Bacterial lipases for biotechnological applications

Refolding with Simultaneous Purification of Recombinant Serratia marcescens Lipase by One-Step Ultrasonication Process

A new lipase from Serratia marcescens SRICI-01 (Trx-SmL) was successfully overexpressed in Escherichia coli with thioredoxin (Trx) fusion tag. Intriguingly, the concentration of potassium phosphate buffer (KPB) showed significant impact on the aggregation state of Trx-SmL during ultrasonic disruption. The proportion of inclusion bodies increased dramatically with the increase of KPB concentration from almost completely soluble in 10 mM KPB to insoluble in 200 mM KPB. Based on this new finding, a novel method for refolding and purification of recombinant Trx-SmL was developed by one-step ultrasonication. The Trx-SmL was firstly precipitated in 200 mM KPB, washed for three times, and subsequently subjected to ultrasonic process in 10 mM KPB where refolding and purification occurred simultaneously. This established method was proved to be a straightforward, economical, and efficient purification approach to facilely obtain recombinant Trx-SmL protein with high purity (> 90%) and activity recovery yield (> 80%) from cell lysates. The application potential of the purified fusion Trx-SmL was further demonstrated by kinetic bioresolution of (±)-trans-3-(4-methoxyphenyl)glycidic acid methyl ester [(±)-MPGM] producing optically pure (-)-MPGM, a key intermediate for diltiazem, with an overall yield of 41.5% and ee of 99%.

Enhanced Biocatalytic Activity of Recombinant Lipase Immobilized on Gold Nanoparticles

BACKGROUND

Bacterial lipases especially Pseudomonas lipases are extensively used for different biotechnological applications.

OBJECTIVES

With the better understanding and progressive needs for improving its activity in accordance with the growing market demand, we aimed in this study to improve the recombinant production and biocatalytic activity of lipases via surface conjugation on gold nanoparticles.

METHODS

The full length coding sequences of lipase gene (lipA), lipase specific foldase gene (lipf) and dual cassette (lipAf) gene were amplified from the genomic DNA of Pseudomonas aeruginosa PA14 and cloned into the bacterial expression vector pRSET-B. Recombinant lipases were expressed in E. coli BL-21 (DE3) pLysS then purified using nickel affinity chromatography and the protein identity was confirmed using SDS-PAGE and Western blot analysis. The purified recombinant lipases were immobilized through surface conjugation with gold nanoparticles and enzymatic activity was colorimetrically quantified.

RESULTS

Here, two single expression plasmid systems pRSET-B-lipA and pRSET-B-lipf and one dual cassette expression plasmid system pRSET-B-lipAf were successfully constructed. The lipolytic activities of recombinant lipases LipA, Lipf and LipAf were 4870, 426 and 6740 IUmg-1, respectively. However, upon immobilization of these recombinant lipases on prepared gold nanoparticles (GNPs), the activities were 7417, 822 and 13035 IUmg-1, for LipA-GNPs, Lipf-GNPs and LipAf-GNPs, respectively. The activities after immobilization have been increased 1.52 and 1.93 -fold for LipA and LipAf, respectively.

CONCLUSION

The lipolytic activity of recombinant lipases in the bioconjugate was significantly increased relative to the free recombinant enzyme where immobilization had made the enzyme attain its optimum performance.

N-terminal domain replacement changes an archaeal monoacylglycerol lipase into a triacylglycerol lipase

BACKGROUND

Lipolytic enzymes of hyperthermophilic archaea generally prefer small carbon chain fatty acid esters (C₂-C₁₂) and are categorized as esterases. However, a few have shown activity with long-chain fatty acid esters, but none of them have been classified as a true lipase except a lipolytic enzyme AFL from Archaeglobus fulgidus. Thus, our main objective is to engineer an archaeal esterase into a true thermostable lipase for industrial applications. Lipases which hydrolyze long-chain fatty acid esters display an interfacial activation mediated by the lid domain which lies over active site and switches to open conformation at the oil-water interface. Lid domains modulate enzyme activities, substrate specificities, and stabilities which have been shown by protein engineering and mutational analyses. Here, we report engineering of an uncharacterized monoacylglycerol lipase (TON-LPL) from an archaeon Thermococcus onnurineus (strain NA1) into a triacylglycerol lipase (rc-TGL) by replacing its 61 N-terminus amino acid residues with 118 residues carrying lid domain of a thermophilic fungal lipase-Thermomyces lanuginosus (TLIP).

