A fixed-bed bioreactor is a type of bioreactor where microorganisms or cells are immobilized on a solid support, creating a "fixed bed." This design allows for continuous flow of nutrients and waste products through the bed, promoting efficient biological reactions. Fixed-bed bioreactors are commonly used in processes like wastewater treatment and the production of biofuels. These bioreactors can be made from various materials, including ceramics or polymers, and are often preferred for their simplicity and ease of operation. They provide a stable environment for microbial growth, making them suitable for long-term applications in industrial biotechnology.