PAH-degrading rhizobacteria of Lepironia articulata for phytoremediation enhancement

Abstract This study identified plant rhizobacteria that have the capability to degrade polycyclic aromatic hydrocarbons (PAHs) and assist the plant in enhancing the phytoremediation process of PAH-contaminated wastewater. Rhizobacteria were isolated from the rhizosphere zone of Lepironia articulata exposed to 1%, 2% and 3% diesel concentrations (VDiesel/VWater). Thirty colonies were isolated, and after morphological and biochemical tests, they were classified into 23 colonies. These colonies were screened with a 3% diesel concentration (VDiesel/VWater) and only nine rhizobacteria (coded as A, B, C, D, E, F, G, H and I) were able to tolerate and sustain this. The extensive biodegradation of PAHs was carried out on the nine isolated rhizobacteria (individually as a monoculture), and it was found that the three rhizobacteria identified as Pseudomonas toyotomiensis strain ND1 (E), Microbacterium resistens strain ND2 (G) and Bacillus pumilus train ND3 (I) were highly able to remove PAHs (>80 % removal). Further biodegradation studies on the 16 components of PAHs were conducted for mixed cultures (E + G + I, G + E, G + I and E + I), and a mixed culture of G + E was found to be the best group in degrading PAHs (89 % removal). The existence of rhizobacteria, either as a monoculture or mixed culture, assisted the degradation of PAHs, thus enhancing the removal of PAH from wastewater. This study revealed the promising potential of the newly identified PAH degraders as candidates in enhancing the phytoremediation efficiency of PAH.