The cell handling line includes products such as fermenters and bioreactors and cell culture supplies. Bioaugmentation is commonly used in municipal wastewater treatment to restart activated sludge bioreactors. Other options for bioreactors are biopolymers and biofuels. Membrane bioreactors (MBR) are activated sludge systems using a membrane liquid-solid phase separation process. Genetic engineering may enable hydrogen to be generated in bioreactors from woody biomass. This phenomenon has been intensively characterized for shake flask bioreactors. The Biochemical reactors or bioreactors form the base of the Bioreaction step. Another alternative considered was more expensive but less land-intensive membrane bioreactors. Bacteria are grown in bioreactors (e.g., "Haemophilus influenzae" type b). A microcarrier is a support matrix allowing for the growth of adherent cells in bioreactors. Fish can also be used to detect aquatic pollution or function as bioreactors. There are a variety of Bioreactors designed for 3D cell cultures. This susceptibility could potentially shut down entire bioreactors.