Chitosan Microbeads as Supporter for Pseudomonas putida with Surface Displayed Laccases for Decolorization of Synthetic Dyes

Various untreated wastewaters contaminated with industrial dyes pose significant pollution hazards to the natural environment as well as serious risks to public health. The current study reports a new material with a configurative chitosan matrix and engineered Pseudomonas putida cells with surface-displayed laccases that can decolorize five industrial dyes. Through a self-configuring device, five chitosan microbeads (CTS-MBs) with different particle sizes were prepared. P. putida cells were then immobilized onto the CTS-MBs under optimized immobilization conditions, forming a degrading-biosorbent dual-function decolorization complex. Scanning electron microscope and infrared analysis confirmed the successful immobilization of the cells onto the CTS-MB matrix. The optimized CTS-MB1 with surface-grafted aldehyde groups (aCTS-MB1) complex was capable of decolorizing Acid Green 25 and Acid Red 18 over a pH range of 2.5–8.5 and a relatively broad temperature range of 15–85 °C, with a maximum relative decolorization value of over 94%; the complex was also able to efficiently decolorize Direct Red 243, Reactive Blue 220 and Reactive Blue 198. Moreover, the aCTS-MB1 composite showed favorable activity in continuous and regenerative decolorization reactions. Therefore, the chitosan-immobilized decolorizing material, with both improved mechanical strength and performance, shows potential for further large-scale or continuous processes.