Prospecção de atividade biossurfactante e bioemulsificante de Bactérias de solo de manguezal e seus metabolitos

Abstract

The great environmental impact caused by contamination by oil spills and their derivatives has aroused great interest in natural sources that can be used in the remediation of affected soils and waters. Microorganisms, as the main source of biotechnological resources, have become a great alternative to produce biosurfactants and bioemulsifiers, which have a history of bioactive activities. We aimed to conduct a survey of bacteria from mangrove soil that is influenced by solar radiation and that is impacted by the presence of hydrocarbons to assess the resistance and production of biosurfactants of the strains and their metabolites. The bacteria and their metabolic liquids were submitted to drop collapse test, Parafilm M test, oil displacement, index, stability and emulsification activity with kerosene and mineral oil as carbon sources. A total of 82 strains were isolated from two mangrove soil collection points in Porto dos Tatus (Ilha Grande-Piauí), named P1 and P2. From the bacterial growth on Plate Count Agar (PCA), counting and observation of colony morphology was performed to isolate the greatest bacterial diversity producing biosurfactants. Then the isolates were characterized using the Gram stain technique. Regarding the morphotintorial characteristic, all strains are Gram positive rods. For resistance activity to UV radiation, 47 strains were tested, of which, 15 strains from point one (P1) showed resistance at 5- and 15- min. of exposure to UV and 10 strains of point two (P2) showed resistance at 5 and 15 min. exposure. For the drop collapse and emulsification index tests, 37 bacteria (20 from P1 and 17 from P2) were tested and grown in saline Bushnell-Hass broth (BH saline) plus 2% kerosene and 2% mineral oil. The strains tested showed growth potential in the presence of kerosene and mineral oil. For the tests of the collapse of gout with kerosene, 15 strains were positive and 17 were positive with the metabolic fluid. For mineral oil as a carbon source 16 were positive (11 from P1 and 5 from P2) and with metabolic liquid 4 they were positive (3 from P1 and 1 from P2). Metabolic fluids were tested for the emulsification index, 7 strains showed results above 40% with kerosene and 12 strains showed results above 40%) with mineral oil. Eight strains were chosen that presented the best results, 4 were identified as Bacillus sp., And the eight were tested for emulsification activity, emulsification stability, Parafilm M test and oil displacement. We observed that all of them have resistance to UV radiation, six have emulsifying potential with some characteristics of biosurfactant and two have biosurfactant potential with little bioemulsifying activity. To improve the capacity of the strains, an antagonism test was performed using the Cross Streak Plate technique, three consortia were formed with the strains that managed to get close and all tests were repeated. It was observed that two of the consortia manage to improve the activities of emulsification and surfactant, presenting greater results than the bacteria separately.