Pullulan fermentation in a reciprocating plate bioreactor

Reciprocating plate bioreactors are particularly well suited for conducting fermentations which give rise to highly viscous broth. To evaluate their performance for polysaccharide fermentations, a series of pullulan fermentations were performed with a particular emphasis placed on the influence of aeration on both the quantity and quality of the product. Two experiments were conducted at constant aeration rates and two others with constant dissolved oxygen concentrations. For the latter two experiments, the dissolved oxygen concentration was controlled by manipulating either the aeration flow rate or the reciprocating frequency of the perforated plates. It was found that, in general, a higher dissolved oxygen concentration leads to a higher productivity but the quality of the product, expressed in terms of the viscosity of the fermentation broth, was nevertheless reduced. It appears that the optimum yield, in terms of both quantity and quality, would be achieved at an intermediate dissolved oxygen concentration.