Cloning, sequencing and expression in Escherichia coli of a thermophilic lipase from Bacillus thermoleovorans ID-1

A polylactic acid degrading lipase from Bacillus safensis: Characterization and structural analysis

A polylactic acid degrading triacylglycerol lipase (TGL) was identified from Bacillus safensis based on genome annotation and validated by real-time quantitative PCR. TGL displayed optimal activity at pH 9.0 and 55 °C. It maintained stability at pH 9.0 and temperatures 45 °C. The activity of TGL was found to benefit from the presence of potassium sodium ions, and low concentrations of Triton X-100. The TGL could erode the surface of polylactic acid films and increase its hydrophilicity. The hydrolysis products of polylactic acid by TGL were lactate monomer and dimer. TGL contains a classical catalytic triad structure of lipase (Ser77, Asp133, and His156) and an Ala-X-Ser-X-Gly sequence. Compared with some lipases produced by the same genus Bacillus, TGL is highly conserved in its amino acid sequence, mainly reflected in the amino acid residues that exercise the enzyme activity, including the catalytic activity center and the substrate binding sites.

Genome sequence analysis and characterization of Bacillus altitudinis B12, a polylactic acid- and keratin-degrading bacterium

Keratin-rich wastes, mainly in the form of feathers, are recalcitrant residues generated in high amounts as by-products in chicken farms and food industry. Polylactic acid (PLA) is the second most common biodegradable polymer found in commercial plastics, which is not easily degraded by microbial activity. This work reports the 3.8-Mb genome of Bacillus altitudinis B12, a highly efficient PLA- and keratin-degrading bacterium, with potential for environmental friendly biotechnological applications in the feed, fertilizer, detergent, leather, and pharmaceutical industries. The whole genome sequence of B. altitudinis B12 revealed that this strain (which had been previously misclassified as Bacillus pumilus B12) is closely related to the B. altitudinis strains ER5, W3, and GR-8. A total of 4056 coding sequences were annotated using the RAST server, of which 2484 are core genes of the pan genome of B. altitudinis and 171 are unique to this strain. According to the sequence analysis, B. pumilus B12 has a predicted secretome of 353 proteins, among which a keratinase and a PLA depolymerase were identified by sequence analysis. The presence of these two enzymes could explain the characterized PLA and keratin biodegradation capability of the strain.

Identification and Heterologous Production of a Lipase from Geobacillus kaustophilus DSM 7263T and Tailoring Its N-Terminal by a His-Tag Epitope

Lipases are versatile biocatalysts with many biotechnological applications and the necessity of screening, production and characterization of new lipases from diverse microbial strains to meet industrial needs is constantly emerging. In this study, the lipase gene (gklip) from a thermophilic bacterium, Geobacillus kaustophilus DSM 7263 ^T was cloned into the pET28a ( +) vector with N-terminal 6xHis-tag. The recombinant gklip gene was heterologously expressed in host E. coli BL21 (DE3) cells and purified by Ni-NTA affinity chromatography. Histidine tag was removed from the purified 6xHistag-Gklip enzyme with thrombin enzyme and the molecular mass was determined to be approximately 43 kDa by SDS-PAGE. Gklip showed optimal activity at pH 8.0 and 50 °C. The specific hydrolytic activities against substrates were significantly increased by the removal of the His-tag. K_m and k_cat values of Gklip against p-nitrophenyl palmitate (pNPP, 4-nitrophenyl palmitate) as the target substrate were found to be as 1.22 mM and 417.1 min^-1, respectively. Removing His-tag changed the substrate preference of the enzyme leading to maximum lipolytic activity towards C10 and C12 lipids. Similarly, the activity against coconut oil that containing 62% medium-chain fatty acids was significantly higher than other oils. Furthermore, preservation of activity in the presence of inhibitors, organic solvents support the effect of lid structure of the enzyme.

