Medium-chain substrate preference of lipases from a novel deep-sea halotolerant bacterium revealed by enzymatic...

Lipases from halotolerant bacteria represent promising biocatalysts for industrial applications due to their stability under extreme conditions. In this study, a halotolerant strain Salegentibacter sp. MHS1-6 was isolated from Western Pacific deep-sea sediments, and its lipase was characterized for the first time. The crude enzyme was first precipitated with 60% ammonium sulfate and then purified by Superdex 200 Increase. The final purified enzyme exhibited a specific activity of 187.4 ± 11.8 U/mg and a recovery yield of 24.7 ± 1.8%. Enzymatic characterization showed that the lipase retained high activity in 4.5 mol/L NaCl and at pH 11, revealing substantial tolerance to combined salinity and alkaline stress. Substrate specificity analysis showed a distinct preference for medium-chain substrates, including tricaprylin and p-nitrophenyl caprylate. Molecular docking provided preliminary insights into the potential structural basis of this chain-length preference, suggesting that C8-C10 acyl chains may form relatively favorable hydrogen-bonding and hydrophobic contacts within the catalytic pocket. This work presents the first detailed characterization of a deep-sea lipase, highlighting its potential for biocatalysis in high-salt and alkaline environments. While the precise catalytic mechanism requires further validation, its robust properties make it a promising candidate for industrial processes that demand exceptional stability.