzymatic acidolysis of lard with caprylic acid was investigated. Of the five lipases that were tested in the initial screening, immobilised lipase TL IM from Thermomyces lanuginosus resulted in the highest incorporation of caprylic acid into lard. This enzyme was further studied for the effect of enzyme load, organic solvent, substrate ratio, reaction time and temperature. HPLC was used to analyse the products from the acidolysis reaction. The highest incorporation was attained at 15% enzyme load. Among the solvents tested, n‐hexane was the best reaction medium for the acidolysis of lard with caprylic acid. Time course studied suggests that the incorporation of caprylic acid into lard was increased up to 37.7 mol% after 24 h. Desirable mole ratio of lard to caprylic acid was 1:2, caprylic acid incorporation up to 34.2 mol%. Temperature had no significant effect on enzyme activity in the range of 40–80 °C.     

The kinetics of hydrolysis ofNigella sativa (black cumin) seed oil catalyzed by native lipase in ground seed

Kinetics of the lipolysis ofNigella sativa oil catalyzed by native lipase in crushed seed were studied between 20 and 90°C. Data fitted the pseudo first-order rate equation at 20, 30 and 40°C; and the pseudo second-order equation at 50, 60 and 70°C, but neither equation fit at 80 and 90°C. Lipolysis approximated first-order with respect to water.     

Component triacylglycerols of six seed oils of malvaceae

The component triacylglycerols of six seed oils of the Malvaceae family—Gossypium barbadense (Egyptian cotton),Hibiscus cannabinus (kenaf),Hibiscus sabdarifa (roselle), two varieties ofHibiscus esculentas (okra) andAlthea rosea (ketmia, hollyhock or Egyptian hemp)—have been determined by using the lipase hydrolysis technique. The oils were found to contain triacylglycerols belonging to trisaturated (1.0–2.1), disaturated-monounsaturated (12.3–20.9), monosaturated-diunsaturated (42.3–46.6) and triunsaturated (30.1–44.2) types of triacylglycerols.     

Optimised immobilisation of microbial lipase on hydrous niobium oxide

The aim of this work was to establish appropriate conditions for immobilising Candida rugosa lipase on a low‐cost inorganic matrix, hydrous niobium oxide, using a multivariate statistical approach. A 2³ full factorial design was employed to determine the effects of support activation with glutaraldehyde (concentration 2.5–4.5%, pH 7–10) and lipase loading (200‐700 U g^?1 matrix) on the hydrolytic and synthetic activities of the immobilised derivatives. From the results the following conditions were established: lipase loading of 450 U g^?1 matrix and niobium oxide activation with glutaraldehyde at a concentration of 2.5% and pH 8. Under these conditions, high activity recovery (47.21%) and esterification yield (86.90%) were attained. The results also show that hydrous niobium oxide can be a valid alternative to replace high‐cost, commercially available inorganic matrices such as controlled pore silica. Copyright © 2006 Society of Chemical Industry     

The use of lipase (acetone powder) from Vernonia galamensis in the fatty acid analysis of seed oils

Examined in this study is a potential application of Vernonia galamensis lipase (acetone powder) in enzyme-catalyzed hydrolysis of seed oils, most especially of those containing reactive functionalities which are easily affected under drastic hydrolytic and methylating/transesterification conditions during fatty acid analysis. Eight seed oils from V. galamensis, Ximenia kaffra, castor, corn, soyabean, palm kernel, sunflower and olive were hydrolyzed by lipase (acetone powder) followed by methylation using diazomethane in ethyl ether. Results obtained showed that the lipolytic hydrolysis of triglycerides by V. galamensis lipase (acetone powder) was probably nonspecific and did not result in isomerization and as such hydrolyzed the triglycerides of the seed oil in a fashion that the resulting fatty acids were unaltered during hydrolysis. The fatty acids obtained were representative of the parent seed oils. Values reported for the various seed oils were similar to those of previous studies.