The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1–1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE , aarA , and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.
Inoculating functional bacterial strains is a cost-effective strategy for enhancing treatment of anaerobic digestion liquids in swine wastewater. This study systematically evaluated inoculation of heterotrophic nitrification aerobic denitrification strain Acinetobacter indicus CZH-5 in an internal circulation airlift zeolite sphere-based sequencing batch reactor (IR) for aerobic removal of nitrogen (N), phosphorus (P), and tetracycline (TEC). Inoculation with CZH-5 promoted secretion of quorum sensing signaling molecules, specifically N-acyl-homoserine lactones (C6-HSL and C10-HSL). These signaling molecules enhance quorum sensing and reinforce cooperation among functional bacteria. Under optimal conditions, average removal efficiencies of total nitrogen, total phosphate, and TEC were 92.8%, 88.4%, and 93.1%, respectively. The removal performance in IR exceeded that of the control by 26%–71%. N removal involved complete nitrification-denitrification, while accumulated P was transformed into phosphate monoesters within biofilm. Metagenomic analysis identified Thauera and Acinetobacter as the dominant genera, and Acinetobacter indicus as predominant species. Inoculation enhanced microbial richness and diversity to improve system operational stability. The abundance of functional genes associated with N, P, and TEC transformations significantly increased compared to the control. This study aimed to investigate the characteristics and mechanisms of inoculating a heterotrophic nitrification aerobic denitrification strain into an aerated biofilm system for swine wastewater remediation.
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