Scale-Up studies of non-aerated fed-batch fermentation of dextransucrase and the industrial synthesis of dextran using the enzymatic route

High activities of the enzyme dextransucrase were repeatedly produced using slowly agitated non-aerated fed-batch fermentations of Leuconostoc mesenteroides B-512(F). Activities in excess of 24.0 U cm^?3 were obtained consistently in a 16 dm³ laboratory fermenter using a 6 dm³ initial work volume. Yeast extract type was identified to be one of the important factors influencing the enzyme yield. Studies on aerating the medium with different gases indicated that the presence of carbon dioxide in the medium favoured high enzyme production. Agitation rates did not appear to have significant effects on either cell growth or enzyme production. One type of antifoam (silicone antifoam) was observed to affect enzyme production but not the cell growth. Scale-up of the non-aerated process was carried out up to a 1000 dm³ scale with enzyme broths containing up to 21.0 U cm^?3 being produced. Two batches of the enzyme that were produced at the large scale were used for the first time to synthesize dextran at a 50000 dm³ industrial scale. The dextran yields were up to 95.5% of the conventional industrial yields and were achieved in much shorter reaction time intervals.