An extreme halophilic enzyme active at low salt in reversed micelles

Expression and functional study of VpV262 Pol, a moderately halophilic DNA polymerase from the Vibrio parahaemolyticus phage VpV262

Halophilic organisms are found widely in environments where the salt concentration is higher than 0.2 M. Halophilic proteins isolated from these organisms maintain structural integrity and function under high salt stress, whereas their non-halophilic homologs tend to aggregate and collapse. Here we report for the first time the expression and function of a DNA polymerase (DNAPol) VpV262 Pol, which belongs to DNAPol Family A from Vibrio parahaemolyticus phage VpV262. Enzymatic activity assay revealed that VpV262 Pol possessed 5'-3' polymerase activity as well as 3'-5' proofreading exonuclease activity. VpV262 Pol requires Mg²⁺ or Mn²⁺ to catalyze the polymerization reaction. Polymerization activity assay under a wide range of salt concentrations showed that VpV262 Pol maintains the highest polymerase activity with 0-0.3 M of NaCl/KCl and 0-0.5 M KAc (potassium acetate) /KGlc (potassium gluconate) when treated with 0-1 M corresponding salts, in contrast to significantly decreased activity of Phi29 Pol and Taq Pol above 0.2 M. Consistent with typical features of other halophilic proteins, negatively-charged amino acids are more frequently distributed on the surface of VpV262 Pol, contributing to highly solubility and enhanced halotolerance. While 3D-Structure of VpV262 Pol needs to be confirmed by experimental data further, this study here has added a member for the relatively small family of halotolerant DNA polymerase, and provides a valuable reference in isolation and characterization of DNA polymerases from halophilic organisms.

Hydrotrope induced structural modifications in CTAB/butanol/water/isooctane reverse micellar systems

SAXS and NMR studies to gain insight of structural alterations in reverse micellar nanotemplates in presence of hydrotropes.

Lipases and esterases from extremophiles: overview and case example of the production and purification of an esterase from Thermus thermophilus HB27

Extremophiles are organisms that have evolved to exist in a variety of extreme environments. They fall into a number of different classes that include thermophiles, halophiles, acidophiles, alkalophiles, psychrophiles, and barophiles (piezophiles). Extremophiles have the potential to produce uniquely valuable biocatalysts that function under conditions in which usually the enzymes of their nonextremophilic counterparts could not. Among novel enzymes isolated from extremophilic microorganisms, hydrolases, and particularly lipases and esterases are experiencing a growing demand. Lipases (EC 3.1.1.3) and esterases (EC 3.1.1.1) catalyze the cleavage of ester bounds in aqueous media and the reverse reaction in organic solvents. Both lipolytic enzymes have relevant applications in food, dairy, detergent, biofuel, and pharmaceutical industries. Here, we summarize the properties of lipases and esterases from the main extremophile groups: thermophiles and hyperthermophiles, psychrophiles, halophiles, alkalophiles/acidophiles, and solvent-resistant microorganisms.We report the biomass and lipolytic activity production by Thermus thermophilus HB27 in 5-L stirred-tank bioreactor at 70°C. Suitability of thermal spring water for culture media formulation is shown. In addition, a protocol to isolate and purify a cell-bound esterase from this microorganism is described.

Crystallization and preliminary X-ray analysis of D-2-hydroxyacid dehydrogenase from Haloferax mediterranei

D-2-hydroxyacid dehydrogenase (D2-HDH) from Haloferax mediterranei has been overexpressed in Escherichia coli, solubilized in 8 M urea and refolded by rapid dilution. The protein was purified and crystallized by the hanging-drop vapour-diffusion method using ammonium sulfate or PEG 3350 as precipitant. Two crystal forms representing the free enzyme and the nonproductive ternary complex with alpha-ketohexanoic acid and NAD(+) grew under these conditions. Crystals of form I diffracted to beyond 3.0 A resolution and belonged to the monoclinic space group P2(1), with unit-cell parameters a = 66.0, b = 119.6, c = 86.2 A, beta = 96.3 degrees . Crystals of form II diffracted to beyond 2.0 A resolution and belonged to the triclinic space group P1, with unit-cell parameters a = 66.5, b = 75.2, c = 77.6 A, alpha = 109.1, beta = 107.5, gamma = 95.9 degrees. The calculated values for V(M) and analysis of the self-rotation and self-Patterson functions suggest that the asymmetric unit in both crystal forms contains two dimers related by pseudo-translational symmetry.

Surfactants in microbiology and biotechnology: Part 2. Application aspects

Surfactants are amphiphilic compounds which can reduce surface and interfacial tensions by accumulating at the interface of immiscible fluids and increase the solubility, mobility, bioavailability and subsequent biodegradation of hydrophobic or insoluble organic compounds. Chemically synthesized surfactants are commonly used in the petroleum, food and pharmaceutical industries as emulsifiers and wetting agents. Biosurfactants produced by some microorganisms are becoming important biotechnology products for industrial and medical applications due to their specific modes of action, low toxicity, relative ease of preparation and widespread applicability. They can be used as emulsifiers, de-emulsifiers, wetting and foaming agents, functional food ingredients and as detergents in petroleum, petrochemicals, environmental management, agrochemicals, foods and beverages, cosmetics and pharmaceuticals, and in the mining and metallurgical industries. Addition of a surfactant of chemical or biological origin accelerates or sometimes inhibits the bioremediation of pollutants. Surfactants also play an important role in enhanced oil recovery by increasing the apparent solubility of petroleum components and effectively reducing the interfacial tensions of oil and water in situ. However, the effects of surfactants on bioremediation cannot be predicted in the absence of empirical evidence because surfactants sometimes stimulate bioremediation and sometimes inhibit it. For medical applications, biosurfactants are useful as antimicrobial agents and immunomodulatory molecules. Beneficial applications of chemical surfactants and biosurfactants in various industries are discussed in this review.

Extremophiles as a source for novel enzymes

Microbial life does not seem to be limited to specific environments. During the past few decades it has become clear that microbial communities can be found in the most diverse conditions, including extremes of temperature, pressure, salinity and pH. These microorganisms, called extremophiles, produce biocatalysts that are functional under extreme conditions. Consequently, the unique properties of these biocatalysts have resulted in several novel applications of enzymes in industrial processes. At present, only a minor fraction of the microorganisms on Earth have been exploited. Novel developments in the cultivation and production of extremophiles, but also developments related to the cloning and expression of their genes in heterologous hosts, will increase the number of enzyme-driven transformations in chemical, food, pharmaceutical and other industrial applications.

Extreme halophilic enzymes in organic solvents

The use of halophilic extremozymes in organic media has been limited by the lack of enzymological studies in these media. To explore the behaviour of these extremozymes in organic media, different approaches have been adopted, including the dispersal of the lyophilised enzyme or the use of reverse micelles. The use of reverse micelles in maintaining high activities of halophilic extremozymes under unfavourable conditions could open new fields of application such as the use of these enzymes as biocatalysts in organic media.