16 Chapter 2 2.3.2 Whole cell process e can also use microbial cells(fermentation) containing the desired catalytic activity without isolating the enzymes responsibl Advantages of whole cell processes include: cell disruption not necessary enzyme isolation not necessary; cofactor regeneration not a problem reduced catalyst preparation costs Among the disadvantages of whole cell processes are system not fully understood(black box situation) product contamination by cellular enzymes or other end products of metabolism reduced catalytic specific activity cell structures acting as diffusion barriers; contamination by other micro-organisms may be a problem. Synthesis of industrial chemicals by microbial cells may be by fermentation (free, living ells), immobilised growing cells, immobilised resting cells or immobilised dead cells immobilised Immobilised cells have all the advantages of immobilised enzymes. cell immobilisation cell is preferred for reactions catalysed by intracellular enzymes because it avoids tedious and expensive extraction and purification procedures, which often result in preparations of low yield and stability SAQ 2.1 Identify which of the following statements are true for immobilised biocatalysts hen compared to free enzyme or free cell system 1)Conversions carried out by immobilised cells give higher yields than those carried out by growing and dividing cells 2)Downstream processing can be much easier 3)Smaller reactor volumes achieve similar rates of product formation. 4) The volume of effluent can be reduced SAQ 2.2 Benzene dioxygenase is a complex enzyme consisting of three protein components, that catalyse the conversion of benzene to benzene cis-dihydrodio Give two reasons why this biotransformation should be carried out using whole cells as opposed to using enzyme preparations16 Chapter 2 2.3.2 Whole cell processes We can also use microbial cells (fermentation) containing the desired catalytic activity without isolating the enzymes responsible. Advantages of whole cell processes include: cell disruption not necessary; enzyme isolation not necessary; advantages 0 more suited to multiple step processes; 0 cofactor regeneration not a problem; 0 increased enzyme stability; reduced catalyst preparation costs. Among the disadvantages of whole cell processes are: 0 system not fully understood (black box situation); 0 product contamination by cellular enzymes or other end products of metabolism; 0 cell structures acting as diffusion barriers; contamination by other micro-organisms may be a problem. Synthesis of industrial chemicals by microbial cells may be by fermentation (free, living cells), immobilised growing cells, immobilised resting cells or immobilised dead cells. Immobilised cells have all the advantages of immobilised enzymes. Cell immobilisation is preferred for reactions catalysed by intracellular enzymes because it avoids tedious and expensive extraction and purification procedures, which often result in preparations of low yield and stability. disadvantages 0 reduced catalytic specific activity; immobilii cells Idenbfy which of the following statements are true for immobilised biocatalysts, when compared to free enzyme or free cell systems. 1) Conversions carried out by immobilised cells give higher yields than those carried out by growing and dividing cells. 2) Downstream processing can be much easier. 3) Smaller reactor volumes achieve similar rates of product formation. 4) The volume of effluent can be reduced. Benzene dioxygenase is a complex enzyme consisting of three protein components, that catalyse the conversion of benzene to benzene cis-dihydrodiol. Give two reasons why this biotransformation should be canied out using whole cells as opposed to using enzyme preparations