PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

A variety of microorganisms generate highly potent surface-active bio-molecules or biosurfactants, which vary in their chemical properties and molecular size. In the present study, bioremediation effect of Pseudomonas fluorescence RE1 (GenBank: MF102882.1) and RE17 (GenBank: MF103672.1) endophytes on heavy metals Zn, Cr, Cd, and Ni were investigated. A total of 56 morphologically distinct isolates from indigenous rice roots were selected and subsequently characterised genotypically by using 16S rRNA sequencing approach. Next, biosurfactant production and heavy metal removal ability by the isolates were screened on the basis of α and β hemolysis on blood agar plates, BATH assay, and CTAB method. Analysis of bioremediation of heavy metals was done by using atomic adsorption spectroscopy. Bioremediation analysis revealed that isolates RE1 and RE17 reduced the concentration of Zn by up to 92% and 90% at pH 7.5, respectively, while for Ni, % removal was the same for both strains at 95% at pH 7.5. Biosorption results for Cr and Cd showed highest metal removal efficiency by Pseudomonas fluorescence RE17 at pH 8, 92% and 98%, respectively. Both isolates showed significant metal removal efficiency at 32±1°C for all experimental heavy metals. The present study suggests that all endophytes withstand at high concentration of testing heavy metals and can be used for bioremediation of heavy metals in contaminated environments.