Functional expression of a novel methanol-stable esterase from Geobacillus subterraneus DSM13552 for biocatalytic synthesis of cinnamyl acetate in a solvent-free system

BACKGROUND

Esterases are widely distributed in nature and have important applications in medical, industrial and physiological. Recently, the increased demand for flavor esters has prompted the search of catalysts like lipases and esterases. Esterases from thermophiles also show thermal stability at elevated temperatures and have become enzymes of special interest in biotechnological applications. Although most of esterases catalyzed reactions are carried out in toxic and inflammable organic solvents, the solvent-free system owning many advantages such as low cost and easy downstream processing.

RESULTS

The gene estGSU753 from Geobacillus subterraneus DSM13552 was cloned, sequenced and overexpressed into Escherichia coli BL21 (DE3). The novel gene has an open reading frame of 753 bp and encodes 250-amino-acid esterase (EstGSU753). The sequence analysis showed that the protein contains a catalytic triad formed by Ser97, Asp196 and His226, and the Ser of the active site is located in the conserved motif Gly95-X-Ser97-X-Gly99 included in most esterases and lipases. The protein catalyzed the hydrolysis of pNP-esters of different acyl chain lengths, and the enzyme specific activity was 70 U/mg with the optimum substrate pNP-caprylate. The optimum pH and temperature of the recombinant enzyme were 8.0 and 60 °C respectively. The resulting EstGSU753 showed remarkable stability against methanol. After the incubation at 50% methanol for 9 days, EstGSU753 retained 50% of its original activity. Even incubation at 90% methanol for 35 h, EstGSU753 retained 50% of its original activity. Also, the preliminary study of the transesterification shows the potential value in synthesis of short-chain flavor esters in a solvent-free system, and more than 99% conversion was obtained in 6 h (substrate: cinnamyl alcohol, 1.0 M).

CONCLUSIONS

This is the first report of esterase gene cloning from Geobacillus subterraneus with detailed enzymatic properties. This methanol-stable esterase showed potential value in industrial applications especially in the perfume industry.

Characterization of ML-005, a Novel Metaproteomics-Derived Esterase

A novel gene encoding for a lipolytic enzyme, designated ML-005, was recently identified using a functional metaproteomics approach. We heterologously expressed this protein in Escherichia coli and biochemically characterized it. ML-005 exhibited lipolytic activity toward short-chained substrates with the preferred substrate being p-nitrophenyl-butyrate, suggesting that ML-005 is an esterase. According to homology analysis and site-directed mutagenesis, the catalytic triad of the enzyme was identified as Ser-99, Asp-164, and His-191. Its optimal pH was determined to be at pH 8. Optimal activity was observed at 45°C. It also exhibited temperature, pH and salt tolerance. Residual relative activity after incubating at 50–60°C for 360 min was above 80% of its initial activity. It showed tolerance over a broad range of pH (5–12) and retained most of its initial activity. Furthermore, incubating ML-005 in 1 – 5M NaCl solution had negligible effect on its activity. DTT, EDTA, and ß-mercaptoethanol had no significant effect on ML-005’s activity. However, addition of PMSF led to almost complete inactivation consistent with ML-005 being a serine hydrolase. ML-005 remains stable in the presence of a range of metal ions, but addition of Cu²⁺ significantly reduces its relative activity. Organic solvents have an inhibitory effect on ML-005, but it retained 21% of activity in 10% methanol. SDS had the most pronounced inhibitory effect on ML-005 among all detergents tested and completely inactivated it. Furthermore, the V_max of ML-005 was determined to be 59.8 μM/min along with a K_m of 137.9 μM. The k_cat of ML-005 is 26 s^-1 and k_cat/K_m is 1.88 × 10⁵ M^-1 s^-1.

Application of Rigidity Theory to the Thermostabilization of Lipase A from Bacillus subtilis

