New sources of halophilic lipases: Isolation of bacteria from Spanish and Turkish saltworks

Abstract

High-salinity biotopes in Turkey and Spain have been demonstrated to be a suitable source of lipolytic enzyme-producing halophilic microorganisms. Three strains turned out to grow at high NaCl concentration (greater than 15%) and their ability to synthesize lipolytic enzymes was demonstrated on tributyrin and olive oil-containing plates by the formation of transparent or orangish halos around the colonies. The three isolates were cultivated in liquid medium and one of them was cherry-picked in terms of the enzyme production levels. It was subsequently genetically identified as Halomonas sp. LM1C. Response Surface Methodology (RSM) based on central composite design was used to optimize the culture conditions for lipase production, concluding that the maximum levels of lipase biosynthesis were obtained at 21.6 °C and pH 6.9. The impact of NaCl on the lipolytic activity of the obtained halophilic crude enzyme revealed an improved resistance against deactivation, when compared with a commercial lipase from Candida rugosa. The optimum reaction conditions (obtained by RSM) for the crude enzyme-biocatalyzed hydrolysis of p-nitrophenyl laurate turned out to be neutral pH and 29 °C. The process at optimum conditions was kinetically characterized by means of logistic equations, obtaining maximum activities near to 250 U/L and the use of a Luedeking & Piret type model allowed elucidating the metabolic characteristics of the synthesized lipolytic enzymes. The present investigation lays the foundation for implementing a biotechnological process to produce highly resistant lipolytic enzymes able to perform its biocatalytic function under extreme salt conditions.