Abstract:
[gamma]-Alumina ([gamma]-Al[subscript 2]O[subscript 3]) doped alginate gel (AEC) was developed as a cell carrier in this study. The immobilization system of Saccharomyces cerevisiae M.30 for ethanol production from molasses and Clostridium butylicum DSM 5431 for 1,3-propanediol production from glycerol were used to evaluate the performance of the new carrier. Its feasibility for cell immobilization was examined and compared with suspended cell (SC) culture and immobilized cell on [gamma]-Al[subscript 2]O[subscript 3] (AC). Reusability of the carrier was evaluated by repeated batch mode. In a single batch system of ethanol fermentation, the final ethanol concentration of suspended cell, AC and AEC cultures were 82.4, 77.1 and 74.6 g/l, respectively. In repeated batch modes, AEC culture demonstrated a good potential of reusability. Its ethanol production and conversion yield of the 1[superscript st], 2[superscript nd] and 3[superscriptrd] repeated batch were comparable to those of SC and AC cultures. In addition, its ethanol production was more stable than that of SC culture. The yeast cell immobilization yield of the new carrier was approximately 85.6 %. AEC and AC were also found to be effective for the cell immobilization of C. butylicum with the immobilization yield of 79.6% and 83.2%, respectively. However, the strong inhibition effect of cell-[gamma]-Al[subscript 2]O[subscript 3] immobilization on 1,3-propanediol production was observed. In a single batch system, although the final cell concentration of AC and AEC culture were slightly higher than that of the suspended culture, the final 1,3-propanediol concentration and the conversion yield were significantly decreased. After 33 hours of the cultivation, the final 1,3-propanediol concentration of suspended cell, AC and AEC culture were 41.4, 20.6 and 15.5 g/l, with the conversion yield of 0.75, 0.58 and 0.48, respectively. In the repeated batch fermentation, the strong inhibitory effect of [gamma]-Al[subscript 2]O[subscript 3], towards 1, 3-propanediol production, especially in the system of AEC culture was confirmed. Moreover, the instability of SC and AEC cultures for reuse was observed. Interfering of positive charge of [gamma]-Al[subscript 2]O[subscript 3] on the cell membrane was thought as the cause of inactivity of C. butylicum DSM 5431 on 1,3-propanediol production.
