Complete degradation of dimethyl isophthalate requires the biochemical cooperation between Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr Isolated from Wetland sediment

Abstract

Two bacterial strains Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr were isolated and identified from enrichment cultures using dimethyl isophthalate (DMI) as the sole source of carbon and energy, and mangrove sediment as an inoculum. DMI was rapidly transformed by K. oxytoca Sc in the culture with formation of monomethyl isophthalate (MMI), which accumulated in the culture medium. M. mesophilicum Sr, incapable of utilizing DMI, showed high capability of degrading MMI to a transitory intermediate isophthalic acid (IPA), which was further mineralized by this strain. The biochemical pathway of DMI degradation by these two bacteria in a consortium was proposed: DMI to MMI by K. oxytoca Sc, MMI to IPA by M. mesophilicum Sr, and IPA by both K. oxytoca Sc and M. mesophilicum Sr based on the identified degradation intermediates. The consortium comprising K. oxytoca Sc and M. mesophilicum Sr was effective in mineralization of DMI. The results suggest that complete degradation of environmental pollutant DMI requires the biochemical cooperation between different microorganisms of the mangrove environment. © 2006 Elsevier B.V. All rights reserved.