Research Scholar, Deparment of Biotechnology, IIT Guwahati. 2010-ongoing
Proteins carry out catalytic tasks in living cells and interact specifically with other molecules. This requires that they fold to a unique, globular conformation that is only marginally more stable than the large ensemble of unfolded states. The folded state is stabilized mainly by the burial and tight packing of over 80% of the peptide groups and non-polar side chains. But these proteins do not behave same as in vitro. If life as we know it is to exist in a solvent other than water or thrive in different conditions such as pH and temperature, the folded state must be stable and soluble in the new conditions. But recent days a variety of methods have been developed to allow the in vitro evolution of a range of biomolecules including novel and improved biocatalysts (enzymes). Many solvent stable proteins have been reported till date. Gupta et al. 2006 isolated a solvent tolerant strain of Pseudomonas aeruginosa (PseA) protease. This bacterium grew well on the medium plates overlaid with isooctane, n-octane, n-heptane, cyclohexane, hexane but did not grow in the presence of toluene, chloroform, benzene, isopropanol, 1-butanol and ethanol, thus indicating its tolerance for hydrophobic solvents rather than hydrophilic.
Towards my doctoral thesis, my objective is focused on search of novel organic-solvent stable lipases from different plant sources which involve purification, cloning and over-expression, biochemical characterization of plant lipases and its structural insights in wide range of organic solvents. Organic solvent-stable lipases have pronounced impact on industrial economy because of its increases solubility of substrates and products in solvents over the water mediated reactions; also there is increase in synthesis over hydrolysis reactions by switch in thermodynamic equilibrium and elimination of microbial contamination in the reaction mixtures. The plant lipases are still under exploited and can be easily acceptable. The plant lipases are mostly concentrated in energy reserve tissues and behave as attractive biocatalysts because of its interesting features, such as its specificity; low cost; easy availability and easy acceptance. Furthermore, the chemo-, regio- and enantio-specific behavior of these enzymes has drawn remarkable interest among different industrial applications via the use of esterifictaion, interesterfication and transesterification reactions. The high specificity of plant lipases for fatty acids is one important interesting characteristic that could be exploited for various biotechnological purposes. And also their good substrate selectivity and specificity makes them valuable to the oil and chemical industry. Another important characteristic of lipases that has to be considered for applications in organic synthesis is the level of hydration that is needed for the enzyme to attain maximum activity. It can be exploited in several industries as organic synthesis, modifications of fats and oils, flavour enhancement and infant formula in food processing, resolution of racemic mixtures, and detergent industries.