Takafumi Futamura

Application of Maxblend Fermentor® for microbial processes

Abstract Application of the Maxblend® impeller (which was originally developed for mixing high viscous liquids during chemical reactions) to a bioreactor (Maxblend Fermentor® [MBF]) was investigated. In comparison with turbine impeller fermentor (TBN), the MBF showed higher mixing capacity for high viscous liquids and consequently, the mixing time (θ m) was less than 50% of that observed with the TBN. Furthermore, by combining the Maxblend® impeller with a spiral sparger, the kLa 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 fermentor when the viscosity of the broth was high. Consequently, the pH in some parts of the fermentor 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 fermentor was homogeneous throughout the cultivation, resulting to about 20% increase in the hyaluronic acid productivity compared with a TBN. In the case of γ-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.

Optimization and scale-up of γ-linolenic acid production by Mortierella ramanniana MM 15-1, a high γ-linolenic acid producing mutant

Abstract Optimum conditions for cultivation of Mortierella ramanniana mutant MM 15-1 were investigated with an aim of producing a lipid which contains high γ-linolenic acid (GLA). The optimum initial glucose concentration and pH control level were 300 g/ l and 4.0, respectively. Although both pellet and filamentous forms of this mutant were observed during the cultivation, the pellets accumulated lipid with higher GLA content than the filamentous forms. The effects of culture conditions on pellet formation were therefore investigated in a 30- l jar fermentor. The results showed that with an inoculum spore concentration of 5.0 × 10 3 /ml and an agitation speed of 800 rpm, 0.15–0.5 mm pellets were formed and consequently, the GLA content of the lipid increased to a very high value of 18.3%. Furthermore, when this process was scaled up to a 10-kl fermentor, using the impeller tip velocity as the scale-up parameter, both the pellet formation and the lipid production as well as the GLA content of the lipid were consistent with those obtained in the 30- l jar fermentor.

γ-Linolenic acid production by a low temperature-resistant mutant of Mortierella ramanniana

As a result of breeding experiments using low temperature growth as an index, Mortierella ramanniana mutant MM 15-1, which produces lipids with a high γ-linolenic acid (GLA) content, was obtained. The results of cultivation experiments in Erlenmeyer flasks showed that although the total lipid produced by the MM15-1 mutant was about 14% lower than that of the parent strain (M. ramanniana IFO 8187), the GLA content of the lipid was 16.5%, which represents about a 2-fold increase over that of the parent strain. In particular, there was a significant increase in the GLA proportion of the phospholipid fraction in the MM15-1 mutant. Furthermore, the results of the lipid composition analysis after phospholipid fractionation by TLC showed that there was a significant increase in the GLA proportions in the phosphatidylethanolamine (PE) and phosphatidylinositol (PI) of the MM 15-1 mutant. When the MM 15-1 mutant was cultivated in a 600-l fermentor, it produced lipid with 18.3% GLA. This was a 2-fold higher than the value obtained with the parent strain under the same cultivation conditions.