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

An Appraisal on Prominent Industrial and Biotechnological Applications of Bacterial Lipases

Microbial lipases expedite the hydrolysis and synthesis of long-chain acyl esters. They are highly significant commercial biocatalysts to biotechnologists and organic chemists. The market size of lipase is anticipated to reach $590 million by 2023. This is all owing to their versatility in properties, including stability in organic solvents, interfacial activation in micro-aqueous environments, high substrate specificity, and activity in even non-aqueous milieu. Lipases are omnipresent and synthesized by various living organisms, including animals, plants, and microorganisms. Microbial lipases are the preferred choice for industrial applications as they entail low production costs, higher yield independent of seasonal changes, easier purification practices, and are capable of being genetically modified. Microbial lipases are employed in several common industries, namely various food manufactories (dairy, bakery, flavor, and aroma enhancement, etc.), leather tanneries, paper and pulp, textiles, detergents, cosmetics, pharmaceuticals, biodiesel synthesis, bioremediation and waste treatment, and many more. In recent decades, circumspection toward eco-friendly and sustainable energy has led scientists to develop industrial mechanisms with lesser waste/effluent generation, minimal overall energy usage, and biocatalysts that can be synthesized using renewable, low-cost, and unconventional raw materials. However, there are still issues regarding the commercial use of lipases which make industrialists wary and sometimes even switch back to chemical catalysis. Industrially relevant lipase properties must be further optimized, analyzed, and explored to ensure their continuous successful utilization. This review comprehensively describes the general background, structural characteristics, classifications, thermostability, and various roles of bacterial lipases in important industries.

Production Optimization and Biochemical Characterization of Cellulase from Geobacillus sp. KP43 Isolated from Hot Spring Water of Nepal

This study is aimed at isolating and identifying a thermophilic cellulolytic bacterium from hot spring water and characterizing thermostable cellulase produced by the isolate. Enrichment and culture of water sample was used for isolation of bacterial strains and an isolate with highest cellulase activity was chosen for the production, partial purification, and biochemical characterization of the enzyme. Different staining techniques, enzymatic tests, and 16s ribosomal DNA (16s rDNA) gene sequencing were used for the identification of the isolate. The cellulase producing isolate was Gram positive, motile, and sporulated rod-shaped bacterium growing optimally between 55°C and 65°C. Based on partial 16s rDNA sequence analysis, the isolate was identified as Geobacillus sp. and was designated as Geobacillus sp. KP43. The cellulase enzyme production condition was optimized, and the product was partially purified and biochemically characterized. Optimum cellulase production was observed in 1% carboxymethyl cellulose (CMC) at 55°C. The molecular weight of the enzyme was found to be approximately 66 kDa on 12% SDS-PAGE analysis. Biochemical characterization of partially purified enzyme revealed the temperature optimum of 70°C and activity over a wide pH range. Further, cellulase activity was markedly stimulated by metal ion Fe^2+. Apart from cellulases, the isolate also depicted good xylanase, cellobiase, and amylase activities. Thermophilic growth with a variety of extracellular enzyme activities at elevated temperature as well as in a wide pH range showed that the isolated bacteria, Geobacillus sp. KP43, can withstand the harsh environmental condition, which makes this organism suitable for enzyme production for various biotechnological and industrial applications.

Not All That Glitters Is Gold: The Paradox of CO-dependent Hydrogenogenesis in Parageobacillus thermoglucosidasius

The thermophilic bacterium Parageobacillus thermoglucosidasius has recently gained interest due to its ability to catalyze the water gas shift reaction, where the oxidation of carbon monoxide (CO) is linked to the evolution of hydrogen (H2) gas. This phenotype is largely predictable based on the presence of a genomic region coding for a carbon monoxide dehydrogenase (CODH-Coo) and hydrogen evolving hydrogenase (Phc). In this work, seven previously uncharacterized strains were cultivated under 50% CO and 50% air atmosphere. Despite the presence of the coo-phc genes in all seven strains, only one strain, Kp1013, oxidizes CO and yields H2. The genomes of the H2 producing strains contain unique genomic regions that code for proteins involved in nickel transport and the detoxification of catechol, a by-product of a siderophore-mediated iron acquisition system. Combined, the presence of these genomic regions could potentially drive biological water gas shift (WGS) reaction in P. thermoglucosidasius.

