RESUMO
The present study was conducted to investigate the capability of Haloarcula marismortui to synthesize esterases and lipases, and the effect of physicochemical conditions on the growth and the production of esterases and lipases. Finally, the effect of NaCl concentration and temperature on esterase and lipase activities was studied using intracellular crude extracts. In order to confirm the genomic prediction about the esterase and lipase synthesis, H. marismortui was cultured on a rich medium and the crude extracts (intra- or extracellular) obtained were assayed for both activities using p-nitrophenyl esters and triacylglycerides as substrates. Studies on the kinetics of growth and production of esterase and lipase of H. marismortui were performed, reaching a maximum growth rate of 0.053 h(-1) and maximal productions of intracellular esterase and lipase of 2.094 and 0.722 U l(-1) using p-nitrophenyl valerate and p-nitrophenyl laurate, respectively. Both enzymes were produced as growth-associated metabolites. The effects of temperature, pH, and NaCl concentration on the growth rate and production of enzymes were studied by using a Box-Behnken response surface design. The three response variables were significantly influenced by the physicochemical factors and an interaction effect between temperature and NaCl concentration was also evidenced. The surface response method estimated the following maximal values for growth rate and productions of esterase and lipase: 0.086 h(-1) (at 42.5 degrees C, pH 7.4, and 3.6 mol l(-1) NaCl), 2.3 U l(-1) (at 50 degrees C, pH 7.5, and 4.3 mol l(-1) NaCl), and 0.58 U l(-1) (at 50 degrees C, pH 7.6, and 4.5 mol l(-1) NaCl), respectively. Esterases were active at different salt concentrations, showing two optimal activities (at 0.5 and 5 mol l(-1) NaCl), which suggested the presence of two different esterases. Interestingly, in the absence of salt, esterase retained 50% residual activity. Esterases and lipase activities were maximal at 45 degrees C and inactive at 75 degrees C. This study represents the first report evidencing the synthesis of esterase and lipase by H. marismortui.