RESULTS

TON-LPL and rc-TGL were cloned and overexpressed in E. coli, and the proteins were purified by Ni-NTA affinity chromatography for biochemical studies. Both enzymes were capable of hydrolyzing various monoglycerides and shared the same optimum pH of 7.0. However, rc-TGL showed a significant decrease of 10 °C in its optimum temperature (T_opt). The far UV-CD spectrums were consistent with a well-folded α/β-hydrolase fold for both proteins, but gel filtration chromatography revealed a change in quaternary structure from trimer (TON-LPL) to monomer (rc-TGL). Seemingly, the difference in the oligomeric state of rc-TGL may be linked to a decrease in temperature optimum. Nonetheless, rc-TGL hydrolyzed triglycerides and castor oil, while TON-LPL was not active with these substrates.

CONCLUSIONS

Here, we have confirmed the predicted esterase activity of TON-LPL and also performed the lid engineering on TON-LPL which effectively expanded its substrate specificity from monoglycerides to triglycerides. This approach provides a way to engineer other hyperthermophilic esterases into industrially suitable lipases by employing N-terminal domain replacement. The immobilized preparation of rc-TGL has shown significant activity with castor oil and has a potential application in castor oil biorefinery to obtain value-added chemicals.

Investigating Enzyme Activity of Immobilized Candida rugosa Lipase

Candida rugosa lipase is a food-grade enzyme that is extensively utilized in the dairy processing industry for milk fat hydrolysis. The enzyme is mainly employed to modify the fatty acid chain length that results in the enhancement of flavors. The hydrolytic activities of C. rugosa lipase (fungal source) in its free and immobilized forms were investigated at different pH and temperature settings. The main objective of this study was to understand how different support materials (Celite-545, Sephadex G-25, and chitosan) and immobilization techniques alter lipase activity and stability. Our results indicated that hydrolytic activity increased significantly with immobilization on Celite-545. In general, immobilization resulted in considerable improvements in the stability of the enzyme with variations in pH and temperature. Immobilization on Celite-545 led to the highest catalytic efficiency. Remarkable improvements in the recovery and reusability of the immobilized lipases were noted. Comparatively, the acetone immobilization procedure resulted in higher activities than alcohol immobilization. In conclusion, the activity of C. rugosa lipase was enhanced most significantly when immobilized on Celite-545 using acetone as an adsorption solvent.

Effect of Environmental and Nutritional Parameters on the Extracellular Lipase Production by <i>Aspergillus niger</i>

Abstract- The present investigation was carried out to evaluate the effect of different growth conditions on lipase production by Aspegillus niger. The extracellular lipase producing fungus was isolated from spent bleaching earths. Optimization of physical and chemical parameters was done for maximum lipase production using this isolate. Growth of the organism and lipase production were measured usig varying pH (4 – 9), incubation temperature (20 – 30 °C), incubation time (8 – 80 hrs.), carbon sources, nitrogen sources, and shaking speed. Enhanced lipase production was observed at 24 °C, pH 7 and after 72hrs of incubation. Olive oil 5 % was observed as the most effective carbon source and Yeast extract 1.0 % as the most effective nitrogen source for lipase production. The optimum shaking value to get maximum lipase activity by Aspergillusniger was 200 rpm.

Effect of Environmental and Nutritional Parameters on the Extracellular Lipase Production by Aspergillus niger

Abstract- The present investigation was carried out to evaluate the effect of different growth conditions on lipase production byAspegillus niger. The extracellular lipase producing fungus was isolated from spent bleaching earths. Optimization of physical and chemical parameters was done for maximum lipase production using this isolate. Growth of the organism and lipase production were measured usig varying pH (4 – 9), incubation temperature (20 – 30 °C), incubation time (8 – 80 hrs.), carbon sources, nitrogen sources, and shaking speed. Enhanced lipase production was observed at 24 °C, pH 7 and after 72hrs of incubation. Olive oil 5 % was observed as the most effective carbon source and Yeast extract 1.0 % as the most effective nitrogen source for lipase production. The optimum shaking value to get maximum lipase activity byAspergillusnigerwas 200 rpm.

Fast and economic immobilization methods described for non-commercial Pseudomonas lipases

BACKGROUND

There is an increasing interest to seek new enzyme preparations for the development of new products derived from bioprocesses to obtain alternative bio-based materials. In this context, four non-commercial lipases from Pseudomonas species were prepared, immobilized on different low-cost supports, and examined for potential biotechnological applications.

