Efficient medium-chain alkane degradation by two isolated bacterial strains: performance and synergistic mechanisms

Medium-chain alkanes from petrochemical off-gases pose severe risks to human health. Microbial degradation provides an environmentally friendly approach without generating secondary pollutants, but efficient strains for mixed alkane gases are rarely reported. Here, two novel strains, Pseudomonas toyotomiensis 414 and Tsukamurella paurometabola LXY, were isolated, respectively, using n-heptane and n-nonane as the sole carbon source. Strain LXY degraded 360 mg/L n-nonane within 18 h, representing the first report of such high removal efficiency, while strain 414 degraded 360 mg/L n-heptane within 45 h. Functional genes including alkB, ADH, FrmA, adhP, ALDH, actA, fadA and echA were identified, indicating typical alkane degradation pathways. A co-culture enhanced n-nonane removal by 1.44 to 1.89-fold and n-heptane by 1.13-fold compared with strain 414 alone. Strain 414 dominated in co-culture, likely due to high metabolism of alcohols and carboxylic acids, electron transfer and growth. Strain LXY primarily contributes to energy generation and substrate degradation, whereas strain 414 enhances biofilm formation, signal transduction, and metabolite exchange. Their complementary roles underpin the synergistic degradation of mixed alkane gases. This study provides a strategy for efficient mixed gaseous alkanes removal via interspecies synergy.