Characterization of esterase activity in Geobacillus sp. HBB-4

AMWEst, a new thermostable and detergent-tolerant esterase retrieved from the Albian aquifer

A fosmid library was constructed with the metagenomic DNA from the high-temperature sediment-rich water of the Albian aquifer (Algeria). Functional screening of this library was subsequently done looking for genes encoding lipolytic enzymes. We identified a novel gene named AMWEst (1209 base pairs) encoding a protein of 402 amino acids with a predicted molecular weight of 43.44 kDa and conferring esterase activity. AMWEst was successfully overexpressed in the yeast mesophilic host Saccharomyces cerevisiae, and the expression system used proved to be efficient and produced sufficient activity for its biochemical characterization. Multiple sequence alignment indicated that AMWEst contained a conserved pentapeptide motif (Gly120-His121-Ser122-Gln123-Gly124). The optimum pH and temperature of the recombinant esterase AMWEst were 8 and 80 °C, respectively. Additionally, AMWEst showed higher activity towards short carbon substrates and showed maximum activity for p-nitrophenyl hexanoate (C6). Notably, AMWEst has a remarkable thermostability, and the enzyme retains almost maximum activity at 70 °C after incubation for 1 h. Moreover, enzyme activity was enhanced by high concentrations of SDS and Triton X-100 detergents. KEY POINTS: • A novel thermostable esterase has been retrieved through functional metagenomics • The esterase is detergent-tolerant, which is attractive for some applications • The esterase can be expressed in a yeast mesophilic host to enhance its yield.

Role of the C-Terminal β Sandwich of Thermoanaerobacter tengcongensis Thermophilic Esterase in Hydrolysis of Long-Chain Acyl Substrates

To search for a novel thermostable esterase for optimized industrial applications, esterase from a thermophilic eubacterium species, Thermoanaerobacter tengcongensis MB4, was purified and characterized in this work. Sequence analysis of T. tengcongensis esterase with other homologous esterases of the same family revealed an apparent tail at the C-terminal that is not conserved across the esterase family. Hence, it was hypothesized that the tail is unlikely to have an essential structural or catalytic role. However, there is no documented report of any role for this tail region. We probed the role of the C-terminal domain on the catalytic activity and substrate preference of T. tengcongensis esterase EstA3 with a view to see how it could be engineered for enhanced properties. To achieve this, we cloned, expressed, and purified the wild-type and the truncated versions of the enzyme. In addition, a naturally occurring member of the family (from Brevibacillus brevis) that lacks the C-terminal tail was also made. In vitro characterization of the purified enzymes showed that the C-terminal domain contributes significantly to the catalytic activity and distinct substrate preference of T. tengcongensis esterase EstA3. All three recombinant enzymes showed the highest preference for paranitrophenyl butyrate (pNPC4), which suggests they are true esterases, not lipases. Kinetic data revealed that truncation had a slight effect on the substrate-binding affinity. Thus, the drop in preference towards long-chain substrates might not be a result of substrate binding affinity alone. The findings from this work could form the basis for future protein engineering allowing the modification of esterase catalytic properties through domain swapping or by attaching a modular protein domain.

Production of PETase by engineered Yarrowia lipolytica for efficient poly(ethylene terephthalate) biodegradation

There has been a growing interest in poly(ethylene terephthalate) PET degradation studies in the last few years due to its widespread use and large-scale plastic waste accumulation in the environment. One of the most promising enzymatic methods in the context of PET degradation is the use of PETase from Ideonella sakaiensis, which has been reported to be an efficient enzyme for hydrolysing ester bonds in PET. In our study, we expressed a codon-optimized PETase gene in the yeast Yarrowia lipolytica. The obtained strain was tested for its ability to degrade PET directly in culture, and a screening of different supplements that might raise the level of PET hydrolysis was performed. We also carried out long-term cultures with PET film, the surface of which was examined by scanning electron microscopy. The efficiency of PET degradation was tested based on the concentration of degradation products released, and the results showed that supplementation of the culture with olive oil resulted in 66 % higher release of terephthalic acid into the medium compared to the mutant culture without supplementation. The results indicate the possibility of ethylene glycol uptake by both strains, and, additionally, the PETase produced by the newly engineered strain hydrolyses MHET. The structure of the PET film after culture with the modified strain, meanwhile, had numerous surface defects, cracks, and deformations.