RESULTS

To reduce costs of eventual scaling-up, the new lipases were obtained directly from crude cell extracts or from growth culture supernatants, and immobilized by simple adsorption on Accurel EP100, Accurel MP1000 and Celite®545. The enzymes evaluated were LipA and LipC from Pseudomonas sp. 42A2, a thermostable mutant of LipC, and LipI.3 from Pseudomonas CR611, which were produced in either homologous or heterologous hosts. Best immobilization results were obtained on Accurel EP100 for LipA and on Accurel MP1000 for LipC and its thermostable variant. Lip I.3, requiring a refolding step, was poorly immobilized on all supports tested (best results for Accurel MP1000). To test the behavior of immobilized lipases, they were assayed in triolein transesterification, where the best results were observed for lipases immobilized on Accurel MP1000.

CONCLUSIONS

The suggested protocol does not require protein purification and uses crude enzymes immobilized by a fast adsorption technique on low-cost supports, which makes the method suitable for an eventual scaling up aimed at biotechnological applications. Therefore, a fast, simple and economic method for lipase preparation and immobilization has been set up. The low price of the supports tested and the simplicity of the procedure, skipping the tedious and expensive purification steps, will contribute to cost reduction in biotechnological lipase-catalyzed processes.

Thermostable lipase from Geobacillus sp. Iso5: bioseparation, characterization and native structural studies

The extracellular thermoalkaline lipase from Geobacillus sp. Iso5 was purified to homogeneity by ultrafiltration, 6% cross-linked agarose and Phenyl spehrose HIC column chromatography. The final purified lipase resulted in 8.7-fold with 6.2% yield. The relative molecular weight of the enzyme was determined to be a monomer of 47 kDa by SDS-PAGE and MALDI-TOF MS/MS spectroscopy. The purified enzyme exhibit optimum activity at 70 °C and pH 8.0. The enzyme retained above 90% activity at temperatures of 70 °C and about 35% activity at 85 °C for 2 h. However, the stability of the enzyme decreased at the temperature over 90 °C. The enzyme activity was promoted in the presence of Ca(2+) and Mg(2+) and strongly inhibited by HgCl2 , PMSF, DTT, K(+) , Co(2+) , and Zn (2+) . EDTA did not affect the enzyme activity. The secondary structure of purified lipase contains 36% α-helix and 64% β-sheet which was determined by Circular dichromism, FTIR, and Raman Spectroscopy.

Improved PCR method for the creation of saturation mutagenesis libraries in directed evolution: application to difficult-to-amplify templates

Saturation mutagenesis constitutes a powerful method in the directed evolution of enzymes. Traditional protocols of whole plasmid amplification such as Stratagene’s QuikChange™ sometimes fail when the templates are difficult to amplify. In order to overcome such restrictions, we have devised a simple two-primer, two-stage polymerase chain reaction (PCR) method which constitutes an improvement over existing protocols. In the first stage of the PCR, both the mutagenic primer and the antiprimer that are not complementary anneal to the template. In the second stage, the amplified sequence is used as a megaprimer. Sites composed of one or more residues can be randomized in a single PCR reaction, irrespective of their location in the gene sequence.The method has been applied to several enzymes successfully, including P450-BM3 from Bacillus megaterium, the lipases from Pseudomonas aeruginosa and Candida antarctica and the epoxide hydrolase from Aspergillus niger. Here, we show that megaprimer size as well as the direction and design of the antiprimer are determining factors in the amplification of the plasmid. Comparison of the results with the performances of previous protocols reveals the efficiency of the improved method.

Cloning, sequence analysis and expression of bacterial lipase-coding DNA fragments from environment in Escherichia coli

Thirteen pairs of primers were designed, synthesized and used to clone the whole coding sequences or mature peptide-coding sequences of lipases. Bacteria producing extracellular lipases were enriched for the extraction of total DNAs. Eight fragments with 500-1,200 bp in length were obtained by using touchdown PCR and sequenced. Five of them were found to be lipase-coding DNAs. One fragment called BL9 that was 95.9% similar to a coding sequence of putative lipase. This lipase contained a Gly-His-Ser-Met-Gly motif which is matched to the consensus Gly-X-Ser-X-Gly conserved among lipolytic enzymes. The BL9 DNA fragment was inserted into the expression vector pET32a(+) of Escherichia coli. A functional product was yielded in the supernatant and produced a hydrolyzed zone on the tributyrin agar.

