Gluconate downstream processing

Downstream processing to obtain caldum gluconate is different to that employed to obtain either sodium gluconate or the free gluconic add. 

A second approach to efficient synthesis of gluconic acid and sorbitol has been the use of cell-free GFOR from Z. mobilis. Using a crude extract of Z. mobilis in a continuous ultrafiltration membrane reactor, excellent substrate conversion and enzyme stability were maintained for about 10 days (Silva-Martinez et al. 1998). However, it has been concluded that the strict requirements for enzyme stability would be costly for commercial production and downstream processing, which is a strong argument favoring use of permeable cells (Nidetzky et al. 1997). 

The chemical conversion of o-glucose to D-glucono-5-lactone and thence to o-gluconic acid has been used in manufacturing processes. Electrochemical oxidation in the presence of bromide (Isbell et al. 1932) and oxidation with air or oxygen (employing a catalyst deWilt 1972) are examples of methods in use. However, because of the appearance (during chemical production) of unwanted side products that require difficult downstream purification, the more specific microbial fermentations and other biochemical processes are definitely competitive. 

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