A robust immobilized system using Rhodococcus pyridinivorans YY802 for the efficient dissipation of refractory monomethylanilines in wastewater.

The discharge of industrial wastewater containing refractory and toxic monomethylaniline (MMA) isomers poses a severe threat to aquatic ecosystems. To address this, a degrading bacterium, Rhodococcus pyridinivorans YY802, was isolated and immobilized in a composite carrier comprising sodium alginate (SA), bamboo charcoal (BC), and chitosan (CA). Strain YY802 demonstrated a versatile capacity to degrade o-, m-, and p-toluidine, with sodium pyruvate (SP) serving as a critical co-metabolic substrate to overcome substrate inhibition. Compared to single carriers, the SA+BC+CA composite provided a superior "micro-nest" structure due to the high specific surface area of bamboo charcoal. This structure facilitated a synergistic process of "adsorption-enrichment-biotransformation" significantly enhancing removal ability and robustness against environmental fluctuations (temperature and salinity). Although Response Surface Methodology (RSM) predicted an optimal degradation peak at 46 °C and pH 6.73, the immobilized system exhibited excellent environmental adaptability, maintaining high removal efficiencies (>90%) at a cost-effective ambient temperature of 28 °C. Consequently, operating at 28 °C in a continuous Sequencing Batch Reactor (SBR) system, the immobilized cells exhibited remarkable stability and high dissipation capability, removing approximately 85% of COD from mixed toluidine wastewater, significantly outperforming free cells. Furthermore, a phytotoxicity assessment using Lemna minor confirmed that the biotreatment effectively eliminated oxidative stress factors and restored plant growth, verifying the ecological safety of the effluent. This study presents a highly efficient, stable, and eco-friendly biotechnology for the remediation of complex dye-contaminated wastewater.