Biocatalytic ketone reduction--a powerful tool for the production of chiral alcohols--part I: processes with isolated enzymes

Enzymes are able to perform reactions under mild conditions, e.g., pH and temperature, with remarkable chemo-, regio-, and stereoselectivity. Because of this feature, the number of biocatalysts used in organic synthesis has rapidly increased during the last decades, especially for the production of chiral compounds. The present review highlights biotechnological processes for the production of chiral alcohols by reducing prochiral ketones. These reactions can be catalyzed by either isolated enzymes or whole cells that exhibit ketone-reducing activity. The use of isolated enzymes is often preferred because of a higher volumetric productivity and the absence of side reactions. Both types of catalysts have also deficiencies limiting their use in synthesis of chiral alcohols. Because reductase-catalyzed reactions are dependent on cofactors, one major task in process development is to provide an effective method for regeneration of the consumed cofactors. In this paper, strategies for cofactor regeneration in biocatalytic ketone reduction are reviewed. Furthermore, different processes carried out on laboratory and industrial scales using isolated enzymes are presented. Attention is turned to process parameters, e.g., conversion, yield, enantiomeric excess, and process strategies, e.g., the application of biphasic systems or methods of in situ (co)product recovery. The biocatalytic production of chiral alcohols utilizing whole cells is presented in part II of this review.

Learning from directed evolution: Further lessons from theoretical investigations into cooperative mutations in lipase enantioselectivity

An earlier experimental study, which involved the directed evolution of enantioselective lipase variants from Pseudomonas aeruginosa as catalysts in the hydrolytic kinetic resolution of 2-methyl-decanoic acid p-nitrophenyl ester, provided a mutant with six mutations. Consequently, the selectivity factor was found to increase from E = 1.1 for the wild-type to E = 51 for the best mutant. Only one of the amino acid exchanges in this mutant was found to occur next to the binding pocket, the other mutations being remote. Our previous theoretical analysis with molecular-dynamics simulations helped to unveil the source of enhanced enantioselectivity: a relay mechanism that involves two of the six mutations was shown to induce strong cooperativity. In this investigation, single, double, and triple mutants were constructed and tested as enantioselective catalysts. This study supports our original postulate regarding the relay mechanism, offers further mechanistic insight into the role of individual mutations, and provides mutants that display even higher enantioselectivity (E of up to 64).

Expanding the substrate scope of enzymes: combining mutations obtained by CASTing

In a previous paper, the combinatorial active-site saturation test (CAST) was introduced as an effective strategy for the directed evolution of enzymes toward broader substrate acceptance. CASTing comprises the systematic design and screening of focused libraries around the complete binding pocket, but it is only the first step of an evolutionary process because only the initial libraries of mutants are considered. In the present study, a simple method is presented for further optimization of initial hits by combining the mutational changes obtained from two different libraries. Combined lipase mutants were screened for hydrolytic activity against six notoriously difficult substrates (bulky carboxylic acid esters) and improved mutants showing significantly higher activity were identified. The enantioselectivity of the mutants in the hydrolytic kinetic resolution of two substrates was also studied, with the best mutant-substrate combination resulting in a selectivity factor of E=49. Finally, the catalytic profile of the evolved mutants in the hydrolysis of simple nonbranched carboxylic acid esters, ranging from acetate to palmitate, was studied for theoretical reasons.

Functional Cell-Surface Display of a Lipase-Specific Chaperone

Lipases are important enzymes in biotechnology. Extracellular bacterial lipases from Pseudomonads and related species require the assistance of specific chaperones, designated "Lif" proteins (lipase specific foldases). Lifs, a unique family of steric chaperones, are anchored to the periplasmic side of the inner membrane where they convert lipases into their active conformation. We have previously shown that the autotransporter protein EstA from P. aeruginosa can be used to direct a variety of proteins to the cell surface of Escherichia coli. Here we demonstrate for the first time the functional cell-surface display of the Lif chaperone and FACS (fluorescence-activated cell sorting)-based analysis of bacterial cells that carried foldase-lipase complexes. The model Lif protein, LipH from P. aeruginosa, was displayed at the surface of E. coli cells. Surface exposed LipH was functional and efficiently refolded chemically denatured lipase. The foldase autodisplay system reported here can be used for a variety of applications including the ultrahigh-throughput screening of large libraries of foldase variants generated by directed evolution.

