Abstract:
Development of ready-to-use inoculum, which is high potential, long-term storage, and expedient transportation, is important for bioremediation. Granular bacteria has above possession and is suitable for applying in contaminated soil treatment owing to the carrier materials properties such as adsorption of contaminants, increasing the contaminants bioavailability, and increment of soil porosity, increasing the air in soil and enhancing the contaminant degradation activity by aerobic bacteria. This study aimed to develop granular bacteria for PAHs-contaminated soil treatment, which was started with the finding of effective bacterium from the environment and then the characterization of its toxic degradation performances and other properties leading to the granular bacterial development. PAHs-degrading bacteria belonging to Proteobacteria and Actinobacteria were isolated from mangrove sediment, an environmental source of the diversity and novelty of bacteria capable of both degrading PAHs and producing biosurfactants. Among them, Novosphingobium sp. PCY has high versatility to degrade 3-4 rings PAHs, especially pyrene and phenanthrene, and medium-chain alkane and also has feasible ability to produce biosurfactants. Furthermore, megaplasmid-encoded gene responsible for pyrene degradation in strain PCY was pyrene dioxygenase gene (nidA), which is well-known exist in pyrene-degrading Mycobacterium in contrast to its absence in PAHs-degrading Sphingomonads. In addition, alkane monooxygenase (alkB) of Mycobacterium, which has substrate specificity to medium-chain alkanes, was also found in strain PCY, indicating the adaptation tendency of strain PCY to effectively degrade contaminants in the environment. Due to its characteristics and non-pathogenicity, strain PCY could moreover be the candidate for the development of ready-to-use inoculum. Granular bacteria of strain PCY using corncob as carrier material and sucrose as protective agent makes this inoculum suitable for prolonged storage. Furthermore, this inoculum could enhance the pyrene removal from soil by the pyrene degradation ability of strain PCY and the properties, including PAHs adsorption, soil porosity increment, and PAHs-degrading indigenous microorganisms activation, of corncob