Protein thermostability is a crucial factor for biotechnological enzyme applications. Protein engineering studies aimed at improving thermostability have successfully applied both directed evolution and rational design. However, for rational approaches, the major challenge remains the prediction of mutation sites and optimal amino acid substitutions. Recently, we showed that such mutation sites can be identified as structural weak spots by rigidity theory-based thermal unfolding simulations of proteins. Here, we describe and validate a unique, ensemble-based, yet highly efficient strategy to predict optimal amino acid substitutions at structural weak spots for improving a protein’s thermostability. For this, we exploit the fact that in the majority of cases an increased structural rigidity of the folded state has been found as the cause for thermostability. When applied prospectively to lipase A from Bacillus subtilis, we achieved both a high success rate (25% over all experimentally tested mutations, which raises to 60% if small-to-large residue mutations and mutations in the active site are excluded) in predicting significantly thermostabilized lipase variants and a remarkably large increase in those variants’ thermostability (up to 6.6°C) based on single amino acid mutations. When considering negative controls in addition and evaluating the performance of our approach as a binary classifier, the accuracy is 63% and increases to 83% if small-to-large residue mutations and mutations in the active site are excluded. The gain in precision (predictive value for increased thermostability) over random classification is 1.6-fold (2.4-fold). Furthermore, an increase in thermostability predicted by our approach significantly points to increased experimental thermostability (p < 0.05). These results suggest that our strategy is a valuable complement to existing methods for rational protein design aimed at improving thermostability.

Protein thermostability is a crucial factor for biotechnological enzyme applications. However, performance studies of computational approaches for predicting effects of mutations on protein (thermo)stability have suggested that there is still room for improvement. We describe and validate a novel and unique strategy to predict optimal amino acid substitutions at structural weak spots. At variance with other rational approaches, we exploit the fact that in the majority of cases an increased structural rigidity of the folded state is the underlying cause for thermostability. When applied prospectively on lipase LipA from Bacillus subtilis, a high success rate in predicting thermostabilized lipase variants and a remarkably large increase in their thermostability is achieved. This demonstrates the value of the novel strategy, which extends the existing portfolio of methods for rational protein design.

Analysis of Comparative Sequence and Genomic Data to Verify Phylogenetic Relationship and Explore a New Subfamily of Bacterial Lipases

Thermostable and organic solvent-tolerant enzymes have significant potential in a wide range of synthetic reactions in industry due to their inherent stability at high temperatures and their ability to endure harsh organic solvents. In this study, a novel gene encoding a true lipase was isolated by construction of a genomic DNA library of thermophilic Aneurinibacillus thermoaerophilus strain HZ into Escherichia coli plasmid vector. Sequence analysis revealed that HZ lipase had 62% identity to putative lipase from Bacillus pseudomycoides. The closely characterized lipases to the HZ lipase gene are from thermostable Bacillus and Geobacillus lipases belonging to the subfamily I.5 with ≤ 57% identity. The amino acid sequence analysis of HZ lipase determined a conserved pentapeptide containing the active serine, GHSMG and a Ca²⁺-binding motif, GCYGSD in the enzyme. Protein structure modeling showed that HZ lipase consisted of an α/β hydrolase fold and a lid domain. Protein sequence alignment, conserved regions analysis, clustal distance matrix and amino acid composition illustrated differences between HZ lipase and other thermostable lipases. Phylogenetic analysis revealed that this lipase represented a new subfamily of family I of bacterial true lipases, classified as family I.9. The HZ lipase was expressed under promoter P_lac using IPTG and was characterized. The recombinant enzyme showed optimal activity at 65°C and retained ≥ 97% activity after incubation at 50°C for 1h. The HZ lipase was stable in various polar and non-polar organic solvents.

Thermus thermophilus as a Source of Thermostable Lipolytic Enzymes

Lipolytic enzymes, esterases (EC 3.1.1.1) and lipases (EC 3.1.1.3), catalyze the hydrolysis of ester bonds between alcohols and carboxylic acids, and its formation in organic media. At present, they represent about 20% of commercialized enzymes for industrial use. Lipolytic enzymes from thermophilic microorganisms are preferred for industrial use to their mesophilic counterparts, mainly due to higher thermostability and resistance to several denaturing agents. However, the production at an industrial scale from the native organisms is technically complicated and expensive. The thermophilic bacterium Thermus thermophilus (T. thermophilus) has high levels of lipolytic activity, and its whole genome has been sequenced. One esterase from the T. thermophilus strain HB27 has been widely characterized, both in its native form and in recombinant forms, being expressed in mesophilic microorganisms. Other putative lipases/esterases annotated in the T. thermophilus genome have been explored and will also be reviewed in this paper.