Improving the catalytic efficiency and substrate affinity of a novel esterase from marine Klebsiella aerogenes by random and site-directed mutation

A novel esterase (EstKa) from marine Klebsiella aerogenes was characterized with hydrolytic activity against p-nitrophenyl caprylate (pNPC, C₈) under optimum conditions (50 °C and pH 8.5). After two rounds of mutagenesis, two highly potential mutants (I6E9 and L7B11) were obtained with prominent activity, substrate affinity and thermostability. I6E9 (L90Q/P96T) and L7B11 (A37S/Q100L/S133G/R138C/Q156R) were 1.56- and 1.65-fold higher than EstKa in relative catalytic efficiency. The influence of each amino acid on enzyme activity was explored by site-directed mutation. The mutants Pro96Thr and Gln156Arg showed 1.29- and 1.48-fold increase in catalytic efficiency (Kcat/Km) and 54.4 and 36.2% decrease in substrate affinity (Km), respectively. The compound mutant Pro96Thr/Gln156Arg exhibited 68.9% decrease in Km and 1.41-fold increase in Kcat/Km relative to EstKa. Homology model structure analysis revealed that the replacement of Gln by hydrophilic Arg on the esterase surface improved the microenvironment stability and the activity. The replacement of Pro by Thr enabled the esterase enzyme to retain 90% relative activity after 3 h incubation at 45 °C. Structural analysis confirmed that the formation of a hydrogen bond leads to a notable increase of catalytic efficiency under high temperature conditions.

Biochemical and Structural Characterization of a novel thermophilic esterase EstD11 provide catalytic insights for the HSL family

A novel esterase, EstD11, has been discovered in a hot spring metagenomic library. It is a thermophilic and thermostable esterase with an optimum temperature of 60°C. A detailed substrate preference analysis of EstD11 was done using a library of chromogenic ester substrate that revealed the broad substrate specificity of EstD11 with significant measurable activity against 16 substrates with varied chain length, steric hindrance, aromaticity and flexibility of the linker between the carboxyl and the alcohol moiety of the ester. The tridimensional structures of EstD11 and the inactive mutant have been determined at atomic resolutions. Structural and bioinformatic analysis, confirm that EstD11 belongs to the family IV, the hormone-sensitive lipase (HSL) family, from the α/β-hydrolase superfamily. The canonical α/β-hydrolase domain is completed by a cap domain, composed by two subdomains that can unmask of the active site to allow the substrate to enter. Eight crystallographic complexes were solved with different substrates and reaction products that allowed identification of the hot-spots in the active site underlying the specificity of the protein. Crystallization and/or incubation of EstD11 at high temperature provided unique information on cap dynamics and a first glimpse of enzymatic activity in vivo. Very interestingly, we have discovered a unique Met zipper lining the active site and the cap domains that could be essential in pivotal aspects as thermo-stability and substrate promiscuity in EstD11.

Influence of Culture Conditions on the Production of Extracellular Esterase from Bacillus licheniformis and Its Characterization

Esterases catalyze the hydrolysis of ester bonds in fatty acid esters with short-chain acyl groups. In the present study, thirty-seven bacterial isolates were isolated from soil contaminated with waste cooking oil, dairy waste etc. from Shimla and Solan district of H.P. Out of 37 isolates, the isolate RL-1, which gave maximum activity, was identified as Bacillus licheniformis MH061919. The optimization of various production parameters resulted in maximum activity at inoculum age of 24 h and inoculum size of 1.5% (v/v). Esterase gave considerable activity in production medium containing sodium chloride (0.5 % w/v), galactose (1%, w/v), coconut oil (2.0%, v/v) and beef extract (0.3%, w/v) at a temperature of 45℃ and pH 8.5.The enzyme production was enhanced by 3-fold after optimization of production parameters. Further, on optimizing reaction conditions, enzyme gave maximum activity at a temperature of 45℃ and pH 8.5. The para-nitrophenyl acetate (p-NPA) was found to be optimum substrate and metal ions and detergents have inhibitory effect on esterase activity.

