Cloning, Purification and Characterization of a Highly Thermostable Amylase Gene of Thermotoga petrophila into Escherichia coli

Heterologous expression, molecular studies and biochemical characterization of a novel alkaline esterase gene from Bacillus thuringiensis for detergent industry

Present study was aimed to clone and express the esterase encoding gene from Bacillus thuringiensis in E. coli BL21. Purification of recombinant esterase enzyme was achieved up to 48.6 purification folds by ion exchange chromatography with specific activity of 126.36 U mg^-1. Molecular weight of esterase enzyme was 29 kDa as measured by SDS-PAGE. Purified esterase enzyme showed stability up to 90% at 90 °C and remained stable in a wide pH range (8-11). Molecular docking strengthens the experimental results by showing the higher binding energy with p-NP-butyrate. Enzyme activity was found to be reduced by EDTA but enhanced in the presence of other metal ions. Enzyme activity was reduced with 1% SDS, PMSF, and urea but organic solvents did not show considerable impact on it even at higher concentrations. Purified recombinant esterase was also found to be compatible with commercial laundry detergents and showed very good stability (up to 90%). All these properties proved the esterase enzyme from B. thuringensis a significant addition in detergent industry.

Bacillus velezensis Identification and Recombinant Expression, Purification, and Characterization of Its Alpha-Amylase

Amylases account for about 30% of the global market of industrial enzymes, and the current amylases cannot fully meet industrial needs. This study aimed to identify a high α-amylase producing bacterium WangLB, to clone its α-amylase coding gene, and to characterize the α-amylase. Results showed that WangLB belonged to Bacillus velezensis whose α-amylase gene was 1980 bp coding 659 amino acids designated as BvAmylase. BvAmylase was a hydrophilic stable protein with a signal peptide and a theoretical pI of 5.49. The relative molecular weight of BvAmylase was 72.35 kDa, and was verified by SDS-PAGE. Its modeled structure displayed that it was a monomer composed of three domains. Its optimum temperature and pH were 70 °C and pH 6.0, respectively. It also showed high activity in a wide range of temperatures (40–75 °C) and a relatively narrow pH (5.0–7.0). It was a Ca2+-independent enzyme, whose α-amylase activity was increased by Co2+, Tween 20, and Triton X-100, and severely decreased by SDS. The Km and the Vmax of BvAmylase were 3.43 ± 0.53 and 434.19 ± 28.57 U/mg. In conclusion, the α-amylase producing bacterium WangLB was identified, and one of its α-amylases was characterized, which will be a candidate enzyme for industrial applications.

Amylases from thermophilic bacteria: structure and function relationship

Amylases hydrolyze starch to diverse products including dextrins and progressively smaller polymers of glucose units. Thermally stable amylases account for nearly 25% of the enzyme market. This review highlights the structural attributes of the α-amylases from thermophilic bacteria. Heterologous expression of amylases in suitable hosts is discussed in detail. Further, specific value maximization approaches, such as protein engineering and immobilization of the amylases are discussed in order to improve its suitability for varied applications on a commercial scale. The review also takes into account of the immobilization of the amylases on nanomaterials to increase the stability and reusability of the enzymes. The function-based metagenomics would provide opportunities for searching amylases with novel characteristics. The review is expected to explore novel amylases for future potential applications.

Scale-up fermentation of Escherichia coli for the production of recombinant endoglucanase from Clostridium thermocellum

Endoglucanase (EC 3.2.1.4) catalysing the hydrolysis of β-1.4-glycosidic linkage of cellulose molecules is an enzyme of tremendous industrial importance. The present study describes a response surface methodology based predicted model to deduce a set of fermentation conditions for optimum growth and activity of recombinant endoglucanase in E. coli BL21 (DE3). Numerous significant parameters including fermentation media composition, temperature (Celsius), pH and agitation rate (rpm) were analysed systemically by employing central composite design. This effort reports highly efficient recombinant endoglucanase overproduction (6.9 gl^-1 of biomass) with 30% expression by E. coli in modified M9NG media incubated at 37 °C and pH 7 agitated at 200 rpm. Addition of 3 mM glucose and 24 mM glycerol in the M9NG media has shown positive effect on the enzyme yield and activity. The CMCase activity experimentally estimated was found to be 1185 U/mg with the optimized parameters. The outcomes of both the responses by the predicted quadratic model were found in consensus with the obtained values. Our results well depicted the favourable conditions to further scale-up the volumetric yield of other relevant recombinant enzymes and proteins.