New extremophilic lipases and esterases from metagenomics

Lipolytic enzymes catalyze the hydrolysis of ester bonds in the presence of water. In media with low water content or in organic solvents, they can catalyze synthetic reactions such as esterification and transesterification. Lipases and esterases, in particular those from extremophilic origin, are robust enzymes, functional under the harsh conditions of industrial processes owing to their inherent thermostability and resistance towards organic solvents, which combined with their high chemo-, regio- and enantioselectivity make them very attractive biocatalysts for a variety of industrial applications. Likewise, enzymes from extremophile sources can provide additional features such as activity at extreme temperatures, extreme pH values or high salinity levels, which could be interesting for certain purposes. New lipases and esterases have traditionally been discovered by the isolation of microbial strains producing lipolytic activity. The Genome Projects Era allowed genome mining, exploiting homology with known lipases and esterases, to be used in the search for new enzymes. The Metagenomic Era meant a step forward in this field with the study of the metagenome, the pool of genomes in an environmental microbial community. Current molecular biology techniques make it possible to construct total environmental DNA libraries, including the genomes of unculturable organisms, opening a new window to a vast field of unknown enzymes with new and unique properties. Here, we review the latest advances and findings from research into new extremophilic lipases and esterases, using metagenomic approaches, and their potential industrial and biotechnological applications.

Expression and biochemical characterization of a thermophilic organic solvent-tolerant lipase from Bacillus sp. DR90

The objective of the present study was the isolation, molecular cloning and biochemical characterization of a thermophilic organic solvent-resistant lipase from Bacillus sp. DR90. The lipase gene was expressed in Escherichia coli BL21(DE3) using pET-28a(+) vector. The purification of recombinant lipase was conducted by nickel affinity chromatography and its biochemical properties were determined. The lipase sequence with an ORF of 639 bp contains the conserved pentapeptide Ala-His-Ser-Met-Gly. His-tagged recombinant lipase had a specific activity of 1,126 U/mg with a molecular mass of 26.8 kDa. The cloned lipase was optimally active at pH 8.0 and 75 °C representing high stability in broad ranges of temperature and pH. High performance liquid chromatography was used to determine the major compounds released during the lipase-catalyzed reaction of p-nitrophenyl derivatives as well as the substrate specificity. The purified lipase showed high compatibility towards various organic solvents, surfactants and commercial solid/liquid detergents; therefore the recombinant DR90 lipase could be considered as a probable candidate for future applications, predominantly in detergent processing industries.

The conserved lid tryptophan, W211, potentiates thermostability and thermoactivity in bacterial thermoalkalophilic lipases

We hypothesize that aggregation of thermoalkalophilic lipases could be a thermostability mechanism. The conserved tryptophans (W211, W234) in the lid are of particular interest owing to their previous involvements in aggregation and thermostability mechanisms in many other proteins. The thermoalkalophilic lipase from Bacillus thermocatenulatus (BTL2) and its mutants (W211A, W234A) were expressed and purified to homogeneity. We found that, when aggregated, BTL2 is more thermostable than its non-aggregating form, showing that aggregation potentiates thermostability in the thermoalkalophilic lipase. Among the two lid mutants, the W211A lowered aggregation tendency drastically and resulted in a much less thermostable variant of BTL2, which indicated that W211 stabilizes the intermolecular interactions in BTL2 aggregates. Further thermoactivity and CD spectroscopy analyses showed that W211A also led to a strong decrease in the optimal and the melting temperature of BTL2, implying stabilization by W211 also to the intramolecular interactions. The other lid mutant W234A had no effects on these properties. Finally, we analyzed the molecular basis of these experimental findings in-silico using the dimer (PDB ID: 1KU0) and the monomer (PDB ID: 2W22) lipase structures. The computational analyses confirmed that W211 stabilized the intermolecular interactions in the dimer lipase and it is critical to the stability of the monomer lipase. Explicitly W211 confers stability to the dimer and the monomer lipase through distinct aromatic interactions with Y273-Y282 and H87-P232 respectively. The insights revealed by this work shed light not only on the mechanism of thermostability and its relation to aggregation but also on the particular role of the conserved lid tryptophan in the thermoalkalophilic lipases.

