Wu Shu-Yii, Lin Chi-Num, Chang Jo-Shu, Lee Kuo-Shing, Lin Ping-Jei
Department of Chemical Engineering, Feng Chia University, Taichung, Taiwan 407, Republic of China.
Biotechnol Prog. 2002 Sep-Oct;18(5):921-6. doi: 10.1021/bp0200548.
Municipal sewage sludge was immobilized to produce hydrogen gas under anaerobic conditions. Cell immobilization was essentially achieved by gel entrapment approaches, which were physically or chemically modified by addition of activated carbon (AC), polyurethane (PU), and acrylic latex plus silicone (ALSC). The performance of hydrogen fermentation with a variety of immobilized-cell systems was assessed to identify the optimal type of immobilized cells for practical uses. With sucrose as the limiting carbon source, hydrogen production was more efficient with the immobilized-cell system than with the suspended-cell system, and in both cases the predominant soluble metabolites were butyric acid and acetic acid. Addition of activated carbon into alginate gel (denoted as CA/AC cells) enhanced the hydrogen production rate (v(H2)) and substrate-based yield (Y((H2)/sucrose)) by 70% and 52%, respectively, over the conventional alginate-immobilized cells. Further supplementation of polyurethane or acrylic latex/silicone increased the mechanical strength and operation stability of the immobilized cells but caused a decrease in the hydrogen production rate. Kinetic studies show that the dependence of specific hydrogen production rates on the concentration of limiting substrate (sucrose) can be described by Michaelis-Menten model with good agreement. The kinetic analysis suggests that CA/AC cells may contain higher concentration of active biocatalysts for hydrogen production, while PU and ALSC cells had better affinity to the substrate. Acclimation of the immobilized cells led to a remarkable enhancement in v(H2) with a 25-fold increase for CA/AC and ca. 10- to 15-fold increases for PU and ALSC cells. However, the ALSC cells were found to have better durability than PU and CA/AC cells as they allowed stable hydrogen production for over 24 repeated runs.
城市污水污泥在厌氧条件下被固定化以产生氢气。细胞固定化主要通过凝胶包埋法实现，通过添加活性炭（AC）、聚氨酯（PU）以及丙烯酸乳胶加硅树脂（ALSC）对其进行物理或化学改性。评估了各种固定化细胞系统的氢发酵性能，以确定实际应用中最佳的固定化细胞类型。以蔗糖作为限制性碳源时，固定化细胞系统产氢比悬浮细胞系统更高效，且在两种情况下主要的可溶性代谢产物都是丁酸和乙酸。向藻酸盐凝胶中添加活性炭（记为CA/AC细胞），相比于传统的藻酸盐固定化细胞，产氢速率（v(H2)）和基于底物的产率（Y((H2)/蔗糖)）分别提高了70%和52%。进一步添加聚氨酯或丙烯酸乳胶/硅树脂提高了固定化细胞的机械强度和操作稳定性，但导致产氢速率下降。动力学研究表明，比产氢速率对限制性底物（蔗糖）浓度的依赖性可用米氏模型很好地描述。动力学分析表明，CA/AC细胞可能含有更高浓度的用于产氢的活性生物催化剂，而PU和ALSC细胞对底物具有更好的亲和力。固定化细胞的驯化导致v(H2)显著提高，CA/AC细胞提高了25倍，PU和ALSC细胞提高了约10至15倍。然而，发现ALSC细胞比PU和CA/AC细胞具有更好的耐久性，因为它们能够在24次重复运行中稳定产氢。
