Exolaccase Propels Humification to Decontaminate Bisphenol A and Create Humic-like Biostimulants

Exolaccase-propelled humification (E-PH) helps eliminate phenolic pollutants and produce macromolecular precipitates. Herein, we investigated the influencing mechanism of 12 humic precursors (HPs) on exolaccase-enabled bisphenol A (BPA) decontamination and humification. Catechol, vanillic acid, caffeic acid, and gentian acid not only expedited BPA removal but also created large amounts of copolymeric precipitates. These precipitates had rich functional groups similar to natural humic substances, which presented great aromatic and acidic characteristics. The releasing amounts of BPA monomer from four precipitates were 0.08-12.87% at pH 2.0-11.0, suggesting that BPA-HP copolymers had pH stability. More excitingly, certain copolymeric precipitates could stimulate the growth and development of radish seedlings. The radish growth-promotion mechanisms of copolymers were involved in two aspects: (1) Copolymers interacted with root exudates to accelerate nutrient uptake; (2) Copolymers released auxins to provoke radish growth. These results may provide an innovative strategy for decontaminating phenolic pollutants and yielding humic-like biostimulants in E-PH.