Bioaugmentation of weathered petroleum-contaminated soil with a yeast-based consortium: Degradation performance and...

Bioremediation of total petroleum hydrocarbons (TPHs) in weathered soil is often constrained by the inefficiency of indigenous microbial synergistic networks. The mechanisms governing these network responses remain poorly understood, frequently overlooking the system-level functional dynamics. This 7-week study contrasted biostimulation (NZ) with yeast-based bioaugmentation (NS), linking microbial succession and functional network reconstruction to TPHs degradation. The NS group showed a clear advantage in TPHs removal (83.1%) and, crucially, in degrading the heavy C22-C40 fraction (76.3%). The NZ community, despite possessing degradation genes, was trapped in a "functional lock", lacking a cohesive synergistic network. The TPHs and heavy C22-C40 fraction removal efficiencies of the NZ community are only 75.3% and 39.3%, respectively. In contrast, the introduced Saccharomyces cerevisiae in the NS group acted as a pioneer species. It initiated a system-wide reconstruction by (1) altering the soil microenvironment through intense metabolic stress responses (e.g., upregulation of protein quality control systems and high-affinity MFS transporters) and (2) activating a novel, synergistic indigenous consortium, including Altererythrobacter and Cellulosimicrobium. It is indicated that effective bioaugmentation is not the mere addition of strains but a deliberate ecological network reconstruction. The pioneer species alleviates the functional stagnation of the native community, driving the emergence of a novel, highly effective synergistic degradation system. This provides a key theoretical basis for developing bioremediation technologies centered on ecological network regulation.