Recombinant Production and Characterization of SAC, the Core Domain of Par-4, by SUMO Fusion System

Prostate apoptosis response-4 (Par-4), an anticancer protein that interacts with cell surface receptor GRP78, can selectively suppress proliferation and induce apoptosis of cancer cells. The core domain of Par-4 (aa 137-195), designated as SAC, is sufficient to inhibit tumor growth and metastasis without harming normal tissues and organs. Nevertheless, the anticancer effects of SAC have not been determined in ovarian cancer cells. Here, we developed a novel method for producing native SAC in Escherichia coli using a small ubiquitin-related modifier (SUMO) fusion system. This fusion system not only greatly improved the solubility of target protein but also enhanced the expression level of SUMO-SAC. After purified by Ni-NTA affinity chromatography, SUMO tag was cleaved from SUMO-SAC fusion protein using SUMO protease to obtain recombinant SAC. Furthermore, we simplified the purification process by combining the SUMO-SAC purification and SUMO tag cleavage into one step. Finally, the purity of recombinant SAC reached as high as 95% and the yield was 25 mg/L. Our results demonstrated that recombinant SAC strongly inhibited proliferation and induced apoptosis in ovarian cancer cells SKOV-3. Immunofluorescence analysis and competitive binding reaction showed that recombinant SAC could specifically induce apoptosis of SKOV-3 cells through combination with cell surface receptor, GRP78. Therefore, we have developed an effective strategy for expressing bioactive SAC in prokaryotic cells, which supports the application of SAC in ovarian cancer therapy.

Improving the Thermostability of Acidic Pullulanase from Bacillus naganoensis by Rational Design

Pullulanase (EC 3.2.1.41) plays an important role in the specific hydrolysis of branch points in amylopectin. Enhancing its thermostability is required for its industrial application. In this study, rational protein design was used to improve the thermostability of PulB from Bacillus naganoensis (AB231790.1), which has strong enzymatic properties. Three positive single-site mutants (PulB-D328H, PulB-N387D, and PulB-A414P) were selected from six mutants. After incubation at 65°C for 5 min, the residual activities of PulB-D328H, PulB-N387D, and PulB-A414P were 4.5-, 1.7-, and 1.47-fold higher than PulB-WT, and their Tm values (the temperature at which half protein molecule denature) were 1.8°C, 0.4°C, and 0.9°C higher than PulB-WT, respectively. Then the final combined mutant PulB-328/387/414 was constructed. The t1/2 of it was 12.9-fold longer than that of PulB-WT at 65°C and the total increase in Tm of it (5.0°C) was almost 60% greater than the sum of individual increases (3.1°C). In addition, kinetic studies revealed that the kcat and the kcat/Km of PulB-328/387/414 increased by 38.8% and 12.9%. The remarkable improvement in thermostability and the high catalytic efficiency of PulB-328/387/414 make it suitable for industrial applications.

Substrate adaptabilities of Thermotogae mannan binding proteins as a function of their evolutionary histories

The Thermotogae possess a large number of ATP-binding cassette (ABC) transporters, including two mannan binding proteins, ManD and CelE (previously called ManE). We show that a gene encoding an ancestor of these was acquired by the Thermotogae from the archaea followed by gene duplication. To address the functional evolution of these proteins as a consequence of their evolutionary histories, we measured the binding affinities of ManD and CelE orthologs from representative Thermotogae. Both proteins bind cellobiose, cellotriose, cellotetraose, β-1,4-mannotriose, and β-1,4-mannotetraose. The CelE orthologs additionally bind β-1,4-mannobiose, laminaribiose, laminaritriose and sophorose while the ManD orthologs additionally only weakly bind β-1,4-mannobiose. The CelE orthologs have higher unfolding temperatures than the ManD orthologs. An examination of codon sites under positive selection revealed that many of these encode residues located near or in the binding site, suggesting that the proteins experienced selective pressures in regions that might have changed their functions. The gene arrangement, phylogeny, binding properties, and putative regulatory networks suggest that the ancestral mannan binding protein was a CelE ortholog which gave rise to the ManD orthologs. This study provides a window on how one class of proteins adapted to new functions and temperatures to fit the physiologies of their new hosts.