Halophilic Bacteria as a Source of Novel Hydrolytic Enzymes

Abstract

Hydrolases constitute a class of enzymes widely distributed in nature from bacteria to higher eukaryotes. The halotolerance of many enzymes derived from halophilic bacteria can be exploited wherever enzymatic transformations are required to function under physical and chemical conditions, such as in the presence of organic solvents and extremes in temperature and salt content. In recent years, different screening programs have been performed in saline habitats in order to isolate and characterize novel enzymatic activities with different properties to those of conventional enzymes. Several halophilic hydrolases have been described, including amylases, lipases and proteases, and then used for biotechnological applications. Moreover, the discovery of biopolymer-degrading enzymes offers a new solution for the treatment of oilfield waste, where high temperature and salinity are typically found, while providing valuable information about heterotrophic processes in saline environments. In this work, we describe the results obtained in different screening programs specially focused on the diversity of halophiles showing hydrolytic activities in saline and hypersaline habitats, including the description of enzymes with special biochemical properties. The intracellular lipolytic enzyme LipBL, produced by the moderately halophilic bacterium Marinobacter lipolyticus, showed advantages over other lipases, being an enzyme active over a wide range of pH values and temperatures. The immobilized LipBL derivatives obtained and tested in regio- and enantioselective reactions, showed an excellent behavior in the production of free polyunsaturated fatty acids (PUFAs). On the other hand, the extremely halophilic bacterium, Salicola marasensis sp. IC10 showing lipase and protease activities, was studied for its ability to produce promising enzymes in terms of its resistance to temperature and salinity.

Evidence of a Role for Aerobic Bacteria in High Magnesium Carbonate Formation in the Evaporitic Environment of Dohat Faishakh Sabkha in Qatar

“…The occurrence of these moderately halophilic species in saline environments is established in the literature. In a review study carried out by Moreno et al (2013), bacteria belonging to the genera Bacillus, Staphylococcus, and Salinivibrio were isolated from different saline settings across the world, and examined for the production of extracellular enzymes. The long term survivability of Virgibacillus sp.…”

Medium-based optimization of an organic solvent-tolerant extracellular lipase from the isolated halophilic Alkalibacillus salilacus

“…When organic solvent reaction systems offer many advantages over aqueous reaction systems, such as use of hydrophobic substrate, easy separation and recovery of product, reusability of enzyme, reduction of side reactions and microbial contamination, and thermodynamic equilibrium favoring synthesis, use of halophilic lipases in these reactions becomes more critical (de Lourdes Moreno et al 2013;Hun et al 2003;Sinha and Khare 2014). These reasons justify the direction of intensive research to obtain lipases, suitable for industrially applications, by screening of new halophilic strains.…”

“…Lipases from halophiles have the unique properties making them the robust biocatalysts choice for enzymatic processes performed at high salt concentrations, extreme pH and temperatures, and aqueous-organic or non-aqueous media, where most enzymes display a severe reduction in their activity (de Lourdes Moreno et al 2013;Enache and Kamekura 2010;Mevarech et al 2000). When organic solvent reaction systems offer many advantages over aqueous reaction systems, such as use of hydrophobic substrate, easy separation and recovery of product, reusability of enzyme, reduction of side reactions and microbial contamination, and thermodynamic equilibrium favoring synthesis, use of halophilic lipases in these reactions becomes more critical (de Lourdes Moreno et al 2013;Hun et al 2003;Sinha and Khare 2014).…”

Biodiversity for biocatalysis: A review of the α/β-hydrolase fold superfamily of esterases-lipases discovered in metagenomes

“…In addition, a link between tolerance to high salt concentrations, which is common in halo-tolerant microorganisms, and solvent-resistance has been extensively confirmed (de Lourdes Moreno et al 2013). For this reason, within metagenomic-derived EST-LIP with confirmed functions, we screened for those that have been reported to be stable or were activated in the presence of salts (e.g., NaCl) and solvents (e.g., methanol Table I), suggests that solvent-resistance is a general characteristic of EST-LIP enzymes independent of their phylogenetic origin.…”