From Screening to Sequencing: Investigating the monoethylene glycol (MEG) biodegradation by Stutzerimonas stutzeri EX72 strain to optimize Oil and Gas industrial produced water treatment

Monoethylene glycol (MEG) is widely used as a hydrate inhibitor in produced water operations; however, its presence complicates treatment processes by increasing chemical oxygen demand (COD) and posing potential environmental risks to receiving water bodies. This study aimed to isolate and identify efficient MEG-degrading bacteria through systematic screening, followed by whole genome sequencing (WGS) of the top-performing strain to elucidate its biodegradation potential and genetic basis. Among 14 bacterial strains representing 9 genera, Stutzerimonas stutzeri EX72 exhibited the highest degradation performance, achieving a 62.28% reduction in COD within 10 days. Detailed kinetic experiments demonstrated near-complete removal of MEG from the medium within 14 days, confirmed by Gas Chromatography-Flame Ionization Detection (GC-FID). Integrated COD, total organic carbon (TOC), dissolved organic carbon (DOC), and biomass measurements revealed substantial mineralization of MEG, with apparent biomass yields of 0.167-0.188 g biomass per g of MEG-C consumed, indicating efficient carbon partitioning into both biomass formation and respiration. WGS revealed that EX72 encodes pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases (ADH) and aldehyde dehydrogenases (ALDH) responsible for the initial oxidation of MEG to glycolate, followed by assimilation via the glycerate pathway. Phylogenetic and synteny analyses showed that these enzymes cluster with environmental Stutzerimonas/Pseudomonas lineages and possess conserved genomic organization, supporting a conserved catalytic role in MEG oxidation that is mechanistically analogous, though evolutionarily distinct, from well-characterized glycol-degrading systems. Notably, two ADHs (SS.57032 and SS.63794) exhibited 80.58% and 84.91% sequence identity to those encoded by the gene pedH f rom Pseudomonas putida KT2440 and the ExaA gene from Pseudomonas aeruginosa , respectively. Overall, this study advances understanding of microbial MEG biodegradation in produced water systems and establishes S. stutzeri EX72 as a strong candidate for biological MEG removal, providing a foundation for future investigations into pathway regulation and metabolic fate.