Global Research Landscape on Plastic Microfibers in Sludge Treatment: Proteomic Mechanisms and Biotechnological Pathways for Biomass Valorization

Plastic microfibers (PMFs) increasingly accumulate in wastewater treatment plants, impairing sludge dewatering and raising operational costs. This study combines a bibliometric analysis (2000–2025) with a critical review of the recent mechanistic literature to map the evolving research landscape on PMF–extracellular polymeric substance (EPS) interactions. The bibliometric trajectory (R2 = 0.9786) underscores a paradigm shift towards a molecular understanding of the sludge matrix. Our synthesis of recent experimental studies reveals that PMF-induced interference is often driven by the selective adsorption of hydrophobic extracellular proteins, with one study reporting up to 32.5% sequestration. This has been linked to deteriorated dewatering, such as a 45% increase in capillary suction time (CST) under controlled conditions. Proteomic studies have identified more than 40 extracellular proteins with altered expression, directly linking PMFs to impaired sludge rheology. However, this review critically assesses the underlying evidence, highlighting significant methodological heterogeneity, a lack of standardized protocols, and a reliance on laboratory-scale models as key limitations that prevent broad generalization. By identifying these gaps, this work reframes the PMF–EPS research agenda, emphasizing the need for harmonized methods and multi-omics integration to transform mechanistic insights into robust biotechnological solutions for sustainable sludge management within a circular bioeconomy.