Regioselective monohydrolysis of per-O-acetylated-1-substituted-β-glucopyranosides catalyzed by immobilized lipases

The regioselective monohydrolysis of different peracetylated-β-glucopyranosides in aqueous media using immobilized preparations of three different lipases—those from Aspergillus niger (ANL), Candida rugose (CRL) and Candida antarctica B (CAL-B)—has been studied. Three very different immobilization strategies—covalent attachment, anionic exchange and interfacial activation on a hydrophobic support—were employed for each lipase. The role of the immobilization strategy and the effect of the presence of different moieties in the anomeric position of the substrate on the hydrolytic activities, specificities and regioselectivities of the lipases were investigated. For example, the PEI-ANL preparation exhibited 800 times higher activity than the octyl-ANL in the hydrolysis of 2-acetamido-2-deoxy-1-(4-nitrophenyl)-3,4,6-tri-O-acetyl-β-d-glucopyranoside—producing 4-OH derivative in 18% yield—whereas the octyl-ANL was five times more active than the PEI-ANL in the hydrolysis of 1-(4-nitrophenyl)-2,3,4-tri-O-acetyl-β-d-xylopyranoside, producing 4-OH monohydroxy product in >99% yield.The octyl-CRL preparation hydrolyzed regioselectively 3,4,6-tri-O-acetyl-glucal in position 6 in 68% yield while the PEI-CRL produced the 3-OH product in 11% yield, although with moderate specificity. The CNBr-CAL-B hydrolyzed specifically and regioselectively the glucal producing the 3-OH product in >99% yield.     

Influencing the regioselectivity of lipase-catalyzed hydrolysis with [bmim]PF6

An easy preparation of mono-deprotected thioglucopyranosides via a selective Candica cylindracea lipase-catalyzed hydrolysis of a commercially available peracetylated precursor is described. Especially, ethyl 2,3,4-tri-O-acetyl-1-thio-β-d-glucopyranoside and ethyl 2,3,6-tri-O-acetyl-1-thio-β-d-glucopyranoside were obtained in 100% and 54% isolated yields, respectively. The influence of the ratio of [bmim]PF₆/buffer toward the regioselectivity of the deacetylation step and the acyl migration is discussed.     

Separation and Immobilization of Lipase from Penicillium simplicissimum by Selective Adsorption on Hydrophobic Supports

Lipases are an enzyme class of a great importance as biocatalysts applied to organic chemistry. However, it is still necessary to search for new enzymes with special characteristics such as good stability towards high temperatures, organic solvents, and high stereoselectivity presence. The present work’s aim was to immobilize the lipases pool produced by Penicillium simplissicimum, a filamentous fungi strain isolated from Brazilian babassu cake residue. P. simplissicimum lipases were separated into three different fractions using selective adsorption method on different hydrophobic supports (butyl-, phenyl-, and octyl-agarose) at low ionic strength. After immobilization, it was observed that these fractions’ hyperactivation is in the range of 131% to 1133%. This phenomenon probably occurs due to enzyme open form stabilization when immobilized onto hydrophobic supports. Those fractions showed different thermal stability, specificity, and enantioselectivity towards some substrates. Enantiomeric ratio for the hydrolysis of (R,S) 2-O-butyryl-2-phenylacetic acid ranged from 1 to 7.9 for different immobilized P. simplissicimum lipase fractions. Asymmetry factor for diethyl 2-phenylmalonate hydrolysis ranged from 11.8 to 16.4 according to the immobilized P. simplissicimum lipase fractions. Those results showed that sequential adsorption methodology was an efficient strategy to obtain new biocatalysts with different enantioselectivity degrees, thermostability, and specificity prepared with a crude extract produced by a simple and low-cost technology.     

Developing a Library of Mannose-Based Mono- and Disaccharides: A General Chemoenzymatic Approach to Monohydroxylated Building Blocks

Regioselective deprotection of acetylated mannose-based mono- and disaccharides differently functionalized in anomeric position was achieved by enzymatic hydrolysis. Candida rugosa lipase (CRL) and Bacillus pumilus acetyl xylan esterase (AXE) were immobilized on octyl-Sepharose and glyoxyl-agarose, respectively. The regioselectivity of the biocatalysts was affected by the sugar structure and functionalization in anomeric position. Generally, CRL was able to catalyze regioselective deprotection of acetylated monosaccharides in C6 position. When acetylated disaccharides were used as substrates, AXE exhibited a marked preference for the C2, or C6 position when C2 was involved in the glycosidic bond. By selecting the best enzyme for each substrate in terms of activity and regioselectivity, we prepared a small library of differently monohydroxylated building blocks that could be used as intermediates for the synthesis of mannosylated glycoconjugate vaccines targeting mannose receptors of antigen presenting cells.     

