Purification and characterisation of an ester hydrolase from a strain of Arthrobacter species: its application in asymmetrisation of 2-benzyl-1,3-propanediol acylates

A review on Arthrobacter sp. lipase: A versatile biocatalyst for the kinetic resolution to access enantiomerically pure/enriched compounds

Over the last few years, there has been a dramatic increase in the number of reports related to Arthrobacter sp. lipase (ABL:MTCC No. 5125) catalyzed kinetic resolution performed in biphasic media. A strain displaying esterase/lipase activity and designated as ABL was isolated, during the course of a screening program at Indian Institute of Integrative Medicine, Jammu. Considerable research has shown that reactions catalyzed by ABL are more selective than many commercial lipases. Since new applications of this lipase are emerging, there is a great need to provide all the relevant information exclusively. This review article is an attempt to cover all the relevant reports based on isolation, purification, immobilization, and application of ABL in the biopharmaceutical sector.

Macroporous Beads for Lipase Immobilization

Lipase isolated from Arthrobacter sp. (RRLJ-1, MTCC No. 5125, named ABL), is effective in resolving a wide range of racemic drug intermediates. In this study, ABL was immobilized on a series of synthetic macroporous epoxy copolymers beads with varying pore sizes, surface area and hydrophobicity. Poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads, with 75% crosslink density and 10% of epoxy groups modified with dibutyl amine [GMA-EGDM-75 (10% DBA)] had a pore volume of 0.77 mL/g and a surface area of 86.05 m 2/g; these beads were optimally suitable for ABL immobilization. The covalent binding of the lipase was optimized by varying the ionic strength, buffers, pH, temperature and time. The optimal binding was achieved in 100 mM phosphate buffer at 4°C, pH 7.0 in three hours. Under these conditions the polymer retained 34 units and 12 mg of ABL per gram. Immobilized ABL displayed enhanced thermal, organic solvent and pH stability compared to the free enzyme. The immobilized enzyme was used repeatedly (fifteen cycles) to resolve the fluoxitine intermediate (racemic ethyl-3-hydroxy-3-phenyl propanoate) without any loss in stereospecificity. The resolution time of fluoxitine intermediate was reduced to almost half (from 84 to 48 hours) by using the immobilized enzyme.

Impact of extraction parameters on the recovery of lipolytic activity from fermented babassu cake

Enzyme extraction from solid matrix is as important step in solid-state fermentation to obtain soluble enzymes for further immobilization and application in biocatalysis. A method for the recovery of a pool of lipases from Penicillium simplicissimum produced by solid-state fermentation was developed. For lipase recovery different extraction solution was used and phosphate buffer containing Tween 80 and NaCl showed the best results, yielding lipase activity of 85.7 U/g and 65.7 U/g, respectively. The parameters with great impacts on enzyme extraction detected by the Plackett-Burman analysis were studied by Central Composite Rotatable experimental designs where a quadratic model was built showing maximum predicted lipase activity (160 U/g) at 25°C, Tween 80 0.5% (w/v), pH 8.0 and extraction solution 7 mL/g, maintaining constant buffer molarity of 0.1 M and 200 rpm. After the optimization process a 2.5 fold increase in lipase activity in the crude extract was obtained, comparing the intial value (64 U/g) with the experimental design (160 U/g), thus improving the overall productivity of the process.

Immobilization of enantioselective lipase on soluble supports for kinetic resolution of drug intermediates

The microbial lipase, Arthrobacter sp. lipase (MTCC 5125), from the Indian Institute of Integrative Medicine repository, is known as an effective catalyst for high enantioselective kinetic resolution of drug intermediates. The ABL was immobilized on water-soluble linear supports by covalently binding it to the epoxy groups on the N-vinyl pyrrolidone/allyl glycidyl ether and N-vinyl pyrrolidone/glycidyl methacrylate copolymers. The immobilized lipase, on different soluble supports, had 90–110 mg/g protein binding and 500–700 U/g hydrolysis activities for tributyrin substrate. These copolymers had soluble/insoluble characteristics in different pH ranges, which is an advantage over insoluble copolymers. A soluble polymer at neutral pH provided better accessibility to the immobilized enzyme, which was recovered by precipitation at pH 2–3 for reuse. Kinetic resolution of racemic acyl derivatives of chiral auxiliaries and drug intermediates, namely, phenyl ethanol, aminoalcohol, and fluoxetine intermediate resulted in a significant enhancement in enantioselectivity (99%).

