Purification and characterization of a thermo-halophilic, alkali-stable and extremely benzene tolerant esterase from a thermo-halo tolerant Bacillus cereus strain AGP-03, isolated from ‘Bakreshwar’ hot spring, India

• A hot spring bacteria Bacillus cereus strain AGP-03 produced a remarkable esterase.
• The purified esterase comprised of two polypeptides with molecular weight of 41 kDa.
• The purified enzyme exhibited optimal activities at pH 8.5 and 55 °C.
• Enzyme displayed notable thermo, halo, alkali-stability with high catalytic ability.
• The enzyme showed high activity and stability in the presence of benzene.

The study report a novel esterase obtained from a thermotolerant and halotolerant Bacillus cereus strain AGP-03, isolated from the hot spring of Bakreshwar, West Bengal, India. The enzyme was purified to homogeneity with molecular mass of 41 kDa comprising two polypeptide chains of 25 kDa and 16 kDa with specific activity of 740.17 U mg−1 protein. The enzyme was highly active and stable in wide range of pH (5.5–10.0), temperature (30–80 °C) and NaCl concentration (3–11%) with optimum value of 8.5, 55 °C and 4.5% NaCl respectively. The enzyme displayed maximum activity toward para-nitrophenyl butyrate (PNPB), Km and Vmax value of the esterase was found to be 52.46 μM and 1654 U mg−1 protein respectively against PNPB. Significant inhibition by phenylmethylsulfonyl-fluoride (PMSF) and phenylarsine oxide (PAO) indicated serine and cysteine residues are essential for enzyme catalysis. Moreover, the enzyme exhibited high activity and stability in presence of hydrophobic organic solvent. In presence of benzene the enzyme showed astonishingly high activity (136.9%) and stability. The purified esterase with these outstanding features may have great potential to be used in harsh industrial/biotechnological purposes. Besides, extreme stability in benzene may make this enzyme a potential biocatalyst for the application in non-aqueous based biotechnological processes.

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