Kinetic and thermodynamic characterization of novel alkaline lipase from halotolerant Bacillus gibsonii

A halotolerant bacterial strain isolated and identified as Bacillus gibsonii was used for extracellular lipase production. The bacterial strain was able to grow up to 1200 mM salt concentration and showed maximum growth at 600 mM NaCl concentration. The present study includes production of extracellular lipase enzyme and characterization of partially purified lipase with respect to its kinetic and thermodynamic behaviour. Maximum lipase activity was observed at 60 °C under alkaline pH (9.0) condition. The kinetic parameters such as V_max, K_m and K_cat were calculated as 158.73 U/mL, 0.539 mM and 483.93 min^-1 at 60 °C, respectively, suggested thermostable nature of the enzyme. The thermal inactivation energy [E_a(d)] was calculated as 66.98 kJ/mol. The values of Gibb's free energy (86.31 kJ/mol), enthalpy (64.26 kJ/mol) and entropy (- 66.21 × 10^-3 kJ/mol/K) for the enzyme inactivation obtained at 60 °C corroborated the assumption that 60 °C was the optimum temperature. Further, the deactivation rate constant (k_d) values calculated at 60 °C and 80 °C were found to be 0.0907 and 0.182 min^-1, respectively, which suggested that enzyme was more stable at 60 °C and it was partly inactivated at 80 °C.

A systematic review of the genera Geobacillus and Parageobacillus: their evolution, current taxonomic status and major applications

The genus Geobacillus, belonging to the phylum Firmicutes, is one of the most important genera and comprises thermophilic bacteria. The genus Geobacillus was erected with the taxonomic reclassification of various Bacillus species. Taxonomic studies of Geobacillus remain in progress. However, there is no comprehensive review of the characteristic features, taxonomic status and study of various applications of this interesting genus. The main aim of this review is to give a comprehensive account of the genus Geobacillus. At present the genus acomprises 25 taxa, 14 validly published (with correct name), nine validly published (with synonyms) and two not validly published species. We describe only validly published species of the genera Geobacillus and Parageobacillus. Vegetative cells of Geobacillus species are Gram-strain-positive or -variable, rod-shaped, motile, endospore-forming, aerobic or facultatively anaerobic, obligately thermophilic and chemo-organotrophic. Growth occurs in the pH range 6.08.5 and a temperature of 37-75 °C. The major cellular fatty acids are iso-C15:o, iso-C16:0 and iso-C17:o. The main menaquinone type is MK-7. The G-+C content of the DNA ranges between 48.2 and 58 mol%. The genus Geobacillus is widely distributed in nature, being mostly found in many extreme locations such as hot springs, hydrothermal vents, marine trenches, hay composts, etc. Geobacillus species have been widely exploited in various industrial and biotechnological applications, and thus are promising candidates for further studies in the future.

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.

Time-Course Transcriptome of Parageobacillus thermoglucosidasius DSM 6285 Grown in the Presence of Carbon Monoxide and Air

Parageobacillus thermoglucosidasius is a metabolically versatile, facultatively anaerobic thermophile belonging to the family Bacillaceae. Previous studies have shown that this bacterium harbours co-localised genes coding for a carbon monoxide (CO) dehydrogenase (CODH) and Ni-Fe hydrogenase (Phc) complex and oxidises CO and produces hydrogen (H₂) gas via the water-gas shift (WGS) reaction. To elucidate the genetic events culminating in the WGS reaction, P. thermoglucosidasius DSM 6285 was cultivated under an initial gas atmosphere of 50% CO and 50% air and total RNA was extracted at ~8 (aerobic phase), 20 (anaerobic phase), 27 and 44 (early and late hydrogenogenic phases) hours post inoculation. The rRNA-depleted fraction was sequenced using Illumina NextSeq, v2.5, 1x75bp chemistry. Differential expression revealed that at 8 vs.. 20, 20 vs.. 27 and 27 vs.. 44 h post inoculation, 2190, 2118 and 231 transcripts were differentially (FDR < 0.05) expressed. Cluster analysis revealed 26 distinct gene expression trajectories across the four time points. Of these, two similar clusters, showing overexpression at 20 relative to 8 h and depletion at 27 and 44 h, harboured the CODH and Phc transcripts, suggesting possible regulation by O_2. The transition between aerobic respiration and anaerobic growth was marked by initial metabolic deterioration, as reflected by up-regulation of transcripts linked to sporulation and down-regulation of transcripts linked to flagellar assembly and metabolism. However, the transcriptome and growth profiles revealed the reversal of this trend during the hydrogenogenic phase.