Exploring the Enzymatic and Antibacterial Activities of Novel Mycobacteriophage Lysin B Enzymes

Mycobacteriophages possess different sets of lytic enzymes for disruption of the complex cell envelope of the mycobacteria host cells and release of the viral progeny. Lysin B (LysB) enzymes are mycolylarabinogalactan esterases that cleave the ester bond between the arabinogalactan and mycolic acids in the mycolylarabinogalactan-peptidoglycan (mAGP) complex in the cell envelope of mycobacteria. In the present study, four LysB enzymes were produced recombinantly and characterized with respect to their enzymatic and antibacterial activities. Examination of the kinetic parameters for the hydrolysis of para-nitrophenyl ester substrates, shows LysB-His₆ enzymes to be active against a range of substrates (C4–C16), with a catalytic preference towards p-nitrophenyl laurate (C12). With p-nitrophenyl butyrate as substrate, LysB-His₆ enzymes showed highest activity at 37 °C. LysB-His₆ enzymes also hydrolyzed different Tween substrates with highest activity against Tween 20 and 80. Metal ions like Ca²⁺ and Mn²⁺ enhanced the enzymatic activity of LysB-His₆ enzymes, while transition metal ions like Zn²⁺ and Cu²⁺ inhibited the enzymatic activity. The mycolylarabinogalactan esterase activity of LysB-His₆ enzymes against mAGP complex was confirmed by LC-MS. LysB-His₆ enzymes showed marginal antibacterial activity when tested alone against Mycobacterium smegmatis, however a synergetic activity was noticed when combined with outer membrane permealizers. These results confirm that LysB enzymes are lipolytic enzymes with potential application as antimycobacterials.

Biochemical profiles of two thermostable and organic solvent-tolerant esterases derived from a compost metagenome

Owing to the functional versatility and potential applications in industry, interest in lipolytic enzymes tolerant to organic solvents is increasing. In this study, functional screening of a compost soil metagenome resulted in identification of two lipolytic genes, est1 and est2, encoding 270 and 389 amino acids, respectively. The two genes were heterologously expressed and characterized. Est1 and Est2 are thermostable enzymes with optimal enzyme activities at 80 and 70 °C, respectively. A second-order rotatable design, which allows establishing the relationship between multiple variables with the obtained responses, was used to explore the combined effects of temperature and pH on esterase stability. The response curve indicated that Est1, and particularly Est2, retained high stability within a broad range of temperature and pH values. Furthermore, the effects of organic solvents on Est1 and Est2 activities and stabilities were assessed. Notably, Est2 activity was significantly enhanced (two- to tenfold) in the presence of ethanol, methanol, isopropanol, and 1-propanol over a concentration range between 6 and 30% (v/v). For the short-term stability (2 h of incubation), Est2 exhibited high tolerance against 60% (v/v) of ethanol, methanol, isopropanol, DMSO, and acetone, while Est1 activity resisted these solvents only at lower concentrations (below 30%, v/v). Est2 also displayed high stability towards some water-immiscible organic solvents, such as ethyl acetate, diethyl ether, and toluene. With respect to long-term stability, Est2 retained most of its activity after 26 days of incubation in the presence of 30% (v/v) ethanol, methanol, isopropanol, DMSO, or acetone. All of these features indicate that Est1 and Est2 possess application potential.

A novel cold-adapted esterase from Enterobacter cloacae: Characterization and improvement of its activity and thermostability via the site of Tyr193Cys

Background

In industries lipolytic reactions occur in insensitive conditions such as high temperature thus novel stout esterases with unique properties are attracts to the industrial application. Protein engineering is the tool to obtain desirable characters of enzymes. A novel esterase gene was isolated from South China Sea and subjected to a random mutagenesis and site directed mutagenesis for higher activity and thermo-stability compared to wild type.