Unraveling the lipolytic activity of thermophilic bacteria isolated from a volcanic environment

In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70–80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern.

Solution behavior and activity of a halophilic esterase under high salt concentration

Background

Halophiles are extremophiles that thrive in environments with very high concentrations of salt. Although the salt reliance and physiology of these extremophiles have been widely investigated, the molecular working mechanisms of their enzymes under salty conditions have been little explored.

Methodology/Principal Findings

A halophilic esterolytic enzyme LipC derived from archeaon Haloarcula marismortui was overexpressed from Escherichia coli BL21. The purified enzyme showed a range of hydrolytic activity towards the substrates of p-nitrophenyl esters with different alkyl chains (n = 2−16), with the highest activity being observed for p-nitrophenyl acetate, consistent with the basic character of an esterase. The optimal esterase activities were found to be at pH 9.5 and [NaCl] = 3.4 M or [KCl] = 3.0 M and at around 45°C. Interestingly, the hydrolysis activity showed a clear reversibility against changes in salt concentration. At the ambient temperature of 22°C, enzyme systems working under the optimal salt concentrations were very stable against time. Increase in temperature increased the activity but reduced its stability. Circular dichroism (CD), dynamic light scattering (DLS) and small angle neutron scattering (SANS) were deployed to determine the physical states of LipC in solution. As the salt concentration increased, DLS revealed substantial increase in aggregate sizes, but CD measurements revealed the maximal retention of the α-helical structure at the salt concentration matching the optimal activity. These observations were supported by SANS analysis that revealed the highest proportion of unimers and dimers around the optimal salt concentration, although the coexistent larger aggregates showed a trend of increasing size with salt concentration, consistent with the DLS data.

Conclusions/Significance

The solution α-helical structure and activity relation also matched the highest proportion of enzyme unimers and dimers. Given that all the solutions studied were structurally inhomogeneous, it is important for future work to understand how the LipC's solution aggregation affected its activity.

Activation of bacterial thermoalkalophilic lipases is spurred by dramatic structural rearrangements

The bacterial thermoalkalophilic lipases that hydrolyze saturated fatty acids at 60-75 degrees C and pH 8-10 are grouped as the lipase family I.5. We report here the crystal structure of the lipase from Geobacillus thermocatenulatus, the first structure of a member of the lipase family I.5 showing an open configuration. Unexpectedly, enzyme activation involves large structural rearrangements of around 70 amino acids and the concerted movement of two lids, the alpha6- and alpha7-helices, unmasking the active site. Central in the restructuring process of the lids are both the transfer of bulky hydrophobic residues out of the N-terminal end of the alpha6-helix and the incorporation of short side chain residues to the alpha6 C-terminal end. All these structural changes are stabilized by the Zn(2+)-binding domain, which is characteristic of this family of lipases. Two detergent molecules are placed in the active site, mimicking chains of the triglyceride substrate, demonstrating the position of the oxyanion hole and the three pockets that accommodate the sn-1, sn-2, and sn-3 fatty acids chains. The combination of structural and biochemical studies indicate that the lid opening is not mediated by temperature but triggered by interaction with lipid substrate.

Isolation and identification of a lipase producing Bacillus sp. from soil

Lipase production in an indigenous lipolytic Bacillus sp. was detected in media containing Tributyrin-Tween 80 and Rhodamine B-Olive oil. The statistical Taguchi model was used to predict the optimum experimental conditions for bacterial growth and lipase production. Partial optimization was carried out for selection of salt base, oil, glucose, NH4Cl and yeast extract concentrations, inoculum density, pH and agitation. Maximum lipase activity was detected in the cell free supernatants of cultures grown in a medium containing 10 g L(-1) yeast extract, 15 g L(-1) NH4Cl, 3 g L(-1) K2HPO4, 1 g L(-1) KH2PO4, 0.1 g L(-1) MgSO4 x 7H2O, 2 g L(-1) glucose, 0.6 mM MgCl2 and 15 ml L(-1) olive oil, pH 8.5 at 30 degrees C for 24 h and low agitation. The amount oflipase produced in the designed medium was in agreement with the predicted values by the statistical method. 16S rRNA cloning and sequencing identified the test organism as Bacillus pumilus.

