• Microbial nitrogen cycling dominates early bioremediation paradigms: nitrification, denitrification, and associated regulatory pathways govern nutrient removal in waste and soils, with ammonium repression, nitrogen fixation, and NO/N2O flux shaping remediation outcomes across wastewater and algal systems [4], [9], [11], [13], [15], [18].

• Activated sludge biology and process engineering emerge as a unifying framework: flocculation, microbial ecology, and kinetic behavior of mixed populations underpin treatment efficiency in sewage and industrial wastes [1], [2], [5], [10], [16].

• Enzymatic oxidative degradation pathways reveal core bioremediation routes for aromatic pollutants and lignin-derived organics, highlighting catechol formation, ring-cleavage, and humic transformations across microbes [6], [12], [20].

• Soil–plant–microbe interfaces shape remediation potential, through phosphate uptake by mycorrhizal networks and nitrate-reduction capabilities in algae and bacteria, indicating biogeochemical coupling as a remediation driver [13], [17], [18].

• Bioremediation via organismal uptake and accumulation of contaminants (pesticides and metals) underscores pollutant sequestration as a remediation mechanism, informing risk and management frameworks [14], [19].