Capital cost immobilized

It is a simpler and more cost effective immobilization process with lower energy consumption and no additional capital costs due to consumption of support materials. 

The use of continuous immobilized cell biofilm reactors eliminates downtime and hence results in superior reactor productivity (2,3). Adsorbed cell continuous biofilm reactors have been shown to favorably affect process economics (4). Application of these reactors reduces capital and operational cost, thus making the process simpler. Within these reactors, cells are immobilized by adsorption, which is a simpler technique than other techniques such as entrapment and covalent bonding (5). Adsorption is a simple technique and can be performed inside the reactors without the use of chemicals, whereas entrapment and covalent bonding are complicated techniques and require chemicals for bond formation. In anaerobic systems, such as butanol production, adsorption can be performed anaerobically within the reactor. An additional advantage of adsorption is that cells form uniform biofilm layers around the support, which lessens diffusion resistance compared to entrapped and covalently bonded cells. Hence, these reactors are called biofilm reactors. Because of reduction in diffusion resistance, the reaction rate is enhanced. For this reason, adsorption was chosen as the technique to be employed for Clostridium beijerinckii BA101 cell immobilization to produce butanol. In addition to being simple, it has the potential to be used in large-scale reactors. In the present study, clay brick was chosen as the cell adsorption support. It is available at a low cost and is easy to dispose of after use. 

ADM uses an immobilized enzyme particle developed by Novozymes (Illinios, U.S.) to catalyze interesterification of fully hydrogenated oil and unhydrogenated oil to produce lotv-trans-fat vegetable oil. The enzyme replaces the conventional sodium methoxide-based, high-temperature process. The enzyme process is greener and saves capital and operating costs. 

The selection of a bioreactor and operation mode starts with the type of biocatalysts (enzymes or whole cells) that will be used to produce the desired product, and if the biocalalysts will be suspended or immobilized with a recycle option. Each of these possibihties should be examined while taking into consideration the reactions stoichiometry and kinetics, mixing needs, gas exchange, heat removal and capital and operating costs (Merchuk and Asenjo, 1995). 

---