Isolated Enzymes vs. Whole Cell Systems

The physical state of biocatalysts which are used for biotransformations can be very diverse. The final decision as to whether one should use isolated, more-or-less purified enzymes or whole microorganisms - either in a free or immobilized form -depends on many factors, such as ( ) the type of reaction, (ii) whether there are cofactors to be recycled, and (Hi) the scale in which the biotransformation has to be performed. The general pros and cons of using isolated enzymes vs. whole (microbial) cells are outlined in Table 1.2. 

Isolated enzymes Any Simple apparatus, simple workup, better productivity due to higher concentration tolerance Cofactor recycling necessary, limited enzyme stabilities 

Whole cells Any No cofactor recycling necessary, no enzyme purification required Expensive equipment, tedious workup due to large volumes, low productivity due to lower concentratirai tolerance, low tolerance of organic solvents, side reactions likely due to uncontrolled metabolism 

Microbial cells Reaction type Numbta- of reaction steps Numbta- of enzymes active Starting matiaial Product Concentratirai tolerance Product isolatirai Byproducts Resting Growing Short, catalytic Long, life process Few Many Few Many Substrate C -1- N source Natural or nonnatural Only natural High Low Easy Tedious Few Many  

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Table 1.2 Pros and cons of using isolated enzymes vs. whole cell systems...

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