Production of L2 lipase by Bacillus sp. strain L2: nutritional and physical factors

A thermophilic bacterium, Bacillus sp. strain L2 was isolated from a hot spring in Perak, Malaysia. An extracellular lipase activity was detected through plate and broth assays at 70 degrees C after 28 h of incubation. The L2 lipase production was growth dependent as revealed by a number of factors affecting the secretion of extracelullar lipase. As for nutritional factors, casamino acids, trehalose, Ca(2+) and Tween 60 were found to be more effective for lipase production. The optimum physical condition for L2 lipase production was obtained at 70 degrees C after 28 h of cultivation time, at pH 7.0, 150 rpm of agitation rate and 1% of starting inoculum size. The activity staining of crude L2 lipase revealed a clearing zone at 39 kDa.

Cloning and expression of lipP, a gene encoding a cold-adapted lipase from Moritella sp.2-5-10-1

A gene (lipP, 837 bp in length) coding for a cold-adapted lipase of psychrophilic bacterium Moritella sp. 2-5-10-1 isolated from Antarctic region was cloned and sequenced in this study. The deduced amino acid sequence revealed a protein of 278 amino acid residues with a molecular mass of 30,521. The primary structure of the lipase deduced from the nucleotide sequence showed consensus pentapeptide containing the active serine [Gly-Trp-Ser-Leu-Gly] and a conserved His-Gly dipeptide in the N-terminal part of the enzyme. These sequences were involved in the lipase active site conformation. Structure factors that would allow proper enzyme flexibility at low temperatures were discussed. It was suggested that the changes in the primary structure of the psychrophilic lipases compared to the thermophilic ones could account for their ability to catalyze lipolysis at temperatures close to 0 degrees C. For expression, the sequence corresponding to the cold-adapted lipase of strain 2-5-10-1 was subcloned into the pET-28a expression vector to construct a recombinant lipase protein. Expression of the lipase by Escherichia coli BL21 (DE3) cells was observed as clear halos on 1% (vol/vol) tributyrin upon induction with IPTG at 25 degrees C.

Purification and characterization of two highly thermophilic alkaline lipases from Thermosyntropha lipolytica

Two thermostable lipases were isolated and characterized from Thermosyntropha lipolytica DSM 11003, an anaerobic, thermophilic, alkali-tolerant bacterium which grows syntrophically with methanogens on lipids such as olive oil, utilizing only the liberated fatty acid moieties but not the glycerol. Lipases LipA and LipB were purified from culture supernatants to gel electrophoretic homogeneity by ammonium sulfate precipitation and hydrophobic interaction column chromatography. The apparent molecular masses of LipA and LipB determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 50 and 57 kDa, respectively. The temperature for maximal activity of LipA and LipB was around 96 degrees C, which is, so far as is known, the highest temperature for maximal activity among lipases, and the pH optima for growth determined at 25 degrees C (pH(25 degrees C) optima) were 9.4 and 9.6, respectively. LipA and LipB at 100 degrees C and pH(25 degrees C) 8.0 retained 50% activity after 6 and 2 h of incubation, respectively. Both enzymes exhibited high activity with long-chain fatty acid glycerides, yielding maximum activity with trioleate (C(18:1)) and, among the p-nitrophenyl esters, with p-nitrophenyl laurate. Hydrolysis of glycerol ester bonds occurred at positions 1 and 3. The activities of both lipases were totally inhibited by 10 mM phenylmethylsulfonyl fluoride and 10 mM EDTA. Metal analysis indicated that both LipA and LipB contain 1 Ca2+ and one Mn2+ ion per monomeric enzyme unit. The addition of 1 mM MnCl2 to dialyzed enzyme preparations enhanced the activities at 96 degrees C of both LipA and LipB by threefold and increased the durations of their thermal stability at 60 degrees C and 75 degrees C, respectively, by 4 h.