High-level expression and characterization of Galactomyces geotrichum (BT107) lipase I in Pichia pastoris

The mature lipI gene, encoding the lipase I from Galactomyces geotrichum BT107, was obtained by PCR from genomic DNA, sequenced and cloned into a Pichia pastoris expression vector. Clones containing multiple copies of lipI integrated in their genome were analyzed to achieve high-level expression of the recombinant lipase I. One strain with four or more copies of the expression cassette was able to produce more than 200mg/L of extracellular heterologous protein. The lipase I was partially purified using anion exchange chromatography and its activity on monounsaturated (triolein) and polyunsaturated (triEPA) triglycerides was analyzed by a novel HPLC-MS assay.

Newly isolated Streptomyces spp. as enantioselective biocatalysts: hydrolysis of 1,2-O-isopropylidene glycerol racemic esters

AIMS

To identify microbial strains with esterase activity able to enantioselectively hydrolyse esters of (R,S)-1,2-O-isopropylidene glycerol.

METHODS AND RESULTS

The microbial hydrolysis of various racemic esters of 1,2-O-isopropylidene glycerol (IPG) was attempted by screening among Streptomyces spp. previously selected on the basis of their carboxylesterase activity. The best results were observed in the hydrolysis of butyrate ester and two strains appeared promising as they showed opposite enantioselectivity: Streptomyces sp. 90852 gave predominantly (S)-IPG, while strain 90930 mostly gave the R-alcohol. Streptomyces sp. 90930 was identified as Streptomyces violaceusniger, whereas Streptomyces sp. 90852 is a new species belonging to the Streptomyces violaceus taxon. The carboxylesterase belonging to strain 90852 gave a maximum value of enantiomeric ratio (E) of 14-16. This strain was lyophilized and used as dry mycelium for catalysing the synthesis of isopropylidene glycerol butyrate in heptane showing reaction rate and enantioselectivity (E = 6.6) lower than what observed for the hydrolysis.

CONCLUSIONS

A new esterase with enantioselective activity towards (R,S)-IPG butyrate has been selected. The best enantioselectivity is similar or even better than the highest reported value in the literature with commercial enzymes. The enzyme is produced by a new species belonging to the S. violaceus taxon.

SIGNIFICANCE AND IMPACT OF THE STUDY

New esterases from streptomycetes can be employed for the enantioselective hydrolysis of chiral esters derived from primary alcohols, not efficiently resolved with commercial enzymes.

Active lactonizing lipase (LipL) efficiently overproduced by Pseudomonas strains as heterologous expression hosts

Pseudomonas sp. strain 109 secretes lactonizing lipase (LipL), which catalyzes efficient intramolecular transesterification of omega-hydroxyfatty acid esters to form macrocyclic lactones. Because Escherichia coli was found to be unsuitable as an expression host due to the predominant formation of inactive LipL-inclusion bodies and a lack of proper secretion machinery which is also required for the formation of active LipL, Pseudomonas strains were surveyed as expression hosts. Pseudomonas sp. strain 109, an original LipL producer, showed a 7.1-fold higher level of active LipL when the lipL gene under the control of tac-lacUV5 tandem promoter was introduced together with a limL gene encoding a LipL-specific chaperon. Pseudomonas aeruginosa ADD 1976 containing a T7 RNA polymerase gene in the chromosome and plasmid-borne lipL-limL genes under the control of T7 promoter showed a 13-fold higher level of active LipL. Several combinations in the number of lipL and/or limL genes on the plasmid were investigated, and (lipL)3-limL was found to be most efficient, yielding a 67-fold greater production of active LipL than that obtained by the wild-type Pseudomonas sp. strain 109.

Enantioselective aminolysis of an alpha-chloroester catalyzed by Candida cylindracea lipase encapsulated in sol-gel silica glass

[reaction: see text] Lipase from Candida cylindracea (CcL) encapsulated in porous silica glass by a sol-gel method catalyzes enantioselective aminolysis of ethyl 2-chloropropionate. A silica matrix enhances the enzyme activity, i.e., improves the yield. The scope and limitations of the aminolysis reaction were investigated, and dynamic kinetic resolution of the ester was achieved. Encapsulated lipase remains active when used repeatedly. Encapsulation much improves the chiral discrimination by lipase and makes this enzyme even more useful in organic chemistry.