Purification and properties of acetylesterase involved in decolorization of triphenylmethane dyes by Bacillus spp.

Abstract

Esterases [EC 3.1.1.x.] are the enzymes of hydrolase class involved in catalysis of cleavage and formation of ester bonds. Esterases are involved in interesterification, intraesterification and transesterification reactions. In the present study, different bacterial cultures were isolated from soil, screened for esterase activity and the most potent organism was selected for esterase production. Optimum conditions for esterase enzyme production was found to be at temperature of 37°C, pH – 7, ethyl acetate (1% v/v) as substrate concentration. The esterase was extracted and purified using ammonium sulfate precipitation (80%) and dialysis. Enzyme assay was done using para-nitrophenyl acetate. One unit of enzyme activity was defined as the amount of enzyme liberating 1 μmol of para-nitrophenol per minute. Specific activity was expressed in units per min per mg protein under assay conditions. According to the Lineweaver – Burk Plot, the kinetic properties of esterase were found to be Km = 0.91mM, Vm = 213μM/min/mg, Kcat = 234/min, Catalytic efficiency = 257.14/mM/min. The molecular weight of esterase enzyme found was 62kDa, possessing decolorizing property triphenylmethane dyes namely malachite green. However, no such activity was observed with azo dye namely Congo red. The industrial applications of esterases provide an immense contribution to the eco-friendly approaches towards nature. We would like to highlight that esterases are less explored enzymes having low literature survey as compared to lipases so the future scope of research is highly valuable. Amongst the number of reports on enzymatic decolourization of synthetic dyes, esterases also provide a significant decolourization potential.