水酸アパタイト多孔質焼結体を担体とした固定化酵母によるアルコール発酵

抄録

Porous hydroxyapatite (HAp) particles were prepared by sintering HAp powder mixed with carbon powder at 1150°C for 2hr. The HAp powder was synthesized by the method of precipitation from calcium nitrate and diammonium hydrogen phosphate. Ethanol fermentation using the sintered HAp as a carrier was investigated, and compared with that using a commercial carrier, porous glass. First, yeast cells were immobilized on the sintered HAp by the cultivation in a medium at 30°C, and the immobilized yeast reached a maximum 2.2×10⁸ cells per g-carrier with a particle diameter of 2380-3360pm. Secondly, a batch ethanol fermentation with the immobilized yeast on the sintered HAp at 30°C was found to proceed more smoothly than that with immobilized yeast on the porous glass in the medium containing glucose concentration of 10% (w/v). In the medium composed of glucose more than 20% (w/v), although the fermentation with the sintered HAp had the same tendency as the above up to ethanol concentration of about 6% (w/v), the fermentation was inhibited thereafter by the calucium cation eluted from the sintered HAp. In a continuous fermentation with immobilized yeast on the sintered HAp, ethanol concentration of 7.1% (w/v) was stably produced by adjusting the pH of the medium in the reactor to 5.0 at 24hr intervals under the conditions of glucose concentration of 15% (w/v) in the medium and the residence time of 5.8hr.