Single-step purification of different lipases from Staphylococcus warneri

Three different lipases from the extract crude of Staphylococcus warneri have been purified by specific lipase–lipase interactions using different lipases (TLL, RML, PFL, BTL2) covalently attached to a solid support as adsorption matrix. BTL2 immobilized on glyoxyl-DTT adsorbed selectivity only a 30 kDa lipase from the crude, which was desorbed by adding 0.1% triton X-100. Using glyoxyl-PFL as matrix, two new lipases (28 and 40 kDa) were adsorbed, and completely pure 40 kDa lipase was obtained after desorption using 0.01% triton, whereas 28 kDa lipase was desorbed after the incubation of the lipase matrix with 3% detergent. When using other matrixes as glyoxyl-TLL or glyoxyl-RML, different lipases were adsorbed. This methodology could be a very efficient and useful method to purify several lipases from crude extracts from different sources.     

Efficient <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase immobilization on Maghnite clay and application for the production of (<Emphasis Type="Italic">1R</Emphasis>)-(−)-Menthyl acetate

This work focused on the identification of natural, economical, and efficient supports for immobilization of Candida rugosa lipase (CRL) to catalyze the resolution of (±)-menthol. To this purpose, CRL has been immobilized on natural montmorillonite from Algeria (Maghnite-H), ion-exchange resins (Amberjet^®1200-H and Amberjet^®4200-Cl), and diatomaceous earth (Celite^®545). After a preliminary screening of supports, the immobilization of CRL led to a markedly improved enantioselectivity. Excellent enantioselectivity (E ≥ 134) was achieved by the four supported lipases (E = 68 for free enzyme). Compared to the three other supports tested, higher enantioselectivity was observed with Maghnite-H used as immobilization matrix. In this work, the effects of solvent, reaction time, and temperature, on the conversion as well as on enantioselectivity were investigated. The maximum of conversion (% C = 43%) with high enantiomeric excess of products (eep > 99) was obtained when the reaction is catalyzed by CRL immobilized on Maghnite-H at 30 °C for 24 h, and using toluene as selected solvent. Immobilized CRL on Maghnite-H exhibited good thermostability over a wide temperature range (30–90 °C) compared to the free one. These results suggest that CRL immobilized on Maghnite-H has good potential as biocatalyst for the production of (1R)-(?)-menthyl acetate.     

Immobilized Lipase from Candida sp. 99–125 on Hydrophobic Silicate: Characterization and Applications

Lipase Candida sp. 99–125 has been proved to be quite effective in catalyzing organic synthesis reactions and is much cheaper than commercial lipases. Mesoporous silicates are attractive materials for the immobilization of enzymes due to their unique structures. The present research designed a hydrophobic silicate with uniform pore size suitable for the comfort of lipase Candida sp. 99–125 for improving its activity and stability. The resulting immobilized lipase (LP@PMO) by adsorption was employed to catalyze hydrolysis, esterification, and transesterification reactions, and the performances were compared with the lipase immobilized on hydrophilic silicate (LP@PMS) and native lipase. The LP@PMO showed as high activity as that of native lipase in hydrolysis and much increased catalytic activity and reusability in the reactions for biodiesel production. Besides, LP@PMO also possessed better organic stability. Such results demonstrate that immobilization of lipase onto hydrophobic supports is a promising strategy to fabricate highly active and stable biocatalysts for applications.     