Results

A novel esterase showed the highest hydrolytic activity against p-nitrophenyl acetate (pNPA, C2) and the optimal activity at 40 °C and pH 8.5. It was a cold-adapted enzyme and retained approximately 40% of its maximum activity at 0 °C. A mutant, with higher activity and thermo-stability was obtained by random mutagenesis. Kinetic analysis indicated that the mutant Val29Ala/Tyr193Cys shown 43.5% decrease in K_m, 2.6-fold increase in K_cat, and 4.7-fold increase in K_cat/K_m relative to the wild type. Single mutants V29A and Y193C were constructed and their kinetic parameters were measured. The results showed that the values of K_m, K_cat, and K_cat/K_m of V29A were similar to those of the wild type while Y193C showed 52.7% decrease in K_m, 2.7-fold increase in K_cat, and 5.6-fold increase in K_cat/K_m compared with the wild type. The 3-D structure and docking analysis revealed that the replacement of Tyr by Cys could enlarge the binding pocket. Moreover Y193C also showed a better thermo-stability for the reason its higher hydrophobicity and retained 67% relative activity after incubation for 3 h at 50 °C.

Conclusions

The superior quality of modified esterase suggested it has great potential application in extreme conditions and the mutational work recommended that important information for the study of esterase structure and function.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0885-z) contains supplementary material, which is available to authorized users.

Classification of lipolytic enzymes and their biotechnological applications in the pulping industry

In the pulp and paper industry, during the manufacturing process, the agglomeration of pitch particles (composed of triglycerides, fatty acids, and esters) leads to the formation of black pitch deposits in the pulp and on machinery, which impacts on the process and pulp quality. Traditional methods of pitch prevention and treatment are no longer feasible due to environmental impact and cost. Consequently, there is a need for more efficient and environmentally friendly approaches. The application of lipolytic enzymes, such as lipases and esterases, could be the sustainable solution to this problem. Therefore, an understanding of their structure, mechanism, and sources are essential. In this report, we review the microbial sources for the different groups of lipolytic enzymes, the differences between lipases and esterases, and their potential applications in the pulping industry.

Biocatalytic Resolution of Rac-α-Ethyl-2-Oxo-Pyrrolidineacetic Acid Methyl Ester by Immobilized Recombinant Bacillus cereus Esterase

A new esterase-producing strain (Bacillus cereus WZZ001) which exhibiting high hydrolytic activity and excellent enantioselectivity on rac-α-ethyl-2-oxo-pyrrolidineacetic acid methyl ester (R, S-1) has been isolated from soil sample by our laboratory. In this study, the stereoselective hydrolysis of (R, S-1) was performed using the recombinant Bacillus cereus esterase which expressed in Escherichia coli BL21 (DE3). Under the optimized conditions of pH 8.0, 35 °C, and concentration of substrate 400 mM, a successful enzymatic resolution was achieved with an e.e. s of 99.5 % and conversion of 49 %. Immobilization considerably increased the reusability of the recombinant esterase; the immobilized enzyme showed excellent reusability during 6 cycles of repeated 2 h reactions at 35 °C. Thereby, it makes the recombinant B. cereus esterase a usable biocatalyst for industrial application.

A novel thermoalkalostable esterase from Acidicaldus sp. strain USBA-GBX-499 with enantioselectivity isolated from an acidic hot springs of Colombian Andes

Several thermo- and mesoacidophilic bacterial strains that revealed high lipolytic activity were isolated from water samples derived from acidic hot springs in Los Nevados National Natural Park (Colombia). A novel lipolytic enzyme named 499EST was obtained from the thermoacidophilic alpha-Proteobacterium Acidicaldus USBA-GBX-499. The gene estA encoded a 313-amino-acid protein named 499EST. The deduced amino acid sequence showed the highest identity (58 %) with a putative α/β hydrolase from Acidiphilium sp. (ZP_08632277.1). Sequence alignments and phylogenetic analysis indicated that 499EST is a new member of the bacterial esterase/lipase family IV. The esterase reveals its optimum catalytic activity at 55 °C and pH 9.0. Kinetic studies showed that 499EST preferentially hydrolyzed middle-length acyl chains (C6-C8), especially p-nitrophenyl (p-NP) caproate (C6). Its thermostability and activity were strongly enhanced by adding 6 mM FeCl3. High stability in the presence of water-miscible solvents such as dimethyl sulfoxide and glycerol was observed. This enzyme also exhibits stability under harsh environmental conditions and enantioselectivity towards naproxen and ibuprofen esters, yielding the medically relevant (S)-enantiomers. In conclusion, according to our knowledge, 499EST is the first thermoalkalostable esterase derived from a Gram-negative thermoacidophilic bacterium.