A thermoalkaliphilic lipase of Geobacillus sp. T1

A thermoalkaliphilic T1 lipase gene of Geobacillus sp. strain T1 was overexpressed in pGEX vector in the prokaryotic system. Removal of the signal peptide improved protein solubility and promoted the binding of GST moiety to the glutathione-Sepharose column. High-yield purification of T1 lipase was achieved through two-step affinity chromatography with a final specific activity and yield of 958.2 U/mg and 51.5%, respectively. The molecular mass of T1 lipase was determined to be approximately 43 kDa by gel filtration chromatography. T1 lipase had an optimum temperature and pH of 70 degrees C and pH 9, respectively. It was stable up to 65 degrees C with a half-life of 5 h 15 min at pH 9. It was stable in the presence of 1 mM metal ions Na(+), Ca(2+), Mn(2+), K(+) and Mg(2+ ), but inhibited by Cu(2+), Fe(3+) and Zn(2+). Tween 80 significantly enhanced T1 lipase activity. T1 lipase was active towards medium to long chain triacylglycerols (C10-C14) and various natural oils with a marked preference for trilaurin (C12) (triacylglycerol) and sunflower oil (natural oil). Serine and aspartate residues were involved in catalysis, as its activity was strongly inhibited by 5 mM PMSF and 1 mM Pepstatin. The T(m) for T1 lipase was around 72.2 degrees C, as revealed by denatured protein analysis of CD spectra.

Identification and over-expression of a thermostable lipase from Geobacillus thermoleovorans Toshki in Escherichia coli

A newly isolated thermophilic strain producing thermostable lipase was identified based on 16S rRNA sequencing, where phylogenetic analysis revealed its closeness to Geobacillus thermoleovorans. Thermostable lipase from this bacterium was cloned using consensus degenerate PCR primers. For over-expression in Escherichia coli, the lipase gene was sub-cloned in pET 15b vector with a strong T7 promotor. Lipase activity was approximately 4.5-fold higher than in the wild-type strain. The lipase enzyme was thermostable at 60 degrees C and pH 8, whereas a 30% residual activity was retained when incubated for 1h at 100 degrees C. Optimum lipase expression was obtained in 2 x YT medium after 70min of induction by IPTG.

Cloning and Characterization of a Carboxylesterase from Bacillus coagulans 81-11

A genomic library of Bacillus coagulans strain 81-11 was screened in Escherichia coli JM83 for lipolytic activity by using tributyrin agar plates. A 2.4 kb DNA fragment was subcloned from a lipolytic-positive clone and completely sequenced. Nucleotide sequence analysis predicted a 723 bp open reading frame (ORF), designated estC1, encoding a protein of 240 amino acids with an estimated molecular mass of 27,528 Da and a pI of 9.15. The deduced amino acid sequence of the estC1 gene exhibited significant amino acid sequence identity with carboxylesterases from thermophilic Geobacillus spp. and sequence analysis showed that the protein contains the signature G-X-S-X-G included in most esterases and lipases. Enzyme assays using p-nitrophenyl (p-NP) esters with different acyl chain lengths as the substrate confirmed the esterase activity. EstC1 exhibited a marked preference for esters of short-chain fatty acids, yielding the highest activity with p-NP butyrate. Maximum activity was found at pH 8 and 50 degrees C, although the enzyme displayed stability at temperatures up to 60 degrees C.

Co-expression of a prophage system and a plasmid system in Bacillus subtilis

A dual expression system for overexpressing two proteins by a single cell strain has been developed in Bacillus subtilis. This dual expression system combines the phi105MU331 prophage system and a plasmid system within a single cell. Protein expression by the prophage system is heat inducible, while that of the plasmid system is constitutive. Three candidate genes, BPN, BT, and amyE, all of Bacillus origin, were used as test models. Seven strains (BPN, BT, AMY, BS168K, MU331K, BPNK, and BTK) were constructed to investigate the influences of the prophage system and the plasmid system on each other, and to compare the efficiency of the individual expression systems with that of the dual expression system. Individually, the yield of the plasmid system is higher than that of the prophage system, which could be attributed to the constitutive nature of the expression of the plasmid system. Nonetheless, for the dual expression strains, the expression of two enzymes in a single fermentation run can reduce costs in facilities, manpower, and utilities. Fed-batch fermentation of BPNK strains confirmed the feasibility of applying this dual expression system in industrial-scale production.