Synthesis of peracetylated d-galactopyranosylidene dihalides

Upon treatment with aluminium trichloride in absolute chloroform, β-d-galactopyranose penta-O-acetate was converted in high yield into tetra-O-acetyl-β-d-galactopyranosyl chloride. In the presence of N-bromosuccinimide in boiling carbon tetrachloride, homolytic substitution of the anomeric hydrogen atom in this β-chloride occurred selectively to afford tetra-O-acetyl-1-bromo-β-d-galactopyranosyl chloride, in admixture with minor amounts of tetra-O-acetyl-d-galactopyranosylidene chloride. Bromine substitution by fluorine took place with a low stereoselectivity in tetra-O-acetyl-1-bromo-β-d-galactopyranosyl chloride when treated with 1.25 equiv silver fluoride in acetonitrile, whereas tetra-O-acetyl-d-galactopyranosylidene fluoride could be prepared in 54 % yield with 3.3 equiv AgF. The gem-difluoride could be deacetylated quantitatively. Upon treatment with 1,4-diazabicyclo〚2.2.2〛octane, peracetylated 1-bromo-β-d-galactopyranosyl chloride underwent 1,2-elimination of hydrogen bromide to afford 2,3,4,6-tetra-O-acetyl-d-lyxo-hex-1-enopyranosyl chloride in 33 % yield.     

Influence of the support on the reaction course of tributyrin hydrolysis catalyzed by soluble and immobilized lipases

Lipases from different origins have been immobilized in supports chosen by its different aquaphilicity and used as biocatalysts for the hydrolysis of tributyrin. The changes of the concentration of tri-, di-, monobutyrin, glycerol, and butyric acid during the reactions catalyzed by soluble, as well as immobilized, lipases were evaluated by gas chromatography. The experimental data were fitted to a simple kinetic model for the sequential reaction of tributyrin hydrolysis. The calculated apparent rate constants were different for the biocatalysts used and were apparently related to diffusional effects and aquaphilicity of the supports. Maximal yields of dibutyrin were found with the soluble Candida lipase, whereas the highest yield of monobutyrin (90%) was obtained with the least aquaphylic derivative (Candida-Celite).     

Production of FAME and FAEE via Alcoholysis of Sunflower Oil by Eversa Lipases Immobilized on Hydrophobic Supports

The performance of two new commercial low-cost lipases Eversa® Transform and Eversa® Transform 2.0 immobilized in different supports was investigated. The two lipases were adsorbed on four different hydrophobic supports. Interesting results were obtained for both lipases and for the four supports. However, the most active derivative was prepared by immobilization of Eversa® Transform 2.0 on Sepabeads C-18. Ninety-nine percent of fatty acid ethyl ester was obtained, in 3 h at 40 °C, by using hexane as solvent, a molar ratio of 4:1 (ethanol/oil), and 10 wt% of immobilized biocatalyst. The final reaction mixture contained traces of monoacylglycerols but was completely free of diacylglycerols. After four reaction cycles, the immobilized biocatalyst preserved 75% of activity. Both lipases immobilized in Sepabeads C-18 were very active with ethanol and methanol as acceptors, but they were much more stable in the presence of ethanol.     

Preparation of hollow silica nanospheres in O/W microemulsion system by hydrothermal temperature changes

Hollow silica nanospheres with wrinkled or smooth surfaces were successfully fabricated through a hydrothermal method. In this method, oil-in-water microemulsion (composed of cyclohexane, water, ethanol, and cetyltrimethylammonium bromide), and polyvinylpyrrolidone were utilized as template and capping agent, respectively. In such a facile synthesis, we can well realize the morphological transformation of spheres with radially oriented mesochannels to hollow structures of silica nanoparticle only by regulating the hydrothermal temperature from 100 °C to 200 °C. Synthesized samples with different mesostructures were then used as supports to immobilize Candida rugosa lipase (CRL). The immobilized CRL was employed as a new biocatalyst for biodiesel production through the esterification of heptanoic acid with ethanol. The conversion ratio of heptanoic acid with ethanol catalyzed by the immobilized CRL was also evaluated. Results of this study suggest that the prepared samples have potential applications in biocatalysis.     

