Construction of a Novel Bio-reactor System With Semiconductor-Photocatalysts

半导体粉末如TiO_2和Pt浸渍的TiO_2，在光照射下，引起电子从价带激发到导带，并有助于光催化氧化和还原反应性较低的化学物种。在本研究中，我们通过实验研究，以构建具有光催化剂的生物反应器系统，获得了以下几个结果：1。用乙醇脱氢酶在TiO_2悬浮液中的光还原反应研究了辅酶NAD（烟酰胺腺嘌呤二核苷酸）的再生。固定化酶具有光催化氧化和酶还原NAD的双重活性。利用该催化剂可以实现NAD再生的环化反应.在气-液-固分散体系中，由光强度分布估算了光的有效吸收系数。量子效率是从测量的光氧化率的NADH（还原形式的NAD）在一个小的环形光反应器。在环形反应器（10 cm o. d.，4.6cm i. d.）和高度（= 1 m）的气-液-固分散体系中，测量了NADH的光氧化速率，实验结果与用有效吸收系数模型计算的结果吻合较好。

The semiconductor powders such as Tio_2, and Pt-impregnated Tio_2, under irradiation with a light, cause the excitation of electrons from valence to conduction bands and assist the photocatalytic oxidation and reduction of less reactive chemical species. In the present work, we obtained several findings by conducting the experimental studies in order to construct a bioreactor system with photocatalysts as follows :1. The regeneration of the coenzyme NAD (nicotinamide-adenine dinucleotide) with the enzyme (alcohol dehydrogenase) was examined by its photoreduction in Tio_2 suspensions. The enzymeimmobilized TiO_2 had both the activities of photochemical oxidation and enzymatic reduction of NAD. Itwas possible to achieve the cyclic reaction with NAD regeneration by this catalyst.2. Effective absorption coefficients of light were evaluated from the observed profile of light intensity in a square column with gas-liquid-solid dispersion containing TiO_2 particles. Quantum efficiencies were obtained from the measured photooxidation rates of NADH(reduced form of NAD) in a small annular photoreactor. In an annular reactor (10cm o. d., 4.6cm i. d.) and height (=1m) with gas-liquid-solid dispersion, photooxidation rates of NADH were measured and experimental results agreed well with those calculated from the model using the effective absorption coefficient.