Perspectives and Application of Halophilic Enzymes

Abstract

The world of halophilic bacteria is quite diverse. We fi nd representatives of three domains of life, archaea, bacteria and eukarya that are adapted to salt concentration upto saturation. The micro-organisms able to grow upto NaCl concentration (>300 g/l) are found all over the small subunit rRNA based tree of life. Their metabolic diversity is high as well encompassing oxygenic and anoxygenic phototrophs, aerobic heterotrophs, denitrifi ers, sulfate reducers, fermenters and methanogens. The proteins of halophilic bacteria are magnifi cently engineered to function in a milieu containing 2-5 M salt. The proteins and encoding genes of halophiles represent a valuable repository and resource for reconstruction and visualizing processes of habitat selection and adaptive evolution. Search for new enzymes endowed with novel activities and enhanced stability continues to be desirable character for important commercial production. These poly extremophiles are excellent source of enzymes and metabolites possessing inherent ability to function in extreme conditions viz high salt, alkaline pH and facilitating catalysis for biotechnological application in food processing, industrial bioconversion and bioremediation. In brief, we have just begun to realize the great potential and true extent of diversity and suitable industrial applications possible from halophiles.

Biochemical and structural characterization of a novel halotolerant cellulase from soil metagenome

“…3c). The Cel5R retained 100% activity in the presence of 3 M LiCl, 75–80% activity in 4 M NaCl, and 70-80% activity in 2 M KCl which categorized it as an extreme halostable cellulase2829. Surprisingly, Cel5R retained 70–100% activity when incubated for one year in the presence of salts 2 M NaCl, 3 M LiCl and 1 M KCl (Fig.…”

Discovery and Characterization of a Thermostable and Highly Halotolerant GH5 Cellulase from an Icelandic Hot Spring Isolate

“…Halostability and halotolerance are important properties for industrial enzymes, especially for those participating in the processing of biomass where the extraction of cellulose from lignocellulosic materials involves strong alkali pretreatment followed by neutralization with acid solution which result in the formation of high amounts of salts [ 30 ]. Even though a number of thermostable cellulases are halostable and overall polyextremophilic, few are truly halotolerant and can perform catalytic transformations efficiently in high-salinity environments [ 31 ]. Quite surprisingly, CelDZ1 is such an example of a highly halotolerant cellulase, despite the fact that it was not isolated from an organism derived from a saline environment.…”

Increasing Performance and Thermostability of D-Phenylglycine Aminotransferase in Miscible Organic Solvents

“…Owing to decreased water as a molecular lubricant (29) and insufficient flexibility for denaturation (30) protein rigidity increased, so protection against temperature stress developed. Halophilic proteins, owing to their charged residues, manifest interesting interactions with salts in aqueous or organic solutions which maintain their active structures in dry conditions (31). Therefore, it is feasible to assume fusion of halophilic peptides preserves the active structure of D-PhgAT in dehydrated conditions and elevates the thermostability.…”