Unveiling cold Code: Acinetobacter calcoaceticus TY1's adaptation strategies and applications in nitrogen treatment

Overcoming low nitrogen removal efficiency at low temperatures is a challenge in biological treatment. This study investigated the cold-tolerant heterotrophic nitrification-aerobic denitrification by Acinetobacter calcoaceticus TY1. Transcriptomic and biochemical analyses indicated that strain TY1 upregulated genes for energy production, assimilation, cell motility, and antioxidant enzyme production under cold stress, maintaining functions such as energy supply, nitrogen utilization, and oxidative defense. Increasing the synthesis of extracellular polysaccharides, unsaturated fatty acids, and medium-chain fatty acids and secreting large amounts of antioxidant enzymes ensured cell membrane flexibility while enhancing the antioxidant system. Immobilization experiments showed that biofilms accelerated the removal of nitrogen pollutants and demonstrated good stability, with carriers being reusable to five times, maintaining high ammonia nitrogen (63.90 %) and total nitrogen (50.66 %) removal rates. These findings reveal the cold tolerance mechanisms of strain TY1 and its excellent practical potential as a candidate for wastewater treatment in cold regions.