Bacteria-mediated phthalic acid esters degradation and related molecular mechanisms

Phthalic acid esters (PAEs) have long been known as the most widely used plasticizer with a broad range of industrial application. PAEs are ubiquitous in different environments and our daily life due to their large and widespread application. Recent PAEs research mainly focused on their environmental fate (including leaching, migration, transformation) and toxicology and risk assessment. With the comprehensive recognition of their potential hazard, the elimination of PAEs has attracted worldwide concerns. Although many factors may contribute to the degradation of PAEs, the dominant role of biodegradation was widely reported. Many PAEs-degrading bacteria were isolated, metabolites and metabolic pathways were proposed, and enzymes involved in the degradation were identified. The current paper presents an overview of available reports about PAEs-degrading bacteria and related molecular mechanisms. The metabolic pathways deduced from the identified intermediates were presented. The upstream and downstream pathways of PAEs metabolism were summarized, including the aerobic and anaerobic pathways of phthalic acid (PA) degradation. Known enzymes involved in the hydrolysis of ester bonds were characterized according to their properties. Based on phylogenetic analysis, all these enzymes were distributed in four families of esterases and one unknown family. For these five families, conserved sequence motifs were identified and the biological properties of these motifs were characterized. Challenges and emerging opportunities are also discussed.