Substrate structure and computation guided engineering of a lipase for omega-3 fatty acid selectivity

Enrichment of omega-3 fatty acids (ɷ-3 FAs) in natural oils is important to realize their health benefits. Lipases are promising catalysts to perform this enrichment, however, fatty acid specificity of lipases is poor. We attempted to improve the fatty acid selectivity of a lipase from Geobacillus thermoleovorans (GTL) by two approaches. In a semi-rational approach, amino acid positions critical for binding were identified by docking the substrate to the GTL and best substitutes at these positions were identified by site saturation mutagenesis followed by screening to obtain a variant of GTL (CM-GTL). In the second approach based on rational design, a variant of GTL was designed (DM-GTL) wherein the active site was narrowed by incorporating two heavier amino acids in the lining of acyl-binding pocket to hinder access to bulky ɷ-3 FAs. The affinities DM-GTL with designed substrates were evaluated in silico. Both, CM-GTL and DM-GTL have shown excellent ability to discriminate against the ɷ-3 FAs during hydrolysis of oils. Engineering the binding pocket of an enzyme of a complex substrate, such as a triglyceride, by incorporating the information on substrate structure and computationally derived binding modes, has resulted in designing two efficient lipase variants with improved substrate selectivity.

Combining metabolic flux analysis and adaptive evolution to enhance lipase production in Bacillus subtilis

Metabolic fluxes during lipase production by Bacillus subtilis CICC 20034 in synthetic medium were studied using metabolic flux analysis (MFA). The MFA showed that lipase production was dependent on, and coupled to the tributyrin uptake rate, formation of biomass, lactate, ATP, as well as amino acids from the aspartate and glutamate family. Using tributyrin as the sole carbon source, an adaptive evolution strategy was applied to increase the tributyrin uptake rate. B. subtilis SPZ1 was obtained from CICC 20034 by adaptive evolution over 1000 generations of growth-based selection. The tributyrin consumption rate of strain SPZ1 reached 0.89 g/(L·h) which was 1.9-fold higher than that of the original strain. The MFA indicated that the 212% increase of tributyrin uptake flux contributed to the 556% increase of lipase flux. Consequently, the lipase activity (0.65 U/mL) of strain SPZ1 was 1.9-fold higher than that of the original strain. This was the highest lipase activity obtained by fermentation in synthetic medium reported for Bacillus strains. In complex culture medium, lipase activity of SPZ1 reached 3.3 U/mL.

X-ray structure and characterization of a thermostable lipase from Geobacillus thermoleovorans

Thermo-alkalophilic bacterium, Geobacillus thermoleovorans secrets many enzymes including a 43 kDa extracellular lipase. Significant thermostability, organic solvent stability and wide substrate preferences for hydrolysis drew our attention to solve its structure by crystallography. The structure was solved by molecular replacement method and refined up to 2.14 Å resolution. Structure of the lipase showed an alpha-beta fold with 19 α-helices and 10 β-sheets. The active site remains covered by a lid. One calcium and one zinc atom was found in the crystal. The structure showed a major difference (rmsd 5.6 Å) from its closest homolog in the amino acid region 191 to 203. Thermal unfolding of the lipase showed that the lipase is highly stable with T_m of 76 °C. ¹³C NMR spectra of products upon triglyceride hydrolysate revealed that the lipase hydrolyses at both sn-1 and sn-2 positions with equal efficiency.

Development an effective system to expression recombinant protein in E. coli via comparison and optimization of signal peptides: Expression of Pseudomonas fluorescens BJ-10 thermostable lipase as case study

BACKGROUND

Thermostable lipases from microbial sources have been substantially overexpressed in E. coli, however, these enzymes are often produced with low-level enzymatic activity and mainly in the form of inclusion bodies. Several studies have reported that the secretory production of recombinant proteins fused their N-terminus to a signal peptide has been employed to resolve the problem. In general, the feasibility of this approach largely depends on the secretory pathway of signal peptide and the type of target protein to be secreted. This study was performed to compare and optimize signal peptides for efficient secretion of thermostable lipase lipBJ10 from Pseudomonas fluorescens BJ-10. Meanwhile, a comparative study between this method and cytoplasmic secretion was implemented in secreting soluble and active lipases.

