Immobilized Sinirhodobacter sp. 1C5-22 for Multi-Metal Bioremediation: Molecular Resistance Mechanisms and Operational Validation in Industrial Wastewater Systems

A novel heavy metal-resistant bacterium with significant bioremediation capabilities, Sinirhodobacter sp. 1C5-22 was isolated from moderately polluted Shenzhen Futian mangrove rhizosphere sediments. This strain showed exceptional tolerance (MIC ≥ 600 mg/L for Cu/Zn; > 500 mg/L for Ni). Analyses revealed distinct metal-specific distribution strategies: Cd and Ni were predominantly bound extracellularly (>80%); Cu was bound intracellularly (~60%); and Zn exhibited balanced partitioning. Integrated omics analysis identified a molecular defense mechanism coordinated by the CreB transcriptional regulator. This Adsorption–Sequestration–Efflux (ASE) system integrates extracellular polymer binding, periplasmic sequestration via stable metal-binding proteins, and efflux pump activity, resolving the apparent adsorption-tolerance paradox at elevated concentrations. For bioremediation applications, we developed a polyvinyl alcohol–sodium alginate immobilized consortium (PVA-SA 1C5-22). The engineered agent displayed significantly enhanced biosorption capacity compared to free cells and effectively mitigated heavy metal-induced oxidative damage, evidenced by stabilized malondialdehyde levels. It demonstrated robust reusability, maintaining high metal enrichment across five adsorption–desorption cycles in multi-metal wastewater with efficient HCl-driven desorption (55–70%). Critically, it achieved stable nickel removal performance (~20% adsorption, >50% desorption) from authentic electroplating wastewater (1850 mg/L Ni2+) through successive multiple cycles. Our integrated approach bridges microbial ecology and environmental biotechnology, establishing this immobilized system as a highly sustainable strategy for complex industrial effluent remediation.