Korgel B A, Rotem A, Monbouquette H G
Chemical Engineering Department, University of California, Los Angeles 90024-1592.
Biotechnol Prog. 1992 Mar-Apr;8(2):111-7. doi: 10.1021/bp00014a004.
The effective diffusivity of galactose was measured for calcium alginate gel membranes containing immobilized live Zymomonas mobilis cells at concentrations ranging from 0 to 150 g dry wt/L of gel. Since galactose is not taken up by living Z. mobilis organisms, the diffusion of this representative six-carbon sugar could be studied independently of sugar consumption. Various immobilized biomass loadings were achieved by two different techniques: addition of biomass at known concentrations to the sodium alginate solution before membrane formation and growth of cells in the gel to various biomass concentrations. The highest immobilized cell concentration, attained by in situ growth, corresponds to the maximum of this system, as growth beyond this maximum concentration led to disintegration of the gel membrane. The galactose effective diffusivity measurements for both methods of immobilized cell loading overlap within experimental error and follow the same general monotonic decline with entrapped biomass concentration. Most of the data fall below the upper bound predicted by Hashin and Shtrikman (1962) and show good agreement with the random pore model of Wakao and Smith (1962, 1964). Available effective diffusivity data from the literature provide evidence that the random pore model is an excellent predictor of sugar effective diffusivity in gel immobilized cell systems in general.
在固定化运动发酵单胞菌活细胞浓度范围为0至150 g干重/L凝胶的海藻酸钙凝胶膜中，测定了半乳糖的有效扩散系数。由于半乳糖不会被活的运动发酵单胞菌摄取，因此可以独立于糖的消耗来研究这种代表性六碳糖的扩散。通过两种不同技术实现了不同的固定化生物量负载：在膜形成前将已知浓度的生物量添加到海藻酸钠溶液中，以及使凝胶中的细胞生长至不同的生物量浓度。通过原位生长达到的最高固定化细胞浓度对应于该系统的最大值，因为超过该最大浓度的生长会导致凝胶膜解体。两种固定化细胞负载方法的半乳糖有效扩散系数测量值在实验误差范围内重叠，并且随着截留生物量浓度的增加呈现相同的总体单调下降趋势。大多数数据低于Hashin和Shtrikman（1962年）预测的上限，并且与Wakao和Smith（19�2年、1964年）的随机孔模型显示出良好的一致性。文献中现有的有效扩散系数数据表明，一般来说，随机孔模型是凝胶固定化细胞系统中糖有效扩散系数的优秀预测模型。