Enhancement of the activity and enantioselectivity of lipase by sol-gel encapsulation immobilization onto β-cyclodextrin-based polymer

Candida rugosa lipase was encapsulated within a chemically inert sol-gel support prepared by polycondensation with tetraethoxysilane and octyltriethoxysilane in the presence of β-cyclodextrin-based polymer. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yield of the encapsulated lipase was 65 U/g, which is 7.5 times higher than that of the covalently immobilized lipase. The β-cyclodextrin-based encapsulated lipases had higher conversion and enantioselectivity compared with covalently immobilized lipase. The study confirms an excellent enantioselectivity (E >300) for the encapsulated lipase with an enantiomeric excess value of 98% for S-naproxen.

Enantioselective enzymatic hydrolysis of racemic drugs by encapsulation in sol-gel magnetic sporopollenin

Candida rugosa lipase was encapsulated within a sol-gel procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of octyltriethoxysilane and tetraethoxysilane in the presence of magnetic sporopollenin. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e., the hydrolysis of p-nitrophenylpalmitate (p-NPP), and the enantioselective hydrolysis of racemic naproxen methyl ester, mandelic acid methyl ester or 2-phenoxypropionic acid methyl ester that were studied in aqueous buffer solution/isooctane reaction system. The encapsulated magnetic sporopollenin (Spo-M-E) was found to give 319 U/g of support with 342% activity yield. It has been observed that the percent activity yields and enantioselectivity of the magnetic sporopollenin encapsulated lipase were higher than that of the encapsulated lipase without support. The substrate specificity of the encapsulated lipase revealed more efficient hydrolysis of the racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester than racemic mandelic acid methyl ester. It was observed that excellent enantioselectivity (E > 400) was obtained for encapsulated lipase with magnetic sporopollenin with an ee value of S-Naproxen and R-2 phenoxypropionic acid about 98%.

Adding value to a toxic residue from the biodiesel industry: production of two distinct pool of lipases from Penicillium simplicissimum in castor bean waste

In countries with a strong agricultural base, such as Brazil, the generation of solid residues is very high. In some cases, these wastes present no utility due to their toxic and allergenic compounds, and so are an environmental concern. The castor bean (Ricinus communis) is a promising candidate for biodiesel production. From the biodiesel production process developed in the Petrobras Research Center using castor bean seeds, a toxic and alkaline waste is produced. The use of agroindustrial wastes in solid-state fermentation (SSF) is a very interesting alternative for obtaining enzymes at low cost. Therefore, in this work, castor bean waste was used, without any treatment, as a culture medium for fungal growth and lipase production. The fungus Penicillium simplicissimum was able to grow and produce an enzyme in this waste. In order to maximize the enzyme production, two sequential designs-Plackett-Burman (variable screening) followed by central composite rotatable design (CCRD)-were carried out, attaining a considerable increase in lipase production, reaching an activity of 155.0 U/g after 96 h of fermentation. The use of experimental design strategy was efficient, leading to an increase of 340% in the lipase production. Zymography showed the presence of different lipases in the crude extract. The partial characterization of such extract showed the occurrence of two lipase pools with distinct characteristics of pH and temperature of action: one group with optimal action at pH 6.5 and 45°C and another one at pH 9.0 and 25°C. These results demonstrate how to add value to a toxic and worthless residue through the production of lipases with distinct characteristics. This pool of enzymes, produced through a low cost methodology, can be applied in different areas of biotechnology.

Improvement of catalytic activity of lipase from Candida rugosa via sol-gel encapsulation in the presence of calix(aza)crown

Lipase from Candida rugosa (CRL) was encapsulated within a chemically inert sol-gel support in the presence of calix(aza)crowns as the new additives. The catalytic activity of the encapsulated lipases was evaluated both in the hydrolysis of p-nitrophenyl palmitate (p-NPP) and the enantioselective hydrolysis of racemic Naproxen methyl ester. It has been observed that the percent activity yields of the calix(aza)crown based encapsulated lipases were higher than that of the free lipase. Improved enantioselectivity was observed with the calix(aza)crown-based encapsulated lipases as compared to encapsulated free lipase. The reaction of Naproxen methyl ester resulted in 48.4% conversion for 24h and 98% enantiomeric excess for the S-acid, corresponding to an E value of >300 (E=166 for the encapsulated free enzyme). Moreover, the encapsulated lipases were still retained about 18% of their conversion ratios after the sixth reuse in the enantioselective reaction.

