Application of Maxblend Fermentor(R) for microbial processes

Application of the Maxblend(R) impeller (which was originally developed for mixing high viscous liquids during chemical reactions) to a bioreactor (Maxblend Fermentor(R) [MBF]) was investigated. In comparison with turbine impeller fermenter (TBN), the MBF showed higher mixing capacity for high viscous liquids and consequently, the mixing time (theta m) was less than 50% of that observed with the TBN. Furthermore, by combining the Maxblend(R) impeller with a spiral sparger, the k(L)a was much higher than that of the TBN with a ring sparger. During the fermentative production of hyaluronic acid (a biopolymer) in TBN, there was a nonhomogeneous pH distribution inside the fermenter when the viscosity of the broth was high. Consequently, the pH in some parts of the fermenter was Lower than the optimum pH for hyaluronic acid production. On the other hand, when MBF with spiral sparger was used, the pH distribution inside the fermenter was homogeneous throughout the cultivation, resulting to about 20% increase in the hyaluronic acid productivity compared with a TBN. In the case of gamma-linolenic acid (GLA) production by Mortierella ramanniana, although the power consumption for liquid agitation was lower in the MBF equipped with a spiral sparger than in the TBN, small hard pellets were formed in former and this resulted in a higher GLA content of the lipid. Furthermore, in contrast with the pellets of various sizes formed in the TBN, the sizes of the pellets formed in the MBF were uniform. This was because the shear stress distribution was more uniform inside the MBF than in the TBN under the same agitation conditions.