RESULTS

Fusion expression using six signal peptides, i.e., PelB and five native E. coli signal peptides, as fusion partners produced more soluble and functional recombinant lipBJ10 than non-fusion expression. Recombinant lipBJ10, fused to these six diverse signal peptides, was secreted into the periplasm in E. coli. The total lipase activity in all cases of fusion expression was higher than those in non-fusion expression. The relative activity peaked when lipBJ10 was fused to DsbA, yielding a value 73.3 times greater than that of the non-fusion protein. When DsbA was used as the fusion partner, the highest activity (265.41 U/ml) was achieved with the least formation of inclusion bodies; the other four E. coli signal peptides, to some extent, led to low activity and insoluble inclusion bodies. Therefore, DsbA is the optimal signal peptide partner to fuse with lipBJ10 to efficiently produce soluble and functional protein.

CONCLUSION

We found that fusing to these signal peptides, especially that of DsbA, can significantly decrease the formation of inclusion bodies and enhance the function and solubility of lipBJ10 compared to non-fusion lipBJ10. Our results reported here can provide a reference for the high-level expression of other lipases with respect to a possible industrial application.

Optimization of physical conditions for the production of thermostable T1 lipase in Pichia guilliermondii strain SO using response surface methodology

BACKGROUND

Pichia guilliermondii was found capable of expressing the recombinant thermostable lipase without methanol under the control of methanol dependent alcohol oxidase 1 promoter (AOXp 1). In this study, statistical approaches were employed for the screening and optimisation of physical conditions for T1 lipase production in P. guilliermondii.

RESULT

The screening of six physical conditions by Plackett-Burman Design has identified pH, inoculum size and incubation time as exerting significant effects on lipase production. These three conditions were further optimised using, Box-Behnken Design of Response Surface Methodology, which predicted an optimum medium comprising pH 6, 24 h incubation time and 2% inoculum size. T1 lipase activity of 2.0 U/mL was produced with a biomass of OD₆₀₀ 23.0.

CONCLUSION

The process of using RSM for optimisation yielded a 3-fold increase of T1 lipase over medium before optimisation. Therefore, this result has proven that T1 lipase can be produced at a higher yield in P. guilliermondii.

The genus Geobacillus and their biotechnological potential

The genus Geobacillus comprises a group of Gram-positive thermophilic bacteria, including obligate aerobes, denitrifiers, and facultative anaerobes that can grow over a range of 45-75°C. Originally classified as group five Bacillus spp., strains of Bacillus stearothermophilus came to prominence as contaminants of canned food and soon became the organism of choice for comparative studies of metabolism and enzymology between mesophiles and thermophiles. More recently, their catabolic versatility, particularly in the degradation of hemicellulose and starch, and rapid growth rates have raised their profile as organisms with potential for second-generation (lignocellulosic) biorefineries for biofuel or chemical production. The continued development of genetic tools to facilitate both fundamental investigation and metabolic engineering is now helping to realize this potential, for both metabolite production and optimized catabolism. In addition, this catabolic versatility provides a range of useful thermostable enzymes for industrial application. A number of genome-sequencing projects have been completed or are underway allowing comparative studies. These reveal a significant amount of genome rearrangement within the genus, the presence of large genomic islands encompassing all the hemicellulose utilization genes and a genomic island incorporating a set of long chain alkane monooxygenase genes. With G+C contents of 45-55%, thermostability appears to derive in part from the ability to synthesize protamine and spermine, which can condense DNA and raise its Tm.

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.

The Geobacillus paradox: why is a thermophilic bacterial genus so prevalent on a mesophilic planet?

The genus Geobacillus comprises endospore-forming obligate thermophiles. These bacteria have been isolated from cool soils and even cold ocean sediments in anomalously high numbers, given that the ambient temperatures are significantly below their minimum requirement for growth. Geobacilli are active in environments such as hot plant composts, however, and examination of their genome sequences reveals that they are endowed with a battery of sensors, transporters and enzymes dedicated to hydrolysing plant polysaccharides. Although they appear to be relatively minor members of the plant biomass-degrading microbial community, Geobacillus bacteria have achieved a significant population with a worldwide distribution, probably in large part due to adaptive features of their spores. First, their morphology and resistance properties enable them to be mobilized in the atmosphere and transported long distances. Second, their longevity, which in theory may be extreme, enables them to lie quiescent but viable for long periods of time, accumulating gradually over time to achieve surprisingly high population densities.

