**12. Bioreactors used for biosorption**

Various types of bioreactors have been investigated for application at the industrial level. A bioreactor is a system used for the production of microorganisms or desired metabolites employing defined and controllable factors. The typical categories of bioreactors used for the biosorption are stirred tank bioreactors (STRs), air lift bioreactors (ALRs), fluidized bed bioreactors (FBRs), and fixed bed bioreactors (FXRs). These reactors can be operated either in batches or in continuous modes or both (fixed bed and stirred tank bioreactors). Factors (pH, temperature, mixing and agitation, and nutrient availability) affecting the process of biosorption in the bioreactor have to be optimized and controlled by using cooling jackets (temperature), baffles/ agitators (mixing), feed lines (supplies nutrients), and acid/base addition (pH) [188].
