Microbial degradation of polyacrylamide and the deamination product polyacrylate

Polyacrylamides are widely applied for instance in wastewater treatment, papermaking, oil recovery and mining. Since they are bulk chemicals used in large quantities around the world, their fate in nature is of considerable interest. Both single microbial species as well as mixed populations have been investigated for degradation. Biodegradation of polyacrylamide begins with amidase catalysed deamination of polyacrylamide to ammonia and polyacrylate. The liberated ammonia is then used as a nitrogen source for growth by the microbes. The carbon backbone, polyacrylate, is more recalcitrant to biodegradation than the amide moieties. There are nevertheless reports on microbial growth with polyacrylamide and polyacrylate as the carbon sources. Several aerobic bacteria isolated from polyacrylamide and polyacrylate containing environments, as well as from soil, have been shown to catabolize these polymers. Although enzymology of the bacterial degradation is largely unknown, some hypothetical pathways have been suggested. With white-rot fungi degradation has been demonstrated to be initiated by an indirect radical mechanism catalysed by oxidative enzymes. Anaerobic decomposition has been reported for sulfur-reducing bacteria and mixed bacterial populations.