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.

Cloning, expression and characterization of a lipase gene from the Candida antarctica ZJB09193 and its application in biosynthesis of vitamin A esters

Lipase is one of the most important industrial enzymes, which has been widely used in the preparation of food additives, cosmetics and pharmaceuticals industries. In order to obtain a large amount of lipase, the lipase gene from Candida antarctica ZJB09193 was cloned, and expressed in Pichia pastoris with the vector pPICZαA. Under the optimal conditions, the yield of recombinant lipase in the culture broth reached 3.0 g/L. After purification, the properties of recombinant lipase were studied: the optimum pH and temperature were pH 8.0 and 52°C, Ca(2+) activated the activity of lipase, and the apparent K(m) and V(max) values for p-nitrophenyl acetate were 0.34 mM and 7.36 μmol min(-1) mg(-1), respectively. Furthermore, the recombinant lipase was immobilized on pretreated textile for biosynthesis of vitamin A esters. In a system of n-hexane, 0.3 g immobilized recombinant lipase was used in the presence of 0.06 g vitamin A acetate and 0.55 mmol fatty acid (nine different fatty acids were tested). The yield of all vitamin A esters exceeded 78% in 7h at 30°C except using lactic acid and hexanoic acid as substrates. After optimization, the yield of vitamin A palmitate reached 87%. This study has the potential to be developed into industrial application.

Screening and characterization of a novel alkaline lipase from Acinetobacter calcoaceticus 1-7 Isolated from bohai bay in china for detergent formulation

A novel alkaline lipase-producing strain 1–7 identified as Acinetobacter calcoaceticus was isolated from soil samples collected from Bohai Bay, China, using an olive oil alkaline plate, which contained olive oil as the sole carbon source. The lipase from strain 1–7 showed the maximum activity at pH 9.0 under 40 °C. One interesting feature of this enzyme is that it exhibits lipase activity over a broad range of temperatures and good stability. It is also stable at a broad range of pHs from 4.0 to 10.0 for 24 h. Its catalytic activity was highly enhanced in the presence of Ca²⁺, Mg²⁺ and K⁺, but partially inhibited by Cu²⁺, Al³⁺, Fe³⁺, Ba²⁺and Zn²⁺. The fact that it displays marked stability and activity in the presence of TritonX-100, Tween-20, Tween-80, SDS, Hydrogen peroxide, Sodium perborate, Sodium hypochlorite, Sodium citrate, Sodium taurocholate, Glycerine and NaCl suggests that this lipase is suitable as an additive in detergent formulations.

Significant improvement of Geobacillus thermoleovorans CCR11 thermoalkalophilic lipase production using response surface methodology

The medium optimization for the production of the Geobacillus thermoleovorans CCR11 thermoalkalophilic lipase was carried out in shake flask cultures using safflower high oleic oil. In the first step of optimization, a two level fractional factorial design allowed the identification of the concentration of nutrient broth and temperature as the main variables significantly affecting lipase production (P<0.05). In a second step, a D-optimal design was applied to determine the variables optimal values, defined as those yielding maximal lipase production in shaken flasks, thus demonstrating that the optimal concentration of nutrient broth was 3.8 g/l and the optimal culture temperature was 39.5°C. The model was experimentally validated, yielding a lipase production of 2283.70 ± 118.36 U/mL which represents a 6.7-fold increase in comparison to the non-optimized medium.

Molecular cloning, over expression and characterization of thermoalkalophilic esterases isolated from Geobacillus sp

Due to potential use for variety of biotechnological applications, genes encoding thermoalkalophilic esterase from three different Geobacillus strains isolated from thermal environmental samples in Balçova (Agamemnon) geothermal site were cloned and respective proteins were expressed in Escherichia coli (E.coli) and characterized in detail. Three esterases (Est1, Est2, Est3) were cloned directly by PCR amplification using consensus degenerate primers from genomic DNA of the strains Est1, Est2 and Est3 which were from mud, reinjection water and uncontrolled thermal leak, respectively. The genes contained an open reading frame (ORF) consisting of 741 bp for Est1 and Est2, which encoded 246 amino acids and ORF of Est3 was 729 bp encoded 242 amino acids. The esterase genes were expressed in E. coli and purified using His-Select HF nickel affinity gel. The molecular mass of the recombinant enzyme for each esterase was approximately 27.5 kDa. The three esterases showed high specific activity toward short chain p-NP esters. Recombinant Est1, Est2, Est3 have exhibited similar activity and the highest esterase activity of 1,100 U/mg with p-nitrophenyl acetate (pNPC(2)) as substrate was observed with Est1. All three esterase were most active around 65°C and pH 9.5-10.0. The effect of organic solvents, several metal ions, inhibitors and detergents on enzyme activity for purified Est1, Est2, Est3 were determined separately and compared.

