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Water pollution control is presently one of the major scientific research areas. Sol–gel immobilized Pseudomonas sp. able to enzymatically reduce azo groups was used for the decolourization of water containing azo dyes. It was observed that immobilized bacteria produced more than seven times higher amounts of extracellular enzymes involved in the biodegradation of azo dyes. The reusability of the immobilized bacteria was successfully evaluated with repeated-batch decolourization experiments. Indeed, after four repeated experiments, the decolourization was over 75%, 79% and 83% for remazol black, methyl orange and benzyl orange, respectively. The herein sol–gel immobilized bacteria offer advantages such as high viable cell densities, high stability and extended reaction times. Thus it would be applied as a cost-effective and efficient treatment to remove dyes from effluents.