ABSTRACT
Whole cell immobilization is dened as “the physical connement or localization of intact cells to a certain region of space with preservation of some desired catalytic activity.”1,2 Immobilization resembles the conditions in which microbial cells are found in nature, taking into account that they are usually found adhered and growing on different kinds of surfaces. The considerable research and industrial interest in the use of immobilized cells for alcoholic and other food-and fuel-related fermentation applications is due to the numerous advantages that such technologies offer compared to conventional free cell systems. Specically, the advantages of immobilized cells for alcoholic beverages production include: (1) achievement of higher cell densities in the bioreactors, and therefore increased substrate uptake, higher productivities, and shorter process times, (2) protection against shear forces and stress (pH, temperature, substrate concentration and end-product inhibition, presence of heavy metals, etc.), leading to extended operational stability of the biocatalyst, (3) feasibility of continuous processing (Figure 43.1), easy product recovery, and reusability of the biocatalyst, (4) feasibility of low-temperature fermentation, which can lead to improved product quality, (5) reduction of secondary fermentation (maturation) times, (6) reduced contamination risk due to the higher cell densities and increased fermentation activity, (7) reduction of investment and energy costs due to the construction of smaller bioreactors, less separation and ltration requirements, and higher productivities.2-6
43.1 Introduction .......................................................................................................................... 933 43.2Cell Immobilization Techniques ..........................................................................................934