Expression and characterization of a novel heterologous moderately thermostable lipase derived from metagenomics in Streptomyces lividans

Seven lipolytic genes were isolated and sequenced from a metagenomic library that was constructed following biomass enrichment in a fed-batch bioreactor submitted to high temperature (50-70 degrees C) and alkaline pH (7-8.5). Among those sequences, lipIAF1-6 was chosen for further study and cloned in Streptomyces lividans 10-164. The G+C content within the sequence was 64.3%. The encoded protein, LipIAF1-6, was related to various putative lipases previously identified in different genome sequences. Homology of LipIAF-6 with the different lipases did not exceed 31%. The optimum pH (8.5) and temperature (60 degrees C) of the purified enzyme were in agreement with the enrichment conditions. Furthermore, the enzyme was thermostable for as long as 30 min at 70 degrees C. The maximum activity of the purified lipase was 4,287 IU/mg towards p-nitrophenyl (p-NP) butyrate (60 degrees C; pH 8.5). LipIAF1-6 does not seem to need the presence of metal ions for its activity. The enzyme was slightly inhibited by 10 mM CoCl2 (14%), HgCl2 (12%), and dithiothreitol (DTT) (15%). The serine protease inhibitor phenylmethylsulphonyl fluoride (PMSF) reduced activity by 39% and 71% when incubated at concentrations of 1 and 10 mM, respectively. Finally, LipIAF1-6 was stable in different organic solvents, and against several surfactants and oxidative agents commonly found in detergent formulations. These results are quite encouraging for further use of this enzyme in different industrial processes.

A novel endo-glucanase from the thermophilic bacterium Geobacillus sp. 70PC53 with high activity and stability over a broad range of temperatures

A thermophilic Geobacillus bacterium secreting high activity of endo-glucanase (EC 3.2.1.4) was isolated from rice straw compost supplemented with pig manure. A full-length gene of 1,104 bp, celA, encoding this glycosyl hydrolase family 5 endo-glucanase of 368 amino acids was isolated. No related gene from Geobacillus has been reported previously. The recombinant CelA expressed in Escherichia coli had an optimal activity at 65 degrees C and pH 5.0, and it exhibited tenfold greater specific activity than the commercially available Trichoderma reesei endo-glucanase. CelA displayed activity over a broad temperature range from 45 to 75 degrees C and was a thermostable enzyme with 90% activity retained after heating at 65 degrees C for 6 h. Interestingly, CelA activity could be enhanced by 100% in the presence of 2 mM MnSO(4). CelA had high specific activity over beta-D-glucan from barley and Lichenan, making it a potentially useful enzyme in biofuel and food industries.

Gene cloning, expression, and characterization of the Geobacillus Thermoleovorans CCR11 thermoalkaliphilic lipase

The gene for a Geobacillus thermoleovorans CCR11 thermostable lipase was recovered by PCR and cloned. Four genetic constructions were designed and successfully expressed in E. coli: (i) the lipase structural gene (lipCCR11) in the PinPoint Xa vector; (ii) the lipase structural gene (lipACCR11) in the pET-28a(+) vector; (iii) the lipase structural gene minus the signal peptide (lipMatCCR11) in the pET-3b vector; and (iv) the lipase structural gene plus its own promoter (lipProCCR11) in the pGEM-T cloning vector. The lipase gene sequence analysis showed an open reading frame of 1,212 nucleotides coding for a mature lipase of 382 residues (40 kDa) plus a 22 residues signal peptide. Expression under T7 and T7lac promoter resulted in a 40- and 36-fold increase in lipolytic activity with respect to the original strain lipase. All recombinant lipases showed an optimal activity at pH 9.0, but variations were found in the temperature for maximum activity and the substrate specificity among them and when compared with the parental strain lipase, especially in the recombinant lipases that contained fusion tags. Therefore, it is important to find the appropriate expression system able to attain a high concentration of the recombinant lipase without compromising the proper folding of the protein.