Preparation of linear oligosaccharides by a simple monoprotective chemo-enzymatic approach

A monoprotective approach, involving acetyl ester as unique protective group in oligosaccharides synthesis, has been developed. Starting from peracetylated monosaccharides and glycals, by using an efficient and selective chemo-enzymatic ‘one-pot’ strategy (a regioselective hydrolysis catalyzed by immobilized lipases followed by a chemical acyl migration), different carbohydrate acceptors, only protected with acetyl ester, can be achieved. If combined with the use of an acetylated glycosyl donor, the glycosylation reaction with these glycosyl acceptors leads to peracetylated oligosaccharides. These compounds can be directly used as intermediates for the synthesis of glycopeptides used as antitumoral vaccines and, at the end of the process, can be easily fully deprotected in only one step. Thus, these key building blocks have been successfully used in glycosylation reactions for an efficient construction of peracetylated disaccharides, such as the biological relevant lactosamine, in multigram scale. Subsequently, glycosylation with the 3OH-tetraacetyl-α-d-galactose, used as carbohydrate acceptor, allowed the synthesis of a peracetylated N-trisaccharidic precursor of the lacto-N-neo-tetraose antigen. Extending this strategy to a 3OH-di-acetyl galactal, one peracetylated precursor of the T tumor-associated carbohydrate antigen has been synthesized.This efficient approach, characterized by the use of the acetyl ester as only protecting group during all the synthetical steps expected, represents an easy and efficient alternative to the classical synthetic methods in carbohydrate chemistry that involve several protecting group manipulation.     

Enrichment in γ-linolenic acid of acylglycerols by the selective hydrolysis of borage oil

Selective hydrolysis of borage oil byCandida rugosa lipase immobilized on microporous polypropylene was carried out in an iso-octane-water two-phase system in order to obtain glycerides rich in γ-linolenic acid (GLA). Lipase was immobilized on hydrophobic microporous polypropylene supports by physical adsorption, γ-linolenic acid content in the unhydrolyzed acylglycerols could be raised to 51.7 mol% from an initial content of 23.6 mol% in borage oil with a yield of 59%. A simplified kinetic model was proposed for this selective hydrolysis. The Michaelis constantK _M and the maximal-rate constantV _max are 0.107M and 393.9 U/mg-protein, respectively. Product inhibition with a dissociation constant of the enzyme-product complexK _I = 25 mM was confirmed. Some properties of the immobilized lipase were also examined.     

PDA/SiO2大孔复合材料固定化荧光假单胞菌脂肪酶

以具有三维骨架结构的大孔聚合物为模板制备SiO_2大孔材料,通过多巴胺在SiO_2大孔材料孔道表面的原位聚合制得聚多巴胺表面功能化修饰的二氧化硅大孔材料(PDA/SiO_2)。应用SEM、EDX、MIP、BET、TG-DTA和FTIR等技术对修饰前后的材料进行表征。以PDA/SiO_2为载体固定荧光假单胞菌脂肪酶(PFL),优化固定化条件并对比游离脂肪酶和固定化脂肪酶的性质。结果表明SiO_2大孔材料具有三维连续贯通的孔道结构,孔径分布在300~500 nm,聚多巴胺修饰后形成聚多巴胺/二氧化硅复合纳米薄膜构筑的大孔材料。在固定化时间为14 h、p H值为8、初始脂肪酶浓度为0.4 mg·m L-1时,固定化效果最佳,酶活回收率达246%。与游离脂肪酶相比,固定化脂肪酶有更宽的温度和p H适用范围、热稳定性显著提高,并展现出良好的储存稳定性和操作稳定性,固定化脂肪酶的Km低于游离脂肪酶的,酶与底物的亲和性较好。     

Gas-phase enzymatic esterification on immobilized lipases in MCM-41 molecular sieves

Several lipolytic enzymes were immobilized in the pores of MCM-41 and Al-MCM-41 molecular sieves and used as catalysts in the gas-phase esterification of acetic acid with ethanol. The entrapment of enzymes depended on the molecular sieve and the type of enzyme used. The order of enzymatic activity for enzymes entrapped in the pores of MCM-41 and Al-MCM-41 in the esterification reaction was OF (Rhizopus niveus lipases)<FAP-15 (Rhizopus oryzae lipases)<LEX (Mucor javanicus lipases)<PS (Pseudomonas cepacia lipases)<AK (Pseudomonas fluorescens lipases). Experiments carried out between 298 and 318 K showed no effect of temperature on catalyst yield, suggesting that the enzymes were appropriately immobilized in the pores of the molecular sieves, thus avoiding possible processes such as denaturing or autolysis.     

