BIODEGRADATION OF AROMATIC AND ALIPHATIC COMPOUNDS BY RHIZOBIAL SPECIES

Abstract

The biodegradative capabilities of ten rhizobial species and four field isolates were evaluated in this study using growth studies, dense suspension cultures, and soil studies. After a preliminary screening, selected species were chosen for their degradative effect on aromatic, halogenated aromatic, and aliphatic substrates. The substrates utilized were: benzoate, phenol, 2-hydroxybenzoate, 3-hydroxybenzoate, 4-hydroxybenzoate, catechol, resorcinol, 2,3-dihydroxybenzoate, 2,4-dihydroxybenzoate, 2,6-dihydroxybenzoate, 3,4-dihydroxybenzoate, phenoxyacetate, 2,4-dichlorophenoxyacetate, cresols, mandelates, phthalate, 2-bromobenzoate, 2-chlorobenzoate, 4-chlorobenzoate, 2,4-dichlorobenzoate, 2-chlorophenoxyacetate, 4-chlorophenoxyacetate, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, and hexadecane. Sinorhizobium xinjiangensis, Rhizobium leguminosarum, R. leguminosarum biovar trifolii, Bradyrhizobium japonicum, and strain V2 (field isolate) were able to metabolize a variety of organic compounds such as hydroxy- and dihydroxybenzoates, halogenated aromatic compounds, and alkanes. Significant differences were observed among the strains showing interspecies variability in their response to the different compounds. Dense cell suspension experiments conducted evaluating substrate loss, 4-chlorophenol, 4-chlorobenzoate, 4-chlorophenoxyacetate, cresols, resorcinol, and mandelate, among others, were metabolized although they did not support growth. Soil studies were performed showing that the addition of rhizobial inocula increased degradation of hexadecane in a soil environment.