Oil-degrading bacteria from a membrane bioreactor (MBR) system for treatment of saline oily waste: isolation, identification and characterization of the biotechnological potential

Abstract

This study was focused on the microbial community characterization during operation of a Membrane Bioreactor System, used for the treatment of saline oily wastes, originated from marine transportation. A collection of forty-two (42) strains was obtained during microbiological screening and the bacterial diversity analyzed by amplification and 16S rRNA sequencing. Taxonomic analysis has shown a high level of identity with recognized sequences for a total of seven (7) distinct bacterial genera (Alcanivorax, Erythrobacter, Marinobacter, Microbacterium, Muricauda, Rhodococcus and Rheinheimera). The biotechnological potential of all isolates was identified by the estimate of two key factors, such as the production of biosurfactants (drop collapse test, oil spreading and E24 test) and the cellular adhesion percentage of hydrophobicity). These tests have been proposed for their ease of use and reliability in relation to the bacterial culture's ability to reduce the surface tension. The production of biosurfactants, forms part of several adaptations made by the microorganisms to metabolize hydrocarbons and represents a physiological response to specific environmental needs. Fourteen (14) biosurfactant producing bacteria were identified among all isolates and were further selected for growth on crude oil (optical density, OD600nm) and hydrocarbons degradation test(GC-FID analysis). Data obtained from this study confirmed the high potential of bacteria related to genera Alcanivorax (isolates MBR-B11 and MBR-G10), Rhodococcus (isolates MBR-F04 and MBR-G05), Rheinheimera (isolates MBR-H02 and MBR-H05), and Muricauda (isolate MBR-G04) and their possible application in petrolchemical waste water environmental problems. Our overall results suggest that the obtained bacterial isolates may constitute potential candidates for bioremediation and can be useful for biotechnological applications.