Living adsorbent for Congo red removal and value-added product recovery via synergistic integration of photosynthetic bacteria and bacterial cellulose

• A biosorbent comprising photosynthetic bacteria and BC was developed for CR removal • PSB-BC biosorbent achieved a high CR removal efficiency of 97% within 3 days • Immobilized R. faecalis PA2 played a crucial role in CR degradation • BC protected immobilized bacteria from dye toxicity, enhancing their biomass • The biosorbent exhibited good stability upon storage at 4°C for up to 20 days Conventional adsorbents for Congo red (CR) removal pose economic and environmental challenges owing to high energy consumption and secondary pollution from waste adsorbent residues, highlighting a critical need for developing ecofriendly alternatives. This study reports a fully bio-based adsorbent comprising photosynthetic bacteria immobilized within a bacterial cellulose matrix, termed photosynthetic bacteria–bacterial cellulose (PSB–BC), for CR removal in batch and continuous systems. The PSB–BC biosorbent achieved a CR removal efficiency of 97% within 3 days and demonstrated a high cell immobilization efficiency of 472% under shaking for 120 h relative to the initial inoculum concentration. The immobilized cells exhibited enhanced production of value-added compounds after the removal process compared to the free-cell system, indicating 1.75-fold higher biomass, 1.86-fold higher carotenoid, and 2.39-fold higher bacteriochlorophyll a production. Cost-effective CR removal (96%) was achieved with minimal nutrient supplementation (0.2% yeast extract), and the biosorbent retained its activity after 20 days of storage at 4°C. A fixed-bed column study confirmed the continuous CR removal capability of the PSB–BC biosorbent, with dynamic adsorption behavior successfully described by the Thomas and Yoon–Nelson models. The Thomas model showed a maximum adsorption capacity of 468.88 mg/g, while the Yoon–Nelson model determined a 50% breakthrough time of 164.99 min and provided the best fit to the data, reflecting the synergistic adsorption–biodegradation behavior of the biosorbent. This study introduces a cost-effective, biodegradable biosorbent with high CR removal efficiency and storage stability, offering a scalable and environmentally responsible solution for treating dye-contaminated wastewater.