Biodegradation of Polyacrylamide and Its Derivatives

Although polyacrylamide (PAM) and its derivatives have many useful applications, their release in nature can have impacts on the environment and human health, thus bioremediation approaches for residual PAM are urgently needed. Biodegradation of PAM and its derivatives has been studied only in the last two decades, with most emphasis on acrylamide biodegradation. Microorganisms have been shown to utilize, not only acrylamide, but also PAM and its derivatives as the sole source of nitrogen and/or carbon under aerobic as well as anaerobic conditions. Microbial degradation lowered the molecular weight of the polymer, the viscosity, and the amide nitrogen was degraded to ammonia. Few species belonging to the bacterial genera Enterobacter sp., Azomonas sp., Bacillus sp., Acinetobacter sp., Pseudomonas sp., and Clostridium sp., were able to degrade 16–91% of PAM/HPAM under aerobic or anaerobic conditions. The monomer acrylamide is toxic to most microorganisms, however, some bacteria and fungi could degrade it using amidases that deaminate acrylamide to acrylic acid and ammonium, and further utilize acrylic acid to produce CO₂ and water. Some fungi and yeasts could degrade 60–80% of acrylamide. The biodegradation of PAM and its derivatives are initiated by the enzyme amidase, either under aerobic or anaerobic conditions, and are further degraded partially or completely by an array of different enzymes. Future research should focus on elucidating the exact pathways and the enzymes involved in the biodegradation process, especially by fungi and anaerobic bacteria, as well as utilizing PAM-degrading microbes for bioremediation purposes.