Immobilization of Candida rugosa lipase on glass beads for enantioselective hydrolysis of racemic naproxen methyl ester

Candida rugosa lipase (CRL) was immobilized on glutaraldehyde-activated aminopropyl glass beads by using covalent binding method or sol-gel encapsulation procedure and improved considerably by fluoride-catalyzed hydrolysis of mixtures of RSi(OCH3)3 and Si(OCH3)4. The catalytic properties of the immobilized lipases were evaluated into model reactions, i.e. the hydrolysis of p-nitrophenylpalmitate (p-NPP). It has been observed that the percent activity yield of the encapsulated lipase was 166.9, which is 5.5 times higher than that of the covalently immobilized lipase. The enantioselective hydrolysis of racemic Naproxen methyl ester by immobilized lipase was studied in aqueous buffer solution/isooctane reaction system and it was noticed that particularly, the glass beads based encapsulated lipases had higher conversion and enantioselectivity compared to covalently immobilized lipase. In short, the study confirms an excellent enantioselectivity (E>400) for the encapsulated lipase with an ee value of 98% for S-Naproxen.

Immobilization of Lipase by Entrapment in Ca-alginate Beads

The lipase-producing strain, Arthrobacter sp. (ABL), isolated was immobilized in Ca-alginate beads by entrapment. The alginate beads were prepared as an aqueous mixture of sodium alginate, the cells and CaCl2 to increase its reusability, and overall enzyme stability. Various parameters like alginate and CaCl2 concentration, lipase units loading and bead size were evaluated for optimum immobilization yield. It was observed that with the increase in alginate concentration, the yield of immobilized enzyme also increased up to a limit. A similar pattern was observed with CaCl2 addition; the optimum concentrations of alginate and CaCl2 observed were 1.5% (w/v) and 2%, respectively. The concentration of enzyme entrapped in the beads with an activity of 5 units per gram of wet beads was obtained by the addition of 100 units in 10 mL of slurry; beyond this amount a very little increase in activity was observed. The maximum immobilization yield was observed with a 1.2 mm bead size; increased bead sizes decreased the yield of immobilization. After optimization of all the parameters, a 40% yield of lipase (ABL) activity was observed in the Ca-alginate beads. These lipase beads were used for 10 cycles for the hydrolysis of triglycerides without any loss in activity. The entrapped lipase was more stable over a wide range of temperatures, pH, and storage time as compared to free enzyme.

Arthrobacter sp. lipase immobilization for improvement in stability and enantioselectivity

Arthrobacter sp. lipase (ABL, MTCC no. 5125) is being recognized as an efficient enzyme for the resolution of drugs and their intermediates. The immobilization of ABL on various matrices for its enantioselectivity, stability, and reusability has been studied. Immobilization by covalent bonding on sepharose and silica afforded a maximum of 380 and 40 IU/g activity, respectively, whereas sol-gel entrapment provided a maximum of 150 IU/g activity in dry powder. The immobilized enzyme displayed excellent stability in the pH range of 4-10 and even at higher temperature, i.e., 50-60 degrees C, compared to free enzyme, which is unstable under extreme conditions. The resolution of racemic auxiliaries like 1-phenyl ethanol and an intermediate of antidepressant drug fluoxetine, i.e., ethyl 3-hydroxy-3-phenylpropanoate alkyl acylates, provided exclusively R-(+) products ( approximately 99% ee, E=646 and 473), compared to cell free extract/whole cells which gave a product with approximately 96% ee (E=106 and 150). The repeated use (ten times) of covalently immobilized and entrapped ABL resulted in no loss in activity, thus demonstrating its prospects for commercial applications.

