Diethyl phthalate removal in waste gas from plastic formulations by membrane biofilm reactor

Abstract

Diethyl phthalate (DEP), the most extensively used plasticizer in plastic formulations, is categorized as a priority pollutant with carcinogenic, teratogenic, and mutagenic toxicity. A membrane biofilm reactor (MBfR) for diethyl phthalate removal in waste gas from plastic formulations was investigated, MBfR achieved effective DEP removal in 72 days of operation, DEP removal efficiency achieved 91.8 %. DEP hydrolyzing bacteria (Halomonas, Microbacterium, Pseudomonas, Rhodococcus) and phthalic acid (PA)-degrading bacteria (Chelativorans, Halomonas) along with protocatechuic acid-degrading bacteria (Pseudomonas, Microbacterium, Stappia, Rhodococcus, Dietzia, etc.) jointly completed the esterification, ring cleavage, and mineralization of DEP. Functional bacterial consortium formed a complex microbial symbiotic network of DEP degradation. The DEP biodegradation gene clusters, such as pht2345, ligABCIJK, and pcaGHLBCDIJF, encoded corresponding degradation enzymes to accomplish the conversion of DEP→PA, the ring cleavage of PA, and the degradation of protocatechuic acid. DEP was metabolized to PA by de-esterification and re-esterification, further degraded to hydroxyquinol by ring-cleavage before ring-opening, and then further converted into acetyl-CoA, which was eventually metabolized into CO2 and H2O by participating in the tricarboxylic acid (TCA) cycle. This provides a feasible and environmentally friendly biotechnology for the removal of diethyl phthalate in waste gas using a membrane biofilm reactor.