Enzyme-catalyzed regioselective transesterification of peracylated sophorolipids

Regioselective transesterifications and hydrolysis of peracylated sophorolipid (SL) derivatives catalyzed by lipases was investigated. This study is the first evaluation of the lipase-catalyzed reactions on the non-lactonic SL derivatives. Four lipases, namely from porcine pancreas (PPL, Type II), Candida rugosa (AYS, TypeVII), Pseudomonas cepacia (PS-30), and Candida antarctica (Novozym 435, carrier fixed lipase fraction B) were used in anhydrous THF or in phosphate buffer (pH=7.4, 0.2 M). It was confirmed from the detailed spectral analysis of the products that transesterification failed to furnish any free hydroxyls on the sophorose ring. Instead, transesterification took place on the methyl ester located at the carboxylic end of the 17-hydroxyoctadecenoic acid chain attached to the C-1′ position of the sophorose ring. It is proposed that in absence of the lactonic structural motif, the binding of the peracylated non-lactonic SLs in the lipase binding pocket takes place such that the carboxyl group of the octadecenoic acid, not the sophorose sugar, is preferentially accessible to the active site.     

Lipase-catalyzed kinetic resolution approach toward enantiomerically enriched 1-(β-hydroxypropyl)indoles

In a route towards enantiomerically enriched 1-(β-hydroxypropyl)indoles, which are potentially useful building blocks for high value-added chemicals synthesis, a kinetic resolution approach by means of lipase-catalyzed enantioselective acylation as well as hydrolysis/methanolysis has been elaborated for the first time. The enzymatic resolution of chiral N-substituted indole-based sec-alcohols was successfully accomplished, yielding both enantiomeric forms of the employed derivatives with up to >99% enantiomeric purity via an enantioselective transesterification under mild reaction conditions. The most selective resolutions were obtained using fungal (CAL-B and TLL) and bacterial (PFL and BCL) lipases and vinyl acetate as the acyl?group donor. The synthetic protocol described herein is very simple, user-friendly and efficient, thus paving the way for future access towards more complex compounds of this type. The absolute configurations of novel enantiomeric derivatives, and thus stereoselectivity of the described enzymatic reactions were confirmed by application of CDA-based NMR methodology and single-crystal X-ray diffraction analysis.     

Assessment of Activities and Conformation of Lipases Treated with Sub- and Supercritical Carbon Dioxide

In order to illustrate the underlining mechanism of the effect of high pressure on lipases from different resources, the influence of compressed carbon dioxide treatment on the esterification activities and conformation of the three lipases Candida rugosa lipase (CRL), Pseudomonas fluorescens lipase, and Rhizopus oryzae lipase was investigated in the present work. The results showed that the lipases activities were significantly enhanced in most of high-pressure treatments, except the pressure had a negative effect on CRL activity in supercritical condition. Mild depressurization rate could remain the lipase’s activity by protecting its rigid structure under supercritical fluid. Conformational analysis by Fourier transform-infrared spectrometry and fluorescence emission spectra revealed that the variances of lipase activity after high-pressure treatment were correlated with the changes of its α-helix content and fluorescence intensity. Additionally, transesterification catalyzed by three lipases in supercritical carbon dioxide were conducted, and 87.2 % biodiesel conversion was obtained by CRL after 3 h, resulting in a great reduction of reaction time.     

Kinetic resolution of 3-hydroxycyclohexanone using different lipases

A new approach to enantiomerically enriched cyclic β-hydroxy ketones was developed. 3-Hydroxycyclohexanone was successfully resolved using lipase catalyzed transesterification. Among the lipases screened PFL, PCL, and PPL-II gave 57%, 39%, and 25% yield of the (R)-3-oxocyclohexyl acetate with 52%, 75%, and 91% ee. The PPL-II gave the highest E-value (32). The absolute configuration of the product was determined by comparison with the literature data.     

柱状假丝酵母脂肪酶同工酶的一种高效液相色谱分离新方法

建立一种“疏水界面亲和色谱”分离柱状假丝酵母脂肪酶同工酶的高效液相色谱新方法。将商品化的CRL经离子交换色谱分离为两个同工酶组分 (CRLA和CRLB) ,在极低离子强度下 ,根据同工酶活性中心周围处于“开放”构象的疏水腔具亲疏水界面的特性 ,用疏水界面亲和色谱在NucleosilC4 (10 μ ,3 0 0 ,2 5 0× 4.60mm)柱上将CRLA和CRLB都分离为 4种同工酶组分。疏水界面亲和色谱非常适用于分离这种结构差异轻微的同工酶组分