The use of esterases in organic synthesis is of immense significance because of the low environmental impact of this methodology as well as the ability of these enzymes to catalyze synthesis of chiral alcohols, esters, and acids with high chemo-, regio-, and stereo-selectivity. Despite many enzyme-catalyzed reactions having been employed at industrial level, the complete shift from traditional chemical approach to more green biotechnological alternatives (biocatalysis) has been hampered by the instability of esterases when exposed to harsh conditions such as non-aqueous media or high temperature. In this project we studied a new esterase from a moderately halophilic microorganism isolated from the microbial mats in the salterns of Cabo Rojo, (PR). The enzyme was semi-purified from microbial cultures and studied for activity and stability under different experimental conditions (presence of organic solvents or ionic liquids, high temperature and extreme pH). Results show that the enzyme has an optimum activity at: pH 9.5, 45°C, 9% (w/v) NaCl and maintains its activity after 24 hours of incubation, in a broad range of organic solvent/water mixtures at different ratios (15%, 30% and 50% (v/v)). These results are in accordance with other studies in which the presence of organic solvents seems to stabilize the protein’s folded structure by acting as salt mimicking agents in solvent/water mixture. We further studied the chemo-, regio-, and stereo- selectivity of the esterase towards several substrates of synthetic interest. Kinetic resolution of esters of secondary chiral alcohols with different chain lengths, steric hindrance, and electron acceptor/donor groups was evaluated using HPLC equipped with chiral columns. Moderate to high enantioselectivity was observed. This data suggests that the new esterase isolated from moderately halophilic microorganism has a good stability in a broad range of experimental conditions and can catalyze the hydrolysis of different chiral esters in an enantioselective manner.

Solvent stability and synthetic applications of an esterase isolated from moderately halophilic microrganism

253rd National Meeting (2017)

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