Multi-omics insights into micro-oxygen-regulated microbial decolorization and metabolic pathways during hydrolysis and acidification of textile wastewater

Micro-aerobic hydrolysis and acidification (MAHA) is a promising pretreatment for textile wastewater, yet the microbial metabolic mechanisms underlying its efficiency remain unclear. To address this, metagenomic analyses, coupled with the KEGG and MetaCyc databases, were utilized to characterize the functional composition, metabolic pathways, and key enzyme activities of hydrolysis and acidification (HA) microorganisms. Integrating metabolomic profiling, an innovative MAHA degradation pathway for Acid Scarlet GR dye was proposed, offering a comprehensive understanding of the microbial metabolic mechanisms under MA conditions. The results showed that HA bacteria under MA conditions (0.1–0.3 mg/L) were selectively enriched, including Brooklawnia (17.4 %), Bacillus (2.8 %), Paenirhodobacter (16.8 %), and Pinisolibacter (1.4 %), alongside significant upregulation of key enzymes (such as EC:1.2.4.1, EC:2.8.3.1, EC:3.5.1., EC:1.14.13.) involved in dye degradation. Consequently, the system achieved an average decolorization efficiency of 85.5 %, BOD₅/COD ratio of 0.50, COD removal of 29.7 %, and acetic acid production of 107.5 ± 8.7 mg/L. Functional annotation revealed active microbial pathways associated with fermentation, glycolysis, pyruvate metabolism, and the tricarboxylic acid (TCA) cycle. Metabolomic profiling identified 16 intermediates of Acid Scarlet GR degradation, revealing a pathway encompassing azo bond reduction, desulfonation, hydrolytic deamination, and aromatic ring cleavage, ultimately channeling into central carbon metabolism to generate acetic acid and CO₂. This work provides novel mechanistic insights by linking microbial community structure, enzyme activity, and metabolite fluxes, highlighting the specific microbial and enzymatic drivers of enhanced HA performance. These findings advance the understanding of MAHA processes and support its optimized application for textile wastewater treatment.

HA bacteria under MA conditions (0.1–0.3 mg/L) were selectively enriched, including Brooklawnia (17.4 %), Bacillus (2.8 %), Paenirhodobacter (16.8 %), and Pinisolibacter (1.4 %), alongside significant upregulation of key enzymes (such as EC:1.2.4.1, EC:2.8.3.1, EC:3.5.1., EC:1.14.13.) involved in dye degradation. Consequently, the system achieved an average decolorization efficiency of 85.5 %, BOD₅/COD ratio of 0.50, COD removal of 29.7 %, and acetic acid production of 107.5 ± 8.7 mg/L. Functional annotation revealed active microbial pathways associated with fermentation, glycolysis, pyruvate metabolism, and the tricarboxylic acid (TCA) cycle. Metabolomic profiling identified 16 intermediates of Acid Scarlet GR degradation, revealing a pathway encompassing azo bond reduction, desulfonation, hydrolytic deamination, and aromatic ring cleavage, ultimately channeling into central carbon metabolism to generate acetic acid and CO₂. This work provides novel mechanistic insights by linking microbial community structure, enzyme activity, and metabolite fluxes, highlighting the specific microbial and enzymatic drivers of enhanced HA performance. These findings advance the understanding of MAHA processes and support its optimized application for textile wastewater treatment.