Degradation of acrylamide in oilfield produced water by microbial mat microorganisms

Acrylamide degradation, especially by microbial mat microorganisms, remains poorly investigated. This is significant because acrylamide is the toxic monomer of partially hydrolyzed polyacrylamide (HPAM), widely used in enhanced oil recovery (EOR). In this study, microbial mats from a constructed wetland treating oilfield produced water were tested for their ability to tolerate and degrade acrylamide. Respiration assays showed a twofold increase in CO₂ (7%) at 1000 mg/L acrylamide compared to the control, indicating its complete mineralization to CO₂. At 2000 mg/L acrylamide concentration, CO₂ decreased to 2.7% due to toxicity. Acrylamide removal reached ≥ 90% at 500-1000 mg/L, but dropped to 13 ± 5.5% at 2000 mg/L. MiSeq amplicon sequencing revealed increased bacterial richness and enrichment of Gamma- and Alphaproteobacteria after acrylamide degradation. Dominant taxa were Pseudomonas pseudoalcaligenes (41-70% of sequences) and Glycocaulis abyssi (up to 7.8%). Phototrophic cultures (Cyanobacterium stanieri NU2, NU14; Asterarcys quadricellulare RA100) tolerated up to 1000 mg/L. Cyanobacterium stanieri NU14 degraded acrylamide at all tested concentrations (50-1000 mg/L), while Cyanobacterium stanieri NU2 achieved complete removal up to 200 mg/L. Bacterial isolates belonging to Ochrobactrum, Agrobacterium, and Microbacterium grew on acrylamide as a carbon and/or nitrogen source. Ochrobactrum sp. K15 achieved complete acrylamide degradation, and Agrobacterium sp. K16 removed 97 ± 4.5% within 7 days. These findings show that microbial mats, and their associated phototrophic and heterotrophic microorganisms, can efficiently degrade acrylamide over a wide concentration range. They represent a promising bioremediation strategy for produced water.

The online version contains supplementary material available at 10.1007/s13205-025-04683-x.