Isolation and characterization of a heavy metal-resistant, thermophilic esterase from a Red Sea brine pool

The Red Sea Atlantis II brine pool is an extreme environment that displays multiple harsh conditions such as high temperature, high salinity and high concentrations of multiple, toxic heavy metals. The survival of microbes in such an environment by utilizing resistant enzymes makes them an excellent source of extremophilic enzymes. We constructed a fosmid metagenomic library using DNA isolated from the deepest and most secluded layer of this pool. We report the isolation and biochemical characterization of an unusual esterase: EstATII. EstATII is thermophilic (optimum temperature, 65°C), halotolerant (maintains its activity in up to 4.5 M NaCl) and maintains at least 60% of its activity in the presence of a wide spectrum of heavy metals. The combination of biochemical characteristics of the Red Sea Atlantis II brine pool esterase, i.e., halotolerance, thermophilicity and resistance to heavy metals, makes it a potentially useful biocatalyst.

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.

Microbial production of docosahexaenoic acid by a low temperature-adaptive strain Thraustochytriidae sp. Z105: screening and optimization

As an alternative source in addition to fish oil, microbial production of docosahexaenoic acid has been recieved more and more attentions owing to their culture advantage. A unicellular eukaryotic microbe with high DHA production and capable of low temperature-adaptive growth was isolated from seawater and identified as Thraustochytriidae sp. Z105. The siginificant effect of temperature on cell growth and DHA synthesis by the strain was revealed. It could grow and produce DHA even at 4 degrees C, but hardly grow above 35 degrees C. Low temperature (15-25 degrees C) was favorable for formation of biomass, lipids and DHA, but DHA synthesis was completely blocked above 30 degrees C. Conditions for high level DHA production by Thraustochytriidae sp. Z105 in flask culture were optimized as follows: medium containing glucose 80 g/l, yeast extract 5.0 g/l, K2HPO(4) . 3 H2O 1.0 g/l, MgSO4 . 7 H2O 0.5 g/l, seawater crystal 20 g/l, pH 6.0, liquid volume 30 ml/250 ml, temperature 20 degrees C, agitation speed of 200 r/min, and culture for 120 h. Under the optimal conditions, biomass of 16.72 g/l, total lipids of 5.35 g/l, DHA yield of 1.71 g/l (accounting for 32% of the total lipids) were achieved, respectively. In flask cluture level, the DHA productivity of Thraustochytriidae sp. Z105 was higher than most reported results, which suggested the wild type strain was a potential superior candidate for industrialization of DHA production. Moreover, the strain is an unique and valuable resource for investigation of the low temperature adaptive mechanism related to DHA synthesis.

A cold-adapted esterase of a novel marine isolate, Pseudoalteromonas arctica: gene cloning, enzyme purification and characterization

A gene encoding an esterase (estO) was identified and sequenced from a gene library screen of the psychrotolerant bacterium Pseudoalteromonas arctica. Analysis of the 1,203 bp coding region revealed that the deduced peptide sequence is composed of 400 amino acids with a predicted molecular mass of 44.1 kDa. EstO contains a N-terminal esterase domain and an additional OsmC domain at the C-terminus (osmotically induced family of proteins). The highly conserved five-residue motif typical for all alpha/beta hydrolases (G x S x G) was detected from position 104 to 108 together with a putative catalytic triad consisting of Ser(106), Asp(196), and His(225). Sequence comparison showed that EstO exhibits 90% amino acid identity with hypothetical proteins containing similar esterase and OsmC domains but only around 10% identity to the amino acid sequences of known esterases. EstO variants with and without the OsmC domain were produced and purified as His-tag fusion proteins in E. coli. EstO displayed an optimum pH of 7.5 and optimum temperature of 25 degrees C with more than 50% retained activity at the freezing point of water. The thermostability of EstO (50% activity after 5 h at 40 degrees C) dramatically increased in the truncated variant (50% activity after 2.5 h at 90 degrees C). Furthermore, the esterase displays broad substrate specificity for esters of short-chain fatty acids (C(2)-C(8)).