Development of Green Bioreactor for Concentrated Xanthan Production

黄原胶是由野油菜黄单胞菌（Xanthomonascampestris）产生的天然产物，是一种非常有用的食品增稠剂和添加剂。由于黄原胶发酵条件较好，工业生产中通常采用搅拌式生物反应器。然而，培养基的屈服应力随着发酵而迅速增加，使得搅拌罐中的气液混合有时变得很差。即使叶轮的功率输入增加以保持良好的混合，远离叶轮的液体也变得停滞，并且真菌可能被叶轮的大剪切应力剂量损坏。当菌体因缺氧而死亡时，黄原胶发酵结束。对于稀溶液中产生的黄原胶，在分离纯化过程中必须进行大量的蒸发或分离过程。而鼓泡塔作为一种良好的好氧反应器，其混合过程是通过鼓泡反应器进行的， 关于我们 弱对流本研究的目的是开发一种适合于高浓度黄原胶生产的鼓泡塔生物反应器，以保护水环境。本研究按以下步骤进行：（1）琼脂发酵（2）摇瓶和小泡罩塔发酵（3）搅拌罐生物反应器生产黄原胶。（4）标准鼓泡塔中黄原胶的生产（5）新型高氧传递鼓泡塔生物反应器的开发在搅拌槽和标准鼓泡塔中氧浓度都随着发酵而降低。对于黄原胶发酵，由于液体变得非常粘稠，向培养基中的氧气转移限制了黄原胶的生产。在本研究所使用的所有生物反应器中，即使在最粘稠的黄原胶溶液中，分区鼓泡塔也具有较高的氧传递系数。因此，所提出的鼓泡塔生物反应器比其他工艺更适合于生产黄原胶。少

Xanthan which is a natural product by Xanthomonas campestris is very useful thickener and additive for food. The production process for xanthan is usually utilized stirred tank bioreactors due to well fermentation in industry. However, the yield stress of culture medium increases rapidly with fermentation so that gas-liquid mixing in stirred tank becomes sometimes poor. Even if a power input for impeller increases to keep mixing well, the liquid far from the impeller becomes stagnant as well as the fungi may be damaged by large shear stress dose to the impeller. When the fungi die due to shortage of oxygen in medium, the xanthan fermentation finishes. For dilute concentration of xanthan gum produced in the solution, large evaporation or separation processes must be required in separation and purification process. In those downstream process, a large amount of waste solutions generates.On the other hand, bubble columns are well known as good aerobic reactors whose mixture is done by bub … More ble convection. Moreover, bubble columns can be easily sterilized and scaling-up.In this study, the purpose is to develop a bubble column bioreactor for the higher concentrated xanthan production up to protect water environment. This study was proceeded as following steps :(1)Fermentation on agar(2)Fermentation in flask and small bubble column(3)Xanthan production in a stirred tank bioreactor.(4)Xanthan production in a standard bubble column(5)Development of novel bubble column bioreactor having high oxygen transferOxygen concentration decreased with fermentation in both stirred tank and standard bubble column. For the xanthan fermentation, the oxygen transfer into culture medium limited the xanthan production due to the liquid became very viscous. Of all bioreactors used in this study, the partitioned bubble column has the higher oxygen transfer coefficient even in the most viscous xanthan solution. Therefore, the proposed bubble column bioreactor is suitable more efficiently to produce xanthan than the other processes. Less