Degradation of dimethyl phthalate esters by Fusarium Sp. and an unidentified non-sporulating fungus isolated from mangrove sediments

Phthalate esters are synthetic compounds used as plasticizers to improve mechanical properties of the plastic resin, particularly flexibility. In recent years, they have attracted increasing attention owing to their widespread use, ubiquity in the environment, and endocrine-disrupting activity. Degradation mechanisms and pathways of phthalate esters have been consolidated in bacteria while those in fungi have rarely been shown. This study reports the degradation of dimethyl phthalate esters by mangrove soil fungi. Two fungal isolates, Fusarium sp. DMT-5-3 and an unidentified non-sporulating fungus DMI-5-1, were isolated from mangrove sediments by enrichment technique and demonstrated to be able to degrade dimethyl phthalate esters. Fusarium sp. DMT-5-3 metabolized dimethyl terephthalate through monomethyl terephthalate and phthalic acid. While, the unidentified fungus DMI-5-1 has been shown to only catalyse the hydrolytic conversion of dimethyl isophthalate to monomethyl isophthalate. Further metabolism of monomethyl isophthalate was not observed in this fungus. This study proposed the biochemical degradation pathways of dimethyl phthalate esters by mangrove fungi and suggested that the fungal esterases responsible for hydrolysis of the two ester bonds are highly substrate specific.