DEVELOPMENT OF BIOREACTORS FOR PRODUCTION OF MICROBIAL POLYSACCHARIDE

有许多有用的微生物多糖。这肉汤很粘。因此，很难从发酵液中分离微生物细胞，这给微生物多糖的工业生产带来困难。本研究以出芽短梗霉为原料，通过发酵生产由葡萄糖组成的微生物多糖--普鲁兰多糖。为解决普鲁兰发酵液的后处理问题，我们尝试研制了一种带有膜分离装置的生物反应器，取得了如下结果：1）普鲁兰发酵液的膜分离效果好，膜分离效果好;用由聚碳酸酯树脂制成的细通道型模块交叉过滤普鲁兰多糖。它由宽度为24 mm、长度为98 mm的直线路径矩形通道组成。通道深度为2 mm。优化了操作条件，以获得高渗透通量和高普鲁兰多糖透过率。培养基中蔗糖含量和pH值最高， ...更多信息 影响通量和透射率的重要因素。随着培养基中初始蔗糖含量的降低，膜通量和透过率均增大。普鲁兰多糖发酵过程中培养基pH值的控制对过滤性能有很大影响。当初始蔗糖浓度为1%，pH值控制为6时，通量达到2 × 10 - 4 m/s，普鲁兰多糖透过率为100%，这使得能够通过保持来自肉汤的微生物细胞同时进料新鲜培养基来进行普鲁兰多糖的连续生产。2）制备两个配备有来自肉汤的微生物细胞分离单元的生物反应器<-4>：一个是由不锈钢制成的发酵罐，在该发酵罐上设置有标称孔径为5 μ m的底部微滤膜，生物反应器将错流膜组件置于发酵罐外，用旋转泵（配备错流过滤器的生物反应器）使培养基循环。当控制发酵液的pH为6时，加入新鲜培养基，使用配备有错流过滤器的生物反应器连续生产约40小时。在约40小时后，由于细胞形态从酵母样形式变为多孔形式，这增加了在膜上形成的滤饼的比电阻，因此渗透通量变得极低。所以，很难继续下去。需要找出最佳反应条件，例如进料介质的组成。少

There are many useful microbial polysaccharides. The broth is higly viscous. Therefore it is difficult to separate microbial cells from the broth which yields difficulty in industrial production of the microbial polysaccharides. In this study, we cultivated Aureobasidium pullulans to produce pullulan, which is one of the microbial polysaccharides composed from glucose. To solve the problem accompanied with downstream processing of pullulam broth, we attempted to develop a bioreactor equiped with a membrane separation unit.The results obtained are aummarized as follows1) The broth of pullulan from A. pullulans was cross-filtered with a module of thin channel type made of polycarbonate resin. It was composed from a straight path rectangular channel with a dimension of 24 mm in width and 98 mm in length. The channel depth was 2 mm. The operation condition was optimized to obtain a high permeation flux and high transmission of pullulan. The sucrose content in the medium and its pH were mos … More t important factors affecting the flux and transmission. With the decrease in the initial sucrose content in the medium, the flux and transmission became higher. The control of the medium pH during pullulan fermentation affected considerably the performance of filtration. When the pH was controlled to 6 with the initial sucrose concentration of 1 %, the flux reached 2x10^<-4> m/s and pullulan transmission was 100 %, which enables to conduct a continuous production of pullulan by holding microbial cells from the broth while feeding fresh medium.2) Two bioreactors equipped with a separation unit of microbial cells from the broth were prepared : one was a fermentor made of stainless steel at which bottoma microfiltration membrane with a nominal pore diameter of 5mum was set and in the other bioreactor a crossflow membrane module was placed outside the fermentor and the medium was circulated with a rotary pump (bioreactor equipped with a crossflow filtrator). When the broth was controlled at pH 6 feeding a fresh medium, a continuous production continued for about 40 h using a bioreactor equipped with a crossflow filtrator. After about 40 h the permeation flux became extremely low since the morphology of the cells changed to filamentous-form from yeast-like form which increased the specific resistance of the cake to be formed on the membrane. Therefore, it was difficult to continue. It is necessary to find out an optimum reaction condition such as composition of the feeding medium. Less