Effect of organic solvents on the structure and activity of moderately halophilic Bacillus sp. EMB9 protease

Abstract

Halophilic enzymes have been manifested for their stability and catalytic abilities under harsh operational conditions. These have been documented to withstand denaturation in presence of high temperature, pH, presence of organic solvents and chaotropic agents. The present study aims at understanding the stability and activity of a halophilic Bacillus sp. EMB9 protease in organic solvents. The protease was uniquely stable in polar solvents. A clear correlation was evident between the protease function and conformational transitions, validated by CD and fluorescence spectral studies. The study affirms that preservation of protein structure, possibly due to charge screening of the protein surface by Ca(2+) and Na(+) ions provides stability against organic solvents and averts denaturation. Salt was also found to exert a protective effect on dialyzed protease against chaotropism of solvents. Presence of 1 % (w/v) NaCl restored the activity in the dialyzed protease and prevented denaturation in methanol, toluene and n-decane. The work will have further implication on discerning protein folding in saline as well as non-aqueous environments.

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

“…Long-chain alcohols and oleic acid have poor solubility in water, and therefore, for increased yields of ester, organic solvents should be selected as reaction media. Since organic solvents produce various physico-chemical effects on enzyme molecules, suspension of enzymes in organic solvents results in conformational changes and thereby the specificity of substrates (Sinha and Khare 2014). For lipase, such changes were usually effectively overcome by the halophilic and organic solvent-tolerant features of the enzyme.…”

“…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.…”

Perspectives and Application of Halophilic Enzymes

“…Halophilic protease from Bacillus sp. EMB9 was uniquely stable in polar solvents like methanol, toluene and n-decane (Sinha and Khare 2014 ).…”

Detergent‐Compatible Robust Alkaline Protease from Newly Isolated Halotolerant Salinicoccus sp. UN‐12

“…Also, the higher salt concentrations contribute to increasing the surface tension of water and induce competition between protein molecule and salt ions for hydration. Hence, salts are responsible for removal of an essential layer of water molecules from the protein surface and contribute to denaturation of the protein [30]. Interference in hydrophobic interactions within a protein structure by higher salt concentrations is responsible for destabilizing the protein.…”

“…Interference in hydrophobic interactions within a protein structure by higher salt concentrations is responsible for destabilizing the protein. Also, salts affect protein structure by (i) decreasing the inclination for intermolecular hydrogen bond formation, (ii) altering the protein solubility, (iii) causing protein aggregation and precipitation, (iv) increasing the surface tension of water, (v) removal of the water layer from the protein surface, and (vi) promoting hydrophobic interactions [30].…”