Transboundary intercellular communication mechanisms in the treatment of polyvinyl alcohol (PVA) wastewater by Geotrichum candidume enhanced activated sludge.

Polyvinyl alcohol (PVA) wastewater is characterized by low biochemistry and poor biodegradability. Transboundary intercellular communication between fungi and bacteria modulates microbial metabolism activity. This mechanism facilitates the biological treatment of PVA wastewater potentially. In this study, a Geotrichum candidume enhanced activated sludge system was developed to treat PVA wastewater. The transboundary intercellular communication mechanism among fungi and bacteria was elucidated, and the promotion of PVA removal was studied. Results showed that G. geotrichum sensed the N-decanoyl-l-homoserine lactone (C10-HSL) secreted by Acidovorax, leading to the upregulation of functional genes (HAO, LACC1, FAHD) for PVA degradation. Dehydrogenase (DHA) and laccase activities were increased by 15.2 %-38.6 % and 77.1 %-114.5 % after C10-HSL addition. Meanwhile, C10-HSL enhanced metabolic processes such as tricarboxylic acid cycle (TCA cycle), and oxidative phosphorylation in G. geotrichum to accelerate PVA degradation. As a result, G. geotrichum biodegraded PVA into aldehydes and ketones, which were further mineralized by bacteria such as Dechloromonas. For the co-culture system, the synergistic interaction between G. geotrichum and functional bacteria significantly enhanced PVA degradation via the intercellular communication process. The PVA and chemical oxygen demand (COD) removal increased by 31.7 % and 28.3 %, respectively, compared to the activated sludge system. This study offers a novel theoretical foundation and approach for the biological treatment of PVA wastewater through fungal-bacterial transboundary intercellular communication.