Molecular cloning of carboxylesterase gene and biochemical characterization of encoded protein from Bacillus subtilis (RRL BB1)

An isolated strain of Bacillus subtilis identified by 16S rDNA sequence analysis produces an enantioselective ester hydrolase. Whole cells of B. subtilis (RRL BB1) and enzyme derived from it was capable of enantioselective hydrolysis of several racemates including drug intermediates with moderate to high enantioselectivity as already reported by us. In this communication, we describe cloning of the gene encoding the enantioselective esterase designated as estBB1. The primary structure of the enzyme determined from the nucleotide sequence indicated that esterase estBB1 has Mw approximately 52kDa and pI approximately 5.2 and belongs to the family of type B carboxylesterases with 50-60% similarity at amino acid level. Alignment studies of sequences of the estBB1 and Pnb esterase 56C8 from B. subtilis showed that estBB1 has an alpha/beta hydrolase fold with catalytic triad formed by Ser190, Glu305 and His394 at active site and Ser190 is located in the conserved motif -G-X-S-X-G-.

A novel esterase from Bacillus subtilis (RRL 1789): Purification and characterization of the enzyme

An esterase (EC 3.1.1.1) produced by an isolated strain of Bacillus subtilis RRL 1789 exhibited moderate to high enantioselectivity in the kinetic resolution of several substrates like aryl carbinols, hydroxy esters, and halo esters. The enzyme named as B. subtilis esterase (BSE), was purified to >95% purity with a specific activity of 944 U/mg protein and 12% overall yield. The purified enzyme is approximately 52 kDa monomer, maximally activity at 37 degrees C and pH 8.0 and fairly stable up to 55 degrees C. The enzyme does not exhibit the phenomenon of interfacial activation with tributyrin and p-nitrophenyl butyrate beyond the saturation concentration. The enzyme showed preference for triacyglycerols and esters of p-nitrophenol with short chain fatty acid. Presence of Ca2+ ions increases the activity of enzyme by approximately 20% but its presence does not have any influence on the thermostability of the enzyme. The enzyme is not a metalloprotein and belongs to the family of serine proteases. The N-terminal amino acid sequence of BSE determined, as Met-Thr-Pro-Glu-Iso-Val-Thr-Thr-Glu-Tyr-Gly- revealed similarity with the N-terminal amino acid sequence of p-nitrobenzylesterase of B. subtilis.

Identification of a carboxylesterase-producingRhodococcussoil isolate

Subtropical soil microbial isolates were screened for carbohydrate, tributyrin, or olive oil hydrolysis using agar plates supplemented with the corresponding substrates. A heterotrophic, aerobic, Gram-positive strain displaying activity on tributyrin was selected and further characterized. Analysis of the morphological and physiological traits of the strain placed it as a member of the genus Rhodococcus. Further 16S rDNA sequencing revealed a 99% identity to Rhodococcus erythropolis. The strain displayed lipolytic activity on fatty-acid-derivative substrates of short chain length, with cell extract fractions having highest activity, as confirmed by the presence, after zymogram analysis, of a ca. 60-kDa intracellular protein band with activity on 4-methylumbelliferone–butyrate substrate. The presence of such a lipolytic enzyme, similar to those found in other Gram-positive bacteria, indicates that the strain could be of interest for certain biotechnological applications, like the synthesis of pharmaceuticals or biocide detoxification.Key words: Rhodococcus, lipase, esterase, soil, actinomycete.

Purification and characterization of an alkaline lipase from a newly isolated Pseudomonas mendocina PK-12CS and chemoselective hydrolysis of fatty acid ester

Lipase isolated from a soil isolate, Pseudomonas mendocina (PK-12CS) chemoselectively hydrolyzed the fatty ester group in presence of arbamate of compound 5-amino-2,4-dihydro-3H-1,2,4-triazole-3 ones, a class of compounds which are attractive starting materials for the synthesis of triazole annealed heterocycles. The enzymatic method provides an easy access to the synthesis of N-substituted glycine. Under optimized fermentation conditions the culture produced 3510 Lipolytic Units/mL of cell free fermentation broth in 20 h of fermentation. The purified lipase exhibited molecular mass of 80 kDa on SDS polyacrylamide gel electrophoresis. The enzyme was stable at room temperature for more than a month and expressed maximum activity at 37 degrees C and pH 8.